东昆仑清水河东沟铜钼多金属矿区赋矿岩石地球化学特征及构造环境分析

Rock geochemical characteristics and tectonic environment analysis of Cu-Mo polymetallic mining area of Qingshui River Ore District,Eastern Kunlun,Qinghai province

为了研究清水河东沟斑岩型铜钼矿床赋矿岩体英云闪长岩和辉绿玢岩的成因、演化及产出背景,文中通过对该两种岩体的主量元素、微量元素、稀土元素特征和成岩环境进行了分析和探讨。结果表明:英云闪长岩中主量元素SiO_2(64.89%~66.89%)、富Al_2O_3(14.58%~15.84%)、CaO(4.09%~4.88%),属钙碱性过铝质英云闪长岩;稀土含量较高(138.41×10^(-6)~176.21×10^(-6)),轻稀土元素富集,重稀土元素亏损;δEu的变化范围为0.51~0.67,岩石中Ba,Nb,Sr的亏损较明显;结合岩石地球化学图解,认为英云闪长岩形成的环境为火山弧花岗岩环境。辉绿玢岩中主量元素具有低SiO_2(58.43%~58.96%)、富Al_2O_3(16.18%~16.51%)、全碱K_2O+Na_2O(5.15%~5.52%)的特征,属高钾钙碱性过铝质辉绿玢岩;稀土元素总量变化不大(149.75×10^(-6)~155.11×10^(-6)),曲线为右倾型;δEu的变化范围为0.61~0.67,具弱负Eu异常。结合岩石地球化学图解,认为辉绿玢岩形成于板块俯冲条件下的陆—陆碰撞构造环境。

In order to study the genesis,evolution and background of diorite and diabase porphyry in the Dongjiang porphyry copper-molybdenum deposit,tonalite and diabase,the main element,trace element,rare earth element and diagenetic environment were analyzed. Results show that the main element of tonalite is SiO2（ 64.89% ~66.89%）,rich in Al2O3（ 14. 58% ~15. 84%） and CaO（ 4. 09%~ 4. 88%）,belongs to calc-alkaline aluminic orogenic diorite. Rare earth content is high（ 138. 41 ×10^-6~ 176. 21×10^-6）,rich in light rare earth elements,and poor in heavy rare earth elements. δEu changes in the range of 0.51 ~ 0.67,the loss of Ba,Nb and Sr in the rock is obvious. Combined with the rock geochemical map,it is believed that the tonalite was formed by volcanic arc granite environ-ment. The characteristics of the main elements in the diabase porphyrite is low SiO2（ 58. 43% ~58. 96%）,high Al2O3（ 16. 18% ~ 16. 51%）,and alkali K2O ＋Na2O（ 5. 15% ~ 5. 52%）. The diabase belongs to a high-K calc-alkaline peraluminous diabase. The total amount of rare earth elements changes little（ 149. 75×10^-6~ 155. 11 × 10^-6）,curve is the right-leaning type. δEu changes in the range of 0. 61 ~ 0. 67,and it has a weak negative Eu anomaly. Combined with the rock geochemical map,it is believed that the diabasic porphyrite is formed in a continent-continent collision structural environment under effect of plate subduction.