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149-463: Radon-222 is formed as part of the uranium series i.e. the normal radioactive decay chain of uranium-238 that terminates in lead-206 . Uranium has been present since the Earth was formed, and its most common isotope has a very long half-life (4.5 billion years), which is the time required for one-half of uranium to break down. Thus, uranium and radon will continue to occur for millions of years at about

298-420: A completely crystalline rock. Granitic rocks mainly consist of feldspar , quartz , mica , and amphibole minerals , which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende ) peppering the lighter color minerals. Occasionally some individual crystals ( phenocrysts ) are larger than the groundmass , in which case

447-426: A half-life in the range of 100 a–210 ka ... ... nor beyond 15.7 Ma In the four tables below, the minor branches of decay (with the branching probability of less than 0.0001%) are omitted. The energy release includes the total kinetic energy of all the emitted particles ( electrons , alpha particles , gamma quanta , neutrinos , Auger electrons and X-rays ) and the recoil nucleus, assuming that

596-460: A helium-4 nucleus) changes the atomic mass number ( A ) of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same residue mod 4. This divides the list of nuclides into four classes. All the members of any possible decay chain must be drawn entirely from one of these classes. Three main decay chains (or families) are observed in nature. These are commonly called

745-548: A 2003 report EPA's Assessment of Risks from Radon in Homes from the United States Environmental Protection Agency , epidemiological evidence shows a clear link between lung cancer and high concentrations of radon, with 21,000 radon-induced U.S. lung cancer deaths per year—second only to cigarette smoking. Thus in geographic areas where radon is present in heightened concentrations, radon is considered

894-553: A basaltic magma to a granitic magma, but the quantities produced are small. For example, granitic rock makes up just 4% of the exposures in the South Sandwich Islands . In continental arc settings, granitic rocks are the most common plutonic rocks, and batholiths composed of these rock types extend the entire length of the arc. There are no indication of magma chambers where basaltic magmas differentiate into granites, or of cumulates produced by mafic crystals settling out of

1043-486: A daughter isotope, such as Ra, is sometimes called a granddaughter isotope . The time required for an atom of a parent isotope to decay into its daughter is fundamentally unpredictable and varies widely. For individual nuclei the process is not known to have determinable causes and the time at which it occurs is therefore completely random . The only prediction that can be made is statistical and expresses an average rate of decay. This rate can be represented by adjusting

1192-484: A decay chain are referred to by their relationship to previous or subsequent stages. Hence, a parent isotope is one that undergoes decay to form a daughter isotope . For example element 92, uranium , has an isotope with 143 neutrons ( U ) and it decays into an isotope of element 90, thorium , with 142 neutrons ( Th ). The daughter isotope may be stable or it may itself decay to form another daughter isotope. Th does this when it decays into radium-228 . The daughter of

1341-520: A diapir it would expend far too much energy in heating wall rocks, thus cooling and solidifying before reaching higher levels within the crust. Fracture propagation is the mechanism preferred by many geologists as it largely eliminates the major problems of moving a huge mass of magma through cold brittle crust. Magma rises instead in small channels along self-propagating dykes which form along new or pre-existing fracture or fault systems and networks of active shear zones. As these narrow conduits open,

1490-414: A factor of two over an hour, and concentrations can vary greatly even between two adjoining rooms in the same structure. The distribution of radon concentrations is highly skewed : the larger concentrations have a disproportionately greater weight. Indoor radon concentration is usually assumed to follow a lognormal distribution on a given territory. Thus, the geometric mean is generally used to estimate

1639-509: A few (known as leucogranites ) contain almost no dark minerals. Granite is nearly always massive (lacking any internal structures), hard (falling between 6 and 7 on the Mohs hardness scale) , and tough. These properties have made granite a widespread construction stone throughout human history. The word "granite" comes from the Latin granum , a grain, in reference to the coarse-grained structure of such

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1788-423: A given number of radioactive atoms to decay and is inversely related to the isotope's decay constant, λ . Half-lives have been determined in laboratories for many radionuclides, and can range from nearly instantaneous— hydrogen-5 decays in less time than it takes for a photon to go from one end of its nucleus to the other—to fourteen orders of magnitude longer than the age of the universe : tellurium-128 has

1937-476: A given rate; eventually, often after a series of decays, a stable isotope is reached: there are 251 stable isotopes in the universe. In stable isotopes, light elements typically have a lower ratio of neutrons to protons in their nucleus than heavier elements. Light elements such as helium-4 have close to a 1:1 neutron:proton ratio. The heaviest elements such as uranium have close to 1.5 neutrons per proton (e.g. 1.587 in uranium-238 ). No nuclide heavier than lead-208

2086-610: A granite that is derived from partial melting of metasedimentary rocks may have more alkali feldspar, whereas a granite derived from partial melting of metaigneous rocks may be richer in plagioclase. It is on this basis that the modern "alphabet" classification schemes are based. The letter-based Chappell & White classification system was proposed initially to divide granites into I-type (igneous source) granite and S-type (sedimentary sources). Both types are produced by partial melting of crustal rocks, either metaigneous rocks or metasedimentary rocks. I-type granites are characterized by

2235-412: A group at zero to 25 Bq per cubic meter. Additionally, the meta-analysis of many radon studies, which independently show radon risk increase, gives no confirmation of that conclusion: the joined data show log-normal distribution with the maximal value in zero risk of lung cancer below 800 Bq per cubic meter. The primary route of exposure to radon and its progeny is inhalation. Radiation exposure from radon

2384-470: A half-life of 2.2 × 10  years . The Bateman equation predicts the relative quantities of all the isotopes that compose a given decay chain once that decay chain has proceeded long enough for some of its daughter products to have reached the stable (i.e., nonradioactive) end of the chain. A decay chain that has reached this state, which may require billions of years, is said to be in equilibrium . A sample of radioactive material in equilibrium produces

2533-429: A half-life over a million years above U in the 4n+2 chain.) Today some of these formerly extinct isotopes are again in existence as they have been manufactured. Thus they again take their places in the chain: plutonium-239, used in nuclear weapons, is the major example, decaying to uranium-235 via alpha emission with a half-life 24,500 years. There has also been large-scale production of neptunium-237, which has resurrected

2682-565: A high content of sodium and calcium, and by a strontium isotope ratio, Sr/ Sr, of less than 0.708. Sr is produced by radioactive decay of Rb, and since rubidium is concentrated in the crust relative to the mantle, a low ratio suggests origin in the mantle. The elevated sodium and calcium favor crystallization of hornblende rather than biotite. I-type granites are known for their porphyry copper deposits. I-type granites are orogenic (associated with mountain building) and usually metaluminous. S-type granites are sodium-poor and aluminum-rich. As

2831-724: A higher concentration of uranium. In every 1 square mile of surface soil, the first 6 inches (150 mm) (of depth) contains about 0.035 oz of radium (0.4 g per km) which releases radon in small amounts to the atmosphere. Sand used in making concrete is the major source of radon in buildings. On a global scale, it is estimated that 2,400 million curies (91 TBq) of radon are released from soil annually. Not all granitic regions are prone to high emissions of radon. Being an unreactive noble gas, it usually migrates freely through faults and fragmented soils, and may accumulate in caves or water. Due to its very small half-life (four days for Rn ), its concentration decreases very quickly when

2980-820: A much higher proportion of clay with the Cecil soil series a prime example of the consequent Ultisol great soil group. Granite is a natural source of radiation , like most natural stones. Potassium-40 is a radioactive isotope of weak emission, and a constituent of alkali feldspar , which in turn is a common component of granitic rocks, more abundant in alkali feldspar granite and syenites . Some granites contain around 10 to 20 parts per million (ppm) of uranium . By contrast, more mafic rocks, such as tonalite, gabbro and diorite , have 1 to 5 ppm uranium, and limestones and sedimentary rocks usually have equally low amounts. Many large granite plutons are sources for palaeochannel -hosted or roll front uranium ore deposits , where

3129-536: A peculiar mineralogy and geochemistry, with particularly high silicon and potassium at the expense of calcium and magnesium and a high content of high field strength cations (cations with a small radius and high electrical charge, such as zirconium , niobium , tantalum , and rare earth elements .) They are not orogenic, forming instead over hot spots and continental rifting, and are metaluminous to mildly peralkaline and iron-rich. These granites are produced by partial melting of refractory lithology such as granulites in

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3278-600: A primordial origin) can be used in the technique of uranium–lead dating to date rocks. The 4n chain of thorium-232 is commonly called the "thorium series" or "thorium cascade". Beginning with naturally occurring thorium-232, this series includes the following elements: actinium , bismuth , lead, polonium , radium, radon and thallium . All are present, at least transiently, in any natural thorium-containing sample, whether metal, compound, or mineral. The series terminates with lead-208. Plutonium-244 (which appears several steps above thorium-232 in this chain if one extends it to

3427-423: A proton is transformed into a neutron, thus moving towards a stable isotope; however, since fission almost always produces products which are neutron heavy, positron emission or electron capture are rare compared to electron emission. There are many relatively short beta decay chains, at least two (a heavy, beta decay and a light, positron decay) for every discrete weight up to around 207 and some beyond, but for

3576-568: A range of hills, formed by the metamorphic aureole or hornfels . Granite often occurs as relatively small, less than 100 km stock masses ( stocks ) and in batholiths that are often associated with orogenic mountain ranges. Small dikes of granitic composition called aplites are often associated with the margins of granitic intrusions . In some locations, very coarse-grained pegmatite masses occur with granite. Granite forms from silica-rich ( felsic ) magmas. Felsic magmas are thought to form by addition of heat or water vapor to rock of

3725-443: A result of neutron capture in uranium ore. The ending isotope of this chain is now known to be thallium-205 . Some older sources give the final isotope as bismuth-209, but in 2003 it was discovered that it is very slightly radioactive, with a half-life of 2.01 × 10  years . There are also non-transuranic decay chains of unstable isotopes of light elements, for example those of magnesium-28 and chlorine-39 . On Earth, most of

3874-415: A result, they contain micas such as biotite and muscovite instead of hornblende. Their strontium isotope ratio is typically greater than 0.708, suggesting a crustal origin. They also commonly contain xenoliths of metamorphosed sedimentary rock, and host tin ores. Their magmas are water-rich, and they readily solidify as the water outgasses from the magma at lower pressure, so they less commonly make it to

4023-504: A significant indoor air contaminant. Radon concentration in the atmosphere is usually measured in becquerels per cubic meter (Bq/m), which is an SI derived unit . As a frame of reference, typical domestic exposures are about 100 Bq/m indoors and 10–20 Bq/m outdoors. In the US, radon concentrations are often measured in picocuries per liter (pCi/L), with 1 pCi/L = 37 Bq/m. The mining industry traditionally measures exposure using

4172-456: A small number of jewelry pieces, such as rings, in the U.S. Wearing such a contaminated ring could lead to a skin exposure of 10 to 100 millirad/day (0.004 to 0.04 mSv/h). The health effects of high exposure to radon in mines, where exposures reaching 1,000,000 Bq /m can be found, can be recognized in Paracelsus ' 1530 description of a wasting disease of miners, the mala metallorum. Though at

4321-432: A steady and steadily decreasing quantity of radioactivity as the isotopes that compose it traverse the decay chain. On the other hand, if a sample of radioactive material has been isotopically enriched, meaning that a radioisotope is present in larger quantities than would exist if a decay chain were the only cause of its presence, that sample is said to be out of equilibrium . An unintuitive consequence of this disequilibrium

4470-443: A unit risk of approximately 3–6 × 10 per Bq/m, assuming a lifetime risk of lung cancer of 3%. This means that a person living in an average European dwelling with 50 Bq/m has a lifetime excess lung cancer risk of 1.5–3 × 10. Similarly, a person living in a dwelling with a high radon concentration of 1000 Bq/m has a lifetime excess lung cancer risk of 3–6%, implying a doubling of background lung cancer risk. The BEIR VI model proposed by

4619-466: Is grus , which is often made up of coarse-grained fragments of disintegrated granite. Climatic variations also influence the weathering rate of granites. For about two thousand years, the relief engravings on Cleopatra's Needle obelisk had survived the arid conditions of its origin before its transfer to London. Within two hundred years, the red granite has drastically deteriorated in the damp and polluted air there. Soil development on granite reflects

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4768-539: Is microgranite . The extrusive igneous rock equivalent of granite is rhyolite . Granitic rock is widely distributed throughout the continental crust . Much of it was intruded during the Precambrian age; it is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents. Outcrops of granite tend to form tors , domes or bornhardts , and rounded massifs . Granites sometimes occur in circular depressions surrounded by

4917-517: Is 3–6·10 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C (2219–2300 °F); it is strongly reduced in the presence of water, down to 650 °C at a few hundred megapascals of pressure. Granite has poor primary permeability overall, but strong secondary permeability through cracks and fractures if they are present. A worldwide average of the chemical composition of granite, by weight percent, based on 2485 analyses: The medium-grained equivalent of granite

5066-480: Is a coarse-grained ( phaneritic ) intrusive igneous rock composed mostly of quartz , alkali feldspar , and plagioclase . It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions . These range in size from dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite

5215-414: Is a global indicator; the risk estimation is independent of sex, age, or smoking habit. Thus, if a smoker's chances of dying of lung cancer are 10 times that of a nonsmoker's, the relative risks for a given radon exposure will be the same according to that model, meaning that the absolute risk of a radon-generated cancer for a smoker is (implicitly) tenfold that of a nonsmoker. The risk estimates correspond to

5364-410: Is an excess of aluminum beyond what can be taken up in feldspars (Al 2 O 3 > CaO + K 2 O + Na 2 O) are described as peraluminous , and they contain aluminum-rich minerals such as muscovite . The average density of granite is between 2.65 and 2.75 g/cm (165 and 172 lb/cu ft), its compressive strength usually lies above 200 MPa (29,000 psi), and its viscosity near STP

5513-618: Is believed to have a mass of around 81 tonnes. It was the tallest temple in south India. Imperial Roman granite was quarried mainly in Egypt, and also in Turkey, and on the islands of Elba and Giglio . Granite became "an integral part of the Roman language of monumental architecture". The quarrying ceased around the third century AD. Beginning in Late Antiquity the granite was reused, which since at least

5662-434: Is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites, as described below . Another aspect of granite classification is the ratios of metals that potentially form feldspars. Most granites have a composition such that almost all their aluminum and alkali metals (sodium and potassium) are combined as feldspar. This

5811-445: Is commonly called the "actinium series" or "actinium cascade". Beginning with the naturally-occurring isotope uranium-235, this decay series includes the following elements: actinium, astatine , bismuth , francium , lead , polonium , protactinium , radium, radon, thallium , and thorium . All are present, at least transiently, in any sample containing uranium-235, whether metal, compound, ore, or mineral. This series terminates with

5960-477: Is considered to be about 0.16 (after correction for uncertainties in exposure assessment), with about a threefold factor of uncertainty higher or lower than that value. In other words, the absence of ill effects (or even positive hormesis effects) at 100 Bq/m are compatible with the known data. The ICPR 65 model follows the same approach, and estimates the relative lifelong risk probability of radon-induced cancer death to 1.23 × 10 per Bq/(m·year). This relative risk

6109-423: Is dependent on the weather. Radon concentrations found in natural environments are much too low to be detected by chemical means: for example, a 1000 Bq/m (relatively high) concentration corresponds to 0.17 picogram per cubic meter. The average concentration of radon in the atmosphere is about 6 × 10 atoms of radon for each molecule in the air, or about 150 atoms in each mL of air. The entire radon activity of

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6258-447: Is equivalent to 3.6 × 10 J·h/m. An exposure to 1 WL for 1 working month (170 hours) equals 1 WLM cumulative exposure. A cumulative exposure of 1 WLM is roughly equivalent to living one year in an atmosphere with a radon concentration of 230 Bq/m. The radon ( Rn ) released into the air decays to Pb and other radioisotopes. The levels of Pb can be measured. The rate of deposition of this radioisotope

6407-493: Is generally associated with diseases that are not detected until many years after elevated exposure, the public may not consider the amount of radon that children are currently being exposed to. Aside from the exposure in the home, one of the major contributors to radon exposure in children are the schools in which they attend almost every day. A survey was conducted in schools across the United States to detect radon levels, and it

6556-448: Is great uncertainty in applying risk estimates derived from studies in miners to the effects of residential radon, and direct estimates of the risks of residential radon are needed. As with the miner data, the same confounding factor of other carcinogens such as dust applies. The largest natural contributor to public radiation dose is radon, a naturally occurring, radioactive gas found in soil and rock, which comprises approximately 55% of

6705-404: Is higher than that of adults, resulting in more gas exchange and more potential opportunities for radon to be inhaled. The resulting health effects in children are similar to those of adults, predominantly including lung cancer and respiratory illnesses such as asthma, bronchitis, and pneumonia. While there have been numerous studies assessing the link between radon exposure and childhood leukemia,

6854-413: Is indirect. The health hazard from radon does not come primarily from radon itself, but rather from the radioactive products formed in the decay of radon. The general effects of radon to the human body are caused by its radioactivity and consequent risk of radiation-induced cancer . Lung cancer is the only observed consequence of high concentration radon exposures; both human and animal studies indicate that

7003-571: Is known, all heavier elements came into being starting around 100 million years later, in a second phase of nucleosynthesis that commenced with the birth of the first stars . The nuclear furnaces that power stellar evolution were necessary to create large quantities of all elements heavier than helium, and the r- and s-process es of neutron capture that occur in stellar cores are thought to have created all such elements up to iron and nickel (atomic numbers 26 and 28). The extreme conditions that attend supernovae explosions are capable of creating

7152-433: Is limited by the amount of thermal energy available, which must be replenished by crystallization of higher-melting minerals in the magma. Thus, the magma is melting crustal rock at its roof while simultaneously crystallizing at its base. This results in steady contamination with crustal material as the magma rises. This may not be evident in the major and minor element chemistry, since the minerals most likely to crystallize at

7301-514: Is named for American construction engineer Stanley Watras, an employee at the Limerick nuclear power plant in the United States, who triggered radiation monitors while leaving work over several days—even though the plant had not yet been fueled, and despite Watras being decontaminated and sent home "clean" each evening. This pointed to a source of contamination outside the power plant, which turned out to be radon levels of 100,000 Bq /m (2.7 nCi /L) in

7450-404: Is permeated by sheets and channels of light granitic rock (the leucosome ). The leucosome is interpreted as partial melt of a parent rock that has begun to separate from the remaining solid residue (the melanosome). If enough partial melt is produced, it will separate from the source rock, become more highly evolved through fractional crystallization during its ascent toward the surface, and become

7599-454: Is relieved when overlying material is removed by erosion or other processes. Chemical weathering of granite occurs when dilute carbonic acid , and other acids present in rain and soil waters, alter feldspar in a process called hydrolysis . As demonstrated in the following reaction, this causes potassium feldspar to form kaolinite , with potassium ions, bicarbonate, and silica in solution as byproducts. An end product of granite weathering

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7748-411: Is some concern that some granite sold as countertops or building material may be hazardous to health. Dan Steck of St. Johns University has stated that approximately 5% of all granite is of concern, with the caveat that only a tiny percentage of the tens of thousands of granite slab types have been tested. Resources from national geological survey organizations are accessible online to assist in assessing

7897-405: Is stable; these heavier elements have to shed mass to achieve stability, mostly by alpha decay . The other common way for isotopes with a high neutron to proton ratio (n/p) to decay is beta decay , in which the nuclide changes elemental identity while keeping the same mass number and lowering its n/p ratio. For some isotopes with a relatively low n/p ratio, there is an inverse beta decay , by which

8046-452: Is that a sample of enriched material may occasionally increase in radioactivity as daughter products that are more highly radioactive than their parents accumulate. Both enriched and depleted uranium provide examples of this phenomenon. The chemical elements came into being in two phases. The first commenced shortly after the Big Bang . From ten seconds to 20 minutes after the beginning of

8195-479: Is that magma will rise through the crust as a single mass through buoyancy . As it rises, it heats the wall rocks , causing them to behave as a power-law fluid and thus flow around the intrusion allowing it to pass without major heat loss. This is entirely feasible in the warm, ductile lower crust where rocks are easily deformed, but runs into problems in the upper crust which is far colder and more brittle. Rocks there do not deform so easily: for magma to rise as

8344-410: Is the case when K 2 O + Na 2 O + CaO > Al 2 O 3 > K 2 O + Na 2 O. Such granites are described as normal or metaluminous . Granites in which there is not enough aluminum to combine with all the alkali oxides as feldspar (Al 2 O 3 < K 2 O + Na 2 O) are described as peralkaline , and they contain unusual sodium amphiboles such as riebeckite . Granites in which there

8493-485: Is typical of a larger family of granitic rocks , or granitoids , that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF classification ), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though

8642-409: Is typically orthoclase or microcline and is often perthitic . The plagioclase is typically sodium-rich oligoclase . Phenocrysts are usually alkali feldspar. Granitic rocks are classified according to the QAPF diagram for coarse grained plutonic rocks and are named according to the percentage of quartz , alkali feldspar ( orthoclase , sanidine , or microcline ) and plagioclase feldspar on

8791-428: Is uncommon, is classified simply as quartz-rich granitoid or, if composed almost entirely of quartz, as quartzolite . True granites are further classified by the percentage of their total feldspar that is alkali feldspar. Granites whose feldspar is 65% to 90% alkali feldspar are syenogranites , while the feldspar in monzogranite is 35% to 65% alkali feldspar. A granite containing both muscovite and biotite micas

8940-453: The working level (WL) index, and the cumulative exposure in working level months (WLM): 1 WL equals any combination of short-lived Rn progeny ( Po , Pb , Bi , and Po ) in 1 liter of air that releases 1.3 × 10 MeV of potential alpha energy; one WL is equivalent to 2.08 × 10 joules per cubic meter of air (J/m). The SI unit of cumulative exposure is expressed in joule-hours per cubic meter (J·h/m). One WLM

9089-695: The National Academy of Sciences of the USA is more complex. It is a multiplicative model that estimates an excess risk per exposure unit. It takes into account age, elapsed time since exposure, and duration and length of exposure, and its parameters allow for taking smoking habits into account. In the absence of other causes of death, the absolute risks of lung cancer by age 75 at usual radon concentrations of 0, 100, and 400 Bq/m would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong nonsmokers, and about 25 times greater (10%, 12%, and 16%) for cigarette smokers. There

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9238-437: The "average" radon concentration in an area. The mean concentration ranges from less than 10 Bq/m to over 100 Bq/m in some European countries. Typical geometric standard deviations found in studies range between 2 and 3, meaning (given the 68–95–99.7 rule ) that the radon concentration is expected to be more than a hundred times the mean concentration for 2 to 3% of the cases. The so-called "Watras incident" in 1984

9387-588: The "working level", and under 3 WL (546 pCi Rn per liter of air; 20.2 kBq/m measured from 1976 to 1985) 95 percent of the time. The concentration in the air at the (unventilated) Gastein Healing Gallery averages 43 kBq/m (about 1.2 nCi/L) with maximal value of 160 kBq/m (about 4.3 nCi/L). Radon emanates naturally from the ground and from some building materials all over the world, wherever there are traces of uranium or thorium , and particularly in regions with soils containing granite or shale , which have

9536-523: The 1940s and 1950s. Residues from processing of uranium ore can also be a source of radon. Radon resulting from the high radium content in uncovered dumps and tailing ponds can be easily released into the atmosphere. Modern mining techniques, including better ventilation for underground mines, routine radiation monitoring as well as technologies like in-situ leaching have helped decrease the incidence of radon exposure among miners in subsequent decades. The first major studies with radon and health occurred in

9685-403: The 251 stable isotopes known to exist. Aside from cosmic or stellar nucleosynthesis, and decay chains the only other ways of producing a chemical element rely on atomic weapons , nuclear reactors ( natural or manmade ) or the laborious atom-by-atom assembly of nuclei with particle accelerators . Unstable isotopes decay to their daughter products (which may sometimes be even more unstable) at

9834-567: The A-Q-P half of the diagram. True granite (according to modern petrologic convention) contains between 20% and 60% quartz by volume, with 35% to 90% of the total feldspar consisting of alkali feldspar . Granitic rocks poorer in quartz are classified as syenites or monzonites , while granitic rocks dominated by plagioclase are classified as granodiorites or tonalites . Granitic rocks with over 90% alkali feldspar are classified as alkali feldspar granites . Granitic rock with more than 60% quartz, which

9983-493: The CDC in 2012, found that of schools located in counties with high predicted indoor radon levels, only 42.4% had radon testing policies, and a mere 37.5% had policy for radon-resistant new construction practices. Only about 20% of all schools nationwide have done testing, even though the EPA recommends that every school be tested. These numbers are arguably not high enough to ensure protection of

10132-420: The Earth today were formed by such processes no later than the time of our planet's condensation from the solar protoplanetary disc , around 4.5 billion years ago. The exceptions to these so-called primordial elements are those that have resulted from the radioactive disintegration of unstable parent nuclei as they progress down one of several decay chains, each of which terminates with the production of one of

10281-553: The Earth's atmosphere at any one time is due to some tens of grams of radon, constantly being replaced by decay of larger amounts of radium and uranium. Its concentration can vary greatly from place to place. In the open air, it ranges from 1 to 100 Bq/m, even less (0.1 Bq/m) above the ocean. In caves, aerated mines, or poorly ventilated dwellings, its concentration can climb to 20–2,000 Bq/m. In mining contexts, radon concentrations can be much higher. Ventilation regulations try to maintain concentrations in uranium mines under

10430-553: The European Union safety standards (section 4.1.1.1 of the National Health and Engineering study) and radon emission levels well below the average outdoor radon concentrations in the US. Granite and related marble industries are considered one of the oldest industries in the world, existing as far back as Ancient Egypt . Major modern exporters of granite include China, India, Italy, Brazil, Canada, Germany, Sweden, Spain and

10579-643: The United States are found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania. Some of the highest readings have been recorded in Mallow, County Cork , Ireland. Iowa has the highest average radon concentrations in the United States due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within

10728-448: The United States. The Red Pyramid of Egypt ( c.  2590 BC ), named for the light crimson hue of its exposed limestone surfaces, is the third largest of Egyptian pyramids . Pyramid of Menkaure , likely dating 2510 BC, was constructed of limestone and granite blocks. The Great Pyramid of Giza (c. 2580 BC ) contains a huge granite sarcophagus fashioned of "Red Aswan Granite". The mostly ruined Black Pyramid dating from

10877-554: The World Health Organization released a comprehensive global initiative on radon that recommended a reference level of 100 Bq/m for radon, urging establishment or strengthening of radon measurement and mitigation programs as well as development building codes requiring radon prevention measures in homes under construction. Elevated lung cancer rates have been reported from a number of cohort and case-control studies of underground miners exposed to radon and its decay products but

11026-412: The annual background dose. Radon gas levels vary by locality and the composition of the underlying soil and rocks. Radon (at concentrations encountered in mines) was recognized as carcinogenic in the 1980s, in view of the lung cancer statistics for miners' cohorts. Although radon may present significant risks, thousands of persons annually go to radon-contaminated mines for deliberate exposure to help with

11175-404: The area of the plant where propane is processed is often one of the more contaminated areas, because radon has a similar boiling point to propane. Typical domestic exposures are of around 100   Bq/m indoors, but specifics of construction and ventilation strongly affect levels of accumulation; a further complication for risk assessment is that concentrations in a single location may differ by

11324-451: The average annual exposure of uranium miners has fallen to levels similar to the concentrations inhaled in some homes. This has reduced the risk of occupationally induced cancer from radon, although it still remains an issue both for those who are currently employed in affected mines and for those who have been employed in the past. The power to detect any excess risks in miners nowadays is likely to be small, exposures being much smaller than in

11473-419: The base of the chamber are the same ones that would crystallize anyway, but crustal assimilation is detectable in isotope ratios. Heat loss to the country rock means that ascent by assimilation is limited to distance similar to the height of the magma chamber. Physical weathering occurs on a large scale in the form of exfoliation joints , which are the result of granite's expanding and fracturing as pressure

11622-731: The basement of his home. He was told that living in the home was the equivalent of smoking 135 packs of cigarettes a day, and he and his family had increased their risk of developing lung cancer by 13 or 14 percent. The incident dramatized the fact that radon levels in particular dwellings can occasionally be orders of magnitude higher than typical. Radon soon became a standard homeowner concern, though typical domestic exposures are two to three orders of magnitude lower (100 Bq/m, or 2.5 pCi/L), making individual testing essential to assessment of radon risk in any particular dwelling. Radon exists in every U.S. state, and about 6% of American houses have elevated levels. The highest average radon concentrations in

11771-418: The big difference in rheology between mafic and felsic magmas makes this process problematic in nature. Granitization is an old, and largely discounted, hypothesis that granite is formed in place through extreme metasomatism . The idea behind granitization was that fluids would supposedly bring in elements such as potassium, and remove others, such as calcium, to transform a metamorphic rock into granite. This

11920-518: The biological half-life for removal of radon from the body ranges from 30 to 70 minutes. More than 90% of the absorbed radon is eliminated by exhalation within 100 minutes, By 600 minutes, only 1% of the absorbed amount remains in the body. While radon presents the aforementioned risks in adults, exposure in children leads to a unique set of health hazards that are still being researched. The physical composition of children leads to faster rates of exposure through inhalation given that their respiratory rate

12069-466: The body's mucociliary staircase. Deposited radioactive atoms or dust or aerosol particles continue to decay, causing continued exposure by emitting energetic alpha radiation with some associated gamma radiation too, that can damage vital molecules in lung cells, by either creating free radicals or causing DNA breaks or damage, perhaps causing mutations that sometimes turn cancerous. In addition, through ingestion and blood transport, following crossing of

12218-402: The chain below them "alive" with flow. The three long-lived nuclides are uranium-238 (half-life 4.5 billion years), uranium-235 (half-life 700 million years) and thorium-232 (half-life 14 billion years). The fourth chain has no such long-lasting bottleneck nuclide near the top, so almost all of the nuclides in that chain have long since decayed down to just before the end: bismuth-209. This nuclide

12367-489: The combined effect exceeds the sum of their independent effects. This is because the daughters of radon often become attached to smoke and dust particles, and are then able to lodge in the lungs. It is unknown whether radon causes other types of cancer, but recent studies suggest a need for further studies to assess the relationship between radon and leukemia . The effects of radon, if found in food or drinking water, are unknown. Following ingestion of radon dissolved in water,

12516-606: The context of uranium mining, first in the Joachimsthal region of Bohemia and then in the Southwestern United States during the early Cold War . Because radon is a product of the radioactive decay of uranium, underground uranium mines may have high concentrations of radon. Many uranium miners in the Four Corners region contracted lung cancer and other pathologies as a result of high levels of exposure to radon in

12665-560: The country of Japan have radium-rich springs which emit radon. To be classified as a radon mineral water, radon concentration must be above a minimum of 2 nCi/L (7  Bq/L). The activity of radon mineral water reaches 2,000 Bq/L in Merano and 4,000 Bq/L in the village of Lurisia ( Ligurian Alps , Italy). Radon is also found in some petroleum. Because radon has a similar pressure and temperature curve to propane, and oil refineries separate petrochemicals based on their boiling points,

12814-400: The curve of a decaying exponential distribution with a decay constant ( λ ) particular to the isotope. On this understanding the radioactive decay of an initial population of unstable atoms over time t follows the curve given by e . One of the most important properties of any radioactive material follows from this analysis, its half-life . This refers to the time required for half of

12963-422: The diagram.) For example, the third atom of nihonium-278 synthesised underwent six alpha decays down to mendelevium-254 , followed by an electron capture (a form of beta decay) to fermium-254 , and then a seventh alpha to californium-250 , upon which it would have followed the 4n + 2 chain (radium series) as given in this article. However, the heaviest superheavy nuclides synthesised do not reach

13112-487: The distance from the production area increases. Its atmospheric concentration varies greatly depending on the season and conditions. For instance, it has been shown to accumulate in the air if there is a meteorological inversion and little wind. Because atmospheric radon concentrations are very low, radon-rich water exposed to air continually loses radon by volatilization . Hence, ground water generally has higher concentrations of Rn than surface water , because

13261-404: The division between S-type (produced by underplating) and I-type (produced by injection and differentiation) granites, discussed below. The composition and origin of any magma that differentiates into granite leave certain petrological evidence as to what the granite's parental rock was. The final texture and composition of a granite are generally distinctive as to its parental rock. For instance,

13410-467: The early 16th century became known as spolia . Through the process of case-hardening , granite becomes harder with age. The technology required to make tempered metal chisels was largely forgotten during the Middle Ages. As a result, Medieval stoneworkers were forced to use saws or emery to shorten ancient columns or hack them into discs. Giorgio Vasari noted in the 16th century that granite in quarries

13559-487: The early years of mining. A confounding factor with mines is that both radon concentration and carcinogenic dust (such as quartz dust) depend on the amount of ventilation. This makes it very difficult to state that radon causes cancer in miners; the lung cancers could be partially or wholly caused by high dust concentrations from poor ventilation. Radon-222 has been classified by International Agency for Research on Cancer as being carcinogenic to humans. In September 2009,

13708-415: The elements between oxygen and rubidium (i.e., atomic numbers 8 through 37). The creation of heavier elements, including those without stable isotopes—all elements with atomic numbers greater than lead's, 82—appears to rely on r-process nucleosynthesis operating amid the immense concentrations of free neutrons released during neutron star mergers . Most of the isotopes of each chemical element present in

13857-461: The first few million years of the history of the Solar System, there were more kinds of unstable high-mass nuclides in existence, and the four chains were longer, as they included nuclides that have since decayed away. Notably, Pu, Np, and Cm have half-lives over a million years and would have then been lesser bottlenecks high in the 4n, 4n+1, and 4n+3 chains respectively. (There is no nuclide with

14006-579: The first magma to enter solidifies and provides a form of insulation for later magma. These mechanisms can operate in tandem. For example, diapirs may continue to rise through the brittle upper crust through stoping , where the granite cracks the roof rocks, removing blocks of the overlying crust which then sink to the bottom of the diapir while the magma rises to take their place. This can occur as piecemeal stopping (stoping of small blocks of chamber roof), as cauldron subsidence (collapse of large blocks of chamber roof), or as roof foundering (complete collapse of

14155-435: The following elements: astatine, bismuth, lead , mercury , polonium, protactinium , radium , radon , thallium, and thorium. All are present, at least transiently, in any natural uranium-containing sample, whether metal, compound, or mineral. The series terminates with lead-206. The total energy released from uranium-238 to lead-206, including the energy lost to neutrinos, is 51.7 MeV. The 4n+3 chain of uranium-235

14304-452: The formation of the Earth, ignoring the artificial isotopes and their decays created since the 1940s. Due to the relatively short half-life of its starting isotope neptunium-237 (2.14 million years), the fourth chain, the neptunium series with A  = 4 n  + 1, is already extinct in nature, except for the final rate-limiting step, decay of bismuth-209 . Traces of Np and its decay products do occur in nature, however, as

14453-436: The four decay chains, because they reach a spontaneously fissioning nuclide after a few alpha decays that terminates the chain: this is what happened to the first two atoms of nihonium-278 synthesised, as well as to all heavier nuclides produced. Three of those chains have a long-lived isotope (or nuclide) near the top; this long-lived nuclide is a bottleneck in the process through which the chain flows very slowly, and keeps

14602-684: The grotto is a highly regarded piece of Buddhist art , and along with the temple complex to which it belongs, Seokguram was added to the UNESCO World Heritage List in 1995. Rajaraja Chola I of the Chola Dynasty in South India built the world's first temple entirely of granite in the 11th century AD in Tanjore , India . The Brihadeeswarar Temple dedicated to Lord Shiva was built in 1010. The massive Gopuram (ornate, upper section of shrine)

14751-426: The higher mass elements (isotopes heavier than lead) there are only four pathways which encompass all decay chains. This is because there are just two main decay methods: alpha radiation , which reduces the mass by 4 atomic mass units (amu), and beta, which does not change the mass number (just the atomic number and the p/n ratio). The four paths are termed 4n, 4n + 1, 4n + 2, and 4n + 3;

14900-470: The hitherto extinct fourth chain. The tables below hence start the four decay chains at isotopes of californium with mass numbers from 249 to 252. These four chains are summarised in the chart in the following section. The four most common modes of radioactive decay are: alpha decay, beta decay, inverse beta decay (considered as both positron emission and electron capture), and isomeric transition . Of these decay processes, only alpha decay (fission of

15049-505: The important uranium ore pitchblende is in the Ore Mountains and that region was the most important German speaking mining area at the time, it is likely the radon induced lung cancers were associated with uranium. Beyond mining in general, radon is a particular problem in the mining of uranium ; significant excess lung cancer deaths have been identified in epidemiological studies of uranium miners and other hard-rock miners employed in

15198-515: The isotopes involved are found naturally in significant quantities, namely the final two: bismuth-209 and thallium-205. Some of the other isotopes have been detected in nature, originating from trace quantities of Np produced by the (n,2n) knockout reaction in primordial U. A smoke detector containing an americium-241 ionization chamber accumulates a significant amount of neptunium -237 as its americium decays. The following elements are also present in it, at least transiently, as decay products of

15347-474: The lower crust , rather than by decompression of mantle rock, as is the case with basaltic magmas. It has also been suggested that some granites found at convergent boundaries between tectonic plates , where oceanic crust subducts below continental crust, were formed from sediments subducted with the oceanic plate. The melted sediments would have produced magma intermediate in its silica content, which became further enriched in silica as it rose through

15496-697: The lower continental crust at high thermal gradients. This leads to significant extraction of hydrous felsic melts from granulite-facies resitites. A-type granites occur in the Koettlitz Glacier Alkaline Province in the Royal Society Range, Antarctica. The rhyolites of the Yellowstone Caldera are examples of volcanic equivalents of A-type granite. M-type granite was later proposed to cover those granites that were clearly sourced from crystallized mafic magmas, generally sourced from

15645-449: The lung and respiratory system are the primary targets of radon daughter-induced toxicity. Radon has a short half-life (3.8 days) and decays into other solid particulate radium-series radioactive nuclides. Two of these decay products, polonium-218 and 214, present a significant radiologic hazard. If the gas is inhaled, the radon atoms decay in the airways or the lungs, resulting in radioactive polonium and ultimately lead atoms attaching to

15794-399: The lung membrane by radon, radioactive progeny may also be transported to other parts of the body. The risk of lung cancer caused by smoking is much higher than the risk of lung cancer caused by indoor radon. Radiation from radon has been attributed to increase of lung cancer among smokers too. It is generally believed that exposure to radon and cigarette smoking are synergistic; that is, that

15943-435: The magma is inevitable once enough magma has accumulated. However, the question of precisely how such large quantities of magma are able to shove aside country rock to make room for themselves (the room problem ) is still a matter of research. Two main mechanisms are thought to be important: Of these two mechanisms, Stokes diapirism has been favoured for many years in the absence of a reasonable alternative. The basic idea

16092-426: The magma. Other processes must produce these great volumes of felsic magma. One such process is injection of basaltic magma into the lower crust, followed by differentiation, which leaves any cumulates in the mantle. Another is heating of the lower crust by underplating basaltic magma, which produces felsic magma directly from crustal rock. The two processes produce different kinds of granites, which may be reflected in

16241-408: The magmatic parent of granitic rock. The residue of the source rock becomes a granulite . The partial melting of solid rocks requires high temperatures and the addition of water or other volatiles which lower the solidus temperature (temperature at which partial melting commences) of these rocks. It was long debated whether crustal thickening in orogens (mountain belts along convergent boundaries )

16390-456: The main confounding factor in all miners' studies is smoking and dust. Up to the most of regulatory bodies there is sufficient evidence for the carcinogenicity of radon and its decay products in humans for such exposures. However, the discussion about the opposite results is still going on, especially a recent retrospective case-control study of lung cancer risk showed substantial cancer rate reduction between 50 and 123 Bq per cubic meter relative to

16539-569: The majority of children from elevated radon exposures. For exposure standards to be effective, they should be set for those most susceptible. UNSCEAR recommends a reference value of 9 nSv (Bq·h/m). For example, a person living (7000 h/year) in a concentration of 40 Bq/m receives an effective dose of 1 mSv/year. Studies of miners exposed to radon and its decay products provide a direct basis for assessing their lung cancer risk. The BEIR VI report, entitled Health Effects of Exposure to Radon , reported an excess relative risk from exposure to radon that

16688-405: The mantle. Although the fractional crystallisation of basaltic melts can yield small amounts of granites, which are sometimes found in island arcs, such granites must occur together with large amounts of basaltic rocks. H-type granites were suggested for hybrid granites, which were hypothesized to form by mixing between mafic and felsic from different sources, such as M-type and S-type. However,

16837-743: The mid-1950s. The increased incidence of lung cancer was particularly pronounced among Native American and Mormon miners, because those groups normally have low rates of lung cancer. Safety standards requiring expensive ventilation were not widely implemented or policed during this period. In studies of uranium miners, workers exposed to radon levels of 50 to 150 picocuries of radon per liter of air (2000–6000 Bq/m) for about 10 years have shown an increased frequency of lung cancer. Statistically significant excesses in lung cancer deaths were present after cumulative exposures of less than 50 WLM. There is, however, unexplained heterogeneity in these results (whose confidence interval do not always overlap). The size of

16986-467: The natural topsoil and rock would all have to be disposed of as low-level nuclear waste . People in affected localities can receive up to 10 mSv per year background radiation. This led to a health policy problem: what is the health impact of exposure to radon concentrations (100 Bq/m) typically found in some buildings? Uranium series In nuclear science a decay chain refers to the predictable series of radioactive disintegrations undergone by

17135-407: The nearest tissue. If dust or aerosol is inhaled that already carries radon decay products, the deposition pattern of the decay products in the respiratory tract depends on the behaviour of the particles in the lungs. Smaller diameter particles diffuse further into the respiratory system, whereas the larger—tens to hundreds of micron-sized—particles often deposit higher in the airways and are cleared by

17284-496: The neptunium: actinium, astatine , bismuth, francium , lead, polonium, protactinium , radium, radon, thallium, thorium, and uranium . Since this series was only discovered and studied in 1947–1948, its nuclides do not have historic names. One unique trait of this decay chain is that the noble gas radon is only produced in a rare branch (not shown in the illustration) but not the main decay sequence; thus, radon from this decay chain does not migrate through rock nearly as much as from

17433-550: The nuclei of certain unstable chemical elements. Radioactive isotopes do not usually decay directly to stable isotopes , but rather into another radioisotope. The isotope produced by this radioactive emission then decays into another, often radioactive isotope. This chain of decays always terminates in a stable isotope , whose nucleus no longer has the surplus of energy necessary to produce another emission of radiation. Such stable isotopes are then said to have nuclei that have reached their ground states . The stages or steps in

17582-880: The original nucleus was at rest. The letter 'a' represents a year (from the Latin annus ). In the tables below (except neptunium), the historic names of the naturally occurring nuclides are also given. These names were used at the time when the decay chains were first discovered and investigated. From these historical names one can locate the particular chain to which the nuclide belongs, and replace it with its modern name. The three naturally-occurring actinide alpha decay chains given below—thorium, uranium/radium (from uranium-238), and actinium (from uranium-235)—each ends with its own specific lead isotope (lead-208, lead-206, and lead-207 respectively). All these isotopes are stable and are also present in nature as primordial nuclides , but their excess amounts in comparison with lead-204 (which has only

17731-477: The other three. Another unique trait of this decay sequence is that it ends in thallium (practically speaking, bismuth) rather than lead. This series terminates with the stable isotope thallium-205. The total energy released from californium-249 to thallium-205, including the energy lost to neutrinos , is 66.8 MeV. The 4n+2 chain of uranium-238 is called the "uranium series" or "radium series". Beginning with naturally occurring uranium-238, this series includes

17880-441: The overlying crust. Early fractional crystallisation serves to reduce a melt in magnesium and chromium, and enrich the melt in iron, sodium, potassium, aluminum, and silicon. Further fractionation reduces the content of iron, calcium, and titanium. This is reflected in the high content of alkali feldspar and quartz in granite. The presence of granitic rock in island arcs shows that fractional crystallization alone can convert

18029-448: The piping carrying freshly separated propane in oil refineries can become partially radioactive due to radon decay particles. Residues from the oil and gas industry often contain radium and its daughters. The sulfate scale from an oil well can be radium rich, while the water, oil, and gas from a well often contains radon. The radon decays to form solid radioisotopes which form coatings on the inside of pipework. In an oil processing plant,

18178-419: The radon is continuously replenished by radioactive decay of Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere. As a below-ground source of water, some springs —including hot springs —contain significant amounts of radon. The towns of Boulder, Montana ; Misasa ; Bad Kreuznach , and

18327-669: The radon-related increase in lung cancer risk varied by more than an order of magnitude between the different studies. Heterogeneities are possibly due to systematic errors in exposure ascertainment, unaccounted for differences in the study populations (genetic, lifestyle, etc.), or confounding mine exposures. There are a number of confounding factors to consider, including exposure to other agents, ethnicity, smoking history, and work experience. The cases reported in these miners cannot be attributed solely to radon or radon daughters but may be due to exposure to silica, to other mine pollutants, to smoking, or to other causes. The majority of miners in

18476-702: The reign of Amenemhat III once had a polished granite pyramidion or capstone, which is now on display in the main hall of the Egyptian Museum in Cairo (see Dahshur ). Other uses in Ancient Egypt include columns , door lintels , sills , jambs , and wall and floor veneer. How the Egyptians worked the solid granite is still a matter of debate. Tool marks described by the Egyptologist Anna Serotta indicate

18625-415: The remainder from dividing the atomic mass by four gives the chain the isotope will use to decay. There are other decay modes, but they invariably occur at a lower probability than alpha or beta decay. (It should not be supposed that these chains have no branches: the diagram below shows a few branches of chains, and in reality there are many more, because there are many more isotopes possible than are shown in

18774-526: The results are largely varied. Many ecological studies show a positive association between radon exposure and childhood leukemia; however, most case control studies have produced a weak correlation. Genotoxicity has been noted in children exposed to high levels of radon, specifically a significant increase of frequency of aberrant cells was noted, as well as an "increase in the frequencies of single and double fragments, chromosome interchanges, [and] number of aberrations chromatid and chromosome type". Because radon

18923-551: The risk factors in granite country and design rules relating, in particular, to preventing accumulation of radon gas in enclosed basements and dwellings. A study of granite countertops was done (initiated and paid for by the Marble Institute of America) in November 2008 by National Health and Engineering Inc. of USA. In this test, all of the 39 full-size granite slabs that were measured for the study showed radiation levels well below

19072-418: The rock's high quartz content and dearth of available bases, with the base-poor status predisposing the soil to acidification and podzolization in cool humid climates as the weather-resistant quartz yields much sand. Feldspars also weather slowly in cool climes, allowing sand to dominate the fine-earth fraction. In warm humid regions, the weathering of feldspar as described above is accelerated so as to allow

19221-414: The rocks often bear a close resemblance. Under these conditions, granitic melts can be produced in place through the partial melting of metamorphic rocks by extracting melt-mobile elements such as potassium and silicon into the melts but leaving others such as calcium and iron in granulite residues. This may be the origin of migmatites . A migmatite consists of dark, refractory rock (the melanosome ) that

19370-489: The roof of a shallow magma chamber accompanied by a caldera eruption.) There is evidence for cauldron subsidence at the Mt. Ascutney intrusion in eastern Vermont. Evidence for piecemeal stoping is found in intrusions that are rimmed with igneous breccia containing fragments of country rock. Assimilation is another mechanism of ascent, where the granite melts its way up into the crust and removes overlying material in this way. This

19519-458: The same concentrations as they do now. Radon is responsible for the majority of public exposure to ionizing radiation . It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as attics and basements. It can also be found in some spring waters and hot springs. According to

19668-484: The stable isotope lead-207 . In the early Solar System this chain went back to Cm. This manifests itself today as variations in U/ U ratios, since curium and uranium have noticeably different chemistries and would have separated differently. The total energy released from uranium-235 to lead-207, including the energy lost to neutrinos, is 46.4 MeV. Granite Granite ( / ˈ ɡ r æ n ɪ t / GRAN -it )

19817-486: The starting isotopes of these chains before 1945 were generated by cosmic radiation . Since 1945, the testing and use of nuclear weapons has also released numerous radioactive fission products . Almost all such isotopes decay by either β or β decay modes, changing from one element to another without changing atomic mass. These later daughter products, being closer to stability, generally have longer half-lives until they finally decay into stability. No fission products have

19966-424: The state, such as Iowa City , have passed requirements for radon-resistant construction in new homes. In a few locations, uranium tailings have been used for landfills and were subsequently built on, resulting in possible increased exposure to radon. In the early 20th century, Pb -contaminated gold, from gold seeds that were used in radiotherapy which had held Rn , were melted down and made into

20115-503: The studies are smokers and all inhale dust and other pollutants in mines. Because radon and cigarette smoke both cause lung-cancer, and since the effect of smoking is far above that of radon, it is complicated to disentangle the effects of the two kinds of exposure; misinterpreting the smoking habit by a few percent can blur out the radon effect. Since that time, ventilation and other measures have been used to reduce radon levels in most affected mines that continue to operate. In recent years,

20264-435: The surface than magmas of I-type granites, which are thus more common as volcanic rock (rhyolite). They are also orogenic but range from metaluminous to strongly peraluminous. Although both I- and S-type granites are orogenic, I-type granites are more common close to the convergent boundary than S-type. This is attributed to thicker crust further from the boundary, which results in more crustal melting. A-type granites show

20413-475: The symptoms of arthritis without any serious health effects. Radon as a terrestrial source of background radiation is of particular concern because, although overall very rare, where it does occur it often does so in high concentrations. Some of these areas, including parts of Cornwall and Aberdeenshire have high enough natural radiation levels that nuclear licensed sites cannot be built there—the sites would already exceed legal limits before they opened, and

20562-440: The texture is known as porphyritic . A granitic rock with a porphyritic texture is known as a granite porphyry . Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy . The alkali feldspar in granites

20711-496: The thorium series, the radium or uranium series, and the actinium series, representing three of these four classes, and ending in three different, stable isotopes of lead . The mass number of every isotope in these chains can be represented as A  = 4 n , A  = 4 n  + 2, and A = 4 n  + 3, respectively. The long-lived starting isotopes of these three isotopes, respectively thorium-232 , uranium-238 , and uranium-235 , have existed since

20860-401: The time radon itself was not understood to be the cause—indeed, neither it nor radiation had even been discovered—mineralogist Georg Agricola recommended ventilation of mines to avoid this mountain sickness ( Bergsucht ). In 1879, the "wasting" was identified as lung cancer by Herting and Hesse in their investigation of miners from Schneeberg, Saxony , Germany. Given that the type locality of

21009-439: The transuranics) was present in the early Solar System, and is just long-lived enough that it should still survive in trace quantities today, though it is uncertain if it has been detected. The total energy released from thorium-232 to lead-208, including the energy lost to neutrinos, is 42.6 MeV. The 4n + 1 chain of neptunium-237 is commonly called the "neptunium series" or "neptunium cascade". In this series, only two of

21158-423: The universe the earliest condensation of light atoms was responsible for the manufacture of the four lightest elements. The vast majority of this primordial production consisted of the three lightest isotopes of hydrogen — protium , deuterium and tritium —and two of the nine known isotopes of helium — helium-3 and helium-4 . Trace amounts of lithium-7 and beryllium-7 were likely also produced. So far as

21307-502: The uranium washes into the sediments from the granite uplands and associated, often highly radioactive pegmatites. Cellars and basements built into soils over granite can become a trap for radon gas, which is formed by the decay of uranium. Radon gas poses significant health concerns and is the number two cause of lung cancer in the US behind smoking. Thorium occurs in all granites. Conway granite has been noted for its relatively high thorium concentration of 56±6 ppm. There

21456-599: The use of flint tools on finer work with harder stones, e.g. when producing the hieroglyphic inscriptions. Patrick Hunt has postulated that the Egyptians used emery , which has greater hardness. The Seokguram Grotto in Korea is a Buddhist shrine and part of the Bulguksa temple complex. Completed in 774 AD, it is an artificial grotto constructed entirely of granite. The main Buddha of

21605-489: Was equivalent to 1.8% per megabecquerel hours per cubic meter (MBq·h/m) (95% confidence interval: 0.3, 35) for miners with cumulative exposures below 30 MBq·h/m. Estimates of risk per unit exposure are 5.38×10 per WLM; 9.68×10/WLM for ever smokers; and 1.67×10 per WLM for never smokers. According to the UNSCEAR modeling, based on these miner's studies, the excess relative risk from long-term residential exposure to radon at 100 Bq/m

21754-466: Was estimated that about one in five schools has at least one room (more than 70,000 schoolrooms) with short-term levels above 4pCi/L. Many states have active radon testing and mitigation programs in place, which require testing in buildings such as public schools. However, these are not standardized nationwide, and the rules and regulations on reducing high radon levels are even less common. The School Health Policies and Practices Study (SHPPS), conducted by

21903-404: Was long thought to be stable, but in 2003 it was found to be unstable, with a very long half-life of 20.1 billion billion years; it is the last step in the chain before stable thallium-205. Because this bottleneck is so long-lived, very small quantities of the final decay product have been produced, and for most practical purposes bismuth-209 is the final decay product. In the distant past, during

22052-405: Was sufficient to produce granite melts by radiogenic heating , but recent work suggests that this is not a viable mechanism. In-situ granitization requires heating by the asthenospheric mantle or by underplating with mantle-derived magmas. Granite magmas have a density of 2.4 Mg/m , much less than the 2.8 Mg/m of high-grade metamorphic rock. This gives them tremendous buoyancy, so that ascent of

22201-564: Was supposed to occur across a migrating front. However, experimental work had established by the 1960s that granites were of igneous origin. The mineralogical and chemical features of granite can be explained only by crystal-liquid phase relations, showing that there must have been at least enough melting to mobilize the magma. However, at sufficiently deep crustal levels, the distinction between metamorphism and crustal melting itself becomes vague. Conditions for crystallization of liquid magma are close enough to those of high-grade metamorphism that

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