内蒙古东南部晚古生代裂谷区花岗质岩石锆石SHRIMP U-Pb定年及其地质意义
Zircon SHRIMP U-Pb dating of granitoids in a Late Paleozoic rift area, southeastern Inner Mongolia, and its implications
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摘要: 提要：该区花岗质岩石主要岩性为石英闪长岩、英云闪长岩、花岗闪长岩、二长花岗岩和正长花岗岩。通过对石英闪长岩锆石SHRIMP U-Pb定年[1]，所获得年龄为（313±5）Ma～（323±4）Ma，属于晚石炭世侵入体；前进场和达青二长花岗岩各单元岩体均侵入了该区早二叠世寿山沟组海陆交互相碎屑沉积岩，侵入接触关系明确，红柱石角岩发育。测得前进场岩体和达青岩体锆石SHRIMP U-Pb年龄分别为（280.8±3.6）Ma和（281.5±0.5）Ma，说明岩体形成于早二叠世晚期；乌兰陶勒盖正长花岗岩岩体获得了259 Ma、羊角林高勒二长花岗岩为246～216 Ma的U-Pb同位素年龄，说明在晚二叠世—三叠世又有一次侵入高峰。石炭—二叠纪裂谷发育时期，部分跨入三叠纪，先后有3次侵入高峰，即晚石炭世的石英闪长岩、早二叠世的英云闪长岩—二长花岗岩、晚二叠世—三叠纪的二长花岗岩-正长花岗岩。
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关键词:
- 花岗质岩石 /
- 锆石SHRIMP U-Pb定年 /
- 晚古生代裂谷区 /
- 内蒙古东南部
Abstract: Abstract：The major granitoid rocks in a Late Paleozoic rift area, southeastern Inner Mongolia, are quartz diorite, tonalite, granodiorite, monzogranite and syenogranite. SHRIMP zircon U-Pb dating of the quartz diorite yielded ages of 313±5-323±4 Ma, indicating a Late Carboniferous age. Both the Qianjinchang and Daqên monzogranite plutons are intruded into paralic clastic rocks of the Permian Shoushangou Formation (P1ss) with a clear intrusive contact relationship. The SHRIMP U-Pb zircon ages for the two plutons are 280.8±3.6 Ma and 281.5±0.5 Ma respectively, indicating a late Early Permian age. The Ulan Tolgoi syenogranite has an age of 259 Ma and the Yangjiaolin Gol monzogranite has U-Pb ages of 246-216 Ma, suggesting that another intrusion peak occurred during the Late Permian-Triassic. There were three intrusion peaks in the Carboniferous-Permian (partly Triassic) rifting period, i.e. the Late Carboniferous quartz diorite intrusion peak, Early Permian tonalite-monzogranite intrusion peak and Late Permian monzogranite-syenogranite intrusion peak. -
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