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首页> 外文学位 >Hydrothermal alteration of oceanic basalts from DSDP hole 504B: An electron microscopic study of microstructures, alteration mechanisms, and variations in mineral chemistry.
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Hydrothermal alteration of oceanic basalts from DSDP hole 504B: An electron microscopic study of microstructures, alteration mechanisms, and variations in mineral chemistry.

机译：DSDP孔504B中的海洋玄武岩的水热蚀变：微观结构，蚀变机理和矿物化学变化的电子显微镜研究。

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摘要

Transmission and analytical electron microscopy integrated with conventional electron microprobe analysis, X-ray diffraction, scanning electron microscopy, and optical microscopy were used to investigate hydrothermally altered basalts in the transition and sheeted dike zones, Deep Sea Drilling Project (DSDP) hole 504B, Leg 83. Compositions, microstructures, alteration mechanisms, and paragenetic sequences of secondary minerals in the altered basalts were utilized to infer conditions during hydrothermal alteration.;Phyllosilicates are the most abundant secondary minerals in the altered basalts. Saponite is dominant only in the uppermost level of the transition zone. Chlorite and corrensite are the major phyllosilicates in the transition zone and upper level of the sheeted dike zone, while talc and chlorite are dominant in the lower level of the sheeted dike zone. Corrensite is inferred to be a unique mineral phase rather than a 1:1 mixed-layer chlorite/smectite. The occurrence of mixed-layer phyllosilicates appears to be mainly controlled by kinetic factors. Parageneses and compositions of phyllosilicates strongly depend upon available chemical components from precursor minerals or fluids. The alteration of other phases such as plagioclase and titanomagnetite provides components for formation of phyllosilicates. The degree of alteration in the basalts is mainly controlled by fluid/rock ratios, which in turn are determined by rock permeability.;Alteration of clinopyroxenes gave rise to amphiboles, biopyriboles and a secondary Ca-rich clinopyroxene (magnesian hedenbergite) that formed via dissolution of clinopyroxenes and crystallization of the secondary phases on a submicroscopic scale. Clinopyroxene composition should be used as an indicator of petrogenesis and igneous history for oceanic basalts only with great care. Primary titanomagnetite has been altered by a sequence of processes, including oxidation, exsolution, and hydrothermal alteration, that give rise to end-member magnetite of single magnetic domain size. Magnetization of the sheeted dike basalts is thus contributed from a stable thermoremanent (or chemical) magnetization obtained after (or during) exsolution and modified by chemical remanent magnetization during hydrothermal alteration.
机译：腿部深海钻探项目（DSDP）504B孔的透射和分析电子显微镜与常规电子显微镜分析，X射线衍射，扫描电子显微镜和光学显微镜相结合，用于研究过渡区和片状堤防区中热液蚀变的玄武岩83.改变后的玄武岩中次生矿物的组成，微观结构，蚀变机理和亚生序列被用来推断水热蚀变过程中的条件。硅酸盐是改变后的玄武岩中含量最高的次生矿物。皂石仅在过渡区的最上层占主导地位。亚氯酸盐和堇青石是过渡带和片状堤防区上部的主要页硅酸盐，而滑石和亚氯酸盐在片状堤防区的下部占主导。推测Corrensite是独特的矿物相，而不是1：1的混合层亚氯酸盐/绿土。混合层状页硅酸盐的出现似乎主要受动力学因素控制。页硅酸盐的共生和组成在很大程度上取决于来自前体矿物或流体的可用化学成分。其他相如斜长石和钛磁铁矿的变化提供了形成页硅酸盐的成分。玄武岩的蚀变程度主要受流体/岩石比的控制，而岩石/岩石比又取决于岩石的渗透率。斜向辉石的改变产生了闪石，生物吡咯烷酮和通过溶解而形成的次生富钙斜向辉石（镁铝辉石）环吡咯的合成和次相结晶的亚微观尺度。单斜辉石的组成仅应非常小心地用作海洋玄武岩成岩和火成岩历史的指标。原生钛磁铁矿已通过一系列过程进行了改变，包括氧化，析出和水热蚀变，这些过程产生了单磁畴尺寸的末端成员磁铁矿。因此，片状堤坝玄武岩的磁化是由析出后（或溶出过程中）获得的稳定的热剩磁（或化学）磁化贡献的，并在水热蚀变过程中通过化学剩磁的磁化来改性。

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  • 作者

    Shau, Yen-Hong.;

  • 作者单位

    University of Michigan.;

  • 授予单位 University of Michigan.;
  • 学科 Geology.;Mineralogy.
  • 学位 Ph.D.
  • 年度 1991
  • 页码 296 p.
  • 总页数 296
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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