Intergrowths of Feldspars with Other Minerals

Smith, J. V.

doi:10.1007/978-3-642-65743-6_8

Cited by 8 publications

(4 citation statements)

References 67 publications

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“…Agreeva et al, 2012). Essa textura é usualmente associada a processos metassomáticos, de alteração de fases preexistentes e de desestabilização dos cristais (Smith, 1974;Mitchell e Platt, 1979;Deer et al, 2013). Os intercrescimentos de nefelina vermiforme em feldspato alcalino pertítico em rochas do BSI são caracterizados:…”

Section: Discussionunclassified

Mineraloquímica das rochas do Batólito Sienítico Itabuna, Sul do estado da Bahia

Leandro,

Conceição,

Rosa

et al. 2022

Geol. USP. Sér. Cient.

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O Batólito Sienítico Itabuna (450 km2), com idade de 476 Ma, é intrusivo em rochas granulíticas do Cráton São Francisco e faz parte da Província Alcalina do Sul do Estado da Bahia. Esse batólito neoproterozoico é constituído de sienitos, monzonitos, foid sienitos, dioritos e gabros. Rochas representativas do batólito foram estudadas por petrografia ótica e eletrônica (MEV) e as análises químicas pontuais foram obtidas com WDS e EDS. As rochas possuem granulação que varia de fina a grossa. Os minerais presentes são: feldspatos alcalinos, plagioclásio, nefelina, anfibólio, clinopiroxênio, biotita apatita, sodalita, cancrinita, ilmenita, magnetita, pirita, calcopirita, zirconolita, olivina, allanita, baddeleyíta, zircão, calcita, monazita, titanita, barita, bastnäsita e thorita. A matriz em algumas rochas é composta essencialmente de feldspatos alcalinos (albita e microclina), plagioclásio e nefelina. Identificaram-se feldspatos alcalinos pertítico, antipertítico, albita, microclina e plagioclásio com composições de albita até labradorita. A mica marrom corresponde a siderofilita, lepidomelano e Fe-biotita. O clinopiroxênio tem composições de diopsídio, hedenbergita e augita. Os anfibólios são de variedades cálcica, Fe-Mg-Mn-Li e Na-Ca. Os dados químicos indicam que os cristais de biotita, anfibólio, allanita e zirconolita são primários. Os cristais de clinopiroxênio registram temperaturas máximas de 939°C no foid sienito, 959°C nos sienitos e 916°C no monzonito, com cristalização sob alta fugacidade de oxigênio. A pressão máxima obtida em cristal de clinopiroxênio de monzonito foi de 5,2 kbar. A biotita registra temperatura e pressão máximas de 797°C e 2,2 kbar, respectivamente. A exsolução ilmenita-magnetita processou-se a temperaturas inferiores a 600°C. A compilação e a interpretação dos dados gerados permitem inferir a cristalização fracionada como principal processo responsável pela evolução das rochas do Batólito Sienítico Itabuna...

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Section: Discussionunclassified

Mineraloquímica das rochas do Batólito Sienítico Itabuna, Sul do estado da Bahia

Leandro,

Conceição,

Rosa

et al. 2022

Geol. USP. Sér. Cient.

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“…Statistical U‐stage, X‐ray diffraction and EBSD measurements reveal close crystallographic orientation relationships between intergrowth quartz grains and the host feldspar, suggesting a most likely simultaneous growth mechanism (e.g. Smith, ; Xu et al ., ). Such primary information of crystallographic relations is mainly retained in euhedral and subhedral quartz crystals with rectilinear boundaries.…”

Section: Discussionmentioning

confidence: 99%

Oriented inclusions of pyroxene, amphibole and rutile in garnet from the Lüliangshan garnet peridotite massif, North Qaidam UHPM belt, NW China: an electron backscatter diffraction study

2016

Journal Metamorphic Geology

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Oriented inclusions of clinopyroxene, orthopyroxene, sodic amphibole and rutile have been identified in garnet from the L€ uliangshan garnet peridotite massif in the North Qaidam ultrahigh-pressure metamorphic (UHPM) belt, northern Tibetan Plateau, NW China. Electron backscatter diffraction (EBSD) analyses demonstrate that nearly half of the measured intracrystalline clinopyroxene (8 out of 17) have topotactic crystallographic relationships with host garnet, that is, (100) Cpx //{112} Grt , (010) Cpx //{110} Grt and [001] Cpx //<111> Grt . One-fifth of the oriented sodic amphibole (23 out of 110) inclusions of have topotactic crystallographic relationships with host garnet, that is, (010) Amp // {112} Grt , (100) Amp //{110} Grt and [001] Amp //<111> Grt . Over a third of rutile (36 out of 99) inclusions also show a close crystallographic orientation relationship with host garnet in that one <103> Rt and one <110> Rt parallel to two <111> Grt while the axes of [001] Rt exhibit small girdles centred the axes of <111> Grt . But, no 'well-fit' crystallographic relationship was observed between orthopyroxene inclusions and host garnet. Considering a very long and complex history for the L€ uliangshan garnet peridotite, we suggest that the low fit rates for these oriented minerals may result from several possible assumptions including different generations or multi-stage formation mechanisms, heterogeneous nucleation and growth under non-equilibrium conditions, and partial changes of initial crystallographic orientations of some inclusions. However, the residual quantitative 'well-fit' crystallographic information is sufficient to indicate that the nucleation and growth of many pyroxene, amphibole and rutile are controlled by the lattice of the host garnet. The revealed close topotactic relationships accompanied by clear shape orientations provide quantitative microstructural evidence demonstrating a most likely exsolution/precipitate origin for at least some of the oriented phases of pyroxene, sodic amphibole and rutile from former majoritic garnet and support an ultra-deep (>180 km depth) origin of the L€ uliangshan garnet massif.

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“…In spite of easy identification and clear illustration in every fundamental geology textbook for such a masterpiece of nature, its origin has been debated in the literature for more than a century (e.g. Wahlstrom, 1939;Simpson, 1962;erný, 1971;Smith, 1974;Fenn, 1986;Lentz and Fowler, 1992;Stel, 1992;London, 2009;London and Morgan, 2012). Two principal models have been proposed for the formation of the graphic texture, simultaneous growth of quartz and feldspar (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Systematic, quantitative knowledge on the crystallographic relationship between quartz and feldspar in the graphitic granite should contribute to solve the above disagreement in the origin of graphic texture. Understanding the graphic texture is important for deciphering the origin and the crystallization process of granite pegmatites in a volatile-rich magma (e.g Smith, 1974;London and Morgan, 2012). The conventional U-stage petrographic microscopy and X-ray diffraction have proven to be unsatisfactory tools.…”

Section: Introductionmentioning

confidence: 99%

Crystallographic evidence for simultaneous growth in graphic granite

Zhang

et al. 2015

Gondwana Research

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Intergrowths of Feldspars with Other Minerals

Cited by 8 publications

References 67 publications

Mineraloquímica das rochas do Batólito Sienítico Itabuna, Sul do estado da Bahia

Mineraloquímica das rochas do Batólito Sienítico Itabuna, Sul do estado da Bahia

Oriented inclusions of pyroxene, amphibole and rutile in garnet from the Lüliangshan garnet peridotite massif, North Qaidam UHPM belt, NW China: an electron backscatter diffraction study

Crystallographic evidence for simultaneous growth in graphic granite

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