Chemical Diagenesis of the Devonian Carbonate Rock in the Fankou Lead -Zinc Mine Area
-
摘要: 阴极发光技术揭示了碳酸盐岩成岩作用的多阶段性。主要成岩作用发生于浅埋条件。这种环境的Ｅｈ、ｐＨ值较低，矿物中含锰，导致弱发光。岩石的碳、氧同位素值偏离了海相环境的值域。根据Ｓｒ/Ｃａ比推算，成岩溶液相当于淡水中加入不足１０%的海水。基于这些研究，作者提出一种新的成岩作用方式—溶实作用，用以解释灰泥沉积物在近地表淡水环境中的固结成岩.Abstract: The multiple - stage diagenesis was revealed by the cathodoluminescence of carbonate rock samples.The minerals pre-cipitated in shallow - burial condition where the primary diagenesis occured are higha in a Mn content with weak lumines-cence, which resulted from the drop of Eh and pH values due to the decomposition of organic substances.With furtherfalling of the Eh and pHvalues, the increase of Fe 2+ contained in the minerals quenched the luminescence.Being in a deep -burialcondition, the pHvalue was controlled by the equilibrium between carbonate minerals and water, so the environmentis alkalescent.The condition is favourable to the formation of M n (Ⅱ ) cation and contrary to Fe (Ⅱ ) cation.As a result,this precipitated minerals have a bright luminousness.The carbon and oxygen isotope compositions of the whole rocks deviated from the range of marine environment butweve close to that of fresh - water diagenetic environment.Diagenetic solution based on the Sr / Ca ratio in the minerals wasanalogous to that of fresh - water mixed with less than 10 % marine - water.This solution made the minerals in lime - mudsediments dissolved and brougt about dissolved - reprecipitatlon a dynamic equilibrium with the increase of saturation.Baced on the studies above, the authors suggested “ dissolved - solidification ” is a new diagenetic pattem of lime - mudsediments solidified in fresh - water by way of dissolved - reprecipitation, which made the new minerals arranged inseparably.
-
Key words:
- diagenesis /
- dissolved - solidification /
- carbonate rock /
- Fankou
-
[1] (1) 赖健清等.凡口铅锌矿区含矿碳酸盐岩沉积相特征及其控矿意义.地质与勘探, 1989, (12): 12～16 。
(2)Nickel E., et al, The present status of cathode luminescenceas a tool in sedimentolog y, Minerals Science and Engineering,1978, 10(2): 73～100.
(3) Frank J.R., Carpenter A.B.and Oglesby T.W., Cathodolu-minescence and composition of calcite cement in the TaumSauk limestone (Upper Cambrian), Southeast Missouri.J.Sediment.Petrol, 1982, 52: 631～638.
(4) Wedepohl K.H., Handbook of Geochemistry, Springer-Ver-lag Berlin, Heidelberg, New York, 1969, 1: 297～319.
(5) 魏菊英等.同位素地球化学.地质出版社, 1988, 115 。
(6) 程伟基.碳同位素与矿物成因.地质地球化学, 1982, (3): 22 。
(7) Churnet H.G., et al, Genetic implications of the trace ele-ment distribution pattern in the upper Knox carbonate rocks,Copper Ridge district, East Tennessee, Sedimentary Geolo-gy, 1981, 30: 173～194. -
点击查看大图
计量
- 文章访问数: 657
- HTML全文浏览量: 76
- PDF下载量: 362
- 被引次数: 0
下载:
