Constraining long-term fault activity in the brittle domain through in situ dating of hydrothermal monazite
Constraining long-term fault activity in the brittle domain through in situ dating of hydrothermal monazite
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DOI：
10.1111/ter.12360
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发表时间：
2018-12-01
期刊：
影响因子：
2.4
通讯作者：
Bojar, Hans-Peter
中科院分区：
文献类型：
--
作者：
Bergemann, Christian A.;Gnos, Edwin;Bojar, Hans-Peter
热液裂隙脉型独居石-(Ce)的SIMS Th-Pb测年具有独特的潜力，可以在大的时间范围内测定低级变质脆韧性条件下的多个构造事件。来自东阿尔卑斯山脆性断裂系统的独居石(Ce)使我们能够将其白垩纪活动限制在单晶内，超过20 Ma，记录了所有主要的构造事件。充满流体的裂隙静脉形成于90 Ma前，温度为352+/-19℃，压力为342+/-42 Mpa。这与白垩纪碰撞推覆堆积的区域变质过程中的峰值条件相对应。在84~70 Ma之间，有几个阶段的溶解-再沉淀/重结晶作用记录了断层的活动。相应的流体包裹体显示了229+/-10℃和143+/-20兆帕的条件。这与造山后伸展过程中与走滑运动有关的沉积盆地的形成有关。这些结果支持了东阿尔卑斯山许多大型断裂系统在白垩纪造山期间发育，并在新近纪阿尔卑斯构造运动期间重新活动的假设。
SIMS Th-Pb dating of hydrothermal fissure-vein monazite-(Ce) has the unique potential to date multiple tectonic events under low-grade metamorphic brittle/ductile conditions over large time frames. Monazites-(Ce) from brittle fault systems in the Eastern Alps allow us to constrain their Cretaceous activity over 20 Ma within single crystals, recording all major tectonic events. Eo-Alpine formation of the fluid-filled fissure-veins occurred 90 Ma ago at 352 +/- 19 degrees C and 342 +/- 42 MPa. This corresponds to peak conditions during regional metamorphism of the Cretaceous collisional nappe stacking. Several stages of dissolution-reprecipitation/recrystallization record fault activity between 84 and 70 Ma. Corresponding fluid inclusions indicate conditions of 229 +/- 10 degrees C and 143 +/- 20 MPa. This correlates with the formation of sedimentary basins during post-orogenic extension associated with strike-slip movements. The results strengthen the hypothesis that many large fault systems in the Eastern Alps developed during the Cretaceous orogeny and became reactivated during Neogene Alpine tectonics.