后碰撞环境下富S岩浆起源和斑岩成矿作用

形成斑岩矿床需要大量的硫，并且这些硫大部分都来自岩浆。陆陆碰撞环境下的大型斑岩矿床的成因存在争议。普遍认为被俯冲改造的新生下地壳熔融产生的熔体构成主要的成矿岩浆，可是下地壳能否提供足够的硫来形成大的斑岩型矿床并不清楚。磷灰石是常见的岩浆-热液矿物，富含成矿元素，例如S、F和Cl。研究磷灰石的硫同位素组成并结合其主微量元素特征，可以有效地示踪硫的起源和演化，从而限定成矿过程。本研究选取西藏冈底斯带内的驱龙斑岩Cu-Mo矿床和三江成矿段代表性的北衙斑岩-矽卡岩型Au矿床为陆陆碰撞环境下的典型斑岩矿床开展系统研究。通过锆石Hf-O同位素和微量元素分析结合已有年龄来限定不同期次岩浆的属性。对各期次岩体中的磷灰石进行系统的硫同位素研究，参考岩浆期次和属性来示踪陆陆碰撞环境下富硫岩浆的起源和演化过程。

Porphyry Cu deposits are, first and foremost, large sulfur anomalies with development of extensive sulfide alteration around the mineralization over several KMs. Formation of porphyry deposits require a large amount of sulfur, which is mainly derived from magma. The genesis of large continental collision-related porphyry deposits (PCDs) remains controversial. Although partial melting of subduction-modified lower crust has been proposed to generate such magmas, the main debate arises from the discussion that whether the lower crust can provide enough S for giant porphyry deposit formation. In addition, the porphyry system is common with several pulses of magmatism coeval with mineralization, including mafic dykes or mafic microgranular enclaves (MMEs). It is unclear that why one pulse of magma is ore causative but the rest. In addition, is the mafic melt input essential for providing enough S for mineralization? Apatite is a common magmatic-hydrothermal mineral, and characterized with enrichment of ore-related components, such as S, F, Cl. Study of apatite S-isotopic composition can track the origin and evolution of S in magmatic-hydrothermal system, and therefore this can improve our understanding of porphyry deposit formation. Qulong porphyry Cu-Mo deposit, Yulong porphyry Cu-Mo deposit, and Beiya porphyry-skarn Au deposit as the representative porphyry deposits in collisional settings are selected for systematic studies. Zircon Hf-O isotope and trace element analysis of multiple intrusions will constrain the magma source, temperature, water contents, oxidation state, which are key factors in controlling S evolution in the magmas. The systematic study of apatites will ultimately elucidate the S evolution in porphyry system.