黑龙江洋灰洞子铜矿床花岗闪长斑岩地球化学、锆石U--Pb定年及地质意义

Geochemistry and zircon U--Pb dating of the granodiorite porphyry in the Yanghuidongzi copper deposit,Heilongjiang Province, and its geological implications

黑龙江洋灰洞子斑岩型铜矿床地处兴蒙造山带东段、吉黑褶皱带北部,矿体主要赋存在花岗闪长斑岩和构造角砾岩中.为厘定洋灰洞子铜矿床的成岩成矿时代和构造背景,笔者对洋灰洞子花岗闪长斑岩进行了元素地球化学和LA-ICP-MS锆石U-Pb年代学的相关研究.岩石地球化学特征显示,花岗闪长斑岩富硅贫镁,属于过铝质钙碱性系列,富集轻稀土元素（LREE）,（La/Yb）N =10.49～19.79,Eu显示弱负异常或正异常,高Sr低Y和Yb,富集大离子亲石元素（LILE）,相对亏损高场强元素（HFSE）,具有埃达克岩或埃达克质岩的特征.LA-ICP-MS锆石U-Pb测年结果显示,花岗闪长斑岩锆石206 pb/238U加权平均年龄为204.4±2.8 Ma和201.2±1.7 Ma.综合研究认为,洋灰洞子斑岩型铜矿床的成岩成矿时代可能为晚三叠世—早侏罗世之交,该矿床形成于古亚洲洋闭合后的陆陆碰撞造山环境,是加厚下地壳部分熔融形成的岩浆流体作用的结果.

Yanghuidongzi porphyry copper deposit of Heilongjiang,is located in the northern Jilin-Heilongjiang fold belt and the eastern Xing-Meng orogenic belt.The orebodies are mainly hosted in granodiorite porphyry and tectonic breccia.The authors studied the zircon U-Pb dating and element geochemistry of the granodiorite porphyry of the Yanghuidongzi copper deposit,in which the geochemistry characteristics indicate that the granodiorite porphyry is enriched in Si while depleted in Mg,pertain to peraluminous calcium-alkaline series.The light rare earth element （LREE） is enriched,and the ratio of （La/Yb） N is （10.49 ～ 19.79）.The δEu contents show weak negative or positive Eu anomalies,high Sr and low Y and Yb in content,the enrichment of large-ion lithophile elements （LILE）,and the absence of high field strength elements （HFSE）.Element geochemicd characteristics indicate that the granodiorite porphyry shows characteristics of adakitic rocks.The LA-ICP-MS zircon UPb dating indicates that the weight average 206pb/238U ages of zircon grains from granodiorite porphyry are 204.4 ± 2.8 Ma and 201.2 ± 1.7 Ma.According to comprehensive research,the diagenesis and mineralization age of the Yanghuidongzi porphyry copper deposit is probably at the transition time of the Late Triassic and Early Jurassic.The Yanghuidongzi porphyry copper deposit originated from granite magmatism of partial melting of the thickened lower crust occurred in continental collision orogeny regime after the closure of Paleo-Asia Ocean.