气候变化领域集成服务门户(CCPortal): Petrology and U–Pb zircon age of the Variscan porphyroclastic Rand Granite at the southeastern margin of the Central Schwarzwald Gneiss Complex (Germany)

CCPortal

DOI	10.1007/s00531-019-01738-2
	Petrology and U–Pb zircon age of the Variscan porphyroclastic Rand Granite at the southeastern margin of the Central Schwarzwald Gneiss Complex (Germany)
	Altherr R.; Hanel M.; Schwarz W.H.; Wimmenauer W.
发表日期	2019
ISSN	14373254
起始页码	1879
结束页码	1895
卷号	108 期号:6
英文摘要	The Variscan Rand Granite as defined in this paper is a deformed I-type biotite granite that intruded along the southern-to-southeastern margin of the Central Schwarzwald Gneiss Complex. Former K-feldspar megacrysts (now porphyroclasts) of this K–Mg-rich alkali-calcic granite frequently show zonal crystallographic arrangement of mineral inclusions and are enclosed in a matrix of plagioclase, K-feldspar, quartz, biotite, apatite, zircon, and magnetite. Minor sphene and allanite are mostly altered. K-feldspar is orthoclase with perthitic exsolutions. Myrmekite is common and typically replaces marginal K-feldspar. Both feldspars show cataclastic and incipient ductile deformation that took place within the stability field of biotite (≥ 400 °C) as proven by grey varieties of Rand Granite with stable biotite. At most places, however, the Rand Granite shows a reddish colour, caused by late-stage chloritization of biotite and formation of hematite within K-feldspar. Furthermore, plagioclase became partially altered to sericite. This hydrothermal alteration took place at temperatures below the stability of biotite (< 400 °C). In situ ion probe U–Pb dating on zircon gave a concordant age of 330.9 ± 4.8 Ma (2σ), interpreted as the intrusion age of the Rand Granite. A large number of younger concordant to slightly discordant zircon ages between 309 and 90 Ma are interpreted to be due to episodic Pb loss during hydrothermal alteration. The Rand Granite apparently does not contain zircon domains older than the intrusion age and, furthermore, shows relatively high Zr contents (247–358 µg/g). These characteristics suggest high magma temperatures of at least 850–900 °C. The granitic magma most probably resulted from remelting of K-rich mafic to intermediate rocks in the middle crust at H2O-undersaturated conditions. Low Sr/Y ratios suggest a garnet-free residuum, which is only possible at pressures below ~ 0.9 GPa. © 2019, Geologische Vereinigung e.V. (GV).
英文关键词	Badenweiler–Lenzkirch Zone; Rand Granite; Schwarzwald (Germany); U–Pb dating; Variscan orogeny; Zircon thermometry
语种	英语
scopus关键词	ductile deformation; formation mechanism; granite; Hercynian orogeny; I-type rock; igneous geochemistry; petrology; porphyry; thermometry; uranium-lead dating; zircon; Baden-Wurttemberg; Black Forest; Germany
来源期刊	International Journal of Earth Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/147801
作者单位	Institut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld 234-236, Heidelberg, 69120, Germany; Klaus-Tschira-Labor für Kosmochemie, Universität Heidelberg, Im Neuenheimer Feld 234-236, Heidelberg, 69120, Germany; Institut für Geo- und Umweltnaturwissenschaften, Mineralogie und Petrologie, Universität Freiburg, Albertstr. 23b, Freiburg im Breisgau, 79104, Germany
推荐引用方式 GB/T 7714	Altherr R.,Hanel M.,Schwarz W.H.,等. Petrology and U–Pb zircon age of the Variscan porphyroclastic Rand Granite at the southeastern margin of the Central Schwarzwald Gneiss Complex (Germany)[J],2019,108(6).
APA	Altherr R.,Hanel M.,Schwarz W.H.,&Wimmenauer W..(2019).Petrology and U–Pb zircon age of the Variscan porphyroclastic Rand Granite at the southeastern margin of the Central Schwarzwald Gneiss Complex (Germany).International Journal of Earth Sciences,108(6).
MLA	Altherr R.,et al."Petrology and U–Pb zircon age of the Variscan porphyroclastic Rand Granite at the southeastern margin of the Central Schwarzwald Gneiss Complex (Germany)".International Journal of Earth Sciences 108.6(2019).