华南下寒武统昆阳和织金含磷岩系成磷机制对比研究  

A comparative study on formation mechanisms of phosphorites of the Lower Cambrian P-bearing rock series in the Zhijin and Kunyang deposits in South China

作　　者：晁江琴 张迪 赖志滨 杨海英[2] CHAO Jiang-qin;ZHANG Di;LAI Zhi-bin;YANG Hai-ying(School of Geographical Sciences and Tourism,Zhaotong University,Zhaotong Yunnan 657000,China;School of Earth Sciences,Yunnan University,Kuming 650500,China)

机构地区：[1]昭通学院地理科学与旅游学院,云南昭通657000 [2]云南大学地球科学学院,昆明650500

出　　处：《矿物岩石地球化学通报》2024年第3期502-520,共19页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(42202089,92062221);云南省科技厅科技计划项目(202101BA070001-145);云南省教育厅科学研究基金资助项目(2022J0976)。

摘　　要：早寒武世发生了全球大规模的成磷事件,在华南地区形成了以贵州织金和云南昆阳为代表的大型磷矿床。为探讨两地磷块岩成磷作用的异同及其制约因素,本研究对织金新华和昆阳王家湾含磷岩系开展了矿物学和地球化学分析。结果表明,昆阳地区的胶磷矿和磷灰石矿物粒径大于织金地区的,暗示昆阳地区具有更浅的海水深度、更强的水动力条件;两地含磷岩系的P_(2)O_(5)与Al_(2)O_(3)、SiO_(2)、Zr/Hf及Sr均具有显著-不显著的正相关关系,暗示陆源风化物质的输入提供了早寒武世海洋磷的来源;氧化还原敏感元素(V、Ni、Cr、Mo、U)以及Ce/Ce*在织金含磷岩系中变化范围大于昆阳含磷岩系,指示织金地区海水的氧化还原条件波动更大;两地含磷岩系中的稀土元素均呈现“帽型”配分特征,具有负Ce异常、显著正Y异常、负-弱正Eu异常,表明成磷过程受生物/有机质和铁锰氧化物控制。本研究认为织金新华和昆阳王家湾含磷岩系在成磷机制上可类比性高,岩相古地理和氧化还原条件的差异是导致两地含磷岩系差异的重要原因。Large-scale phosphogenesis occurred globally during the early Cambrian Epoch,meanwhile large phosphorite deposits,represented by the Zhijin deposit in Guizhou and Kunyang deposit in Yunnan,were formed in South China.In order to explore similarities and differences of mineralization mechanisms and constraining factors of the Zhijin and Kunyang deposits,mineralogical and geochemical analyses of P-bearing rock series in the Xinhua oreblock of the Zhijin deposit and the Wangjiawan oreblock of the Kunyang deposit have been carried out in this paper.The results show that grain sizes of both collophane and apatite minerals in the P-bearing rock series of the Kunyang deposit are significantly larger than those of the Zhijin deposit,implying that the P-bearing rock series in the Kunyang area were formed in a relatively shallow seawater with strong hydrodynamic condition;There are significantly-weakly positive relationships between P_(2)O_(5)and Al_(2)O_(3),SiO_(2),Zr/Hf and Sr contents in P-bearing rock series of both Zhijin and Kunyang deposits,indicating that terrestrial weathering input provided the material sources of phosphorous in Cambrian Ocean;The variation ranges of redox-sensitive elements(V,Ni,Cr,Mo,U)contents and Ce/Ce*values of P-bearing rock series in the Zhijin area are larger than those of P-bearing rock series in the Kunyang area,showing that there was a relative strongly fluctuated oxic-suboxic deposition condition in the zhijin area comparing to the Kunyang area;The P-bearing rock series of the Zhijin and Kunyang deposits have"hat-shaped"PAAS-normalized REE distribution patterns,with characteristics of negative Ce anomalies,significantly positive Y anomalies,and negative or weak-positive Eu anomalies Eu anomalies,indicating that their phosphogenetic processes were controlled by biological/organic matters and/or Fe-Mn(oxyhydr)oxides.It is concluded that the formation mechanisms of P-bearing rock series in the Zhijin and Kunyang deposits are highly similar,but differences of lithofacies paleogeographical

关 键 词：华南 早寒武世 磷块岩 成矿机制 织金新华磷矿 昆阳王家湾磷矿 

分 类 号：P618.7[天文地球—矿床学]