摘要
小石头泉铜多金属矿位于新疆哈密市东北200km,在区域地质构造上处于东天山哈尔里克岛弧东段。本文主要对矿区火山岩的主量、微量元素及同位素组成进行测试和研究。含矿岩石以流纹斑岩、英安岩、英安斑岩为主,SiO_2含量为51.96%～72.58%,Na_2O+K_2O 为3.1%～7.73%,计算里特曼指数σ<3.3,显示具有钙碱性岩的特征;稀土元素配分形式为轻稀土相对富集,其中英安岩 Eu 负异常比安山岩更为明显,说明源区有斜长石的残留或岩浆演化经历了结晶分异作用;微量元素具有典型的岛弧火山岩的地球化学特征,如 Ta、Nb、Ti 等元素较板内火山岩的明显亏损;岩石初始锶(^(87)Sr/^(86)Sr)_i 平均值为0.7043,εNd(t)为4.7,反映火山岩形成源区以幔源为主,混有部分壳源物质。以上岩石地球化学研究结果表明,该区火山岩形成于火山岛弧环境。通过与东天山大南湖岛弧火山岩对比,发现两地区的同时代火山岩地球化学属性存在一定差异,大南湖岛弧火山岩区以发育 Adakite 岩为特征,而哈尔里克岛弧缺少Adakite 岩,可能反映该区火山岩的形成与部分熔融的洋壳交代地幔楔有关。本文认为小石头泉地区为典型火山岛弧环境,有利于火山热液型多金属矿床的形成。
Xiaoshitouquan ore district was a new prospect district and located on the eastern part of Haerlike island-arc. Based on the study of the host rock, it shows strong characteristics of island-arc suites. Rhyolitic porphyry, dacitic porphyry and dacite are the main host rocks. SiO2 range from 51.96% - 72. 58%, and Na2O ＋ K2O are in 3. 1% - 7. 73%, which shows the calc-alkaline characteristics based on the Rittmann index. The REE showing steep patterns （ rich in light REE and depleted in heavy REE） with Eu negative anomaly, which means plagioclase left in the magma chamber or processed fractional crystallization. The average initial Sr value is 0. 7043, and εNd（ t ） is 4. 7, which means a mixed magma source of mantle and crust. After comparison with volcanic rocks in Dananhu island-arc, there is some difference between two places. Haerlike island arc lack of Adakite different from Dananhu, the characteristics of trace elements and isotopes show the volcanic rocks are contaminated by the mantle wedge. Therefore we believe different types of deposits should be found here such as hydrothermal poly-metallic deposit.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第11期2711-2718,共8页
Acta Petrologica Sinica
基金
科学院知识创新项目(KZCX3-SW-137)
国家自然科学基金(40473028)资助.
