摘要
辽西柏杖子金矿是冀东-辽西成矿带上较大规模的金矿之一,其金成矿与中生代岩浆作用形成的花岗质岩体关系密切。在野外调研的基础上,将柏杖子花岗质岩体划分为黑云母二长花岗岩、含黑云母二长花岗岩、二长花岗岩及花岗斑岩脉,同时开展了岩石学、岩石地球化学、年代学及Hf同位素研究。研究结果显示,花岗斑岩脉的锆石U-Pb年龄为231.0±1.3 Ma和231.7±2.7 Ma,形成于晚三叠世。花岗质岩体的主量元素均表现出高钾钙碱性、准铝到弱过铝质花岗岩的特征,微量元素表现出相对富集Rb、Th、U、K、Hf元素,相对亏损Ba、Ta、Nb、P、Ti元素,无明显Eu、Ce异常,相对富集轻稀土元素而亏损重稀土元素的特征,在构造环境判别图解中均落入后碰撞环境。哈克图解及微量元素协变图显示,从黑云母二长花岗岩到花岗斑岩脉具有I型花岗岩的演化趋势,并经历了黑云母、钾长石、磷灰石、钛铁矿、榍石等矿物的分离结晶。花岗斑岩脉的锆石Hf同位素显示εHf(t)值为-9.02~-5.62(平均-7.43),二阶段Hf模式年龄TMD2为1592~1810 Ma(平均1710 Ma),表明岩浆源区为古元古代晚期大陆地壳物质部分熔融形成。由锆石微量元素计算得到花岗斑岩脉的△FMQ为-1.23~4.65。花岗斑岩脉富碱、高氧逸度及中等演化程度的特征都有利于金成矿,具有较好的成矿潜力。
The Baizhangzi gold deposit in western Liaoning is among the largest gold deposits within the Jidong−Liaoxi metallogenicbelt,where Mesozoic magmatism has led to the formation of granitic rock mass closely associated with gold ore.On the basis of fieldinvestigation,we have identified that the Baizhangzi granite consists of biotite monzogranite,biotite−bearing monzogranite,monzogranite and granitic porphyry dykes,and studied petrology,petrogeochemistry,chronology and Hf isotopic characteristics.Thezircon U−Pb ages of granitic porphyry dykes were determined to be 231.0±1.3 Ma and 231.7±2.7 Ma,indicating formation in theLate Triassic.The major elements of Baizhangzi granitic rock mass exhibit characteristics of a high−K calc−alkaline series,displaying quasi−aluminum to weakly peraluminous granite composition;while the trace elements show enrichment in Rb,Th,U,K,Hf anddepletion in Nb,Ba,P,Ti without obvious Eu and Ce anomalies.Additionally,there is relative enrichment in light rare earth elementsand depletion in heavy rare earth elements placing it within the Post−COLG on tectonic setting discrimination diagrams.The Harkerdiagram and rare element covariant relationship indicate fractional crystallization of biotite,potassium feldspar,apatite,ilmenite andspar from biotite monzogranite to granitic porphyry dykes.The zircon Hf isotope analysis of the granitic porphyry dykes revealsεHf(t)values ranging from−9.02 to−5.62(average−7.43),with two−stage Hf model ages(TMD2)ranging from 1592 Ma to 1810 Ma(average1710 Ma),suggesting derivation of the magma through partial melting of Late Paleoproterozoic crust.The zircon rare elements in thegranitic porphyry dykes show a△FMQ range from−1.23 to 4.65.The enrichment of alkali,high oxygen fugacity(fO2),and mediumdegree of evolution in granite porphyry dykes are favorable conditions for gold mineralization,indicating a strong potential formineralization.
作者
李红宾
许卫军
董国臣
常泽光
李华伟
汤家辉
苏麟
梁景利
LI Hongbin;XU Weijun;DONG Guochen;CHANG Zeguang;LI Huawei;TANG Jiahui;SU Lin;LIANG Jingli(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Lingyuan Baizhangzi Gold Mine,Chaoyang 122521,Liaoning,China;Brigade of North China Geological Exploration Bureau,Chengde 067000,Hebei,China)
出处
《地质通报》
CAS
CSCD
北大核心
2024年第10期1756-1774,共19页
Geological Bulletin of China
基金
重大科技专项计划《岩浆-流体系统成矿作用与空间结构》(编号:202303AA08000601)。
关键词
花岗斑岩
岩脉
锆石U-Pb定年
HF同位素
辽西
柏杖子
金矿
granite porphyry
dykes
zircon U−Pb dating
Hf isotope
western Liaoning
Baizhangzi
gold deposit
作者简介
李红宾(2000-),男,在读硕士生,矿物学、岩石学、矿床学专业。E-mail:136751697@qq.com;通信作者:董国臣(1962-),男,教授,博士生导师,从事岩石学及矿床学研究。E-mail:donggc@cugb.edu.cn。
