Precipitation of Calcite Veins in Serpentinized Harzburgite at Tianxiu Hydrothermal Field on Carlsberg Ridge(3.67°N),Northwest Indian Ocean:Implications for Fluid Circulation

作     者：Yang Chen Xiqiu Han Yejian Wang Jianggu Lu Yang Chen;Xiqiu Han;Yejian Wang;Jianggu Lu

作者机构：School of Earth SciencesZhejiang UniversityHangzhou 310027China Key Laboratory of Submarine GeosciencesState Oceanic AdministrationSecond Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China 

出 版 物：《Journal of Earth Science》 (地球科学学刊（英文版）)

年 卷 期：2020年第31卷第1期

页      面：91-101页

核心收录：

学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 0708[理学-地球物理学] 0704[理学-天文学] 

基　　金：funded by the National Key Research and Development Program of China(No.2018YFC0309903) the Scientific Research Fund of the Second Institute of Oceanography,MNR(No.QNYC1701) the China Ocean Mineral Resources R&D Association Project(No.DY135-S2-1-02&05) the National Science Foundation of China(No.41976076) 

主　　题：calcite veins serpentinized harzburgite isotopes geochemical models Carlsberg Ridge 

摘      要：Serpentinization and calcite precipitation of mantle peridotites exhumed along detachment faults at the slow-to ultraslow-spreading centers can provide important clues to the hydrothermal alteration *** Tianxiu hydrothermal field is a new-found active and ultramafichosted hydrothermal vent site along the Carlsberg Ridge,Northwest Indian *** types of calcite veins are recognized in serpentinized harzburgite samples collected from the seafloor at the water depth of 3 500 m(3.67°N/63.83°E) and 400 m north of Tianxiu hydrothermal *** veins Ⅰ occur in the fractures that cut through mesh texture in the highly serpentinized harzburgite,while calcite veins Ⅱ precipitate within the mesh texture in the relatively weaker serpentinized *** veins show similar δ13CPDB(+0.54‰ and +0.58‰) but different δ18OPDB(-16.67‰ and +4.46‰) values,suggesting that they were derived from the same carbon source but precipitated at different *** the deep seawater temperature of 2℃as the precipitation temperature of the calcite veins I,the equilibrium δ18OV-SMOW of calcite-precipitating fluid was calculated to be 1.78‰,which is close to the average δ18OV-SMOW value(1.74‰) of vent fluid samples from the ultramafic-hosted hydrothermal systems *** formation temperature of calcite veins Ⅱ is inferred to be approximately 134℃,based on the calculated δ18OV-SMOW *** temperature differences of calcite precipitation probably resulted from the fluid cooling conductively and mixing with seawater along the presumed fractures during slow *** low-temperature calcite postdates the mesh texture,while the high-temperature calcite may precipitate under relatively low water/rock ratios,alkaline and reduced conditions among the mesh texture,which is revealed by the geochemical ***,it is suggested that they both have been influenced by hydrothermal fluids and the sampling site is near the discharge zone of hydrothermal circulati