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Microstructures of epidote-prehnite bearing damaged granitoids (northern Victoria Land, Antarctica): clues for the interaction between faulting and hydrothermal fluids
Journal of Structural Geology ( IF 2.6 ) Pub Date : 2021-04-20 , DOI: 10.1016/j.jsg.2021.104350
Malatesta Cristina , Crispini Laura , Ildefonse Benoit , Federico Laura , Lisker Frank , Läufer Andreas

Exhumed faults in granitoids along the Lanterman Fault-Rennick Graben Fault system (northern Victoria Land, Antarctica) show superposed ductile to brittle deformation and pervasive hydrothermal fluid-rock interaction. These processes triggered multiple brittle slip events producing crosscutting epidote and prehnite-rich fault veins, ultracataclasites and pseudotachylytes of crushing origin. Combined microstructural and minerochemical investigations on fault damage zones show three types of alteration: (i) albitization of K-feldspar and Ca-plagioclase; (ii) crystallization of prehnite and calcite in veins; (iii) alteration of magmatic phases by secondary hydrous minerals (e.g. chlorite, white mica, epidote and prehnite). The fault experienced various episodes of strain weakening and hardening, due to alteration of minerals and precipitation of epidote and prehnite within ultracataclastic intervals, at decreasing temperature conditions (200 < T°C < 450) and varying CO2 fugacity of the fluids. Cyclic crystallization of epidote/prehnite within the fault cores caused cementation and locking of faults, concentration of deformation at weaker horizons and a progressive broadening of the fault zone. Our results indicate that multiple co-seismic slip and syntectonic fluid flow very likely occurred prior to the Cenozoic brittle reactivation of inherited anisotropies in the northern Victoria Land crust along the Lanterman Fault-Rennick Graben Fault system and underlines its high potential for polyphasicity.



中文翻译:

带有损坏的花岗岩的露甲石-葡萄石的微观结构(南极维多利亚州北部):断层流体与热液之间相互作用的线索

沿Lanterman断层-Rennick Graben断层系统(南极维多利亚州北部)的花岗岩类中的已发掘断层显示出韧性到脆性变形和普遍的热液-岩石相互作用的叠加。这些过程触发了多次脆性滑移事件,产生了横断的附子和富含海泡石的断层脉,超碎屑的超催化裂殖质和假速溶质。对断层破坏带的显微组织和矿物化学综合研究显示出三种类型的变化:(i)钾长石和斜长石钙化。(ii)脉中的葡萄石和方解石结晶;(iii)次生含水矿物(如绿泥石,白云母,山毛榉石和葡萄石)对岩浆相的改变。断层经历了各种应变减弱和硬化的事件,2混浊的液体。断层岩心中埃迪奥德/绿榴石的循环结晶导致断层的胶结和锁定,较弱地层变形的集中以及断层带的逐渐扩大。我们的结果表明,在维多利亚北部陆壳沿Lanterman断层-Rennick Graben断层系统继承的各向异性新生代脆性再活化之前,极有可能发生了多次同震滑动和构造流体流动,并强调了其多相性的高潜力。

更新日期:2021-04-23
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