Mantled feldspars and synneusis
نویسنده
چکیده
Synneusis, the drifting together and systematic attachment of crystals in a melt, is involved in three of the known origins for mantled feldspars: (1) overgrowth, (2) exsolution, and (3) filling of skeletal plagioclase. Quartz latite dikes of the Chocolate Mountains, California, contain plagioclase crystals in parallel and twinned synneusis. Sanidine mantles consisting of segments, each crystallographically parallel to the adjacent plagioclase crystal, enclose synneusis tructures. One-feldspar biotite granite of the Golden Horn batholith, Washington, has mantled feldspars with complex, multiple albite mantles formed by synneusis of zoned alkali feldspars followed by subsolidus exsolution. Skeletal plagioclase formed by resorption is filled with orthoclase in two-feldspar biotite granite of the Golden Horn batholith. Synneusis, before and after resorption, produced mantled feldspars with systematic rystal orientations. Wiborgite granite of Finland has anhedral orthoclase enclosed in large numbers of plagioclase crystals. An origin by synneusis is suggested for this texture.
منابع مشابه
بررسی رفتار ژئوشیمیایی سنگکل و شیمیکانیهای فلدسپار و بیوتیت در پهنهی برشی شرق قروه (کردستان)
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