副矿物对过铝质花岗岩岩浆来源和演化历史的指示：以钨矿化的赣南西华山花岗岩为例

The tungsten mineralization related peraluminious granites are widespread in the Nanling region of South China,many researches have been done on it. Howerer, the lack of researches toward the source and evolution history of peraluminous magmas seriously restrict the recognition of petrogenesis of granite and the relationship between the mineralization and peraluminous granites. This study takes the typical Xihuashan peraluminous granite as a example, and accessory minerals and isotope geochemistry are carried out,based on the detail field observation and laboratory researches, combined with the petrogical and geochemical characteristics of the granites,this study has the significances as follows:(1)effectively restricting the source and evolution history of peralumious magmas,which help to reveal the petrogenesis of granites and relationship between granite and minerlization.(2) We emphasize the utility of exploiting isotopic composition characteristics of hydrothemal zircon in quartz vein and the garnet, zircon, pyrite and arsenopyrite in granites as monitors of evolving magmas and crystallization processes, This technique provides a powerful new means for deciphering the petrogenesis of peraluminious granites,espescially provide the reliable evidences for identifying whether or not the mantle-derived materials are involved in peraluminous granites.(3)Carrying out the study of accessory minerals in detail which are used for tracing the magmatic process, preliminary creating the method of using the micro-scale mineralogy to trace the large-scale magmatic process.(4)facilitating the understanding the deep geodynamic background of the petrogenesis of peraluminious granites in the Xihuashan, even throughout the Nanling region.

南岭地区，与钨矿化有关的过铝质花岗岩广泛分布，人们对其进行了大量研究，但目前对该类岩石的岩浆来源和演化历史仍不太清楚，这严重制约了对该区过铝质花岗岩成岩、成矿机理的认识。本项目拟以该区西华山花岗岩为研究对象，在扎实的野外观察和室内研究基础上，结合岩石学及地球化学研究，系统开展过铝质花岗岩中精细的副矿物（锆石、石榴子石和硫化物）及其同位素研究，试图查明其岩浆来源和演化过程。开展该研究，具有以下重要意义：（1）有效限定过铝质花岗岩的岩浆来源和演化历史，有助于揭示该区过铝质花岗岩的成因及成岩成矿关系。（2）对石榴子石、不同类型锆石、黄铁矿和毒砂的同位素研究，将为揭示过铝质花岗岩的成因提供新思路，特别是可为判别幔源物质是否参与成岩作用提供可靠依据。（3）开展精细的副矿物研究，将初步建立小尺度矿物学示踪大范围岩浆过程的方法。（4）有助于揭示西华山花岗岩、甚至整个南岭地区花岗岩形成的深部动力学背景。

南岭地区，与钨矿化有关的过铝质花岗岩广泛分布，人们对其进行了大量研究，但目前对该类岩石的岩浆来源和演化历史仍不太清楚，这严重制约了对该区过铝质花岗岩成岩、成矿机理的认识。本项目以西华山钨矿化的过铝花岗岩为研究对象，系统开展了花岗岩中精细副矿物矿物学和同位素地球化学研究。通过研究发现，西华山过铝花岗岩和西华山钨矿存在一种准同时性，都形成于157Ma左右，二者具有密切的成因联系。西华山花岗岩具有富集的全岩Nd同位素[εNd(t)=-9.8~-11.5]和磷灰石原位Nd同位素[εNd(t)=-9~-12]及锆石Hf-O同位素[εHf(t)＝﹣5.3～﹣18.0；δ18O＝8.3‰～9.2‰]，三种岩性具有相似的岩浆源区，主要为中上地壳物质发生部分熔融形成。岩浆侵位过程中发了强烈的结晶分异，并且经历了岩浆—热液过渡演化过程，分异流体具有高F特征，导致亚固相线下Zr-Hf和Nb-Ta发生了强烈的分异，并且锆石、磷灰石、独居石和石榴石矿物学结构特征及矿物化学特征均明确指示了这个过程，这个过程是促使钨成矿的关键。本项目提出过铝花岗岩具有稀有金属矿化潜力的重要指标为Zr/Hf比值小于26，Nb/Ta比值小于6。通过该项目的研究，（1）有效限定过铝质花岗岩的岩浆来源和演化历史，揭示了该区过铝质花岗岩的成因及成岩成矿关系。（2）对副矿物开展精细矿物学研究和原位同位素研究，为揭示过铝质花岗岩的成因提供新思路。（3）开展精细的副矿物研究，初步建立了小尺度矿物学示踪大范围岩浆过程的方法。