南黄海沉积物中自生黄铁矿的形态标型研究

MORPHOLOGICAL FEATURES OF AUTHIGENIC PYRITE FROM SOUTH YELLOW SEA SEDIMENTS

利用1989年采于南黄海的样品，通过实体显微镜、反光显微镜和电子显微镜对自生黄铁矿的集合体形态和晶体形态进行研究，结合前人成果，对现代海底沉积物中自生黄铁矿集合体进行形态分类和成因一形态分类，在此基础上讨论其特征形态的成因及标型意义。研究表明启生黄铁矿集合体形态可以分为聚萄、单莓和细粒3种，其中前二者可作为沉积物中自生黄铁矿和层控或沉积成因矿床黄铁矿集合体形态标型；成因一形态分类将黄铁矿集合作分为两种，即Ⅰ型充填作用为主和Ⅱ型充填、交代作用两种形成方式；所形成的3种集合体形态间可按一定方式演化，其演化特征能够反映形成条件及经历的后期变化；沉积物中矿物形成的地质背景是氧化水体中局部的还原环境，形成层段为表层或次表层，其中Ⅰ型为弱碱－碱性条件下形成，Ⅱ型为弱酸一弱碱性条件下形成；黄铁矿每体特征的形态是早期成岩作用阶段沉积物随机堆积的结果，是生物体或沉积物以五次对称抗拒“石化”的表现形式。

Aggregate and crystal morphology of authigenic pyrite collected in 1989 from the South Yellow Sea were studied with a binocular microscope, reflecting microscope and an electron microscope. The author combined the research results of others in his classification of the authigenic pyrite aggregate of the recent sediments by morphology and morphology-genesis. The genesis-morphology and typomorphic significance of pyrite are discussed. Aggregate morphology of pyrite can be classified into three types, i.e., aggregate framboids, single framboids and tiny grain types.The former two types can be represented by aggregate typomorphic features of authigenic pyrite from sedimellts and sedimentary deposit. According to genesismorphology, pyrite aggregate can be classified into two types, filling predominates in type I, filling and replacement in type II. Evolution of the three types of pyrite aggregate in a certain way can reflect tbe forination condition and deutervariation.The geological background of themineral formation in the sediments is local reducing environment in an oxidized water body. The layer member of formation is surface and subsurface. Type I was formed under weak alkaline-alkaline condition. Type II was formed under weak acid-weak alkaline conditions. Characteristic morphology of pyrite framboids is the result of random accumulation of sediment in the early diagenetic period.