Magmagenesis in the ordovician backarc basins of the Northern Qilian;Mountains, China

doi:10.1130/B25269.1

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	Magmagenesis in the ordovician backarc basins of the Northern Qilian;Mountains, China
	Xia, LQ; Xia, ZC; Xu, XY
刊名	GEOLOGICAL SOCIETY OF AMERICA BULLETIN
	2003
卷号	115 期号:12 页码:1510-1522
关键词	backarc lava arc lava petrogeochemistry magmagenesis Northern Qilian Mountains
ISSN号	0016-7606
DOI	10.1130/B25269.1
英文摘要	This paper reports the results of a petrologic and geochemical study of lavas from early Paleozoic backarc basins in the Northern Qilian Mountains in the People's Republic of China. Petrographic and geochemical characteristics of lavas reflect the changing styles of extension: typical basic lavas due to backarc seafloor spreading are found in the north, but to the south, the lava compositions become increasingly similar to arc lavas. Glassy (devitrified now), sparsely phyric basic lavas characterize the regions of seafloor spreading. Felsic lavas and porphyritic basic lavas occur in the southern, island-arc rifting part of the study area. Geochemical compositions distinguish between mature arc rocks (Y < 20 ppm, TiO2 < 0.60 wt%, Th/Yb > 0.60) in the north and rocks formed during backarc spreading (Y > 20 ppm, TiO2 > 1.0 wt%, Th/Yb < 0.30) in the south. These changes reflect the changing processes of melt generation associated with an evolving backarc basin such as the Ordovician backarc basin that is preserved in the Northern Qilian Mountains. The rift axis captured the arc magmatic flux in the early island-arc rifting stage so that the lavas that erupted from this part of the rift cannot be compositionally distinguished from arc lavas. As backarc extension continued and the backarc basin widened, the rift axis moved progressively away from the arc magmatic flux. The distance between the axis of extension and the zone of subarc mantle downwelling was eventually sufficient to allow mantle upwelling to become established under the axis of extension and to generate a mid-ocean ridge-like decompression melting system to support backarc-basin spreading.
学科主题	火成岩岩石学
WOS关键词	MARIANA TROUGH ; MAGMATIC EVOLUTION ; FLOOD BASALTS ; ARC BASINS ; SUBDUCTION ; TECTONICS ; LAVAS ; CONSTRAINTS ; GEOMETRY ; MANTLE
WOS研究方向	Geology
语种	英语
出版者	ASSOC ENGINEERING GEOLOGISTS GEOLOGICAL SOCIETY AMER
WOS记录号	WOS:000187010400005
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/37549]
专题	中国地质调查局西安地质调查中心
作者单位	Xian Inst Geol & Mineral Resources, Minist Land & Resources China, Xian 710054, Peoples R China.
推荐引用方式 GB/T 7714	Xia, LQ,Xia, ZC,Xu, XY. Magmagenesis in the ordovician backarc basins of the Northern Qilian;Mountains, China[J]. GEOLOGICAL SOCIETY OF AMERICA BULLETIN,2003,115(12):1510-1522.
APA	Xia, LQ,Xia, ZC,&Xu, XY.(2003).Magmagenesis in the ordovician backarc basins of the Northern Qilian;Mountains, China.GEOLOGICAL SOCIETY OF AMERICA BULLETIN,115(12),1510-1522.
MLA	Xia, LQ,et al."Magmagenesis in the ordovician backarc basins of the Northern Qilian;Mountains, China".GEOLOGICAL SOCIETY OF AMERICA BULLETIN 115.12(2003):1510-1522.