Petrogenesis of Miocene adakitic diorite-porphyrite in middle Gangdese batholith, southern Tibet: Constraints from geochemistry, geochronology and Sr-Nd-Hf isotopes

	Petrogenesis of Miocene adakitic diorite-porphyrite in middle Gangdese batholith, southern Tibet: Constraints from geochemistry, geochronology and Sr-Nd-Hf isotopes
	Chen XiJie 2; Xu ZhiQin ; Meng YuanKu ; He ZhenYu
刊名	ACTA PETROLOGICA SINICA
	2014
卷号	30 期号:8 页码:2253-2268
关键词	Adakitic Miocene Diorite-porphyrite Juvenile lower crust Middle Gangdese belt Southern Tibet
ISSN号	1000-0569
英文摘要	The petrogenesis and geodynamic setting of the Miocene adakitic magmatism in middle Gangdese belt which is closely related to the porphyry copper deposit belt remain controversial. In order to reveal this issue, we investigate the bulk-rock major element, trace element, Sr-Nd isotopes and zircon Hf isotopes of the diorite-porphyrite exposed in the west of Xigaze City to impose some restrictions on the geodynamic setting of Miocene magmatism. The LA-ICP-MS analysis on zircons from two diorite-porphyrites yielded similar ages at 13. 9Ma and 14. 3Ma respectively, and can be considered as representing one of the Mid-Miocene magmatic rock bodies in the southern Gangdese. All samples show an adakitic affinity and medium-K alkaline characterize, and exhibit high SiO, (59. 19% - 63. 66%), high Al2O3 (16. 55% - 17. 16%) with A/CNK values of 0. 91 - 1. 13, high Na2O and low 1(20 contents (K2O = 1. 1 2. 09%; Na2O = 5. 53 -6. 17%) with low 1(20/Na20 ratios (0. 18 similar to 0. 37), high Sr, low Y, Yb, high Sr/Y ratios (85. 2 - 141. 7) and relative high compatible element concentration (Cr =35 x 10(-6) '"-" 104 x 10(6), Ni =29. 2 x 106 48. 3 x 10(-6)). The diorite-porphyxites are characterized by are enriched in large-ion lithophile element (LILE) and Pb, and depleted in high field strength elements (HFSE) and Ba, together with slight enrichment in LREE contents and depletion in HREE contents with slight negative Eu anomalies (0. 85 similar to 0. 94). The Xigaze diorite-porphyrites are heterogeneous in zircon sH, (t) values (- 1. 75 + 7. 35) and Hf isotopic compositions (0. 282714 similar to 0. 282982), yielding younger zircon Hf crustal modal ages of 640 - 1151Ma. The characters of Th-Nb-Zr incompatible element show obviously the affinity of partial melting of subducted ocean crust. However, the Miocene adakitic rocks have lower eNa (t) values (-6. 33 similar to -2. 26) and high initial 87 Sr/gSr ratios (0. 7055 -0. 7076) indicating the input of middle-upper crust or enriched mantle material. Besides, the relative high Mg0 and Me value also demonstrate that these adakitic rocks were likely derived from the melting of garnet-bearing amphibolite in the thickened juvenile arc mafic lower crust. Based on the analyses of petrology, geochemistry and geochronology of the adakitic-porphyrite, we propose that the juvenile lower crust is derived from the melting of the mantle wedge that was metasomatized by slab fluid or sediment during the Neotethyan ocean subduction. During the 20 - 14Ma, the E-W extensional collapse owing to lateral variation of crust thicken gradient in Lhasa terrain may have contributed to partial melting of previous juvenile lower crust and the formation of particular adakitic rocks.
学科主题	火成岩岩石学
WOS关键词	EAST-WEST EXTENSION ; CONTINENTAL-CRUST ; VOLCANIC-ROCKS ; U-PB ; MANTLE WEDGE ; ZIRCON ; SLAB ; MAGMATISM ; COLLISION ; EVOLUTION
WOS研究方向	Geology
语种	中文
出版者	SCIENCE PRESS
WOS记录号	WOS:000340023300010
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/40581]
专题	中国地质科学院地质研究所
作者单位	1.CAGS, Inst Geol, State Key Lab Continental Tecton & Dynam, Beijing, Peoples R China 2.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Chen XiJie,Xu ZhiQin,Meng YuanKu,et al. Petrogenesis of Miocene adakitic diorite-porphyrite in middle Gangdese batholith, southern Tibet: Constraints from geochemistry, geochronology and Sr-Nd-Hf isotopes[J]. ACTA PETROLOGICA SINICA,2014,30(8):2253-2268.
APA	Chen XiJie,Xu ZhiQin,Meng YuanKu,&He ZhenYu.(2014).Petrogenesis of Miocene adakitic diorite-porphyrite in middle Gangdese batholith, southern Tibet: Constraints from geochemistry, geochronology and Sr-Nd-Hf isotopes.ACTA PETROLOGICA SINICA,30(8),2253-2268.
MLA	Chen XiJie,et al."Petrogenesis of Miocene adakitic diorite-porphyrite in middle Gangdese batholith, southern Tibet: Constraints from geochemistry, geochronology and Sr-Nd-Hf isotopes".ACTA PETROLOGICA SINICA 30.8(2014):2253-2268.