The geological setting of the ultramafic-hosted Logatchev hydrothermal field (14°45′N, Mid-Atlantic Ridge) and its influence on massive sulfide formation
The geological setting of the ultramafic-hosted Logatchev hydrothermal field (14°45′N, Mid-Atlantic Ridge) and its influence on massive sulfide formation
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DOI：
10.1016/j.lithos.2009.02.008
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发表时间：
2009-09
期刊：
影响因子：
3.5
通讯作者：
S. Petersen;K. Kuhn;T. Kuhn;N. Augustin;R. Hékinian;L. Franz;C. Borowski
中科院分区：
文献类型：
--
作者：
S. Petersen;K. Kuhn;T. Kuhn;N. Augustin;R. Hékinian;L. Franz;C. Borowski
洛加切夫热液区（MAR上14°45′N）是少数与超镁铁岩有关的海底热液系统之一。它位于裂谷壁的东部内侧，距离扩张轴7公里，其形成以前与拆离断层和核杂岩形成有关。在不同的勘探，地质取样，浅钻地质测绘揭示了热液活动的结构控制，以及它的位置在泥石流组成的异质超镁铁和镁铁侵入岩。混合的镁铁质/超镁铁质寄主岩石岩性与已发表的喷口流体和气体化学数据一致，显示出与镁铁质和超镁铁质岩石相互作用的特征。块状硫化物的形成比以前认为的更集中，可能仅限于海底的薄单板。洛加切夫热液场显示出许多其他热液系统不寻常的特点。其中之一是所谓的"冒烟的火山口”，即几米宽的海底洼地，其特征是火山口边缘升高，部分由硫化物堆积物组成，但也有丰富的围岩材料。在这些冒烟的陨石坑中，热液直接从陨石坑内的洞中喷出，从厘米到厘米高的小烟囱中喷出，在陨石坑边缘富含铜。根据地质测绘和采样，我们认为，这些吸烟火山口的产品相关的区域和当地的地质环境中的超镁铁质托管，离轴位置丰富的滑坡，以及离轴辉长岩侵入体提供热液对流细胞的热量的过程。
The Logatchev hydrothermal field (14°45′N on the MAR) is one of a few submarine hydrothermal systems associated with ultramafic rocks. It is situated on the eastern inner flank of the rift valley wall, 7 km away from the spreading axis and its formation has previously been linked to detachment faulting and core complex formation. Geological mapping during various ROV dives, geological sampling, and shallow drilling reveal a structural control of hydrothermal activity as well as its location in a debris flow consisting of heterogeneous ultramafic and mafic intrusive rocks. The mixed mafic/ultramafic host rock lithology is in agreement with published vent fluid and gas chemical data showing characteristics for interaction with mafic as well as with ultramafic rocks. Massive sulfide formation is more focused than previously thought and likely limited to a thin veneer at the seafloor. The Logatchev hydrothermal field shows a number of peculiarities that are unusual for most other hydrothermal systems. One of these are so-called ,,smoking craters“, seafloor depressions that are several meters wide, characterized by an elevated crater rim made up partly of sulfide talus but also of abundant wall rock material. At these smoking craters hydrothermal venting occurs directly from holes within the craters and from small, cm to dm high, Cu-rich chimneys occurring at the crater rim. Based on geological mapping and sampling we suggest that these smoking craters are the product of processes related to the regional and local geological setting in an ultramafic-hosted, off-axis location with abundant landslides, as well as off-axis gabbroic intrusions providing the heat for the hydrothermal convection cell.