摘要:
北海涠洲岛的现代淡水白云石产于由珊瑚碎屑组成的石灰岩孔洞中,白云石具有完好自形,粒度粗大,经X光粉晶衍射分析,红外光谱分析及折光率、比重、晶体光性等测试,此种白云石的各种数据均与标准的白云石相符。白云石及其海滩岩的氧碳同位素组成均具较高负值,岩石中渗流胶结作用亦较明显,珊瑚碎屑灰岩的14C年龄为2120年左右,故此类白云石为现代淡水渗流成岩作用带产物。经与国内外各类“原生”白云石比较,涠洲岛的现代白云石不具交代特征而为原白云石。
Abstract:
The bioclastic limestone, most of which consist of coral fragment, is sedimented at northwest beach of the Weizhou Island, Guangxi A dolomite was discovered in its intergranular space. The age of bioclastic limestone, determined by C14, is about 2120 ± 90 years. The dolomite formed perhaps later than it. So it ought to belong to modern dolomite. The dolomite possesses variant crystal size, most of which are about 2-0.5mm. The crystal is perfect clear, transparent, and most of them are the aggregate form. The dolomite is characterized by optic monoaxial crystal negative optic character, No=1.678 Ne =1.514. specific gravity-equals 3.1, hardness equals 4. The dolomite was deiinitely testified by staining method, differential thermal analysis, infrared spectrometry and X-ray. According to lower much value of the δ13C , δ13C and seeping diagenetic environment in which the bioclastic limestone exists. we can firmly belive that the dolomite formed under the condition where mixed fresh water in to sea water.
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