K-feldspar megacrysts in granites — Phenocrysts, not ... Abstract K-feldspar megacrysts in granitoid plutons have been interpreted as either phenocrysts or porphyroblasts. Most of the microstructural, mineralogical and chemical evidence (e.g., shape, alignment, concentration, Ba content, zoning, inclusions, and twinning) favours a phenocryst origin. Geol. Mag. 147 3, 2010, pp. 451–468. doi:10.1017 ... Huaco granite and the orbicular granitoid (Fig. 2). In general, the Huaco granite that crops out around the orbicular granitoid is similar to the porphyritic granite described in Section 2. However, the granite bordering the orbicular granitoid shows a strong increase in the abundance of K-feldspar megacrysts in Rb-Sr chronological charac- teristics of Jurassic ... components, K-feldspar, biotite, amphibole and whole rock divided from two selected granitoid gravel samples, their Rb-Sr isotopes are measured, which gives two formation ages of granitoids: (428f20) Ma and (430f54) Ma, and means that the Early Paleozoic granitoid intrusive rocks once ex-isted in the Dabie Mountain provenances of Jurassic. The    Read More

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  • Preliminary Geologic Map of the

    Xgg Gneissic granitoid—Orange colored, medium– to coarse–grained gneissic granitoid is the dominant rock type exposed south of the Santa Fe river and west of the Borrego fault zone. The unit is composed of plagioclase, K-feldspar, quartz, biotite and iron oxides.

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  • Petrography of an unknown granitoid body in the Blue Ridge ...

    Petrography of an unknown granitoid body in the Blue Ridge of northwest Georgia Pearce, Darren, Columbus State University, Department of Earth and Space Science, Spring 2010 EASTERN BLUE RIDGE ALKALI FELDSPAR GRANITE This sample consists of approximately 25 - 30% subhedral to euhedral alkali feldspar, ranging from 0.25mm to 3mm in size.

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  • Petrochemical evolution of subvolcanic granitoid ...

    K-feldspar (1– 12 mm in grain size) occurs as subhedral, most commonly rectangular, crystals, but rarely euhedral crystals are observed. Coarse patch perthite is common. K-feldspar is also very altered to sericite and clay minerals. Micrographic texture, in which quartz is intergrown in K-feldspar .

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  • Granitoid building stone, Beijing, China - turnstone.ca

    Granitoid building stone (a Rapakivi Granite)--- at China University of Geosciences- Beijing, China. 1-2. Two photographs of the rock, which takes an excellent polish. It appears to be composed largely of pink orthoclase (potassium [K] feldspar, or alkali feldspar), granular grey quartz and a greenish plagioclase feldspar.

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  • Geochemical and radiogenic isotope (Sr–Nd) characteristics ...

    clinic K-feldspar often contain sericite and epidote dustings. The foliated (defined by K-feldspar and hornblende clots) granitoid intrusive lies in sinistral strike-slip fault contact with the Archean Nain Province amphibolites, mafic granu-lites, and quartzofeldspathic gneisses, and exhibits the same structural grain as the gneisses (Fig. 2).

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  • p1 B v4 ai12 - USGS

    granodiorite and monzogranite that contains K–feldspar phenocrysts. Present in Fenner Hills, Piute Range, Homer Mountain, and nearby areas. Feldspar phenocrysts are 1–2 cm wide except in southern Piute Range, where they are 2–4 cm wide Kg Younger granitoid rocks (Cretaceous)—Monzogranite and granodiorite probably of Late Cretaceous age.

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  • SHOCKED QUARTZ AND LOCAL SELECTIVE FELDSPAR .

    [6] in the target rocks at Santa Fe. The melting of K-feldspar requires post-shock temperatures of 8≥50°C [2,7], in-compatible with such moderate shock pressure conditions. Thus, K-feldspar melting may have been driven by local friction melting. The occurence of K-feldspar melt at Santa Fe is of interest regarding future 40Ar/39Ar dating.

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  • Solution-precipitation of K-feldspar in deformed ...

    Abstract We have investigated K-feldspar recrystallisation in granitoid mylonites within a ductile shear zone from the Ryoke metamorphic belt, SW Japan. Fine-grained K-feldspar (20 μm on average) occurs in the matrix and in pull-apart areas within fractured K-feldspar porphyroclasts.

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  • Geochemical Classification for Granitic Rocks | Journal of ...

    Previous granitoid classification schemes have involved diverse criteria such as the presumed origin of the granitoid, mineralogy, geochemistry, ... This makes it an ideal projection for mafic rocks; however, it is less suitable for granitic rocks because K-feldspar and albite plot at the same point.

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  • Ar-Ar geochronology study on K-feldspar in Xishan W-Sn ore ...

    K-feldspar has been able to preserve the radiogenetic argon as biotite does. Combined with the consistence with published K-Ar age, this result implies that K-Ar method is still a useful tool to produce accurate ages (though less precise than Ar-Ar method) when the sample is suitable. Acknowledgements

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  • CHEMICAL ZONING OF FELDSPARS IN LUNAR GRANITOIDS ...

    show that granitoid clasts found in 14303,353 have alkali feldspar (rich in Ba) and plagioclase, but lack a silica polymorph. In addition, the chemical zoning in the feldspars in 14303,353 is very patchy (Fig. 1A,B). The patchy texture is either an exsolution feature of a high temperature feldspar, or intergrowths of two feld-spars during cooling.

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  • Rb‐Sr and 40Ar/39Ar Mineral Ages of Granitoid Intrusives ...

    Pegmatites are composed of plagioclase, K‐feldspar, quartz, white mica, ±biotite, ±garnet, secondary epidote (clinozoisite), and chlorite, as well as accessory phases such as zircon and apatite. Laumontite has been observed as a secondary product within the splayed edges of kinked primary white mica.

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  • Geochemical and Sm–Nd isotopic study of titanite from ...

    abundant quartz, K-feldspar, biotite, hornblende, and accessory titanite and zircon. Mafic enclaves and quartz and quartzo-feldspathic veins are com-mon. To the northwest of the Kolar schist belt, a foliated granodiorite pluton referred to as the Patna granitoid crops out, which contains abun-dant quartz, K-feldspar, plagioclase, biotite, horn-

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  • Igneous phenocrystic origin of K-feldspar megacrysts in ...

    Geosphere (2008) 4 (2): 387-400. Study of four K-feldspar megacrystic granitic plutons and related dikes in the Sierra Nevada composite batholith indicates that the megacrysts are phenocrysts that grew in contact with granitic melt. Growth to megacrystic sizes was due to repeated replenishment of ...

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  • Rb-Sr chronological charac- teristics of Jurassic ...

    components, K-feldspar, biotite, amphibole and whole rock divided from two selected granitoid gravel samples, their Rb-Sr isotopes are measured, which gives two formation ages of granitoids: (428f20) Ma and (430f54) Ma, and means that the Early Paleozoic granitoid intrusive rocks once ex-isted in the Dabie Mountain provenances of Jurassic. The

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  • GENESIS OF THE GRANITOID ROCKS OF THE MECSEK AND .

    3. Myrmekitization, beginning on the K-feldspar-plagioclase border; 4. Albite of perthitic intergrowth and plagioclase being on the limit of K-feldspar with albitic edge. The plagioclase, characterized in 1. was particularly studied, because it is the most frequent one in the rocks examined. .

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  • Petrological and Geochemical Constraints in the Origin and ...

    peralkaline-peraluminous alkali feldspar granites and is composed of K-feldspar, quartz, alkali amphibole, plagioclase, bio-tite and accessory minerals are iron oxides, monozite, zircon, apatite, and annite. This granitoid is associated with acid vol-canic and minor basic volcanic-plutonic and dykes.

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  • LAB 5: COMMON MINERALS IN IGNEOUS ROCKS

    LAB 5: COMMON MINERALS IN IGNEOUS ROCKS Part 1: Minerals in Granitic Rocks Learning Objectives: Students will be able to identify the most common minerals in granitoids Students will be able to identify the most common accessory minerals in granitoids Students will be able to classify granitoid rocks based on mineral content

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  • Home | Department of Geology & Geography | West ia ...

    Her research focused on investigating the origin of potassium feldspar (K-feldspar) megacrysts from a small granitoid intrusion in western Nevada. Kenneth Brown, a teaching assistant professor of geology, said he nominated Pettus because he was impressed with her work and dedication to science.

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  • Petro-Chemical Studies of Granitoid At Rajawaram Area ...

    The granitoid includes quartz, K-feldspar and plagioclase as felsic phases and biotite, hornblende represent ferromagnesian phases, and apatite, sphene, ilmenite occurs as major mineralogical accessory constituents. The geochemical discriminations of major, trace and REE have revealed their affinity to A-type Granitoid (based on the ratio A/CNK ...

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  • Albite-chlorite and talc-chlorite deposits in ...

    The leucogranites are composed of quartz, K-feldspar (orthoclase and minor microcline), less abundant plagioclase (albite-oligoclase) and rare Fe-bearing biotite, which is commonly chloritised. Accessory minerals include apatite, zircon and allanite (Fiori & Grillo, 1991). Monzogranites and granodiorites are medium grained and equigranular.

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  • Geologic units containing Granitic gneiss - mrdata.usgs.gov

    Stony Creek Granite Gneiss plus Narragansett Pier Granite - Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite.

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  • conservancy.umn.edu

    biotite granite, medium-grained, granitoid. Contains K-feldspar, quartz, biotite, and hornblende. granite, medium- to coarse-grained, granitoid. Contains K-feldspar, quartz, biotite, and hornblende. Lake 1800 mv 'Frederick 900 bgr, nalcer Olg 25 Seat gr— gan 35 le Lake 25 63 N (50-60%), K-feldspar, hornblende, biotite, gr, and opaques.

    Authigenic K-feldspar in the Precambrian basement of Ohio ...

    Authigenic K-feldspar of apparent low-temperature origin is widespread in the uppermost part of the two main Precambrian basement terranes of Ohio: the subsurface extension of the Grenville Province of Canada, and the anorogenic granite–rhyolite terrane of the Transcontinental Proterozoic Province of .

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  • LAB 5: COMMON MINERALS IN IGNEOUS ROCKS

    2 Amphiboles are a diverse group of rock-forming inosilicate minerals that are composed of double chain SiO 4 tetrahedra. Amphiboles are hydrous minerals, contain Fe and/or Mg, and most amphiboles contain Ca, Na or K as well.

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  • NCGS OFR 98-2 Flowers 200 - North Carolina

    Granite outcrops- ARolesville main granitoid - medium- to coarse-grained, locally foliated, biotite-muscovite monzogranite; Archers Lodge megacrystic granite - coarse-grained biotite monzogranite with K-feldspar megacrysts up to 3 cm long. Locally intruded by finer grained, nonmegacrystic granitoid.

    Petrology and geochemistry of Aligoodarz granitoid ...

    Petrology and geochemistry of Aligoodarz granitoid, Western Iran: implications. 71 The granodiorite, the main rock type occurring in the area, is medium to coarse-grained . Plagioclase, quartz, biotite and K-feldspar are the major mineral components of the granodiorite (table 1 and Figs. 3c-d).

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  • Field Geology and Petrography of Granitoid rocks in ...

    Three main types of granitoids were identified in the study area viz., older granites, gneissic/foliated granites and younger granites. These granitoid rocks are traversed by dykes, veins and veinlets of felsic and mafic composition. Although these granitoids are similar in mineralogy, they exhibit differences in petrographic characteristics.

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  • Compositional Variations and Abundances of Selected ...

    abundant quartz, K-feldspar, and sodic plagioclase, and are void of hornblende. Lateral gross compositional changes across the en­ tire batholith are superimposed on the recurrent com­ positional variations within individual sequences. A study by Bateman and Dodge (1970) of variation of major chemical constituents showed clearly that K^O

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  • Petrography and petrology granitoid Rocks of Nokeh, NE of ...

    the contact of granitoid rocks with host rocks is resulted to form iron skarn. Skarnization (in general concept) and producing garnet-megnetite-diposide paragenesis and scapolitization in the alkali-feldspar granites and their tuffaceous host rocks. ... K-feldspar, plagioclase and clinopyroxene form of to. Their main minerals include titanite ...

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  • PETROLOGI BATUAN BEKU - PowerPoint PPT Presentation

    Siklus Batuan Distribusi batuan PETROLOGI BATUAN BEKU Batuan beku adalah batuan yang terbentuk akibat membekunya magma pada waktu perjalanannya ke permukaan bumi. – A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow - id: 56baa8-OTA4M

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  • PROTEROZOIC GRANITOID MAGMATISM IN THE SAWATCH .

    New U-Pb zircon geochronology constrains the ages of four Proterozoic granitoid intrusions exposed in the Sawatch Range, central Colorado. Only one intrusion yielded a Paleoproterozoic age. Coarse-grained to K-feldspar megacrystic granite (Henry Mountain granite) exposed along Taylor Canyon 20 km north of Gunnison crystallized at ca. 1700 Ma.

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