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冈底斯-念青唐古拉成矿带矿床成矿元素组合由南向北存在着Cu-Au、Cu-Mo向Pb-Zn-Cu-Fe、Pb-Zn过渡的变化规律,但引起该变化规律的原因目前少研究。本文通过对成矿带典型矿床Pb同位素特征较为系统的总结,并结合成矿年代学和区域构造演化研究成果,从成矿物质来源的角度对该分带性进行了初步探讨。研究表明成矿带由南到北成矿物质来源存在着差异:最南端Cu-Au矿床Pb同位素组成具幔源特征(207Pb/204Pb和208Pb/204Pb平均值分别为15.490和38.016),反映成矿物质来自于俯冲过程中的交代地幔楔;最北端的Pb-Zn矿床Pb同位素组成与念青唐古拉群基底片麻岩相近(207Pb/204Pb和208Pb/204Pb分别变化于15.641～15.738和38.976～39.362),反映成矿物质来自于基底片麻岩。Pb-Zn-Cu-Fe矿床Pb同位素组成介于幔源Pb和上地壳Pb之间,且具混合线特征,反映了同碰撞期成矿物质同时从俯冲板片和念青唐古拉基底片麻岩活化的混源模式;而Cu-Mo矿床不具混合线特征的造山带Pb同位素组成,反映了成矿物质来源于俯冲阶段楔形地幔部分熔融并底侵到地壳底部与地壳发生物质交换后所形成的新生下地壳源区。甲马Cu多金属矿床Pb同位素组成具幔源和造山带两个端元,推测除新生下地壳源区提供成矿物质外,叶巴组火山岩也提供了部分成矿物质。由南向北成矿物质来源的差异很大程度上与板片俯冲的“距离效应”有关,正是由于成矿物质来源的差异导致成矿带成矿元素分带性的形成。
The variation of Cu-Au, Cu-Mo to Pb-Zn-Cu-Fe, Pb-Zn transition from south to north in the Gangdese-Nyainqentanglha metallogenic belt shows the variation pattern The reason for the current less research. Based on the systematic summary of the Pb isotopic characteristics of the typical ore deposits, combining with the research results of metallogenic chronology and regional tectonic evolution, this paper discussed the zonation from the perspective of ore-forming material sources. The study shows that there is a difference in mineralization source from south to north in the metallogenic belt: the Pb isotopic composition of the southernmost Cu-Au deposit is characterized by mantle (average 207Pb / 204Pb and 208Pb / 204Pb are 15.490 and 38.016, respectively) The Pb isotopic composition of the Pb-Zn deposit in the northernmost part is similar to that of Nyainqentangulla gneiss (207Pb / 204Pb and 208Pb / 204Pb change from 15.641 to 15.738 and 38.976 to 39.362, respectively) , Reflecting the ore-forming material from the gneiss. The Pb isotope composition of Pb-Zn-Cu-Fe deposits lies between mantle Pb and upper crust Pb and is characterized by mixed lines. It reflects that the ore-forming materials at the same collision stage are formed from subducted slabs and Nyainqentanglt gneiss Activated mixed source rocks. The Pb isotopic composition of the orogenic belt with no mixed line in the Cu-Mo deposit reflects that the wedge-shaped mantle partially melted during the subduction stage of the ore-forming material and migrated to the bottom of the crust to exchange with the crustal material Newborn crust source area. The Pb isotope composition of the Cu polymetallic deposit in Jiama has two mantle andOrogenic belt endpoints. It is speculated that besides the newly formed crust source area, ore-forming materials are provided, and the Yeba Group volcanics also provide some ore-forming materials. The source of ore-forming materials from south to north is largely related to the “distance effect” of plate subduction, which is caused by the difference of source of ore-forming materials.