Late Paleoproterozoic to Early Mesoproterozoic Tangdan Sedimentary Rock-Hosted Strata-bound Copper Deposit, Yunnan Province, Southwest China
Late Paleoproterozoic to Early Mesoproterozoic Tangdan Sedimentary Rock-Hosted Strata-bound Copper Deposit, Yunnan Province, Southwest China
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DOI：
10.2113/econgeo.107.2.357
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发表时间：
2012-03
期刊：
影响因子：
5.8
通讯作者：
Xin-Fu Zhao;Mei‐Fu Zhou;M. Hitzman;Jian-wei Li;M. Bennett;C. Meighan;E. Anderson
中科院分区：
文献类型：
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作者：
Xin-Fu Zhao;Mei‐Fu Zhou;M. Hitzman;Jian-wei Li;M. Bennett;C. Meighan;E. Anderson
滇中-川南康滇地区广泛分布着以沉积岩为容矿介质的层控铜矿。矿床产于古元古代晚期至中元古代早期东川群的弱变质岩石中，在空间上与不整合角砾岩体相关，这些角砾岩体被解释为形成于盐底辟。唐丹存款，在该地区最大的，由层状和不整合矿体主要托管在白云岩紧接在赤铁矿砂岩和粉砂岩和黑色页岩白云岩之上。存款的赋矿岩石显示出复杂的蚀变-矿化共生序列。早期钠化蚀变导致钠长石和铁白云石的生长。后期钾蚀变导致钾长石和局部黑云母在泥质层中沉淀。硫化物矿化在时间和空间上与硅化有关，后者晚于钠化和钾化蚀变。结构表明，硅化作用可能优先影响白云岩中的蒸发岩矿物。铜硫化物形成层理平行浸染、细脉，在较小程度上形成网状构造。铜硫化物以黄铜矿为主，少量辉铜矿和辉铜矿。唐丹存款的深成黄铜矿和硫铁矿的δ 34 S值范围为-12.7至+9.3‰，群集在-3至+5‰之间。这些值表明来源于中元古代海相硫酸盐。白云岩容矿岩石的碳、氧同位素相对均一，δ 13 CV-PDB值为0.2 ~ 1.3‰，δ 18 OV-SNOW值为19.1 ~ 22.4‰。石英硫化物脉中的碳酸盐矿物既有氧同位素值变轻的趋势，也有碳同位素值显著变轻的趋势。轻碳同位素值表明有机碳参与了成矿过程。唐丹的蚀变和矿化可能是通过来自下伏红层序列的氧化盐水与部分或全部石化的白云岩的相互作用而发生的。硫化物沉淀可能是由于氧化还原反应和白云石和硫酸盐溶解导致的成矿流体pH值变化。唐丹存款的蚀变和矿化的风格是类似于在中非铜矿带，特别是在刚果的矿山系列白云岩容矿体观察。
Sedimentary rock-hosted strata-bound copper deposits are widespread in the Kangdian region of the Central Yunnan and southern Sichuan provinces, southwest China. The deposits occur within weakly metamorphosed rocks of the late Paleoproterozoic to early Mesoproterozoic Dongchuan Group and are spatially associated with discordant breccia bodies that are interpreted as having formed from salt diapirs. The Tangdan deposit, the largest in the region, consists of stratiform and discordant orebodies predominantly hosted in dolostones immediately above hematitic sandstones and siltstones and in black shales above the dolostones. Host rocks for the deposit display a complex paragenetic sequence of alteration and mineralization. Early sodic alteration resulted in the growth of both albite and ferroan dolomite. Later potassic alteration resulted in the precipitation of potassium feldspar and locally biotite in argillaceous layers. Sulfide mineralization was temporally and spatially associated with silicification that postdated both sodic and potassic alteration. Textures suggest that silicification may have preferentially affected evaporite minerals in the dolostones. Copper sulfides form bedding-parallel disseminations, veinlets and, to a lesser extent, stockworks. Copper sulfides are dominated by chalcopyrite with lesser bornite and chalcocite. Hypogene chalcopyrite and bornite from the Tangdan deposit have δ34S values that range from −12.7 to +9.3‰ and cluster between −3 to +5‰. The values suggest derivation from Mesoproterozoic marine sulfates. The dolostone host rocks have relatively homogeneous C and O isotope values ranging from 0.2 to 1.3‰ δ13CV-PDB and from 19.1 to 22.4‰ δ18OV-SNOW. Carbonate minerals in quartz sulfide veins display both a trend toward lighter oxygen isotope values and a trend to significantly lighter carbon isotope values. The light carbon isotope values suggest involvement of organic carbon in the mineralizing process. Alteration and mineralization at Tangdan probably occurred via interaction of oxidized saline brines derived from the underlying red-bed sequence with partially to wholly lithified dolostones. Sulfide precipitation was likely due to both redox reactions and mineralizing fluid pH changes resulting from dolomite and sulfate dissolution. The styles of alteration and mineralization at the Tangdan deposit are similar to those observed in the Central African Copperbelt, particularly the dolostone-hosted orebodies in the Mines Series of the Democratic Republic of Congo.