内蒙古阿贵浑德伦铅锌矿花岗岩类年代学及地球化学特征

Chronology and geochemistry of the granites in Aguihundelun lead-zinc deposit,Inner Mongolia

赤峰阿贵浑德伦铅锌矿是黄岗梁—甘珠尔庙成矿带上新发现的矿床,成矿与花岗岩类关系密切。矿区出露的花岗岩主要为黑云母花岗岩和花岗斑岩,对黑云母花岗岩的LA-ICP-MS锆石U-Pb测年结果显示其形成年龄为(130.6±1.0)Ma(MSWD=0.095),为早白垩世岩浆活动产物,岩石地球化学测试结果显示黑云母花岗岩与花岗斑岩特征具有一致性,均具有高硅(SiO_272.55%~78.22%)、富碱(Na_2O+K_2O 4.48%~878%)、贫P_2O_5的特征,A/CNK在1.32~2.79之间,属过铝质岩石,富集微量元素K、U、Th、Rb、Pb,亏损Ba、Sr、P、Ti,10000Ga/Al比值高(2.49~3.59),表现出A型花岗岩典型的地球化学特征。稀土元素含量较高,相对富集LREE,花岗岩稀土元素呈右倾海鸥型配分模式,负Eu异常明显,δEu为0.10~0.48,表明花岗岩在成岩过程中分异出了斜长石。花岗岩Sr、Yb含量分别为(31.91~185.01)×10^(-6)、(217~6.18)×10^(-6),属低Sr高Yb型花岗岩。阿贵浑德伦铅锌矿花岗岩类与大兴安岭地区锡多金属成矿花岗岩的年代学及地球化学特征均十分相似,指示了该区除铅锌矿外还具有锡矿的找矿前景。

The Aguihundelun lead-zinc ore deposit is a newly discovered deposit in Huanggangliang-Ganzhuermiao metallogenic belt, the mineralization is closely related to the granite intrusion. The ore district mainly outcrops biotite granite and granite porphyry. The dating result of zircon U-Pb by LA-ICP-MS shows the emplacement age of biotite granite is about （130.6±1.0） Ma, which indicates that the biotite granite is a product of Cretaceous magmatism. Biotite granite and granite porphyry have a consistent characteristic in geochemistry, which turns out to be high silicon （72.55%～78.22%） and alkali （4.48%～8.78%） but P2O5 depletion. ACNK values range from 1.32 to 2.79, showing the peraluminous affinity. Trace elements of K, U, Th, Rb and Pb are enriched and Ba, Sr, P, and Ti are depleted which indicate the geochemical charateristics of A-type granite with 10000 Ga/Al value ranging from 2.49 to 3.59. The REE patterns are characterized with enrichment of LREEs and prominent negative Eu anomalies with a δEu value from 0.10 to 0.48 in chrondrite-normalized REE diagram, which reveals the separation of plagioclase in diagenetic process. The Sr and Yb content in granites are （31.91～185.01）×10-6and （2.17～6.18）×10-6 respectively, which indicate the features of low Sr-high Yb granite. These granites in Aguihundelun lead-zinc deposit show the similarity to that mineralization in the Da Hinggan Mountains area where the tin polymetallic mineralization occurs in both geochronology and geochemistry. Therefore, there is great potential for tin prospecting in this area.