摘要:
阿尔泰南缘发育大量火山岩及硫化物-Fe 多金属矿床。从东向西,成矿元素组合依次为 Pb-Zn、Fe-Pb-Zn和Cu-Zn。本文对阿尔泰南缘东部的萨吾斯矿床的火成岩做了主微量元素、Sr-Nd和锆石Hf-O同位素及闪锌矿的Pb同位素组成测定。对比了阿尔泰南缘东部、中部和西部5个铁-硫化物矿床的Pb和Sr-Nd同位素。康布铁堡组流纹岩来自于多旋回风化-剥蚀-搬运-再沉积碎屑物质的重熔,富集Zn,表现出碎屑物质的微量元素特征,导致萨吾斯和可可塔勒 Pb-Zn 矿床的高207Pb/204Pb、208Pb/204Pb 及低206Pb/204Pb、εNd(t)。康布铁堡组下亚组中基性火山喷发为蒙库Fe矿的初始富集奠定了基础。中部的克兰盆地形成于洋陆过渡弧或属弧间盆地,康布铁堡组中下段中基性火山岩和上段流纹岩分别为Fe和Zn的富集奠定了基础,碳酸盐岩则造成了Pb的富集,从而形成铁木尔特Fe-Pb-Zn矿床。铁木尔特和蒙库矿床的206Pb/204Pb比值最高且变化大,反映了大洋岛弧火山岩的特征。在西部,阿舍勒组富镁英安岩来自流体交代的地幔楔,导致了阿舍勒矿床Cu的富集,赋矿岩石的εNd(t)值高,(87Sr/86Sr)i和矿石Pb同位素比值低。
Abstract:
Voluminous volcanic rocks and numerous sulfide-Fe deposits occur in the southern Chinese Altay Mountains. From the east to the west, metallogenetic associations vary from Pb-Zn through Fe-Pb-Zn to Cu-Zn. This study performed major and trace element, Sr-Nd and zircon Hf-O and sphalerite Pb isotopic analyses of volcanic rocks and ore minerals of the Sawusi Zn-Pb deposit in the east of the southern Chinese Altay. Sulfide Pb and volcanic-rock Sr-Nd isotopic compositions of five representative Fe-sulfide deposits from the east, middle and west of the southern Chinese Altay are compared. Rhyolites of the Early Devonian Kangbutiebao Formation were derived from detrital materials. The latter experienced poly-cycled weathering, erosion, transportation and re-deposition from the Gondwana land through the Tuva-Mongol or from the Caledonian province to the Chinese Altay, which itself was compressed and uplifted at~400 Ma, and finally delivered to the then trench on the south after erosion from top of the Chinese Altay Mountains. These poly-cycled detrital materials are rich in Zn, possess arc or continental trace element characteristics, and caused high 207Pb/204Pb, 208Pb/204Pb and low 206Pb/204Pb,εNd(t) in the Sawusi and Keketale Pb-Zn deposits in the east of the southern Chinese Altay. The intermediate-basic volcanic eruption resulted in initial enrichment of Fe for the Mengku deposit. The Kelan basin in the middle of the southern Chinese Altay was formed in the ocean continent transition arc or was an interarc basin. In the Kelan basin, intermediate-basic volcanic rock in the middle-lower section and rhyolite in the upper section respectively resulted in Fe and Zn mineralization, whereas Pb mineralization was related to carbonate. These rocks collectively contributed to the formation of the Tiemuerte Fe-Pb-Zn deposit. The Tiemuerte and Mengku deposits exhibit high and variable 206Pb/204Pb, a characteristic of intra-oceanic arc volcanic rocks. The host rock of the Ashele Cu deposit, the west of the southern Chinese Altay, exhibit high εNd(t) and low (87Sr/86Sr)i and Pb isotopic ratios. Mg-rich dacites as derived from the slab fluid-metasomatized mantle wedge resulted in Cu mineralization.
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