Neoarchean to Paleoproterozoic high-pressure mafic granulite from the Jiaodong Terrain, North China Craton: Petrology, zircon age determination and geological implications
Neoarchean to Paleoproterozoic high-pressure mafic granulite from the Jiaodong Terrain, North China Craton: Petrology, zircon age determination and geological implications
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DOI：
10.1016/j.gr.2014.07.006
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发表时间：
2015-09
影响因子：
6.1
通讯作者：
Shoujie Liu;B. Jahn;Y. Wan;H. Xie;Shijin Wang;S. Xie;C. Dong;M. Ma;Dunyi Liu
中科院分区：
文献类型：
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作者：
Shoujie Liu;B. Jahn;Y. Wan;H. Xie;Shijin Wang;S. Xie;C. Dong;M. Ma;Dunyi Liu
华北盆地保存了较好的2.5Ga构造-热事件，是研究太古宙-元古宙界线地球热结构和构造转换的理想场所。本文报道了在华北胶东地体中发现的高压镁铁质麻粒岩。镁铁质麻粒岩以石榴子石-单斜辉石-斜方辉石-角闪石片麻岩包体产于晚太古代奥长英云闪长岩-花岗闪长岩（TTG）片麻岩中。确定了典型的石榴石-单斜辉石-斜长石-石英±金红石高压矿物组合。还观察到斜长石+单斜辉石±斜方辉石±角闪石合辉岩包围石榴石（"白色眼"）。利用常规的地质温压测量和拟剖面模拟，确定了一个顺时针的变质P-T轨迹，峰值条件为~17 kbar和~880 ° C。对同一露头中的两个样品进行锆石U-Pb分析（SHRIMP），得到变质年龄为2473 ± 6Ma（MSWD = 0.8）。岩浆核分析结果表明，岩浆年龄为2527 ± 12Ma（MSWD = 1.9）。高压麻粒岩相变质作用对应于华北古元古代早期2.5Ga地壳与2.9Ga地壳的碰撞事件。它也代表了一个新的，但罕见的情况下，俯冲-碰撞构造在太古代-元古代过渡，并提供洞察地球的热结构的变化。
The North China Craton is an ideal place for studying the transition of the Earth's thermal structure and tectonics at the Archean–Proterozoic boundary due to its good preservation of the ~ 2.5 Ga tectono-thermal events. We report the discovery of a high-pressure mafic granulite from the Jiaodong Terrain in the North China Craton. The mafic granulite occurs as garnet–clinopyroxene–orthopyroxene–hornblende gneiss enclaves within a late-Archean trondhjemite–tonalite–granodiorite (TTG) gneiss. Typical high-pressure mineral assemblage of garnet–clinopyroxene–plagioclase–quartz ± rutile has been identified. Plagioclase + clinopyroxene ± orthopyroxene ± hornblende symplectite surrounding garnet (“white eye”) is also observed. Using the conventional geothermobarometry and the pseudosection modeling, a clockwise metamorphic P–T path with the peak conditions at ~ 17 kbar and ~ 880 °C was determined. Zircon U–Pb analyses (SHRIMP) on the overgrowth rim of zircon grains of two samples from the same outcrop yielded a metamorphic age of 2473 ± 6 Ma (MSWD = 0.8). The analyses on magmatic core gave a probable magmatic age of 2527 ± 12 Ma (MSWD = 1.9). The high-pressure granulite facies metamorphism corresponds to a collisional event between the ~ 2.5 Ga crust and ~ 2.9 Ga crust at the dawn of Paleoproterozoic in the North China Craton. It also represents a new but rare case of a subduction–collision tectonics at the Archean–Proterozoic transition and provides insight into the change of the Earth's thermal structure.