Mineralogy and geochemistry of weathered serpentinites in DSDP Leg 84 sediments@en

At Sites 566, 567, and 570 of Leg 84, ophiolitic serpentinite basement was covered by a sequence of serpentinitic mud that was formed by weathering of the serpentinites under sea- or pore-water conditions. Several mineralogical processes were observed: (1) The serpentinitic mud that consists mainly of chrysotile was formed from the lizardite component of the serpentinites by alteration. (2) Slightly trioctahedral smectites containing nonexpandable mica layers, trioctahedral smectites containing nonexpandable chlorite layers, and swelling chlorites were presumably formed from detrital chlorite and/or serpentine. (3) The occurrence of tremolite, chlorite, analcime, and talc can be attributed to reworking of gabbroic ophiolite rocks. (4) Dolomite, aragonite, and Mg-calcite, all authigenic, occur in the serpentinitic mud.在第84航次（Leg 84）的566、567和570站位，蛇绿岩套蛇纹岩基底（ophiolitic serpentinite basement）被一套蛇纹岩质泥所覆盖，该套泥质沉积物由蛇纹岩在海水或孔隙水条件下风化形成。本次研究观测到四类矿物学作用过程： (1) 以纤蛇纹石（chrysotile）为主要组分的蛇纹岩质泥，系由蛇纹岩中的利蛇纹石（lizardite）组分经蚀变作用形成； (2) 含不可膨胀云母层的三八面体蒙脱石（trioctahedral smectites）、含不可膨胀绿泥石（chlorite）层的三八面体蒙脱石以及膨胀绿泥石（swelling chlorites），推测均由碎屑绿泥石和/或蛇纹石（serpentine）生成； (3) 透闪石（tremolite）、绿泥石（chlorite）、方沸石（analcime）及滑石（talc）的产出，可归因于辉长岩质蛇绿岩岩石的再改造作用； (4) 蛇纹岩质泥中产出的白云石（dolomite）、文石（aragonite）与镁方解石（Mg-calcite）均为自生矿物。