Slab-derived adakites and subslab asthenosphere-derived OIB-type rocks at 156 ± 2 Ma from the north of Gerze, central Tibet: Records of the Bangong–Nujiang oceanic ridge subduction during the Late Jurassic
Slab-derived adakites and subslab asthenosphere-derived OIB-type rocks at 156 ± 2 Ma from the north of Gerze, central Tibet: Records of the Bangong–Nujiang oceanic ridge subduction during the Late Jurassic
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西藏中部革则以北156±2Ma板片埃达克岩和板下软流圈OIB型岩石：晚侏罗世班公怒江洋脊俯冲记录
DOI：
10.1016/j.lithos.2016.07.029
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发表时间：
2016-10
期刊：
影响因子：
3.5
通讯作者：
Yuan-Chuan Zheng
中科院分区：
文献类型：
--
作者：
Shi-Min Li;Di-Cheng Zhu;Qing Wang;Zhidan Zhao;Liang-Liang Zhang;Sheng-Ao Liu;Qing-Song Chang;Ying-Huai Lu;Jin-Gen Dai;Yuan-Chuan Zheng
本文报道了青藏高原中部格尔泽以北雷纳措英安岩和多布扎镁铁质岩（辉绿岩和玄武岩）的锆石U-Pb年龄和Hf同位素、全岩主量元素和微量元素、全岩Sr-Nd-Hf同位素数据。这些数据揭示了板状埃达克岩（154 ± 1 Ma）和板下软流圈OIB型（洋岛玄武岩）镁铁质岩（157.6 ± 1.4 Ma）的独特岩石组合。中钾钙碱性英安岩（SiO2= 66-69 wt.%）来自雷纳Tso的样品富集Sr（520-1083 ppm），贫重稀土元素（HREE）和Y（9.8-10.8 ppm），类似埃达克岩。这些埃达克质英安岩具有较低的全岩初始87 Sr/86 Sr比值（0.7043-0.7046）、正εNd（t）（+ 1.0 ~+ 3.4）、εHf（t）（+ 6.4 ~+ 7.0）和锆石εHf（t）（+ 1.9 ~+ 7.6）值，表明其成因为大洋板片（地壳和沉积物）。考虑到低的Mg#（32-53）和（La/Yb）N（19-23），埃达克质英安岩很可能是由浅部俯冲板片的部分熔融以及随后在岩浆上升过程中与薄地幔楔中的橄榄岩相互作用形成的。辉绿岩和玄武岩（SiO2= 49-53重量%）显示出富含高场强元素（HFSE）的碱特征（例如，Zr = 213-285 ppm），并显示出正的Nb-Ta-Ti异常，其地球化学性质与OIB相当。这些样品的全岩εNd（t）值为+3.3至+3.7，εHf（t）值为+4.7至+5.7，锆石εHf（t）值为负至正，为− 1.5至+5.2。这些OIB型镁铁质样品被解释为低程度的减压熔融的产物上涌的板下软流圈与一个较小的贡献，从大陆岩石圈地幔（SCLM）。我们的新数据表明，存在着一个独特的岩石组合，同时代板片衍生埃达克岩和板下软流圈衍生OIB型岩石。这种组合沿着班公湖-怒江缝合带（BNSZ）更北的正弧岩，记录了特提斯班公湖-怒江洋在约2000年向北的脊俯冲。156 ± 2 Ma。
This paper reports zircon U–Pb age and Hf isotope, whole-rock major and trace element, and whole-rock Sr–Nd–Hf isotope data of the dacites from Rena Tso and mafic rocks (diabases and basalts) from Duobuza, north of Gerze, central Tibet. These data reveal the presence of a distinct rock association of slab-derived adakites (154 ± 1 Ma) and subslab asthenosphere-derived OIB-type (oceanic island basalt) mafic rocks (157.6 ± 1.4 Ma). The medium-K calc-alkaline dacites (SiO2= 66–69 wt.%) from Rena Tso are enriched in Sr (520–1083 ppm) and depleted in heavy rare earth elements (HREEs) and Y (9.8–10.8 ppm), resembling adakites. These adakitic dacites have low whole-rock initial87Sr/86Sr ratios of 0.7043–0.7046, positive εNd(t) (+ 1.0 to + 3.4), εHf(t) (+ 6.4 to + 7.0), and zircon εHf(t) (+ 1.9 to + 7.6) values, indicating an oceanic slab origin (crust and sediment). Considering the low Mg# (32–53) and (La/Yb)N(19–23), the adakitic dacites are most likely derived from the partial melting of the subducting slab at shallow depths and the subsequent interaction with peridotite in a thin mantle wedge during magma ascent. The diabases and basalts (SiO2= 49–53 wt.%) from Duobuza show an alkali signature with enrichment of high field strength elements (HFSEs) (e.g., Zr = 213–285 ppm) and exhibit positive Nb–Ta–Ti anomalies that are geochemically comparable to those of OIB. These samples show positive whole-rock εNd(t) values of + 3.3 to + 3.7, εHf(t) values of + 4.7 to + 5.7, and negative to positive zircon εHf(t) values of − 1.5 to + 5.2. These OIB-type mafic samples are interpreted as the products of low-degree decompression melting of the upwelling subslab asthenosphere with a minor contribution from the sub-continental lithospheric mantle (SCLM). Our new data indicate the presence of a distinct rock association of coeval slab-derived adakites and subslab asthenosphere-derived OIB-type rocks. Such an association along with the normal arc rocks further to the north of the Bangong-Nujiang suture zones (BNSZ) records the northward ridge subduction of the Tethyan Bangong-Nujiang Ocean at ca. 156 ± 2 Ma.
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影响因子：
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影响因子：
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影响因子：
6.1
作者：
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