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 M...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.展开更多
The metamorphosed Early Paleoproterozoic granitoids in the Quanji massif,Northwestern China provide constraints for relationship between the Tarim Craton and North China Craton.Among granitoids batholiths,rocks of the...The metamorphosed Early Paleoproterozoic granitoids in the Quanji massif,Northwestern China provide constraints for relationship between the Tarim Craton and North China Craton.Among granitoids batholiths,rocks of the Mohe quartz-diorite show typically adakitic geochemical characteristics,with medium K2O/Na2O ratios(0.56–1.17)and high Sr(519–619 ppm)low Y(9.37–20.40 ppm)and Yb(0.97–1.77 ppm)concentrations.The rocks haveεNd(t)values between+2.4and+4.4 and depleted mantle Nd model ages of 2.43–2.59 Ga.The magmatic zircons have positiveεHf(t)values ranging from+0.40 to+7.60 and depleted mantle Hf model ages of 2.43–2.70 Ga,with major peaks at^2.54 and^2.65 Ga.The geochemical and Nd-Hf isotopic characteristics indicate that the Mohe quartz-dioritic rocks might be formed by partial melting of high-pressure metamorphosed juvenile crustal rocks in post-orogenic extensional regime in the Early Paleoproterozoic.It suggests that important crustal growth occurred in the Quanji massif and the Tarim Craton at^2.4 and 2.5–2.7 Ga.The Quanji massif and Tarim Craton might share a similar crustal evolution history with the North China Craton in the Neoarchean.展开更多
基金supported by the National Science Foundation of ChinaNSFC grants(Grant Nos.41602056,41372075,41172069)+1 种基金the China Postdoctoral Science Foundation(Grant No.2016M590729)the Fundamental Research Funds for National Universities,China University of Geosciences(Wuhan)(Grant No.CUG160846)
文摘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.
基金supported by the National Natural Science Foundation of China(Nos.40972042 and 41172069)Hong Kong RGC(No.HKU704312P)the Fundamental Research Funds for the Central Universities of of Ministry of Education,China
文摘The metamorphosed Early Paleoproterozoic granitoids in the Quanji massif,Northwestern China provide constraints for relationship between the Tarim Craton and North China Craton.Among granitoids batholiths,rocks of the Mohe quartz-diorite show typically adakitic geochemical characteristics,with medium K2O/Na2O ratios(0.56–1.17)and high Sr(519–619 ppm)low Y(9.37–20.40 ppm)and Yb(0.97–1.77 ppm)concentrations.The rocks haveεNd(t)values between+2.4and+4.4 and depleted mantle Nd model ages of 2.43–2.59 Ga.The magmatic zircons have positiveεHf(t)values ranging from+0.40 to+7.60 and depleted mantle Hf model ages of 2.43–2.70 Ga,with major peaks at^2.54 and^2.65 Ga.The geochemical and Nd-Hf isotopic characteristics indicate that the Mohe quartz-dioritic rocks might be formed by partial melting of high-pressure metamorphosed juvenile crustal rocks in post-orogenic extensional regime in the Early Paleoproterozoic.It suggests that important crustal growth occurred in the Quanji massif and the Tarim Craton at^2.4 and 2.5–2.7 Ga.The Quanji massif and Tarim Craton might share a similar crustal evolution history with the North China Craton in the Neoarchean.
