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<正> 苏南龙潭组为一套海陆过渡相碎屑岩含煤沉积,某些层段的中、细粒砂岩、粉砂岩及砂质灰岩中常见到形态各异的海绿石,虽丰度不大,却分布广泛,与特定的沉积条件和沉积环境息息相关。长期以来,海绿石被认为是一种典型的海相自生矿物,作为鉴定海相和海陆过渡相地层的标志之一,它在含煤地层中的出现,是分析含煤岩系古地理环境的重要 相似文献
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朱而勤 《山东海洋学院学报》1986,16(2):137-157,171
自生形成物是指形成在沉积物(或沉积岩)堆积场所的化学成因的物质。自生物质既可生成在沉积阶段,也可生成在成岩阶段。从其生成时期看来,本节所讨论的自生物质均系早期成岩阶段形成,它们对于查明所赋存沉积物的成岩环境、特征及演化历史等方面有重要意义。 相似文献
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Generation, morphology, and distribution of authigenic minerals directly reflect sedimentary environment and material sources. Surface sediments were collected from the western Gulf of Thailand during 2011–2012, and 159 samples were analyzed to determine detrital minerals. Authigenic minerals, including siderite, pyrite, and glauconite, are abundant whereas secondary minerals, such as chlorite and limonite, are distributed widely in the study area. Siderite has a maximum content of 19.98 g/kg and appears in three types from nearshore to continental shelf, showing the process of forming-maturity-oxidation. In this process, the Mn O content in siderite decreases, but Fe_2O_3 and Mg O content increase. Colorless or transparent siderite pellets are fresh grains generated within a short time and widely distributed throughout the region; high content appears in coastal area where river inputs are discharged. Translucent cemented double pellets appearing light yellow to red are mature grains; high content is observed in the central shelf. Red-brown opaque granular pellets are oxidized grains,which are concentrated in the eastern gulf. Pyrite is mostly distributed in the central continental shelf with an approximately north–south strip. Pyrite are mainly observed in foraminifera shell and distributed in clayey silt sediments, which is similar to that in the Yangtze River mouth and the Yellow Sea. The pyrite in the gulf is deduced from genetic types associated with sulfate reduction and organic matter decomposition. Majority of glauconite are granular with few laminar. Glauconite is concentrated in the northern and southern parts within the boundary of 9.5° to 10.5°N and is affected by river input diffusion. The distribution of glauconite is closely correlated with that of chlorite and plagioclase, indicating that glauconite is possibly derived from altered products of chlorite and plagioclase. The K_2O content of glauconite is low or absent, indicating its short formation time. 相似文献
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徐州大北望寒武系徐庄组发育不同类型海绿石,为探讨不同类型海绿石的成因,基于海绿石的矿物学、地球化学及沉积环境分析,利用偏光显微镜、X 射线衍射及电子探针等方法对各含海绿石岩层及不同类型海绿石进行系统对比研究查明海绿石的指相意义。结果表明,徐庄组发育颗粒状、碎屑假象状和胶团状三种类型海绿石,其中颗粒状海绿石具有中—高含量钾、高含量铁、砂岩中—高含量铝、石灰岩中低含量铝等特征;碎屑假象状海绿石具有变化大的钾、铁、铝,且保持着其母质形态特征;胶团状海绿石具有高钾、高铁、低铝特点。颗粒状海绿石成因符合颗粒绿化理论,砂岩中海绿石易受环境影响;碎屑假象状海绿石成因符合层状晶格理论及假象替代理论,受到交代和溶蚀作用,因受较强的水动力条件影响成分变化较大;胶团状海绿石是凝胶状海绿石通过胶结作用沉淀,形成于稳定环境中。 相似文献
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