东准噶尔卡拉麦里五彩城地区酸性岩脉岩石成因及找矿意义

The Petrogenesis and Prospecting Significance for the Acidic Veins of Wucaicheng in Karamaili from Eastern Junggar

卡拉麦里断裂以南五彩城一带分布有大量以岩脉和小岩滴形式存在的流纹斑岩和花岗斑岩,这些浅成脉体侵位于上石炭统巴塔玛依内山组、上泥盆—下石炭统克安库都克组及志留系。LA-ICP-MS锆石U-Pb年龄显示,花岗斑岩及流纹斑岩形成于晚石炭世中—晚期（花岗斑岩年龄为（309.1±3.1）Ma,流纹斑岩年龄为（302.9±4.1）Ma）。Q’-ANOR图中花岗斑岩及流纹斑岩主要投在碱长花岗岩及正长花岗岩区内,岩石高SiO2（73.38%~77.05%）,K2O/Na2O=1.18%~1.84%,球粒陨石标准化的REE分布型式具LREE略富集的近似海鸥型的分布型式,岩石地球化学特征显示出高分异的A型花岗岩特点。从时空分布上看,这些岩脉应为晚石炭世巴塔玛依内山组火山岩的潜火山岩,后者具明显的的双峰式火山岩特征,形成时间上这些岩脉也与北部邻区的黄羊山、老鸭泉A型花岗岩体的形成年龄（300~311 Ma）十分接近,认为其应属陆内伸展环境产物。本研究在花岗斑岩中发现有岩浆晚期热液蚀变型的Cu,Pb,Zn矿化,与黄羊山、萨北及老鸭泉岩体中的Cu,Pb,Zn矿床成因类型相同,认为卡拉麦里断裂以南广泛发育的晚石炭世的潜火山岩可能具较好的找矿前景。

There are lots of veins and drops including granite porphyry and rhyolite porphyry in Wucaicheng from the south of Karamaili fault,these dike swarm are intruded in Batamayineishan Formation of the Upper Carboniferous,Songkaersu Formation of the lower Carboniferous and Silurian strata.LA-ICP-MS zircon U-Pb dating shows that granite porphyry and rhyolite porphyry are formed in the middle-late stage of Late Carboniferous （Weighted mean ^206pb/238U age of granite porphyry is （2 309.1 ± 3.1） Ma,rhyolite porphyry is （302.9 ± 4.1） Ma）.Granite porphyry and rhyolite porphyry invest in the areas containing alkali feldspar granite and syenite granite in Q ＇-ANOR graph,the characteristics of granite porphyry and rhyolite porphyry are mainly displayed that high SiO2 content （73.38%-77.05%）,K20〉Na：O（K20/Na2O is 1.18M.84）,the approximating seagull REE distribution pattern of LREE slightly enriched LREE and flat HREE. Petro- geochemistry shows the characteristics of High differentiation of A-type granite.From the temporal and spatial distribu- tion,these veins should be subvolcanic rocks of Batamayineishan Formation,which is characterized bimodal volcanic rocks.moreover, formed in intra-continental extensional stage.The formation age of these veins is close to those A-type plutons including Huangyangshan and Laoyaquan from the north of Karamaili fault,therefore,it is believed these contem- poraries veins and plutons are a product of intra-continental extension.And it is found hydrothermal alteration Cu,Pb and Zn mineralizations from late magmatic namely granite porphyry, the genetic type is the same as mineral deposits from Huangyangshan,Sabei and Laoyaquan,consequently, lots of subvolcanic rocks of Late Carboniferous from the south of Karamaili fault （rhyolite porphyry etc.） may have great prospecting potential.