| 海南岛南部一地全新世生物屑灰岩的成岩作用 |
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| 引用本文： | 沙庆安.海南岛南部一地全新世生物屑灰岩的成岩作用[J].地质科学,1977,12(2):172-178. |
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| 作者姓名： | 沙庆安 |
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| 摘 要： | 引言研究标本由我所碳酸岩组采自海南岛南部的一个地点。在那里,沿岸覆于原生礁之上有一套由生物骨屑(主要是珊瑚)砂、砾所组成的、已被碳酸盐胶结的岩层,其厚约3米左右(图1)。此岩层一般称为“次生礁”。它是由当时原生礁盘上的生物被海浪击碎并冲带到礁盘上沉积下来的,这里属连岛砂堤沉积,它现已完全暴露地表。次生礁在它抬升过程中,下部被海蚀形成海蚀龛。
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DIAGENESIS OF HOLOCENE BIOCALCIRUDITE IN THE SOUTHERN PART OF HAINAN ISLAND, GUANGDONG |
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| Sha Qingan.DIAGENESIS OF HOLOCENE BIOCALCIRUDITE IN THE SOUTHERN PART OF HAINAN ISLAND, GUANGDONG[J].Chinese Journal of Geology,1977,12(2):172-178. |
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| Authors: | Sha Qingan |
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| Abstract: | The samples studied were collected from the "secondary reef" overlying primary reef in the southern part of Hainan Island. This "secondary reef" consists mainly of skeletal pebbles and sands cemented by carbonate, about 3m thick. The cementation, neomorphism of skeletal grains and dissolution of the rocks are discussed.Two types of cements can be distinguished: (1) The micrite calcite (crypto-crystlline calcite matrix) mixed with fine bioclastics and terrigenous silt occurs in the lower part of the outcrops. The micrite may be altered from aragojiite muds and high-Mg calcite muds, that filled mechanically in the interstices between grains and chambers of organisms under sea waters. (2) The granular and pillar calcite mosaic (sparry calcite) occurs in the upper part of the outcrops- They precipitated in the vadose zone affected by meteoric water.The aragonite skeletons have mostly inverted in to granular calcite, and the inversion is stronger in the upper part of the outcrops than the lower. This shows that the factor of inversion is essentially affected by environmental changes rather than by the depositional time order. The Mg++ within the high-Mg calcite skeleton’s hasi-mostly lost, and the aragonate altertion is slower than the high-Mg calcite. It can be concluded that this neomorphism occurred under the conditions of normal temperature and pressure. The sequence of susceptibility to alteration of various aragonite skeletons is that gastropods and pelecypods are more susceptible than the corals.The dissolution of aragonite skeletal grains is easier than that of high-Mg calcite both in vadose and phreatic zones. The dissolved voids are common in rocks, but some voids have subsequently been filled with granular calcite, so that many molds were formed. |
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