云南省镇雄县羊场磷矿地球化学特征及其沉积环境分析

羊场磷矿是近年来在云南评价确认的沉积大型磷矿床，磷矿体赋存于下寒武统梅树村组碳酸盐岩-泥质碎屑岩沉积中部的一套含磷岩系中，呈层状、似层状展布于羊场背斜两翼，其产状与地层产状基本一致，含矿岩性为含磷白云岩、磷质岩、磷块岩、硅质岩建造。通过分析该矿床矿体特征和梅树村组磷块岩的主微量元素组成，研究了羊场磷矿的地球化学特征及其沉积环境。结果表明，羊场磷矿磷块岩具有富钙（w（CaO）=42.07%~45.01%）、磷（w（P₂O₅）=27.66%~39.25%）和贫硅（w（SiO₂）=8.27%~15.40%）的特征；w（P₂O₅）与w（CaO）呈较好的正相关关系，与w（MgO）呈负相关关系，与w（Al₂O₃）呈较明显的负相关关系。矿石的w（Th）/w（U）值小于1、Pb （亲硫元素）和Sr富集（Pb平均富集系数16.66，Sr平均富集系数1.17）特征表明，羊场磷矿可能是热水沉积成矿与生物成矿双重作用的结果；微量元素特征值反映，羊场磷矿形成于深海到浅海的变化环境，为海相沉积型磷块岩，沉积时水体呈还原环境。

Geochemical characteristics and sedimentary environment of Yangchang phosphorite deposit in Zhenxiong county, Yunnan province

Yangchang phosphorite deposit is a large sedimentary deposit discovered in recent years. Ore bodies occur in the phosphorous sequence in the middle section of carbonate rock-argilaceous detrital sedimentary rock of Lower Cambrian Meishucun formation. They are located at two limbs of Yangchang anticline in layered or layeroid bodies coincided with the strata. Ore is developed in siliceous rock formation and phosphorous dolomite and P-bearing rock. Based on characteristics of the ore bodies and major and micro-element composition of the phosphorite of Meishucun formation are studied the geochemical characteristics and the sedimentary environment. The phosphorite is characterized by enrichment of Ca (w(CaO)=42.07%~45.01%) and P (w(P₂O₅)=27.66%~39.25%) and depletion of Si (w(SiO₂)=8.27%~15.40%. w(P₂O₅) is positively correlated to w(CaO) and negatively to w(MgO) and w(Al₂O₃). w(Th)/w(U)<1, Pb (sulfophilic element) and Sr enrichment (the averaged enrichment coeficient of Pb, 16.66 and Sr 1.17) suggest that the Yangchang P deposit is formed by combination of hot water sedimentation and biological process under reduced water body sedimentary condition at changing environmental from deep sea to shallow sea.