Post-collisional Ultrapotassic Mafic Magmatism in South Tibet: Products of Partial Melting of Pyroxenite in the Mantle Wedge Induced by Roll-back and Delamination of the Subducted Indian Continental Lithosphere Slab

doi:10.1093/petrology/egv040

CORC > 地质与地球物理研究所 > 中国科学院地质与地球物理研究所 > 中国科学院新生代地质与环境重点实验室

	Post-collisional Ultrapotassic Mafic Magmatism in South Tibet: Products of Partial Melting of Pyroxenite in the Mantle Wedge Induced by Roll-back and Delamination of the Subducted Indian Continental Lithosphere Slab
	Guo, Zhengfu 1; Wilson, Marjorie 2; Zhang, Maoliang 1; Cheng, Zhihui 1; Zhang, Lihong 1
刊名	JOURNAL OF PETROLOGY
	2015-07-01
卷号	56 期号:7 页码:1365-1405
关键词	post-collisional ultrapotassic magmatism Indian continental subduction pyroxenite slab roll-back Lhasa terrane south Tibet
DOI	10.1093/petrology/egv040
文献子类	Article
英文摘要	Post-collisional (25-8 Ma) ultrapotassic mafic magmatic rocks occur to the north of the India-Asia collision zone within the Lhasa terrane of the southern Tibetan Plateau, forming a near 1000 km long semi-continuous igneous belt. They include both extrusive and intrusive facies, although lava flows dominate. To understand their petrogenesis, the mineral chemistry of olivine phenocrysts and xenocrysts and whole-rock major and trace element and Sr-Nd-Pb isotope data are presented for the most primitive mafic magmatic rocks (MgO > 6 wt %) from west to east. The studied samples are characterized by high MgO (6.28-15.75 wt %), K2O (4.76-8.89 wt %), SiO2 (46.44-59.74 wt %), Ba (1368-14076 ppm), Th (69-336 ppm) and Ni (106-527 ppm) contents. Chondrite-normalized rare earth element (REE) patterns show enrichment in light rare earth elements (LREE), flat heavy REE (HREE) patterns and negative Eu anomalies. These REE patterns have a very distinctive inverted 'spoon shape', which appears to be a common characteristic of collision-related ultrapotassic magmas. Primitive mantle-normalized incompatible trace element patterns exhibit strong enrichments in large ion lithophile elements (LILE) relative to high field strength elements (HFSE) and strong negative Ta-Nb-Ti anomalies, which are typical of subduction-related magmas. The ultrapotassic magmatic rocks studied have extremely radiogenic initial Sr isotopic compositions (0.712379-0.737616) and low (Nd-143/Nd-144)(i) (0.511662-0.511984). Combined with their Pb isotope compositions [(Pb-206/Pb-204)(i) = 18.30-18.92; (Pb-207/Pb-204)(i) = 15.65-15.87; (Pb-208/Pb-204)(i) = 39.02-39.76] these data are consistent with the involvement of a subducted continental crustal component in their petrogenesis. The Sr-Nd-Pb isotope compositions exhibit linear trends between depleted mid-ocean ridge basalt (MORB)-source mantle (DMM) and Indian continental crust. The extreme enrichment of the upper mantle below south Tibet is considered to result from the addition of components derived from subducted Indian continental crust to the overlying mantle wedge during northward underthrusting of Indian continental lithosphere beneath the Lhasa terrane since India-Asia collision at similar to 55 Ma. The post-collisional K-rich mafic magmas in south Tibet were generated by partial melting of pyroxenite in a mantle source region that was created by reaction of hydrous fluids and siliceous melts from subducted granulite-eclogite-facies Indian continental crustal rocks with the surrounding peridotitic mantle. A continuous process from slab roll-back, through break-off, to detachment of the slab may have induced partial melting of the pyroxenites. Cessation of the post-collisional ultrapotassic magmatism at similar to 8Ma may be linked to the onset of flat slab subduction beneath southern Tibet and the elimination of the wedge of Tibetan subcontinental lithospheric mantle and underlying asthenosphere; geophysical data indicate that at the present day eclogite-facies Indian continental crust directly underthrusts the crust of the Lhasa terrane with no intervening mantle wedge. The proportion of the Indian continental crustal component in the mantle source of the ultrapotassic mafic magmas decreases eastward, as do the ages and volumes of the magmatic rocks.
WOS研究方向	Geochemistry & Geophysics
语种	英语
WOS记录号	WOS:000361838200005
资助机构	Chinese Academy of Sciences(XDB03010600) ; Chinese Academy of Sciences(XDB03010600) ; National Natural Science Foundation of China (NSFC)(41020124002 ; National Natural Science Foundation of China (NSFC)(41020124002 ; Royal Society of London ; Royal Society of London ; NSFC ; NSFC ; 41130314) ; 41130314) ; Chinese Academy of Sciences(XDB03010600) ; Chinese Academy of Sciences(XDB03010600) ; National Natural Science Foundation of China (NSFC)(41020124002 ; National Natural Science Foundation of China (NSFC)(41020124002 ; Royal Society of London ; Royal Society of London ; NSFC ; NSFC ; 41130314) ; 41130314)
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/62240]
专题	地质与地球物理研究所_中国科学院新生代地质与环境重点实验室
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Cenozo Geol & Environm, Beijing 100029, Peoples R China 2.Univ Leeds, Sch Earth & Environm, Leeds LS2 9JT, W Yorkshire, England
推荐引用方式 GB/T 7714	Guo, Zhengfu,Wilson, Marjorie,Zhang, Maoliang,et al. Post-collisional Ultrapotassic Mafic Magmatism in South Tibet: Products of Partial Melting of Pyroxenite in the Mantle Wedge Induced by Roll-back and Delamination of the Subducted Indian Continental Lithosphere Slab[J]. JOURNAL OF PETROLOGY,2015,56(7):1365-1405.
APA	Guo, Zhengfu,Wilson, Marjorie,Zhang, Maoliang,Cheng, Zhihui,&Zhang, Lihong.(2015).Post-collisional Ultrapotassic Mafic Magmatism in South Tibet: Products of Partial Melting of Pyroxenite in the Mantle Wedge Induced by Roll-back and Delamination of the Subducted Indian Continental Lithosphere Slab.JOURNAL OF PETROLOGY,56(7),1365-1405.
MLA	Guo, Zhengfu,et al."Post-collisional Ultrapotassic Mafic Magmatism in South Tibet: Products of Partial Melting of Pyroxenite in the Mantle Wedge Induced by Roll-back and Delamination of the Subducted Indian Continental Lithosphere Slab".JOURNAL OF PETROLOGY 56.7(2015):1365-1405.