摘要
萨亚克大型铜矿田位于哈萨克斯坦北巴尔喀什斑岩成矿带中部,以矽卡岩型矿床为主。通过对矿区石英闪长岩的矿物化学和地球化学研究,发现石英闪长岩呈斑状结构,斑晶为斜长石和角闪石,其中的斜长石斑晶主要为中长石,角闪石斑晶为镁质普通角闪石;岩石属于高钾钙碱性系列,富集Rb、Sr、Ba等大离子亲石元素和轻稀土元素,亏损Nb、Ta和重稀土元素,高Sr/Y、La/Yb比值,与埃达克岩相似。地球化学特征指示萨亚克矿区侵入岩形成于岛弧环境,为矽卡岩-斑岩型成矿提供了有利的构造背景,岩石可能是岛弧玄武质岩浆在高压下经结晶分异而成。根据角闪石温压计及其成分与氧逸度和岩浆中水含量之间的关系,确定萨亚克石英闪长玢岩中角闪石斑晶结晶时岩浆的温度为799~843℃、处于3.6~9.6km深度范围内(P=1.2~3.2kbar)、氧逸度logfO2=-11.5^-12.0(ΔFMQ=2.0~2.8)、平均水含量为1.2%,相对较高的氧逸度和水含量有利于形成富含挥发分和Cu、Au等成矿物质的岩浆,是最终演化形成大型岩浆-热液型铜矿田(斑岩型、矽卡岩型)的有利条件。
Sayak large copper field is located in the central part of north Balkhash porphyry copper metallogenic belt. It consists mainly of skarn copper deposits and associated porphyry and quartz-vein type copper deposits. Copper mineralization is genetically related to Carboniferous diorite, quartz diorite and granodiorite. Study on mineralogy and geochemistry reveals that the plagioclase and hornblende phenocrysts are andesine and Mg-hornblende. The quartz diorite porphyry samples belong to high-K calc-alkaline, enrched in LILE （such as Rb, Sr and Ba） and LREE, depleted in Na, Ta and HREE. They have high Sr/Y and La/Yb ratios, which is similar to the adakite. The geochemical characteristics of the quartz diorite indicate that they are subduction-related arc magma, formed by differentiation of primary basaltic arc magma. Based on the composition of hornblende, the temperature （ 799 - 843℃ ）, pressure （3.6 -9. 6km）, oxygen fugacity （logfo2 = - 11.5 - - 12. 0, AFMQ =2. 0 -2. 8） and water content in magma （ average 1.2% ） were calculated. The tectonic setting, high oxygen fugacity and water content of the magma are favorable for the subsequent formation of magmatic-hydrothermal （porphyry and skarn） copper deposit.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第2期555-570,共16页
Acta Petrologica Sinica
基金
“十二五”国家科技支撑计划项目(2011BAB06B01-03)
国家自然科学基金项目(41203032
41421002)
大陆动力学国家重点实验室自主研究项目联合资助
