青海乌腊德地区花岗闪长岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及地质意义
华磊 , 孙晓亮 , 孙丽莎 , 王欣 , 唐名鹰 , 朱海波 , 翟孝志 , 管翔 , 高振华
现代地质 ›› 2026, Vol. 40 ›› Issue (3) : 688 -700.
青海乌腊德地区花岗闪长岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及地质意义
LA-ICP-MS Zircons U-Pb Dating, Geochemical Characteristics and Geological Significance of Granodiorite in Wulade Area, Qinghai Province
青海乌腊德地区位于东昆仑复合造山带西段的青海祁漫塔格构造-岩浆岩成矿带内,区域发育与岩浆活动密切相关的矽卡岩型和斑岩型铁、铜、钼、铅、锌多金属矿床。本次研究的乌腊德花岗闪长岩与区内新发现的同期矽卡岩型铁矿床存在密切成因联系,为准确厘定该花岗闪长岩形成时代,探讨其成因类型、构造环境及其对成矿作用的指示,对花岗闪长岩进行了LA-ICP-MS锆石U-Pb年龄测试及岩石地球化学分析。结果表明,花岗闪长岩的形成年龄为(228.2 ± 0.6)Ma,属晚三叠世。全岩全碱含量(Na2O + K2O)为5.53% ~ 9.03%,富K贫Na,铝饱和指数A/CNK值为1.07 ~ 1.54,属高钾钙碱性准铝质花岗岩。岩石稀土元素总量(ΣREE)偏低,轻重稀土出现一定程度的分异,具弱的负Eu异常,微量元素表现出Rb、Sr、Ba、Th等元素明显的富集,Nb、Ta等元素强烈亏损,镜下出现角闪石等矿物,结合岩石判别图解,表现出Ⅰ型花岗岩特征,形成于活动大陆边缘俯冲末期至局部碰撞的转换的构造环境。综合分析表明,乌腊德花岗闪长岩形成时代与区域晚三叠世岩浆活动和矽卡岩型铁矿形成时间一致,区内铁矿的形成与该期次岩浆活动的密切相关。
The Wulade area in Qinghai Province is located in the western section of the East Kunlun Composite orogenic Belt, within the Qimantag tectonic-magmatic rock mineralization belt, and develops skarn type and porphyry type Fe, Cu, Mo, Pb, Zn polymetallic deposits closely related to magmatic activities. The Wulade grandiorite in this study is closely related to the newly discovered skarn type Fe deposit in the area. In order to accurately determine the formation age of the grandiorite, discuss its genetic type, structural environment and its indication for mineralization, LA-ICP-MS zircon U-Pb age test and rock geochemistry analysis of the grandiorite are carried out. The results show that the formation age of granodiorite is (228.2 ± 0.6) Ma, belonging to the Late Triassic. The total alkali content (Na2O + K2O) of the whole rock is 5.53% - 9.03%, rich in K and poor in Na, and the aluminum saturation index A/CNK value is 1.07 - 1.54, which belongs to the high potassium calc-alkaline peraluminous granite.The total amount of rare earth elements (ΣREE) in the rocks is low, and the light and heavy rare earth elements are distinguished to a certain extent, with weak negative Eu anomalies. The trace elements show obvious enrichment of Rb, Sr, Ba, Th, and strong depletion of Nb, Ta, and ampampole minerals under the microscope. Combined with the rock discrimination diagram, the rocks show the characteristics of type I granite. The tectonic environment formed during the transition from the end of subduction at the edge of active continents to local collisions. Comprehensive analysis indicates that the formation age of the Urad granodiorite is consistent with the formation time of the Late Triassic magmatic activities and skarn in the region, and the formation of iron ore in the area is closely related to the magmatic activities of this period.
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泰山学者工程(tstp20240847)
山东省地质矿产勘查开发局第八地质大队总工基金项目(DZG202403)
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