荆襄磷矿优质磷块岩的形成与藻类的关系

中国荆襄磷矿共有4个含矿层,自下而上分别为ph₁、ph₂、ph₃和ph₄,ph₁是该区主要由磷质叠层石构成的最高品位的磷块岩。它不仅具有特征的化学成分和丰富的藻类化石,而巨其中的磷质主要富集在叠层石柱体、富藻层和藻化石中,磷的含量分别达到36.90%、38.10%和40.02%,而在叠层石柱间和富屑层中仅为3.22%和1.32%.这些资料表明,高品位磷块岩的凝聚和富集,主要是由古代生活在清水潮坪中的藻类生物代谢活动造成的生物和生物化学作用所致。

THE FORMATION OF HIGH-GRADE PHOSPHORITE RELATIED TO ANCIENT ALGAE IN JING-XIANG AREA,HUBEI PROVINCE

he Jing-Xiang phosphorite deposites is one of the major phosphorites in China. Located in the west of Hubei province, it was formad during the doushantuo period (700-650Ma) of late Sinian. It not only contains various biogenetic structures, e.g. phosphatic stromatolites, oncolites and algal pellets, but preserves abundant algal fossils.According to the occurring sequence of ore-beds, the Jing-clang phosphorite deposite can be divided into four ore-beds, ph1, ph2, ph3 and ph4 in ascending order. The ph1 ore-bed, with the highest-grade phosphorite in this region region, consists of various phosphatic stromatolites whose laminae show an evident evolution from Flat, through Convex, and to Conical shapes in ascending order. Chemical analysis for the phosphatic stromatolites shows that the content of PRO,is very different in different parts of phi ore-bed' For example, it can be enriched to36.90% in the columns and 38'10% in the alga-rich landnae, and the highest content40'02% in algal fossils, but ohly to 3'22% in the spaces among columns and l'32%in the clast-rich ldrinae' In addition, the organo-chemical materials still show that thecontent of organo-carbon in the phosphatic stromatolites is much higher than that inthe surrounding rocks and the biomarker is characterized by n-alkances (n C,, n C,v)Hopenes and streranes'In addition to the ph, ore-bed, anumber of alga-fossils have been found inphosphorite elastic in ph,-- ph. ore-bed, too which shows that the formation ofprimany phosphorites is related to ancient algae'In general the accumulation and enriclunent of the high-grade phosphorite aremathly related to the biological and biochendcal processes as a result of growth andmetabolic activity of ancient algae'