Calcite composition and stable isotope record of ODP Hole 103-637A peridotites

The peridotite recovered from Ocean Drilling Program Hole 637A, Galicia margin, has suffered extensive low-temperature alteration that includes serpentinization, calcite veining, and calcite replacement. This note presents textural and geochemical data on the serpentine and calcite. Such data indicate that the serpentinization, serpentine veining, and calcite veining of the peridotite occurred in several stages late in the history of the peridotite emplacement, probably after the peridotite was emplaced at crustal levels. It is also apparent that some deformational events (evidenced by faulting and brecciation of both serpentine and calcite veins) continued after the main phase of low-temperature alteration. The geochemistry and petrology, structure, and high-temperature alteration of the peridotite are discussed in separate papers in this volume (Evans and Girardeau, 1988, doi:10.2973/odp.proc.sr.103.138.1988; Girardeau et al., 1988, doi:10.2973/odp.proc.sr.103.135.1988; Kimball and Evans, 1988, doi:10.2973/odp.proc.sr.103.140.1988; Agrinier et al., 1988, doi:10.2973/odp.proc.sr.103.136.1988).

从加利西亚边缘海洋钻探计划（Ocean Drilling Program，ODP）637A孔回收的橄榄岩，经历了广泛的低温蚀变作用，包括蛇纹石化、方解石脉形成及方解石交代作用。本简报提供了蛇纹石与方解石的结构及地球化学数据。此类数据表明，该橄榄岩的蛇纹石化、蛇纹石脉形成与方解石脉作用均发生在橄榄岩就位历史的晚期阶段，大概率是在橄榄岩被安置于地壳层次之后。同时可见，部分变形事件（表现为蛇纹石与方解石脉体的断裂与角砾化）也在主要低温蚀变作用阶段结束后持续发生。关于该橄榄岩的地球化学与岩石学特征、构造特征及高温蚀变作用，已在本卷的其他论文中展开讨论（Evans与Girardeau，1988，doi:10.2973/odp.proc.sr.103.138.1988；Girardeau等，1988，doi:10.2973/odp.proc.sr.103.135.1988；Kimball与Evans，1988，doi:10.2973/odp.proc.sr.103.140.1988；Agrinier等，1988，doi:10.2973/odp.proc.sr.103.136.1988）。