滇西阿面根铅锌矿床成因研究——硫、铅同位素和闪锌矿微量元素证据

保山地块南部的芦子园地区是我国西南重要的铁铜铅锌多金属矿集区之一, 阿面根铅锌矿床是该区近年来新发现的铅锌矿床, 但目前研究程度低, 成矿物质来源、矿床成因不明。本文在详细的野外地质调查和显微观察基础上, 通过阿面根矿床的金属硫化物硫同位素、铅同位素探讨矿质来源, 利用闪锌矿微量元素特征判定矿床成因。结果显示, 阿面根矿床硫化物的δ34SV-CDT值(9.44‰~12.16‰)介于壳源花岗岩硫与围岩地层同期海水硫之间, 显示出二者混合特征; 铅主要来自上地壳; 闪锌矿以富集Fe、Mn、Co、Cu、Cd而贫Ga、Ge、As、Sn、Cr、Ni为特征, 其中Fe、Cd、Mn、Co、Ag、Sb、Ga主要以类质同象形式产出, Cu则以类质同象和矿物包裹体的形式同时进入闪锌矿晶格中, 可能存在Zn2+?Fe2+、Zn2+?Cd2+、2Zn2+?Ag++Sb3+等方式的替代关系; 闪锌矿微量元素组成特征与VMS型、MVT型、矽卡岩型和浅成低温热液型矿床中的闪锌矿明显不同, 其Cd/Fe(0.02~0.04, 均值0.03)、Co/Ni(15~1 019, 均值1 275)和Ga/In(0.11~1.10, 均值0.31)比值特征和较低的Ge元素含量均表明闪锌矿形成与岩浆热液关系密切。综上证据, 本文认为阿面根矿床的成矿物质主要来源于深部隐伏中酸性侵入岩, 有少量地层围岩物质加入。结合矿床地质特征, 认为阿面根矿床属于岩浆热液充填交代型铅锌矿床。

Origins and Geochemical Signatures of the Amiangen Pb-Zn Deposit in Western Yunnan Province: Insights from Sulfur and Lead Isotopic Analysis of Sulfides and Trace Element Profiling of Sphalerites

The Luziyuan region, situated in the southern sector of the Baoshan Block, serves as a significant locus of iron, copper, lead, and zinc polymetallic ore concentration in southwestern China. Recently discovered within this vicinity is the Amiangen Pb–Zn deposit. Despite its newfound status, the deposit has been subject to limited scholarly inquiry, leaving questions about the origin of the ore-forming materials and the genesis of the deposit unresolved. This study employed meticulous geological field survey and microscopic characterizations to analyze the sulfur and lead isotopic compositions, as well as the LA-ICP-MS trace element profiles, of metal sulfides present in the metallogenic stage of the Amiangen deposit. These data were then compared with trace elements of sphalerite from disparate deposit types to elucidate the mineral''s source and genesis. The δ34SV-CDT isotopic ratio of sulfides in the Amiangen deposit, ranging from 9.44‰ to 12.16‰, exceeds that of sulfides associated with magmatic processes but is marginally lower than that of surrounding seawater stratigraphy. These observations suggest the assimilation of both magmatic and stratigraphic sulfur. The primary Pb source is the upper crust. Sphalerite in the deposit is marked by elevated levels of Fe, Mn, Co, Cu, and Cd, while exhibiting a scarcity of Ga, Ge, As, Sn, Cr, and Ni. Elements such as Fe, Cd, Mn, Co, Ag, Sb, and Ga are integrated as solid solutions, whereas Cu exists in both solid forms and as inclusions. Notably, this study identified several coupled elemental substitutions: Zn2+?Fe2+、Zn2+?Cd2+、2Zn2+?Ag++Sb3+. Moreover, the trace elemental composition of the sphalerite in the Amiangen deposit differs significantly from those in VMS, MVT, skarn, and epithermal deposits. The distinct ratios of Cd/Fe (0.02~0.04, mean 0.03), Co/Ni (15~1 019, mean 1 275), and Ga/In (0.11~1.10, mean 0.31), as well as the diminished Ge content, indicate that sphalerite formation is intrinsically linked to magmatic hydrothermal fluids. Crucially, the materials contributing to the genesis of the Amiangen deposit predominantly originate from deep concealed intermediate-acid intrusive rocks with a minor contribution from the surrounding lithology. When considered alongside its geological characteristics, the Amiangen deposit can be categorized as magmatic hydrothermal, filling-metasomatic Pb-Zn deposit.