Paleoproterozoic Nb-enriched meta-gabbros in the Quanji Massif,NW China:Implications for assembly of the Columbia supercontinent  

作　　者：Fan-Xi Liao Neng-Song Chen M.Santosh Qin-Yan Wang Song-Lin Gong Chuan He Hassan Abdelsalam Mustafa 

机构地区：[1]Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China [2]School of Earth Sciences,China University of Geosciences,Wuhan 430074,China [3]International Research Center for Geology and Resources along the Silk Roads,China University of Geosciences,Wuhan 430074,China [4]State Key Lab of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China [5]Centre for Tectonics,Resources and Exploration,Department of Earth Sciences,University of Adelaide,SA 5005,Australia [6]School of Earth Sciences and Resources,China University of Geosciences Beijing,29 Xueyuan Road,Beijing 100083,China [7]School of Earth Sciences,Zhejiang University,Hangzhou,310027,China [8]Three Gorges Geological Hazards Research Center,Ministry of Education,China University of Geosciences,Wuhan 430074,China [9]Faculty of Science,University of Kordofan,EL Obeid,P.O 160,Sudan

出　　处：《Geoscience Frontiers》2018年第2期577-590,共14页地学前缘（英文版）

基　　金：supported by the National Science Foundation of China;NSFC grants(Grant Nos.41602056,41372075,41172069);the China Postdoctoral Science Foundation(Grant No.2016M590729);the Fundamental Research Funds for National Universities,China University of Geosciences(Wuhan)(Grant No.CUG160846)

摘　　要：Diverse models have been proposed for the role of the Tarim Craton within the Paleoproterozoic Columbia supercontinent assembly. Here we report a suite of-1.71 Ga Nb-enriched meta-gabbro lenses in the eastern Quanji Massif, within the Tarim Craton in NW China. The meta-gabbroic rocks have Nb contents of 11.5-16.4 ppm with Nb/La ratios varying from 0.84 to 1.02((Nb/La)_N = 0.81-0.98) and Nb/U ratios from 38.0 to 47.2. They show low SiO_2(45.1-48.5 wt.%) and MgO(5.96-6.81 wt.%) and Mg#(Mg# = Mg/(Mg + Fe) = 43.5-47.7), high FeO^t(13.0-15.7 wt.%) and moderate Ti02(1.70-2.51 wt.%).with tholeiitic affinities. These rocks possess low fractionated REE patterns without obvious Eu anomalies(Eu/Eu~* = 0.87-1.02). Their primitive mantle-normalized elements patterns display significant Zr-Hf troughs, positive Nb anomalies, weak negative Ti and P anomalies, and high contents of Rb and Ba,resembling Nb-enriched basalts generated in arc-related tectonic settings. Their arc-like geochemical signatures together with whole rock εNd(t) values of 0.4-2.1 and corresponding old T_(DM)(2.22-2.37 Ga)as well as(^(143)Nd/^(144)Nd)_t and(^(87)Sr/^(86)Sr)t(t = 1712 Ma) values of 0.5104-0.5105 and 0.7030-0.7058,respectively, suggest that their precursor magma originated from mantle wedge peridotite metasomatised by subduction-derived melts. The results from our study reveal subduction along the eastern periphery of the Tarim Craton and marginal outgrowth continuing to ~1.7 Ga within the Columbia supercontinent.Diverse models have been proposed for the role of the Tarim Craton within the Paleoproterozoic Columbia supercontinent assembly. Here we report a suite of-1.71 Ga Nb-enriched meta-gabbro lenses in the eastern Quanji Massif, within the Tarim Craton in NW China. The meta-gabbroic rocks have Nb contents of 11.5-16.4 ppm with Nb/La ratios varying from 0.84 to 1.02((Nb/La)_N = 0.81-0.98) and Nb/U ratios from 38.0 to 47.2. They show low SiO_2(45.1-48.5 wt.%) and MgO(5.96-6.81 wt.%) and Mg#(Mg# = Mg/(Mg + Fe) = 43.5-47.7), high FeO^t(13.0-15.7 wt.%) and moderate Ti02(1.70-2.51 wt.%).with tholeiitic affinities. These rocks possess low fractionated REE patterns without obvious Eu anomalies(Eu/Eu~* = 0.87-1.02). Their primitive mantle-normalized elements patterns display significant Zr-Hf troughs, positive Nb anomalies, weak negative Ti and P anomalies, and high contents of Rb and Ba,resembling Nb-enriched basalts generated in arc-related tectonic settings. Their arc-like geochemical signatures together with whole rock εNd(t) values of 0.4-2.1 and corresponding old T_(DM)(2.22-2.37 Ga)as well as(^(143)Nd/^(144)Nd)_t and(^(87)Sr/^(86)Sr)t(t = 1712 Ma) values of 0.5104-0.5105 and 0.7030-0.7058,respectively, suggest that their precursor magma originated from mantle wedge peridotite metasomatised by subduction-derived melts. The results from our study reveal subduction along the eastern periphery of the Tarim Craton and marginal outgrowth continuing to ~1.7 Ga within the Columbia supercontinent.

关 键 词：Nb-enriched GABBROS Geochemistry Quanji MASSIF Tarim CRATON Columbia SUPERCONTINENT 

分 类 号：P[天文地球]