Paleo‐Pacific subduction‐accretion: Evidence from Geochemical and U‐Pb zircon dating of the Nadanhada accretionary complex, NE China
Paleo‐Pacific subduction‐accretion: Evidence from Geochemical and U‐Pb zircon dating of the Nadanhada accretionary complex, NE China
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DOI：
10.1002/2014tc003637
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发表时间：
2014-12
期刊：
影响因子：
4.2
通讯作者：
Jian‐Bo Zhou;Jia-Lin Cao;S. Wilde;Guochun Zhao;Jinjiang Zhang;Bin Wang
中科院分区：
文献类型：
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作者：
Jian‐Bo Zhou;Jia-Lin Cao;S. Wilde;Guochun Zhao;Jinjiang Zhang;Bin Wang
位于欧亚大陆东缘沿着的那丹哈达地体是一个典型的与古太平洋板块俯冲-增生作用有关的增生杂岩。跃进山杂岩是第一期增生杂岩，由Meta碎屑岩和变镁铁-超镁铁岩组成，而绕河杂岩则是该杂岩的主要组成部分，由石灰岩、层状硅质岩和镁铁-超镁铁岩组成，它们以岩石块体的形式嵌入碎屑Meta沉积岩的弱剪切基质中。地球化学数据表明，跃进山变质玄武岩具有正常的洋中脊玄武岩（N-MORB）亲合性，而饶河玄武岩枕状熔岩具有洋岛玄武岩（OIB）亲合性。对饶河杂岩体中辉长岩进行了高分辨离子探针（SHRIMP）U-Pb锆石分析，获得206 Pb/238 U加权平均年龄为216 ± 5 Ma，而侵入杂岩体的两个花岗岩样品获得206 Pb/238 U加权平均年龄为128 ± 2 Ma和129 ± 2 Ma。对饶河杂岩玄武岩枕状熔岩进行激光烧蚀电感耦合等离子体质谱（LA-ICPMS）锆石U-Pb分析，确定其加权平均年龄为167 ± 1 Ma。饶河杂岩中的两个砂岩样品记录了较年轻的一致锆石加权平均年龄，分别为167 ± 17和137 ± 3 Ma。这些新资料支持了绕河杂岩的增生时间为170 ~ 137 Ma，最终侵位时间为137-130 Ma的观点。跃进山杂岩的增生可能发生在210 ~ 180 Ma之间，表明古太平洋板块俯冲开始于晚三叠世至早侏罗世。
The Nadanhada Terrane, located along the eastern margin of Eurasia, contains a typical accretionary complex related to paleo‐Pacific plate subduction‐accretion. The Yuejinshan Complex is the first stage accretion complex that consists of meta‐clastic rocks and metamafic‐ultramafic rocks, whereas the Raohe Complex forms the main parts of the terrane and consists of limestone, bedded chert, and mafic‐ultramafic rocks embedded as olistolith blocks in a weakly sheared matrix of clastic meta‐sedimentary rocks. Geochemical data indicate that the Yuejinshan metabasalts have normal mid‐ocean ridge basalt (N‐MORB) affinity, whereas the Raohe basaltic pillow lavas have an affinity to ocean island basalts (OIB). Sensitive high‐resolution ion microprobe (SHRIMP) U‐Pb zircon analyses of gabbro in the Raohe Complex yield a weighted mean 206Pb/238U zircon age of 216 ± 5 Ma, whereas two samples of granite intruded into the complex yield weighted mean 206Pb/238U zircon ages of 128 ± 2 and 129 ± 2 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS) U‐Pb zircon analyses of basaltic pillow lava in the Raohe Complex define a weighted mean age of 167 ± 1 Ma. Two sandstone samples in the Raohe Complex record younger concordant zircon weighted mean ages of 167 ± 17 and 137 ± 3 Ma. These new data support the view that accretion of the Raohe Complex was between 170 and 137 Ma, and that final emplacement of the Raohe Complex took place at 137–130 Ma. The accretion of the Yuejinshan Complex probably occurred between the 210 and 180 Ma, suggesting that paleo‐Pacific plate subduction was initiated in the Late Triassic to Early Jurassic.