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49-709: The Roosevelt Gabbros were originally intruded in the early Cambrian between the Glen Mountain Layered Complex and the Mount Scott Granite as the southern Oklahoma aulacogen was being formed. The formation of this aulacogen resulted from rifting that took place as the Neoproterozoic supercontinent Pannotia was breaking apart. Isotopic analysis of these intrusive units indicate a rifting age of approximately 532 Ma. The Glen Mountain Layered Complex

98-435: A light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope. Buddingtonite is an ammonium feldspar with the chemical formula: NH 4 AlSi 3 O 8 . It is a mineral associated with hydrothermal alteration of the primary feldspar minerals. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. Barium feldspars are sometimes classified as

147-468: A mild abrasive action. The USGS estimated global production of feldspar in 2020 to be 26 million tonnes, with the top four producing countries being: China 2 million tonnes; India 5 million tonnes; Italy 4 million; Turkey 7.6 million tonnes. Typical mineralogical and chemical analyses of three commercial grades used in ceramics are: In October 2012, the Curiosity rover found high feldspar content in

196-604: A section of plutonic and volcanic rocks that once formed the bedrock of the aulacogen, and as a result this aulacogen is "one of the best preserved and best exposed" selections of the igneous results of ancient rift activity. Consequently, the Southern Oklahoma Aulacogen is the designated type in the United States. The mafic rocks of the Southern Oklahoma aulacogen can be separated into two primary groups,

245-399: A separate group of feldspars, and sometimes they are classified as a sub-group of alkali feldspars. The barium feldspars are monoclinic and include the following: The plagioclase feldspars are triclinic . The plagioclase series follows (with percent anorthite in parentheses): Intermediate compositions of exsolve to two feldspars of contrasting composition during cooling, but diffusion

294-613: A short distance in cold and/or dry conditions that did not promote weathering, and that it was quickly buried by other sediment. Sandstones with large amounts of feldspar are called arkoses . Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as filler and an extender in paint, plastics, and rubber. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fibre. Ceramics (including electrical insulators, sanitaryware, tableware and tile) and other uses, such as fillers, accounted for

343-725: A source of alkalies and alumina in glazes. The composition of feldspar used in different ceramic formulations varies depending on various factors, including the properties of the individual grade, the other raw materials and the requirements of the finished products. However, typical additions include: tableware, 15% to 30% feldspar; high-tension electrical porcelains, 25% to 35%; sanitaryware, 25%; wall tile, 0% to 10%; and dental porcelain up to 80% feldspar. Earth sciences : In earth sciences and archaeology, feldspars are used for potassium-argon dating , argon-argon dating and luminescence dating . Minor use : Some household cleaners (such as Bar Keepers Friend and Bon Ami ) use feldspar to give

392-522: A system of transform faults . The Southern Oklahoma Aulacogen formed sometime in the Late Proterozoic Eon , between 525 and 550 million years ago, during the rifting of the Laurentia supercontinent or North American Craton, the geological core of North America. Its formation and bimodal igneous activity occurred simultaneously, with two definite episodes of magma activity, mafic and felsic ,

441-476: A three-dimensional network. Compositions of major elements in common feldspars can be expressed in terms of three endmembers : Solid solutions between K-feldspar and albite are called alkali feldspar. Solid solutions between albite and anorthite are called plagioclase , or, more properly, plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions, immiscibility occurs at temperatures common in

490-460: Is a distinct change in texture in the layers of granite, with earlier deposited layers being very fine-grained in comparison to later, coarse-grained granite layers. Some thought has been put forward as to the corresponding mafic intrusion needed to produce these felsic rocks, either through partial melting of the adjacent crust or through fractional crystallization of the mafic magma itself. Gilbert (1982) suggests that an igneous body related to

539-700: Is a group of rock-forming aluminium tectosilicate minerals , also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust and 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock . Rock formed almost entirely of calcic plagioclase feldspar

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588-629: Is associated with a widespread anomalous area in which seismic waves travel more slowly. A common comparison is drawn from this aulacogen to the Dniepr-Donets Aulacogen in Baltica because both are significant intracratonic rifts. The Southern Oklahoma Aulacogen contains numerous igneous rocks . Among these rocks are a multitude of gabbros , including anorthosite , titanium -rich, iron -rich, phosphorus -rich, and biotite gabbros. Also included are rhyolites and granites . This assemblage

637-514: Is composed of biotite-amphibole-olivine gabbro and contains labradorite , augite , and hypersthene . Magnetite , ilmenite , and olivine can be found in segregated ultramafic concentrations. Small amounts of spinel, apatite, and some sulfides can also be found. The Sandy Group Gabbro is a member of the Roosevelt Gabbros that forms blobby irregular sills which are like small plutons . These intrusive blobs are internally differentiated, with

686-549: Is estimated to contain over 250,000 km of igneous rock. The aulacogen is inverted: rather than extending across the surface it penetrates into the North American craton , and is aligned with the northern edge of a deeply buried Proterozoic basin of uncertain origin which may have formed through igneous layering or deposition. The aulacogen terminates on contact with the Ouachita orogenic belt . The Southern Oklahoma Aulacogen

735-451: Is kinked. Each crankshaft chain links to neighbouring crankshaft chains to form a three-dimensional network of fused four-member rings. The structure is open enough for cations (typically sodium, potassium, or calcium) to fit into the structure and provide charge balance. Chemical weathering of feldspars happens by hydrolysis and produces clay minerals , including illite , smectite , and kaolinite . Hydrolysis of feldspars begins with

784-660: Is known as anorthosite . Feldspars are also found in many types of sedimentary rocks . The name feldspar derives from the German Feldspat , a compound of the words Feld ("field") and Spat ("flake"). Spat had long been used as the word for "a rock easily cleaved into flakes"; Feldspat was introduced in the 18th century as a more specific term, referring perhaps to its common occurrence in rocks found in fields (Urban Brückmann, 1783) or to its occurrence as "fields" within granite and other minerals (René-Just Haüy, 1804). The change from Spat to -spar

833-449: Is much slower than in alkali feldspar, and the resulting two-feldspar intergrowths typically are too fine-grained to be visible with optical microscopes. The immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae known as Bøggild intergrowth. The specific gravity in

882-400: Is very similar to the mid-Proterozoic age anorthosite - mangerite - charnockite - granite (AMCG) complexes of North America, but for the lack of coarse massif anorthosites. This is significant in that AMCG complexes tend to form at huge depths in the Earth's crust and thus cool more slowly, allowing the massif anorthosites to form coarse-grained. The similar igneous assemblage suggests that

931-524: The Wichita Mountains , Taovayan Valley, Anadarko Basin , and Hardeman Basin in Southwestern Oklahoma . The Southern Oklahoma Aulacogen is primarily composed of basaltic dikes , gabbros , and units of granitic rock. The Southern Oklahoma Aulacogen extends roughly 500 miles long (805 km) by ~80–90 miles wide (129–145 km). The two remaining continental plate boundary arms of

980-443: The magmas that formed the igneous rocks of the Southern Oklahoma Aulacogen quickly cooled to at or near their crystallization point, much more quickly than the magmas of AMCG complexes, thus resulting in finer-grained anorthosites. More recently, different interpretations of seismic and outcrop data, as well as stratigraphy in the area have led some studies to postulate that this formation may not be an aulacogen after all, but

1029-475: The Anadarko Basin, forming the Wichita Mountains . This also resulted in the reactivation of Cambrian rift faults, often becoming reverse or listric thrust faults . Anticlines formed in the sedimentary rock layers of the basin, contributing to the formation of the deep hydrocarbon reservoir of the Anadarko Basin. The formation of these listric faults and anticlines indicates that the crustal shortening

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1078-701: The Cambrian to the Mississippian buried the aulacogen underneath 4 to 5 kilometers of sediment. Starting in the late Mississippian the Ouachita Orogeny began to uplift the igneous units of the southern Oklahoma aulacogen. After the end of the Ouachita Orogeny in the early Pennsylvanian, the igneous units were once again buried by material eroding off of the Ouachita mountains. Following this sedimentation, erosion up to

1127-463: The Earth's crust means that clays are very abundant weathering products. About 40% of minerals in sedimentary rocks are clays and clays are the dominant minerals in the most common sedimentary rocks, mudrocks . They are also an important component of soils . Feldspar that has been replaced by clay looks chalky compared to more crystalline and glassy unweathered feldspar grains. Feldspars, especially plagioclase feldspars, are not very stable at

1176-420: The Earth's surface due to their high formation temperature. This lack of stability is why feldspars are easily weathered to clays. Because of this tendency to weather easily, feldspars are usually not prevalent in sedimentary rocks. Sedimentary rocks that contain large amounts of feldspar indicate that the sediment did not undergo much chemical weathering before being buried. This means it was probably transported

1225-604: The Glenn Creek Gabbro, the Sandy Creek Gabbro, and the Mount Sheridan Gabbro. In addition to these named intrusions, there are many smaller biotite rich gabbro dikes found throughout the southern Oklahoma aulacogen which are also considered to be part of the Roosevelt Gabbros. The Glen Creek Gabbro is a member of the Roosevelt Gabbros that forms a sill between two layers of the Glen Mountain Layered Complex. It

1274-483: The Late Diabase Dikes may be responsible, despite the geochemical differences between the "wet" dikes and "dry" felsic rocks. Gilbert also points out that the predicted existence of a felsic-precursor mafic magma precludes the assumption that the positive Bouguer gravity anomaly is due only to the mafic rocks currently observed in the aulacogen. Due to its unique structure and faulting, the area within and around

1323-489: The Mount Scott Granite is dated to 530.45 ± 0.14 Ma. As the felsic magma of the Mount Scott granite intruded above the Glen Mountain Layered Complex, an intermediate hybrid layer formed where the Mount Scott Granite came in contact with the Roosevelt Gabbros. Following the rifting, a basin formed above the igneous units of the southern Oklahoma aulacogen. After the formation of this basin, a period of sedimentation lasting from

1372-792: The Raggedy Mountain Gabbros and the Late Diabase Dikes. The Raggedy Mountain Gabbros can be further separated into two subgroups due to petrographic analysis and field mapping. These subgroups are the Glen Mountains Layered Complex and the Roosevelt Gabbros . The felsic rocks of the Southern Oklahoma aulacogen are broken into two main units, the Carlton Rhyolite Group and the Wichita Granite Group. There

1421-497: The Roosevelt Gabbros forms a large sill between layers of the Glen Mountain Layered Complex. It is intruded by a sill of the Mount Scott Granite. Similarly to the Sandy Creek Gabbro, the Mount Sheridan Gabbro becomes more felsic upwards through the member. It grades upwards from olivine bearing gabbro into ferrogranodiorite, with the uppermost sections bearing the most quartz , alkali-feldspars, and zircon . Plagioclase, augite, hypersthene, biotite, ilmenite, and magnetite make up most of

1470-566: The Sandy Creek member. Southern Oklahoma Aulacogen The Southern Oklahoma Aulacogen (ah-lah-coh-jin) is a failed rift , or failed rift arm ( aulacogen ), of the triple junction that became the Iapetus Ocean spreading ridges . It is a significant geological feature in the Western and Southern United States. It formed sometime in the early to mid Cambrian Period and spans

1519-464: The alkali feldspars occur only in higher temperature environments. Sanidine is stable at the highest temperatures, and microcline at the lowest. Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye. Microperthitic textures in crystals are visible using

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1568-466: The area may have been, at one point, in the temperature range of the "liquid window," the range of temperatures that are ideal for oil formation. The isotherms of this window range from 65 °C to 150 °C. This further suggests that the area may have served as an oil formation bed before a late Ordovician fluid migration pulse. Feldspar Feldspar ( / ˈ f ɛ l ( d ) ˌ s p ɑːr / FEL(D) -spar ; sometimes spelled felspar )

1617-496: The aulacogen developed very deep basins (such as the Anadarko Basin ), forming excellent petroleum sources. Igneous rock deposits often form the hanging walls of anticline reverse faults in this area, leading to an unusual number of petroleum wells drilled into them in order to access the petroleum-bearing rock layers below. A graph of the geothermal history of the Southern Oklahoma Aulacogen suggests that sections of rock in

1666-555: The composition becoming increasingly more felsic upwards approaching the overlying Mount Scott Granite. The more mafic lower material is composed of primarily olivine rich gabbro. The more intermediate material higher in the sills are composed of quartz gabbro. Small amounts of ilmenite, magnetite, sulfides, and apatite can be found throughout the Sandy Creek Gabbros, and some of the more felsic material contains small amounts of alkali-feldspar . The Mount Sheridan Gabbro member of

1715-443: The continuous Bowen's reaction series . K-feldspar is the final feldspar to crystallize from the magma. Alkali feldspars are grouped into two types: those containing potassium in combination with sodium, aluminium, or silicon; and those where potassium is replaced by barium. The first of these include: Potassium and sodium feldspars are not perfectly miscible in the melt at low temperatures, therefore intermediate compositions of

1764-470: The crust of the Earth. Albite is considered both a plagioclase and alkali feldspar. The ratio of alkali feldspar to plagioclase feldspar, together with the proportion of quartz , is the basis for the QAPF classification of igneous rock. Calcium-rich plagioclase is the first feldspar to crystallize from cooling magma, then the plagioclase becomes increasingly sodium-rich as crystallization continues. This defines

1813-429: The feldspar dissolving in water, which happens best in acidic or basic solutions and less well in neutral ones. The speed at which feldspars are weathered is controlled by how quickly they are dissolved. Dissolved feldspar reacts with H or OH ions and precipitates clays. The reaction also produces new ions in solution, with the variety of ions controlled by the type of feldspar reacting. The abundance of feldspars in

1862-412: The former of which being chiefly composed of gabbro-heavy magma and the latter phase being primarily composed of rhyolitic magma. It is hypothesized that between the mafic and felsic stages of magmatic activity substantial uplift occurred, which correlates to the lack of coarse-grained massif anorthosites presented previously. The remaining two arms of its original triple-junction became spreading zones for

1911-462: The mafic material of the Mount Sheridan Group, with small amounts of apatite and sulfides. Roosevelt Gabbros typically contain both biotite and amphibole, with olivine present in the more mafic samples. Pyroxenes and plagioclase can be found in large quantities in some samples. The below oxide percentages represent average whole rock chemistry from samples taken from different sills of

1960-595: The nascent Iapetus Ocean . The aulacogen penetrated the craton, causing normal faults to form in what became the Anadarko Basin . The aulacogen underwent crustal shortening and inversion sometime in the Mississippian Period to the Early Permian Period , roughly 330–280 million years ago. This coincides with the closing of the Iapetus spreading zones and the overthrusting of the Ouachita uplift over

2009-409: The older Glen Mountain Layered Complex. It is almost entirely gabbro, with the exception of where the younger Mount Scott Granite contacts the Roosevelt Gabbros. At these contacts more intermediate to felsic rocks such as quartz gabbro and granodiorite are found. This less mafic material is considered to be a hybrid unit between the two intrusions. The Roosevelt Gabbros has three named members, being

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2058-488: The plagioclase series increases from albite (2.62) to anorthite (2.72–2.75). The structure of a feldspar crystal is based on aluminosilicate tetrahedra. Each tetrahedron consists of an aluminium or silicon ion surrounded by four oxygen ions. Each oxygen ion, in turn, is shared by a neighbouring tetrahedron to form a three-dimensional network. The structure can be visualized as long chains of aluminosilicate tetrahedra, sometimes described as crankshaft chains because their shape

2107-446: The present day has uncovered the igneous units of the southern Oklahoma aulacogen. The Roosevelt Gabbros formation is differentiated from the Glen Mountain Layered Complex by the abundant presence of biotite and the inclusion of pink, brown, and green amphiboles . It is also differentiated from the Glen Mountain Layered Complex by the structures it forms, with the Roosevelt Gabbros forming irregular blobby dikes and sills which intrude

2156-487: The remainder. Glass : Feldspar provides both K 2 O and Na 2 O for fluxing, and Al 2 O 3 and CaO as stabilizers. As an important source of Al 2 O 3 for glassmaking, feldspar is valued for its low iron and refractory mineral content, a low cost per unit of Al 2 O 3 , no volatiles and no waste. Ceramics : Feldspars are used in the ceramic industry as a flux to form a glassy phase in bodies during firing, and thus promote vitrification. They also are used as

2205-555: The triple junction from which the Southern Oklahoma aulacogen formed became spreading zones for the spreading of the Iapetus Ocean during the breakup of the supercontinent, Rodinia , estimated to have occurred in the Cryogenian Period , approximately 750 million years ago. These arms closed in the Pennsylvanian Period (~323.2–298.9 Ma) and formed part of the Ouachita orogenic belt . The Southern Oklahoma Aulacogen

2254-427: Was a period of ceased igneous activity, faulting, uplift, and erosion. Renewed igneous activity then extruded large quantities of felsic lava above the Glen Mountain Layered Complex and intruded Roosevelt Gabbros, forming the overlying Carlton Rhyolite. Further magmatism lead to the intrusion of the Mount Scott Granite above the unconformity between the Glen Mountain Layered Complex and Carlton Rhyolite. The intrusion of

2303-590: Was influenced by the English word spar , meaning a non-opaque mineral with good cleavage. Feldspathic refers to materials that contain feldspar. The alternate spelling, felspar , has fallen out of use. The term 'felsic', meaning light coloured minerals such as quartz and feldspars, is an acronymic word derived from fel dspar and si lica, unrelated to the obsolete spelling 'felspar'. The feldspar group of minerals consists of tectosilicates , silicate minerals in which silicon ions are linked by shared oxygen ions to form

2352-502: Was intruded as massive far spanning sheets during this rifting at approximately 532.49 ± 0.12 Ma. After the cooling of the Glen Mountain Layered Complex, the Roosevelt Gabbros intruded, forming dikes through the layers and irregularly blobby sills between them. The intrusion of the Roosevelt Gabbros is dated to 532.05 ± 0.12 Ma. Throughout the maturation of this extensional regime, faulting and block rotation causes these intruded units to dip northward. Following this period of mafic magmatism

2401-485: Was significant, up to 10–15 km or more. The igneous rocks found in the aulacogen were also uplifted during the Ouachita uplift and subsequently reburied by both local and transported sediments. As there was no major deformation of the midsection of North America during the Mesozoic and Cenozoic eras, the aulacogen's structure and rift assembly were mostly preserved. Erosion in recent eras has eroded sediments overlying

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