ESR AGES EVIDENCES OF MOHE OVERTHRUST STRUCTURE STAGE
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摘要: 对出露于漠河逆冲推覆构造根带、中带及峰带等不同构造部位的10个同构造石英脉进行了电子自旋共振(ESR)测年, 结果显示漠河逆冲推覆构造形成于距今118~149 Ma之间, 由此确定漠河逆冲推覆构造主-活动时期为晚侏罗世晚期-早白垩世晚期。漠河逆冲推覆构造与侏罗纪至白垩纪初杭盖-肯特洋的收缩关闭及古太平洋俯冲导致的地块逆冲及地壳加厚与挤出有关, 并造成漠河盆地挤压回返和抬升萎缩。Abstract: The 10 different structure quartz veins and calcite veins from Mohe basin overthrust structure root zone, the central belt and front belt has been dated by electron spin resonance (ESR). ESRS dating results show Mohe basin overthrust structure formed in (149.3±14.0) Ma~(118.7±11.0) Ma, which indicate the main deformation of Mohe overthrust structure was in the Late Jurassic-Early Cretaceous. The structure has great relationship with Jurassic to Early Cretaceous Hang Gai-Kent Ocean closed, ancient land thrusting and crustal thickening caused by ancient Pacific Ocean subduction. Then it led Mohe Basin atrophy of squeezing and lifting.
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Key words:
- Mohe Basin /
- overthrust structrue /
- ESR dating
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表 1 ESR测年样品的地质特征
Table 1. Geological characteristics of ESR dating samples
样号 采样地点 围岩时代及岩性 样品特征 B095-2 兴华沟林场 漠河组长英质糜棱岩 沿糜棱面理产出,糜棱面理产状314°∠9° B096-1 兴华沟林场 漠河组长英质糜棱岩 沿糜棱面理产出,脉体厚23~3 cm,糜棱面理产状320°∠10° B098-1 兴华沟林场 漠河组长英质糜棱岩 与糜棱面理斜交,脉体厚55 cm,糜棱面理产状317°∠19° B098-2 兴华沟林场 漠河组长英质糜棱岩 与糜棱面理斜交,脉体厚18 cm,糜棱面理产状317°∠19° B028-2 北极村东 漠河组长英质糜棱岩 与糜棱面理斜交,脉体厚15~20 cm,糜棱面理产状25°∠20° B009-1 金沟林场 漠河组泥岩、粉砂岩 产于断层泥中,断面产状20°∠25° B009-2 金沟林场 漠河组泥岩、粉砂岩 产于断层泥中,断面产状20°∠26° B004-1 河湾林场 漠河组砂岩 断面上的方解石脉,脉体厚8 cm,断面产状350°∠44° B121-2 枯林山南 加里东期花岗闪长岩 产于断层泥中,石英脉体厚10 cm,断面产状153°∠31° B105-1 古莲河 漠河组泥岩、粉砂岩 产于断层带内,方解石脉厚30 cm,断面产状140°∠70° 表 2 ESR测年结果
Table 2. Results of ESR dating
序号 样号 采样地点 测试样品 顺磁中心浓度/
(10 15自旋·g - 1)铀当量含量/
(μg·g - 1)年龄/Ma 1 B095-2 兴华沟林场 石英脉 0.112 0.150 149.3±14.0 2 B096-1 兴华沟林场 石英脉 0.089 0.150 118.7±11.0 3 B098-1 兴华沟林场 石英脉 0.089 0.150 118.7±11.0 4 B098-2 兴华沟林场 石英脉 0.133 0.150 177.3±17.0 5 B121-2 枯林山南 石英脉 0.141 0.221 127.6±12.0 6 B004-1 河湾林场 方解石脉含微量石英 0.336 0.478 140.6±14.0 7 B009-1 金沟林场 方解石脉含微量石英 0.186 0.257 144.7±14.3 8 B009-2 金沟林场 方解石脉含微量石英 0.104 0.150 138.7±13.0 9 B105-1 古莲河 方解石脉含微量石英 1.476 2.139 138.0±13.0 10 B028-2 北极村东 石英脉 0.112 0.150 149.3±14.0 -
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