浙江淳安潘家铜钨多金属矿S、Pb同位素地球化学研究

Sulfur and Lead Isotopes Geochemistry of the Panjia Cu-w Polymetallic Ore Deposit in Chun'An, Zhejiang Province

浙江淳安潘家铜钨多金属矿是浙西新近发现的大-中型地层-构造-岩浆综合控制型矿床,矿体主要产于大铜坑岩体与震旦系蓝田组中及其接触带.本文尝试运用黄铁矿S、Pb同位素示踪的方法探讨矿床成矿物质来源.矿区黄铁矿硫同位素组成δ34S值集中在3.7%-5.3%,且花岗闪长斑岩-蚀变花岗闪长斑岩-角岩化围岩中δ34S值有逐渐增加,反映了硫质应为侵入岩体与沉积地层两个端元的有效混合,且以岩浆源为主的地幔源区特征;Pb 同位素组成为高放射成因的Th-型异常铅,同位素组成μ（238U/204Pb）值特征、Zartman构造模式图、Δγ-Δβ成因分类图解显示,矿区铅具沉积成因和岩浆成因两种形成机制,前者为壳源,后者为幔-壳混源.综合研究显示,蓝田组地层和大铜坑岩体均为成矿母岩,且以后者为主,成矿物质为幔-壳混合源区.

The Panjia Cu-W polymetallic ore deposit is a newly-discovered, large-middle scale deposit in Chun’an, Zhejiang Province. This deposit is strictly controlled by the regional stratum-tectonic-mag?ma. The ore bodies mainly occur in the Datongkeng intrusion rock, the Upper Sinian Lantian Formation, and their contact zone. This paper attempts to discusse the sources of ore-forming materials by using the methods of sulfur and lead isotopic tracing. Studies have shown that the compositionδ34S in pyrite has a narrow variation range of 3.7~5.3%and gradually increases from granodiorite porphyry, altered granodio?rite porphyry, to hornfelsic stratum. The characteristic of sulfur isotopic composition suggests that the sul?fur of Panjia deposit has mixing direct sources of intrusion rock and stratum sedimentary strata, and the former is dominant with a characteristic of mantle source area. The lead isotopic compositions of the Pan? jia ore deposit are all rich in radiogenic Th-type lead. The characteristics of μ (238U/204Pb), Zartman diagrams andΔγ-Δβdiagram suggest that the lead has two kinds of formation mechanism of sedimenta?tion and magmatism, which respectively form the lead isotopes of crust source and mantle-crust source. The comprehensive studies show that the mineralizing mother rocks of the Panjia Cu-W polymetallic ore deposit are both Lantian Formation and Datongkeng intrusion rock, and the former is dominant. In the whole, the ore-forming materials have the characteristic of mixing source area of mantle and crust.