9. MICAS in IGNEOUS ROCKS

Speer, J. Alexander

doi:10.1515/9781501508820-013

Cited by 167 publications

(111 citation statements)

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“…The biotite is a common hydrated ferromagnesian silicate in mafic, intermediate and felsic igneous rocks. It is a very sensitive indicator of physico-chemical conditions and compositional evolution in granitoid genesis (Speer 1984). Hence, there is a relation between the compositions of igneous biotites and their host magmas (Abdel-Rahman 1994).…”

Section: Petrography and Mineralogymentioning

confidence: 99%

Geodynamic significance of granitoid magmatism in the southeast Anatolian orogen: geochemical and geochronogical evidence from Göksun–Afşin (Kahramanmaraş, Turkey) region

Parlak

2005

Int J Earth Sci (Geol Rundsch)

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In southeast Anatolia, there are number of tectonomagmatic units in the Kahramanmaras¸-Malatya-Elazıg˘region that are important in understanding the geological evolution of the southeast Anatolian orogenic belt during the Late Cretaceous. These are (a) metamorphic massifs, (b) ophiolites, (c) ophiolite-related metamorphics and (d) granitoids. The granitoids (i.e. Go¨ksun-Afs¸in in Kahramanmaras¸, Dog˘ans¸ehir in Malatya and Baskil in Elazıg˘) intrude all the former units in a NE-SW trending direction. The granitoid in Go¨ksun-Afs¸in (Kahramanmaras¸) region is mainly composed of granodioritic and granitic in composition. The granodiorite contains a number of amphibole-bearing mafic microgranular enclaves of different sizes, whereas the granite is intruded by numerous aplitic dikes. The granitoid rocks have typical calcalkaline geochemical features. The REE-and Ocean ridge granite-normalized multi-element patterns and tectonomagmatic discrimination diagrams, as well as biotite geochemistry suggest that the granitoids were formed in a volcanic arc setting. The K-Ar geochronology of the granitoid rocks yielded ages ranging from 85.76±3.17 to 77.49±1.91 Ma. The field, geochemical and geochronological data suggest the following Late Cretaceous tectonomagmatic scenario for southeast Anatolia. The ophiolites were formed in a suprasubduction zone tectonic setting whereas the ophiolite-related metamorphic rocks formed either during the initiation of intraoceanic subduction or late-thrusting ($90 Ma). These units were then overthrust by the Malatya-Keban platform during the progressive elimination of the southern Neotethys. Thrusting of the Malatya-Keban platform over the ophiolites and related metamorphic rocks was followed by the intrusion of the granitoids (88-85 Ma) along the Tauride active continental margin in the southern Neotethys.

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Section: Petrography and Mineralogymentioning

confidence: 99%

Geodynamic significance of granitoid magmatism in the southeast Anatolian orogen: geochemical and geochronogical evidence from Göksun–Afşin (Kahramanmaraş, Turkey) region

Parlak

2005

Int J Earth Sci (Geol Rundsch)

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“…12) with the compositional mol-percentage of muscovite, paragonite and celadonite. The chemical composition of white mica should reflect the nature of magmatic and metamorphic source rock (Speer 1984;Spear 1993). Mica compositions close to the muscovite corner indicate provenance from granites and regionally metamorphosed rocks.…”

Section: Composition Of Detrital White Micamentioning

confidence: 99%

“…The micas in the thin section from the Late Permian sample also cluster near the muscovite corner, with a slight spread to the phengitic side. (1978, cited in Taylor andMcLennan 1985) Barium and titanium are supposed to be provenancesignificant elements in white mica (Speer 1984). The element barium is more abundant in white micas from granitic/pegmatitic rocks; titanium is more abundant in micas from intermediate plutonic rocks (Speer 1984, with references).…”

Section: Composition Of Detrital White Micamentioning

confidence: 99%

“…A higher abundance of iron (together with magnesium in phengite) in white micas indicates a metamorphic origin. Generally, igneous muscovites have more Ti, Al, Na and less Mg, Si and Fe (Speer 1984). Ba and Ti are plotted against Na/(Na+K), and Fe/(Fe+Mg) ( Fig.…”

Section: Composition Of Detrital White Micamentioning

confidence: 99%

“…The relatively high phengitic components (up to 70 rel.%) of some of the micas point to a possible high-grade metamorphic source region together with paragonitic micas from rocks of low-to medium-grade metamorphic origin. The barium and titanium contents of the micas may be, according to Speer (1984), interpreted as minerals of originally plutonic rocks (granites).…”

Section: Early Carboniferousmentioning

confidence: 99%

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Provenance of Palaeozoic sandstones from the Carnic Alps (Austria): petrographic and geochemical indicators

Mader

Neubauer

2004

International Journal of Earth Sciences

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An integrated approach of petrographic analysis, whole rock geochemistry and microprobe analysis has been applied to obtain information on the geodynamic development and the provenance for Ordovician to Permian siliciclastic successions exposed within the Carnic Alps (Austria). Sandstone detrital mode and geochemical results refine previous geodynamic interpretations. Late Ordovician samples indicate a stable craton and recycled orogenic and, possible, extensional setting. The Early Carboniferous is interpreted to represent a compressional environment, followed by a Late Carboniferous molassetype foreland basin, and a Permian extensional geodynamic setting. Contrasting geochemical patterns of postVariscan and Permian sequences suggest a rift setting. Electron microprobe data of detrital white mica also indicate changes in the provenance. Compositional data reflect a shift from low-to medium-grade metamorphic (Ordovician) to high-grade metamorphic (Carboniferous) to low-to medium-grade metamorphic and plutonic source rocks (Permian). Additionally, our data show that various chemical discrimination diagrams do not include all possible ranges of sandstones, and that high contents of detrital mica and ultra-stable heavy minerals may cause misclassification. Consequently, we propose the use of multi-method approach for provenance studies, including the control of geochemical data by modal analysis and heavy mineral investigations.

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Aluminum in zircon as evidence for peraluminous and metaluminous melts from the Hadean to present

Trail

Tailby

Wang

et al. 2017

Geochem Geophys Geosyst

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Zircon structurally accommodates a range of trace impurities into its lattice, a feature which is used extensively to investigate the evolution of silicate magmas. One key compositional boundary of magmas is defined by whether the molar ratio of Al2O3/(CaO + Na2O + K2O) is larger or smaller than unity. Here we report ∼800 Al in zircon concentrations from 19 different rocks from the Lachlan Fold Belt (southeastern Australia), New England (USA), and Arunachal leucogranites (eastern Himalaya) with Al2O3/(CaO + Na2O + K2O) whole rock values that range from 0.88 to 1.6. Zircons from peraluminous rocks yield an average Al concentration of ∼10 ppm, which distinguishes them from crystals found in metaluminous rocks (∼1.3 ppm). This difference is related to the materials involved in the melting, assimilation, and/or magma differentiation processes; for example, magmas that assimilate Al‐rich material such as metapelites are expected to produce melts with elevated alumina activities, and thus zircons with high Al concentrations. These observations are applied to the Archean and Hadean Jack Hills detrital zircon record. Detrital Archean zircons, with ages from about 3.30 to 3.75 Ga, yield Al in zircon concentrations consistent with origins in peraluminous rocks in ∼8% of the cases (n = 236). A single zircon from the pre‐3.9 Ga age group (n = 39) contains elevated Al contents, which suggests that metaluminous crustal rocks were more common than peraluminous rocks in the Hadean. Weathered material assimilated into these Hadean source melts was not dominated by Al‐rich source material.

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9. MICAS in IGNEOUS ROCKS

Cited by 167 publications

References 0 publications

Geodynamic significance of granitoid magmatism in the southeast Anatolian orogen: geochemical and geochronogical evidence from Göksun–Afşin (Kahramanmaraş, Turkey) region

Geodynamic significance of granitoid magmatism in the southeast Anatolian orogen: geochemical and geochronogical evidence from Göksun–Afşin (Kahramanmaraş, Turkey) region

Provenance of Palaeozoic sandstones from the Carnic Alps (Austria): petrographic and geochemical indicators

Aluminum in zircon as evidence for peraluminous and metaluminous melts from the Hadean to present

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