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Journal articles on the topic "A-Type alkali granite"
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Šuica, Sanja, Vesnica Garašić, and Alan B. Woodland. "Petrography and geochemistry of granitoids and related rocks from the pre-Neogene basement of the Slavonia-Srijem Depression (Croatia)." Geologia Croatica 75, no. 1 (February 28, 2022): 129–44. http://dx.doi.org/10.4154/gc.2022.09.
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The pre-Neogene basement of the Slavonia-Srijem Depression (eastern Croatia) is composed of various types of igneous, metamorphic and sedimentary rocks. Here we present the petrography and geochemistry of a heterogenous group represented by two types of alkali granite, granite, syenite, rhyolite and orthogneiss. The alkali granite type 1 has an A-type geochemical affinity: a ferroan character, high alkali content, high concentration of rare earth elements (REE3+), Rb, Zr, Nb and Y, and low CaO, MgO, P2O5, Ba, Sr and Eu contents. The syenite has similar characteristics, but displays enrichment in Ba, K, Eu and Zr, which could be a consequence of feldspar and zircon accumulation. The alkali granite type 2 is an A-type granite but differs from the alkali granite type 1 in having lower K2O and Rb, accompanied by higher Na2O and Sr concentrations, possibly resulting from alteration or a different parental magma/evolutionary process. The granite and rhyolite are distinguished from both types of alkali granite by their magnesian character, lower Zr, Nb and Y concentrations, less pronounced Eu negative anomaly, as well as higher Ba, Sr and LREE/HREE. The orthogneiss displays differences in major element chemistry compared to the alkali granite type 1, but has similar trace element and REE patterns. The alkali granites are characterized by Y/Nb<1.2, indicating an ocean island basalt-like source, while the granite originated from melting of a crustal, probably metasedimentary source. The A-type granites could belong to the Late Cretaceous A-type magmatism of the Sava Zone, while the granite is significantly different from the Sava Zone A-type granites as well as the other rocks investigated in this study.
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Usman, Ediar. "THE GEOCHEMICAL CHARACTERISTIC OF MAJOR ELEMENT OF GRANITOID OF NATUNA, SINGKEP, BANGKA AND SIBOLGA." BULLETIN OF THE MARINE GEOLOGY 30, no. 1 (February 15, 2016): 45. http://dx.doi.org/10.32693/bomg.30.1.2015.74.
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A study of geochemical characteristic of major elelemnt of granitoid in Western Indonesia Region was carried out at Natuna, Bangka, Singkep and Sibolga. The SiO2 contents of the granites are 71.16 to 73.02 wt%, 71.77 to 75.56wt% and 71.16 to 73.02wt% at Natuna, Bangka, and Singkep respectively, which are classified as acid magma. While in Sibolga the SiO2 content from 60.27 to 71.44wt%, which is classified as intermediate to acid magma. Based on Harker Diagram, the granites from Natuna, Bangka and Singkep as a co-genetic. In other hand the Sibolga Granite show as a scatter pattern. Granites of Natuna, Bangka and Singkep have the alkaline-total (Na2O + K2O) between 6.03 to 8.51 wt% which are classified as granite and alkali granite regime. K2O content ranges from 3.49 to 5.34 wt% and can be classified as calc-alkaline type. The content of alkaline-total of Sibolga granite between 8.12 to 11.81 wt% and classified as a regime of syenite and granite. The range of K2O is about 5.36 to 6.94wt%, and assumed derived from high-K magma to ultra-potassic types. Granites of Natuna, Bangka and Singkep derived from the plutonic rock types and calc-alkaline magma, while Sibolga granite magma derived from K-high to ultra-potassic as a granite of islands arc. Based on the chemical composition of granite in Western Indonesian Region can be divided into two groups, namely Sibolga granite group is representing the Sumatera Island influenced by tectonic arc system of Sumatera Island. Granites of Bangka and Singkep are representing a granite belt in Western Indonesian Region waters which is influenced by tectonic of back arc.Keywords: magma, geochemical characteristic, major element and Western Indonesian Region Kajian karakteristik geokimia dari unsur utama granitoid di Kawasan Barat Indonesia telah dilakukan di daerah Natuna, Bangka, Singkep dan Sibolga. Kandungan SiO2 granit Natuna antara 71,16 - 73,02%, Bangka antara 71,77 - 75,56%, Singkep antara 72,68 - 76,81% termasuk dalam magma asam. Granit Sibolga memiliki kandungan SiO2 antara 60,27 - 71,44% termasuk dalam magma menengah - asam. Berdasarkan Diagram Harker, granit Natuna, Bangka dan Singkep mempunyai asal kejadian yang sama (ko-genetik), sedangkan granit Sibolga membentuk pola pencar. Granit Natuna, Bangka dan Singkep mengandung total alkalin (K2O+Na2O) antara 6,03 - 8,51% termasuk dalam jenis rejim granit dan alkali granit. Berdasarkan kandungan K2O antara 3,49 - 5,34 %berat, bersifat kalk-alkali. Granit Sibolga mengandung total alkali antara 8,12 - 11,81% termasuk dalam rejim syenit dan granit, dan berdasarkan kandungan K2O antara 5,36 - 6,94% berasal dari jenis magma K-tinggi sampai ultra-potassik. Granit Natuna, Bangka dan Singkep berasal dari jenis batuan beku dalam dan magma kalk-alkalin yang berhubungan dengan penunjaman, sedangkan granit Sibolga berasal dari jenis magma K-tinggi - ultra-potassik sebagai granit busur kepulauan. Berdasarkan komposisi unsur kimia utama, granit di Kawasan Barat Indonesia dapat dibagi dalam dua, yaitu granit Sibolga yang mewakili P. Sumatera, dipengaruhi oleh sistem tektonik busur P. Sumatera. Granit Bangka dan Singkep dapat mewakili suatu jalur granit di perairan Kawasan Barat Indonesia yang dipengaruhi oleh tektonik busur belakang. Kata kunci: jenis magma, karakteristik geokimia, unsur utama, dan Kawasan Barat Indonesia
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Lee, Byung Choon, Weon-Seo Kee, Uk Hwan Byun, and Sung Won Kim. "Statherian (ca. 1714–1680 Ma) Extension-Related Magmatism and Deformation in the Southwestern Korean Peninsula and Its Geological Significance: Constraints from the Petrological, Structural, Geochemical and Geochronological Studies of Newly Identified Granitoids." Minerals 11, no. 6 (May 24, 2021): 557. http://dx.doi.org/10.3390/min11060557.
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In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating revealed that the two granites formed around 1.71 Ga and 1.70–1.68 Ga, respectively. The results of the geochemical analyses showed that both of the granites have a high content of K2O, Nb, Ta, and Y, as well as high FeOt/MgO and Ga/Al ratios. Both granites have alkali-calcic characteristics with a ferroan composition, indicating an A-type affinity. Zircon Lu-Hf isotopic compositions yielded negative εHf(t) values (−3.5 to −10.6), indicating a derivation from ancient crustal materials. Both granite types underwent ductile deformation and exhibited a dextral sense of shear with a minor extension component. Based on field relationships and zircon U-Pb dating, it was considered that the deformation event postdated the emplacement of the alkali feldspar granite and terminated soon after the emplacement of the porphyritic alkali feldspar granite in an extensional setting. These data indicated that there were extension-related magmatic activities accompanying ductile deformation in the southwestern part of the Korean Peninsula during 1.71–1.68 Ga. The Statherian extension-related events are well correlated with those in the midwestern part of the Korean and eastern parts of the North China Craton.
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Semblano, Flávio Robson Dias, Moacir José Buenano Macambira, and Marcelo Lacerda Vasquez. "Petrography, geochemistry and Sm-Nd isotopes of the granites from eastern of the Tapajós Domain, Pará state." Brazilian Journal of Geology 46, no. 4 (December 2016): 509–29. http://dx.doi.org/10.1590/2317-4889201620160059.
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ABSTRACT: The Tapajós Domain, located in the southern portion of the Amazonian Craton, is a tectonic domain of the Tapajós-Parima Province, a Paleoproterozoic orogenic belt adjacent to a reworked Archean crust, the Central Amazonian Province. This domain has been interpreted as the product of an assemblage of successive magmatic arcs followed by post-orogenic A-type magmatism formed ca. 1880 Ma-old granites of the Maloquinha Intrusive Suite. The study presented here was carried out in four granitic bodies of this suite (Igarapé Tabuleiro, Dalpaiz, Mamoal and Serra Alta) from the eastern part of the Tapajós Domain, as well as an I-type granite (Igarapé Salustiano) related to the Parauari Intrusive Suite. The A-type granites are syenogranites and monzogranites, and alkali feldspar granites and quartz syenites occur subordinately. These rocks are ferroan, alkalic-calcic to alkalic and dominantly peraluminous, with negative anomalies of Ba, Sr, P and Ti and high rare earth elements (REE) contents with pronounced negative Eu anomaly. This set of features is typical of A-type granites. The Igarapé Salustiano granite encompasses monzogranites and quartz monzonites, which are magnesian, calcic to calc-alkalic, high-K and mainly metaluminous, with high Ba and Sr contents and depleted pattern in high field strength elements (HFSE) and heavy rare earth elements (HREE), characteristic of I-type granites. The source of magma of these A-type granites is similar to post-collisional granites, while the I-type granite keeps syn-collisional signature. Most of the studied granites have εNd (-3.85 to -0.76) and Nd TDM model ages (2.22 to 2.46 Ga) compatible with the Paleoproterozoic crust of the Tapajós Domain. We conclude that the Archean crust source (εNd of -5.01 and Nd TDM of 2.6 Ga) was local for these A-type granites.
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Jia, Ru-Ya, Guo-Chang Wang, Lin Geng, Zhen-Shan Pang, Hong-Xiang Jia, Zhi-Hui Zhang, Hui Chen, and Zheng Liu. "Petrogenesis of the Early Cretaceous Tiantangshan A-Type Granite, Cathaysia Block, SE China: Implication for the Tin Mineralization." Minerals 9, no. 5 (April 29, 2019): 257. http://dx.doi.org/10.3390/min9050257.
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The newly discovered Tiantangshan tin polymetallic deposit is located in the southeast Nanling Range, Cathaysia block, Southeast China. The tin orebodies are mainly hosted in the greisen and the fractured alteration zones of the tufflava and trachydacite. However, the genetic relationship between the hidden alkali-feldspar granite and volcanic rocks and the tin mineralization remains poorly understood. This paper presents SHRIMP zircon U–Pb dating, whole-rock major and trace element analyses, as well as Nd isotopic data of the trachydacite and alkali-feldspar granite. The SHRIMP zircon U–Pb dating of the alkali-feldspar granite and trachydacite yields weight mean 206Pb/238U ages of 138.4 ± 1.2, and 136.2 ± 1.2 Ma, respectively. These granitic rocks have high levels of SiO2 (64.2–75.4 wt%, mostly > 68 wt%), alkalis (K2O + Na2O > 8.3 wt%), REE (except for Eu), HFSE (Zr + Nb + Ce + Y > 350 ppm) and Ga/Al ratios (10,000 × Ga/Al > 2.6), suggesting that they belong to the A-type granite. According to the high Y/Nb and Yb/Ta ratios, they can be further classified into A1 subtype. Their εNd (T) range from −3.8 to −6.5. They were likely generated by the assimilation-fractional crystallization (AFC) of the coeval oceanic island basalts -like basaltic magma. This study suggests that the A1 type granite is also a potential candidate for the exploration of tin deposits.
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Abdel Gawad, Ahmed E., Hassan Eliwa, Khaled G. Ali, Khalid Alsafi, Mamoru Murata, Masoud S. Salah, and Mohamed Y. Hanfi. "Cancer Risk Assessment and Geochemical Features of Granitoids at Nikeiba, Southeastern Desert, Egypt." Minerals 12, no. 5 (May 13, 2022): 621. http://dx.doi.org/10.3390/min12050621.
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Different rock types (syenogranite, alkali feldspar granite and quartz syenite intruded by microgranite dikes and quartz veins) were investigated in the Nikeiba region in Egypt. The main components of the studied intrusive rocks, comprised of granites and quartz syenite, are plagioclase, amphibole, biotite, quartz and K-feldspar in different proportions. Ground gamma ray measurements show that syenogranite, quartz syenite and microgranite dikes have the highest radioactivity (K, eU, eTh and their ratios) in comparison with alkali feldspar granite. Geochemically, syenogranite, alkali feldspar granite and quartz syenite are enriched with large-ion lithophile elements (LILE; Ba, Rb, Sr) and high field-strength elements (HFSE; Y, Zr and Nb), but have decreased Ce, reflecting their alkaline affinity. These rocks reveal calc–alkaline affinity, metaluminous characteristics, A-type granites and post-collision geochemical signatures, which indicates emplacement in within-plate environments under an extensional regime. U and Th are increased in syenogranite and quartz syenite, whereas alkali feldspar granite shows a marked decrease in U and Th. The highest average values of AU (131 ± 49 Bq·kg−1), ATh (164 ± 35) and AK (1402 ± 239) in the syenogranite samples are higher than the recommended worldwide average. The radioactivity levels found in the samples are the result of the alteration of radioactive carrying minerals found inside granite faults. The public’s radioactive risk from the radionuclides found in the investigated granitoid samples is estimated by calculating radiological risks. The excess lifetime cancer (ELCR) values exceed the permissible limit. Therefore, the granitoids are unsuitable for use as infrastructure materials.
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ZHAO, XILIN, YANG JIANG, GUANGFU XING, ZHIHONG CHEN, KAI LIU, MINGGANG YU, and SHENGYAO YU. "A geochemical and geochronological study of the Early Cretaceous, extension-related Honggong ferroan (A-type) granite in southwestern Zhejiang Province, southeast China." Geological Magazine 155, no. 3 (September 27, 2016): 549–67. http://dx.doi.org/10.1017/s0016756816000790.
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AbstractThe Honggong pluton is the largest ferroan alkalic (A-type) granite intrusion emplaced along the Jiangshan–Shaoxing fault zone in southwestern Zhejiang Province, and has important implications for understanding the Late Mesozoic tectonic evolution of SE China. U–Pb ages of 138.7 ± 0.8, 134.2 ± 1.1, 128.5 ± 1.5 and 126.1 ± 0.9 Ma were obtained from zircon by laser ablation–inductively coupled plasma–mass spectrometry, indicating that the Honggong pluton formed in the Early Cretaceous. The Honggong pluton has a clear ferroan alkalic (A-type) granite geochemical signature with, for example, high total alkali contents and FeOt/(FeOt+ MgO) values. The Sr–Nd–Hf isotopic compositions suggest that there was juvenile material in the magma source. Geochemical evidence indicates that the pluton was derived through extensive fractionation of melts that contained both asthenospheric mantle and Mesoproterozoic crustal components. These rare granites in southern China were emplaced during five episodes at 235–225, 190, 165–155, 100–90 and 140–120 Ma. The age of the Honggong pluton suggests that localized extension in southwestern Zhejiang Province began as early as ~138 Ma and continued to 126 Ma. This Early Cretaceous extensional event was triggered by localized rollback of the subducting Pacific Plate.
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Broska, Igor, and Michal Kubiš. "Accessory minerals and evolution of tin-bearing S-type granites in the western segment of the Gemeric Unit (Western Carpathians)." Geologica Carpathica 69, no. 5 (October 1, 2018): 483–97. http://dx.doi.org/10.1515/geoca-2018-0028.
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Abstract The S-type accessory mineral assemblage of zircon, monazite-(Ce), fluorapatite and tourmaline in the cupolas of Permian granites of the Gemeric Unit underwent compositional changes and increased variability and volume due to intensive volatile flux. The extended S-type accessory mineral assemblage in the apical parts of the granite resulted in the formation of rare-metal granites from in-situ differentiation and includes abundant tourmaline, zircon, fluorapatite, monazite-(Ce), Nb–Ta–W minerals (Nb–Ta rutile, ferrocolumbite, manganocolumbite, ixiolite, Nb–Ta ferberite, hübnerite), cassiterite, topaz, molybdenite, arsenopyrite and aluminophosphates. The rare-metal granites from cupolas in the western segment of the Gemeric Unit represent the topaz–zinnwaldite granites, albitites and greisens. Zircon in these evolved rare-metal Li–F granite cupolas shows a larger xenotime-(Y) component and heterogeneous morphology compared to zircons from deeper porphyritic biotite granites. The zircon Zr/Hfwt ratio in deeper rooted porphyritic granite varies from 29 to 45, where in the differentiated upper granites an increase in Hf content results in a Zr/Hfwt ratio of 5. The cheralite component in monazite from porphyritic granites usually does not exceed 12 mol. %, however, highly evolved upper rare-metal granites have monazites with 14 to 20 mol. % and sometimes > 40 mol. % of cheralite. In granite cupolas, pure secondary fluorapatite is generated by exsolution of P from P-rich alkali feldspar and high P and F contents may stabilize aluminophosphates. The biotite granites contain scattered schorlitic tourmaline, while textural late-magmatic tourmaline is more alkali deficient with lower Ca content. The differentiated granites contain also nodular and dendritic tourmaline aggregations. The product of crystallization of volatile-enriched granite cupolas are not only variable in their accessory mineral assemblage that captures high field strength elements, but also in numerous veins in country rocks that often contain cassiterite and tourmaline. Volatile flux is documented by the tetrad effect via patterns of chondrite normalized REEs (T1,3 value 1.46). In situ differentiation and tectonic activity caused multiple intrusive events of fluid-rich magmas rich in incompatible elements, resulting in the formation of rare-metal phases in granite roofs. The emplacement of volatile-enriched magmas into upper crustal conditions was followed by deeper rooted porphyritic magma portion undergoing second boiling and re-melting to form porphyritic granite or granite-porphyry during its ascent.
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Imeokparia, E. G. "Geochemical evolution of the Jarawa Younger Granite complex and its related mineralization, northern Nigeria." Geological Magazine 122, no. 2 (March 1985): 163–73. http://dx.doi.org/10.1017/s0016756800031071.
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AbstractThe Jarawa Younger Granite complex is composed of high silica alkali granites that were emplaced 161 Ma ago. The granites are characterized by high contents of Rb, Li, F, Sn, Nb, W above normal low-Ca granitic rocks and have typical S-type characteristics that are indicative of a substantial component of crustal melt.Mineralization in the complex is associated with the biotite granite which was emplaced as a sheet-like body at relatively shallow depth and occurs as disseminations and as greisen lodes and veins.Chemical studies of the granites have shown that the biotite granite represents a highly fractionated rock that crystallized from a residual magma from which the hornblende-biotite granite had previously crystallized. However the biotite granite is characterized by steep gradients in some minor and trace elements that apparently indicate that liquid-state differentiation and/or volatile complexing processes made significant contributions to their differentiation. Enrichment of Th, Li, Rb, Sn, W and Nb may be more closely linked to roofward migration of F.
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Stone, Maurice. "The Tregonning granite: petrogenesis of Li-mica granites in the Cornubian batholith." Mineralogical Magazine 56, no. 383 (June 1992): 141–55. http://dx.doi.org/10.1180/minmag.1992.056.383.01.
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AbstractLi-mica (zinnwaldite and/or lepidolite)—topaz—albite granites in the Tregonning—Godolphin pluton and similar rocks in the St. Austell pluton appear to be petrogenetically unrelated to the spatially associated biotite granites. Evidence is provided by lack of development of Li-mica granites at roof zones of biotite granites and markedly different trends and composition fields in bivariate plots such as Li vs. Cs, Rb vs. Sr and Nb vs. Zr. Thus, differentiation of biotite granite magma is unlikely to have generated Li-mica granite magma, as also, on its own, is partial melting of biotite granite or biotiteabsent residual lower crust. However, partial melting of biotite-rich residual rocks involving biotite breakdown could yield a trace alkali- and F-enriched melt, although this would require marked femic mineral, K-feldspar and anorthite fractionation, and Na-enrichment. It is proposed that volatiles derwed from either a mantle source or the crust/mantle interface have aided metasomatism of either residual S-type crust that earlier provided S-type biotite granite magma, or basic (biotite-rich) granitoid, to produce a low-temperature, low-viscosity Li-mica granite melt that rose rapidly in the crust soon after the emplacement of associated biotite granites.
Dissertations / Theses on the topic "A-Type alkali granite"
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Rowe, S. E. "Mechanism of formation and age of the Ayyarmalai A-type charnockite – granite association from the south-eastern Palghat- Cauvery Shear System, southern India." Thesis, 2010. http://hdl.handle.net/2440/104030.
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This item is only available electronically.The Ayyarmalai A-type charnockite and A-type alkali granite lies on the south-eastern margin of the Palghat-Cauvery Shear System and provides an example of co-magmatism that was later overprinted with granulite facies metamorphism at ~2.45-2.5Ga. The Palghat-Cauvery Shear System represents an intriguing zone with Neoproterozoic aged granulites (~800-500 Ma) to the south and Archaean granulites (~3000-2500 Ma) to the north; the origins of which are still often disputed. This study presents whole rock major and trace element compositions, mineral chemistry, pressure-temperature estimates and whole rock Sm-Nd, Rb-Sr, Pb-Pb and δ18O isotopic compositions of this A-type charnockite-granite association found at Ayyarmalai, Tamil Nadu, Southern India. The subsequent data from this study suggests that: (1) the Ayyarmalai charnockites from the Palghat-Cauvery Shear System have zircon ages that are synchronous with events in the Northern Granulite Terrain; (2) The Dharwar Craton is a strong candidate for the protolith of these rocks; (3) Evidence of a Neoproterozoic-Cambrian granulite metamorphic event (~520 Ma) appears to be absent in these rocks questioning the existence or location of a Neoproterozoic - Cambrian suture zone proposed for the Palghat-Cauvery Shear System recently. U-Pb zircon ages show zoned igneous cores ~2.65-2.68 Ga ages in both rock types defining the crystallisation age, while the large metamorphic rim overgrowths date the Archaean granulite metamorphic event at ~2.45 - 2.5 Ga. Geochemical data of the Ayyarmalai charnockites reveal a very primitive, unfractionated REE pattern with no Eu-anomaly, ferroan, high K-calc-alkaline, with moderate enrichment of LREE with respect to HREE and fall within the field of high Ba-Sr type granitoids. Extraction of Pyroxene- Hornblende rich cumulates resulted in an intermediate charnockites driving the crystallisation towards the final A-type alkali granite. The A-type alkali granites show a more fractionated REE pattern with a significant Eu-anomaly, ferroan, high-K- calc-alkaline, with enrichment of LREE and depletion in the low Ba-Sr type granitoids. εNd and Nd model ages indicate a highly evolved protolith (εNd(0) =-25.15 to -33.14) that encountered a crustal Archaean source (2.89-3.09 Ga) causing contamination as the magmas ascended. Harker diagrams, Nd data (isochron age, ~2519 Ma) and U-Pb zircon crystallisation ages suggest a co-magmatic relationship between the charnockite and alkali granite. Conventional geothermometry/barometry suggest minimum pressure-temperature conditions existed at 740 – 750°C and P=5.61 – 5.84 kbar. The data presented from this study is consistent with a magmatic origin of these charnockites favouring the early crystallisation of orthopyroxene. The correlation with the data from the Dharwar Craton suggest that the study region may have encountered Dharwar Craton on magmatic ascent causing crustal contamination
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2010
Book chapters on the topic "A-Type alkali granite"
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Pitcher, Wallace Spencer. "Intraplate magmatism: mainly the A-type, alkali feldspar granites." In The Nature and Origin of Granite, 218–37. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-3393-9_15.
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Pitcher, Wallace Spencer. "Intraplate, rift-related magmatism: mainly the A-type, alkali feldspar granites." In The Nature and Origin of Granite, 258–79. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5832-9_15.
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A. El Bahariya, Gaafar. "An Overview on the Classification and Tectonic Setting of Neoproterozoic Granites of the Nubian Shield, Eastern Desert, Egypt." In Geochemistry. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95904.
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Granites constitute the main rock components of the Earth’s continental crust, which suggested to be formed in variable geodynamics environments. The different types of granitic rocks, their compositional characteristics, tectonic settings and magma sources are outlined. Mineralogical classification of granites includes four rock types: tonalites, granodiorites, granite (monzogranite and syenogranites) and alkali-feldspar granites. Alphabetical classification subdivided granites into: I-type, S-type, A-type and M-type granites. Moreover, formation of granitic magmas requires distinctive geodynamic settings such as: volcanic arc granite (Cordilleran); collision-related granites (leucogranites); intra-plate and ocean ridge granites. The Eastern Desert of Egypt (ED) forms the northern part of Nubian Shield. Both older and younger granites are widely exposed in the ED. Old granites (OG) comprise tonalites and granodiorites of syn- to late-orogenic granitoid assemblages. They are calcalkaline, I-type, metaluminous and display island arc tectonic setting. Younger granites (YG) on the other hand, include granites, alkali-feldspar granites and minor granodiorites. They are of I- and A-type granites and of post-orogenic to anorogenic tectonic settings. The majority of the YG are alkaline, A-type granite and of within-plate tectonic setting (WPG). The A-type granites are subdivided into: A2-type postorogenic granites and A1-type anorogenic granites. Granite magma genesis involves: (a) fractional crystallization of mafic mantle-derived magmas; (b) anatexis or assimilation of old, upper crustal rocks (c) re - melting of juvenile mafic mantle – derived rocks underplating the continental crust. Generally, older I-type granitoids were interpreted to result from melting of mafic crust and dated at approximately 760–650 Ma, whereas younger granites suggested to be formed as a result of partial melting of a juvenile Neoproterozoic mantle source. Moreover, they formed from anatectic melts of various crustal sources that emplaced between 600 and 475 Ma.
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Frost, Carol D., and B. Ronald Frost. "Petrologic constraints on the origin of Proterozoic ferroan granites of the Laurentian margin." In Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(10).
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ABSTRACT Ferroan granite is a characteristic rock type of the Laurentian margin. It is commonly associated with anorthosite and related rocks. Ferroan granites are strongly enriched in iron, are alkalic to alkali-calcic, and are generally metaluminous. These geochemical characteristics reflect their tholeiitic parental magma source and relatively reducing and anhydrous conditions of crystallization. Their compositions distinguish them from arc magmas, which are magnesian and calcic to calc-alkalic. Ferroan granite magmas are hot, which promotes partial melting of their crustal wall rocks. Assimilation of these silica-rich and peraluminous melts drives the resulting magmas to higher silica and aluminum saturation values. Where Proterozoic ferroan granites intrude Archean crust, their mantle component is readily identified isotopically, but this is more difficult where they intrude relatively juvenile crust. Ferroan granite forms in tectonic environments that allow partial melts of tholeiitic mantle to pond and differentiate at or near the base of the crust. Phanerozoic examples occur in plume settings, such as the Snake River Plain and Yellowstone, or under certain conditions involving slab rollback, such as those that formed the Cenozoic topaz rhyolites of the western United States or ferroan rhyolites of the Sierra Madre Occidental. It is possible that the long-lived supercontinent Nuna-Rodinia, of which Laurentia was a part, formed an insulating lid that raised underlying mantle temperatures and created a unique environment that enabled emplacement of large volumes of mafic melt at the base of the crust. Ascent of felsic differentiates accompanied by variable crustal assimilation may have created large volumes of Proterozoic ferroan granite and related rocks.
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Indares, Aphrodite, Abdelali Moukhsil, and Pierre-Arthur Groulier. "Geon 14 to early Geon 13 granitoid magmatism in the Grenville Province of Canada, northeastern Laurentia: Distribution, geochemical patterns, and links with an active-margin setting." In Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(17).
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ABSTRACT Mesoproterozoic crust is widely exposed in the Grenville Province portion of northeastern Laurentia, where it is interpreted as an assemblage of two continental-arc segments separated by a composite arc belt (Quebecia) with island-arc remnants. A synthesis of the geologic context, types, and geochemical patterns of 1.5–1.35 Ga granitoids reveals a regional distribution in each segment, with dioritic to granitic plutonism variably associated with arc-related volcano-sedimentary belts in the south and inboard monzonitic to granitic plutonism in the north. In addition, belts of dioritic to granitic orthogneisses occupy intermediate positions in Quebecia and in the west. The inboard granites are consistently old in all segments (1.5–1.45 Ga), but the preserved volcano-sedimentary belts are older in the east and in Quebecia (1.5–1.45 Ga) and younger in the west (1.39? and 1.36 Ga), while the belts of orthogneisses show a large spread of ages at 1.45–1.37 Ga. Granitoids in the volcano-sedimentary belts and the orthogneisses include magnesian, calcic to calc-alkalic components to ferroan, alkali-calcic components. In contrast, the inboard plutons are dominantly ferroan and alkali-calcic to alkalic in the continental-arc segments, where they are locally associated with anorthosite-mangerite-charnockite-granite (AMCG) suites. Collectively, the different types of granitoid magmatism can be linked to an active margin, with subduction under northeastern Laurentia, involving arc building, arc rifting, back-arc opening and inboard extension, and amalgamation processes variably operating at different parts of the margin and at different times. In addition, the data provide a basis for comparison with other parts of the eastern to southwestern Laurentian margin in the 1.5–1.35 Ga time frame.
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Konopelko, Dmitry L. "Chapter 2. Postcollisional intrusions of the Kokshaal Segment of South Tien Shan." In PALEOZOIC GRANITOID MAGMATISM OF WESTERN TIEN SHAN, 35–69. St. Petersburg State University, 2020. http://dx.doi.org/10.21638/11701/9785288060250.03.
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Postcollisional granites of the Kokshaal Segment of South Tien Shan comprise about 20 postkinematic intrusions composed of biotite-amphibole granites, biotite granites and Li-F topaz-bearing leucogranites. The granites were emplaced coevally with tholeiitic mafic rocks and alkaline syenites. Geochemically the granites are classified as A-type and characterized by elevated Fe/(Fe+Mg) and K2O/Na2O values and high concentrations of Na2O+K2O, Rb, HFSE. On the discrimination diagrams Y-Nb and Rb-(Y+Nb) compositions of the granites plot into the field of intra-plate granites. On a regional scale, the compositional variations of the Kokshaal granites can be explained by fractionation of potassium feldspar and amphibole. The granites were probably derived from the crustal protoliths represented by Precambrian metamorphic rocks of the Tarim microcontinent. Crystallization ages of the Kokshaal granites, established utilizing U-Pb zircon dating, fall in the relatively narrow range between 280 and 295 Ma corresponding to the early Permian, which is in agreement with ages of postcollisional granites elsewhere in Tien Shan. Genesis of granites was related to trans-crustal shear zones.
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White, Chris E., Sandra M. Barr, James L. Crowley, Deanne van Rooyen, and Trevor G. MacHattie. "U-Pb zircon ages and Sm-Nd isotopic data from the Cobequid Highlands, Nova Scotia, Canada: New contributions to understanding the Neoproterozoic geologic history of Avalonia." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(07).
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ABSTRACT Forty-three new U-Pb zircon ages from metasedimentary and igneous rock units throughout the Cobequid Highlands of northern mainland Nova Scotia, Canada, provide new insights into the Neoproterozoic evolution of this long-enigmatic part of Avalonia in the northern Appalachian orogen. Contrasts in ages and rock types resulted in the identification of fault-bounded Neoproterozoic assemblages of units forming the Bass River, Jeffers, and Mount Ephraim blocks. In the Bass River block, quartzite, metawacke, and minor calc-silicate rocks and marble (Gamble Brook Formation) with a maximum depositional age of 945 ± 12 Ma are associated with subaqueous mafic volcanic rocks, siltstone, and ironstone (Folly River Formation) and intruded by 615–600 Ma calc-alkalic subduction-related dioritic to granitic rocks of the Bass River plutonic suite. The contrasting Jeffers block forms most of the Cobequid Highlands and consists mainly of intermediate to felsic volcanic, epiclastic, and minor plutonic rocks. The western and eastern areas of that block yielded ages mainly ca. 607–592 Ma for both volcanic and plutonic rocks, whereas the central area has ages of ca. 630–625 Ma from both volcanic and plutonic rocks and inheritance in overlying Devonian conglomerate. The Mount Ephraim block forms the eastern part of the highlands and includes possible ca. 800 Ma quartzofeldspathic, semipelitic and pelitic gneiss and schist of the Mount Thom Formation, ca. 752 Ma volcanic arc rocks of the Dalhousie Mountain Formation and related 752–730 Ma gabbroic/dioritic to granitic plutons of the Mount Ephraim plutonic suite and Six Mile Brook pluton, as well as ca. 631 Ma granitoid rocks of the Gunshot Brook pluton. The pre–750 Ma high-grade regional metamorphism and deformation and 752–730 Ma subduction-related magmatism recorded in the Mount Ephraim block were previously unrecognized in Avalonia. Evidence from zircon inheritance and Sm-Nd isotopic data in igneous units suggests linkages among these now-separate areas, and comparison with other parts of Avalonia in the northern Appalachian orogen suggests similarity to southeastern New England.
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Cahoon†, Emily B., Martin J. Streck†, and Mark Ferns†. "Flood basalts, rhyolites, and subsequent volcanism of the Columbia River magmatic province in eastern Oregon, USA." In From Terranes to Terrains: Geologic Field Guides on the Construction and Destruction of the Pacific Northwest, 301–52. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.0062(08).
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ABSTRACT The Miocene Columbia River Basalt Group (CRBG) is the youngest and smallest continental flood basalt province on Earth. This flood basalt province is a succession of compositionally diverse volcanic rocks that record the passage of the Yellowstone plume beneath eastern Oregon. The compositionally and texturally varied suite of volcanic rocks are considered part of the La Grande–Owyhee eruptive axis (LOEA), an ~300-km-long, north-northwest–trending, Middle Miocene to Pliocene volcanic belt that extends along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the flood basalt–dominated Columbia Plateau to the north, the north and bimodal basalt-rhyolite volcanic fields of the Snake River Plain to the east, the Owyhee Plateau to the south, and the High Lava Plains to the south and east; the latter two have time transgressive rhyolite centers that young to the east and west, respectively. This field-trip guide details a four-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the CRBG and coeval and compositionally diverse silicic rocks associated with the early trace of the Yellowstone plume and High Lava Plains in eastern Oregon. The trip on Day 1 begins in Portland then traverses across the western axis of the Blue Mountains, highlighting exposures of the widespread, Middle Miocene Dinner Creek Welded Tuff and aspects of the Picture Gorge Basalt lava flows and northwest-striking feeder dikes situated in the central part of the CRBG province. Travel on Day 2 progresses eastward toward the eastern margin of the LOEA, examining a transition linking the Columbia River Basalt province with a northwestward-younging magmatic trend of silicic volcanism of the High Lava Plains in eastern Oregon. Initial field stops on Day 2 focus on the volcanic stratigraphy northeast of the town of Burns, which includes regionally extensive Middle to Late Miocene ash-flow tuffs and lava flows assigned to the Strawberry Volcanics. Subsequent stops on Day 2 examine key outcrops demonstrating the intercalated nature of Middle Miocene tholeiitic CRBG flood basalts, temporally coeval prominent ash-flow tuffs, and “Snake River–type” large-volume rhyolite lava flows cropping out along the Malheur River. The Day 3 field route navigates to southern parts of the LOEA, where CRBG rocks are associated in space and time with lesser known and more complex silicic volcanic stratigraphy forming Middle Miocene, large-volume, bimodal basalt-rhyolite vent complexes. Key stops will provide a broad overview of the structure and stratigraphy of the Middle Miocene Mahogany Mountain caldera and of the significance of intercalated sedimentary beds and Middle to Late Miocene calc-alkaline lava flows of the Owyhee basalt. Initial stops on Day 4 will highlight exposures of Middle to Late Miocene silicic ash-flow tuffs, rhyolite domes, and calc-alkaline lava flows overlying the CRBG across the northern and central parts of the LOEA. The later stops on Day 4 examine more silicic lava flows and breccias that are overlain by early CRBG-related rhyolite eruptions. The return route to Portland on Day 4 traverses the Columbia River gorge westward from Baker City. The return route between Baker and Portland on Day 4 follows the Columbia River gorge and passes prominent basalt outcrops of large volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Formations of the CRBG. These sequences of basaltic and basaltic andesite lavas are typical of the well-studied flood basalt dominated Columbia Plateau, and interbedded silicic and calc-alkaline lavas are conspicuously absent. Correlation between the far-traveled CRBG lavas and calcalkaline and silicic lavas considered during the excursion relies on geochemical fingerprinting and dating of the mafic flows and dating of sparse intercalated ashes.
Conference papers on the topic "A-Type alkali granite"
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Rudko, Georgii, Mariia Kyrilo, and Maksym Ozerko. "MULTICOMPONENT DEPOSITS WITH BY-PRODUCT AS THE MAIN SOURCE OF FELDSPAR RAW MATERIALS FOR MODERN TECHNOLOGIES." In GEOLINKS Conference Proceedings. Saima Consult Ltd, 2021. http://dx.doi.org/10.32008/geolinks2021/b1/v3/32.
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"Feldspar is raw materials with a growing volume of production every year, as well as a price for it. Feldspar consumption has been gradually increasing in ceramics, glass industry for solar panels, housing, and building construction. Feldspar raw materials include intrusive, effusive rocks, weathering crust of crystalline rocks, sedimentary altered and altered rocks, as well as partially medium and basic aluminosilicate rocks. It was defined an industrial application for each species of feldspar. Potassium feldspars (orthoclase, microcline, sanidine) are used in electroceramic, electrode, abrasive, and ceramics industries. For these productions, the potash module is fixed in a ratio of 2: 1. For some industries, in particular the manufacture of high-voltage ceramics, the necessary feldspars are as close as possible to pure potassium (with a modulus of at least 4: 1, which corresponds to 80% of the orthoclase component). Potassium-sodium raw materials, from a potassium modulus of at least 0.9, are used for building construction. Sodium minerals with non-standardized potassium modulus are used for the glass industry, the production of enamels, and products such as vitreous porcelain. Calcium feldspars, represented by plagioclase of higher numbers, have limited practical application and their presence in feldspar concentrates is undesirable. According to mineral associations, all types of feldspar raw materials can be divided into five types: 1) feldspar (syenites, trachitis); 2) quartz-feldspar (pegmatites, granites, sands, etc.); 3) nepheline-feldspar (nepheline syenites, alkaline pegmatites); 4) quartz-sericite-feldspar (shales, secondary quartzites); 5) quartz-kaolinite-feldspar (sands, alkaline kaolins, secondary quartzites). It is shown on the example of Ukrainian deposits of feldspar minerals that complex deposits with by-products become the main source for production. Especially if these are new mining operation facilities. The authors have identified three main types of such complex multicomponent deposits: 1) deposits of intrusive rocks where weathering crust of crystalline rocks are mined as a byproduct; 2) complex deposits, where feldspar rocks are enclosing or overburden and can also be considered as byproducts; 3) deposits where feldspar concentrate can be produced as a product of ore components processing."
Reports on the topic "A-Type alkali granite"
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Matte, S., M. Constantin, and R. Stevenson. Mineralogical and geochemical characterisation of the Kipawa syenite complex, Quebec: implications for rare-earth element deposits. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329212.
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The Kipawa rare-earth element (REE) deposit is located in the Parautochton zone of the Grenville Province 55 km south of the boundary with the Superior Province. The deposit is part of the Kipawa syenite complex of peralkaline syenites, gneisses, and amphibolites that are intercalated with calc-silicate rocks and marbles overlain by a peralkaline gneissic granite. The REE deposit is principally composed of eudialyte, mosandrite and britholite, and less abundant minerals such as xenotime, monazite or euxenite. The Kipawa Complex outcrops as a series of thin, folded sheet imbricates located between regional metasediments, suggesting a regional tectonic control. Several hypotheses for the origin of the complex have been suggested: crustal contamination of mantle-derived magmas, crustal melting, fluid alteration, metamorphism, and hydrothermal activity. Our objective is to characterize the mineralogical, geochemical, and isotopic composition of the Kipawa complex in order to improve our understanding of the formation and the post-formation processes, and the age of the complex. The complex has been deformed and metamorphosed with evidence of melting-recrystallization textures among REE and Zr rich magmatic and post magmatic minerals. Major and trace element geochemistry obtained by ICP-MS suggest that syenites, granites and monzonite of the complex have within-plate A2 type anorogenic signatures, and our analyses indicate a strong crustal signature based on TIMS whole rock Nd isotopes. We have analyzed zircon grains by SEM, EPMA, ICP-MS and MC-ICP-MS coupled with laser ablation (Lu-Hf). Initial isotopic results also support a strong crustal signature. Taken together, these results suggest that alkaline magmas of the Kipawa complex/deposit could have formed by partial melting of the mantle followed by strong crustal contamination or by melting of metasomatized continental crust. These processes and origins strongly differ compare to most alkaline complexes in the world. Additional TIMS and LA-MC-ICP-MS analyses are planned to investigate whether all lithologies share the same strong crustal signature.