皖南伏岭岩体岩石成因及对铷富集的指示

Petrogenesis and rubidium enrichment indication of the Fuling rock mass in southern Anhui Province

皖南伏岭岩体位于江南隆起带东段,为一复式花岗岩体经多阶段演化形成,主体主要分为两种岩性:二长花岗岩和钾长花岗岩。本文对皖南伏岭岩体进行了地质、岩相学、岩石地球化学特征研究,探讨了伏岭花岗岩体演化特征、成因类型、构造环境,试图阐明岩体对铷富集的指示意义。结果显示,伏岭岩体地球化学特征表现出较高的SiO2、Na2O、K2O、Al2O3含量和w(K2O)/w(Na2O)比值,铝饱和指数(A/CNK)为0.95~1.08,平均值为0.99,属于高钾钙碱性准铝质—过铝质花岗岩;Li、Rb、Nd、Ta等微量元素含量较高,Sr、Ba含量明显偏低,这可能与长石的分离结晶作用有关;微量元素w(Nb)/w(Ta)比值范围5.71~10.94,平均值8.41,Mg#范围0.02~0.31,平均值0.13,指示伏岭岩体可能主要来源于下地壳岩石的部分融熔,属于非造山伸展环境中的A型花岗岩;岩体中Rb含量随着岩浆演化程度的增加而升高,相对于二长花岗岩,演化程度高的钾长花岗岩具有更高的Rb含量,表明伏岭岩体Rb含量变化整体受控于岩浆演化过程。本次开展伏岭岩体的研究工作,对理解皖南燕山期成岩成矿作用具有一定的借鉴意义。

The Fuling rock mass in southern Anhui Province,located in the eastern section of the Jiangnan uplift zone,is a complex granitic rock mass that has experienced multi-stage evolution.It primarily comprises two lithologies:Monzogranite and K-feldspar granite.By investigating the geological,petrographic,and petrogeochemical characteristics of the Fuling rock mass,this study delved into its evolutionary characteristics,genetic types,and tectonic environment,aiming to clarify its indication significance for rubidium enrichment.The results of this study are as follows:①The geochemical characteristics of the Fuling rock mass demonstrate high SiO 2,Na 2 O,K 2 O,and Al 2 O 3 contents,high w(K 2 O)/w(Na 2 O)ratios,and aluminum saturation indices(A/CNK)ranging from 0.95~1.08(average:0.99),suggesting high-K calc-alkaline quasi-aluminous to peraluminous granites;②In terms of trace elements,the Fuling rock mass possesses high Li,Rb,Nd,and Ta contents and significantly low Sr and Ba contents,which may be associated with the fractional crystallization of feldspar;③The w(Nb)/w(Ta)ratios ranging from 5.71~10.94(average:8.41)and Mg#values ranging from 0.02~0.31(average:0.13)indicate that the Fuling rock mass was primarily derived from the partial melting of lower crust rocks,suggesting A-type granites in a non-orogenic extensional environment;④The Rb content in the Fuling rock mass increases with the magmatic evolution degree.Compared to monzogranites,K-feldspar granites with a higher evolution degree display higher Rb content,implying that the Rb content in the Fuling rock mass is generally controlled by magmatic evolution.Overall,this study holds some reference significance for understanding the Yanshanian diagenesis and mineralization of southern Anhui Province.