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研究Mg/Ca比对生物成因的碳酸盐矿物种类和形态的影响是研究各种含镁方解石形成机理的关键。本文在Mg/Ca摩尔比分别为1、2、4、6和8的条件下进行了为期55d的硫酸盐还原细菌诱导碳酸盐矿物形成的实验,利用X射线衍射仪和扫描电子显微镜研究了Mg/Ca比对碳酸盐矿物种类和形态的影响。实验结果表明:①Mg/Ca比与矿物的种类之间存在密切的关系。在Mg/Ca摩尔比较低(1和2)时仅形成高镁方解石,在Mg/Ca摩尔比为4时,形成的矿物组合为含镁方解石+高镁方解石,在Mg/Ca摩尔比为6和8时,矿物组合为高镁方解石+单水碳钙石+钙白云石;②Mg/Ca比影响矿物的生长速率。Mg/Ca比越高,晶体生长速率越快;③Mg/Ca比明显影响矿物的形态。随着Mg/Ca比的增大,矿物的形态有如下发展规律:哑铃形→花菜状→光球状→刺球状。这些研究结果将有助于探讨制约含镁碳酸盐矿物种类和形态的机制。
Studying the effect of Mg / Ca ratio on the biogenic genetic types and morphologies of carbonate minerals is the key to studying the formation mechanism of various Mg-bearing calcite. In this paper, the carbonate-rock formation induced by sulfate-reducing bacteria of 55d at Mg / Ca molar ratios of 1, 2, 4, 6 and 8 was carried out respectively. The effects of the carbonate minerals on the formation of carbonate minerals were investigated by X-ray diffraction and scanning electron microscopy Effect of Mg / Ca ratio on carbonate mineral species and morphology. The experimental results show that: ① There is a close relationship between Mg / Ca ratio and mineral types. Only high-Mg calcite was formed at lower Mg / Ca molar ratios (1 and 2), and the mineral combination was Mg-rich calcite + Mg-rich calcite at a Mg / Ca molar ratio of 4, And 8, the mineral assemblages were high-Mg calcite + single-water carnallite + calcium dolomite; ② the Mg / Ca ratio affected the mineral growth rate. The higher the Mg / Ca ratio is, the faster the crystal growth rate is. (3) The Mg / Ca ratio obviously affects the morphology of the minerals. With the increase of Mg / Ca ratio, the morphology of minerals has the following rules of development: dumbbell shape → cauliflower shape → light globular shape → spine globular shape. These findings will help to explore mechanisms that constrain species and morphology of Mg-bearing carbonate minerals.