Wan Bo, Windley Brian F, Xiao Wenjiao, Feng Jianyun, Zhang Ji'en
State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China.
Nat Commun. 2015 Sep 21;6:8344. doi: 10.1038/ncomms9344.
The connection between the North China Craton (NCC) and contiguous cratons is important for the configuration of the Nuna supercontinent. Here we document a new Paleoproterozoic high-pressure (HP) complex dominated by garnet websterite on the northern margin of the NCC. The peak metamorphism of the garnet websterite was after ∼1.90 Ga when it was subducted to eclogite facies at ∼2.4 GPa, then exhumed back to granulite facies at ∼0.9 GPa before ∼1.82 Ga. The rock associations with their structural relationships and geochemical affinities are comparable to those of supra-subduction zone ophiolites, and supported by subduction-related signatures of gabbros and basalts. We propose that a ∼1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northern margin of the NCC. Presence of the coeval Sharyzhalgai complex with comparable HP garnet websterites in the southern Siberian active margin favours juxtaposition against the NCC in the Paleoproterozoic.
华北克拉通（NCC）与相邻克拉通之间的联系对于努纳超大陆的构造至关重要。在此，我们记录了一个新的古元古代高压（HP）杂岩，其位于华北克拉通北缘，以石榴石二辉橄榄岩为主。石榴石二辉橄榄岩的峰期变质作用发生在约1.90 Ga之后，当时它在约2.4 GPa的压力下俯冲到榴辉岩相，然后在约1.82 Ga之前以约0.9 GPa的压力折返至麻粒岩相。其岩石组合及其结构关系和地球化学亲和性与俯冲带之上的蛇绿岩相当，并得到了辉长岩和玄武岩的俯冲相关特征的支持。我们认为，一个约1.90 Ga的大洋板块沿着华北克拉通北缘俯冲到增生杂岩中并折返。同时期的沙雷扎尔盖杂岩在南西伯利亚活动边缘具有类似的高压石榴石二辉橄榄岩，这有利于在古元古代与华北克拉通并列。
