江南造山带东北缘唐舍复式岩体成岩序列、岩石成因及找矿前景

为了解江南造山带东北缘唐舍复式岩体成岩序列、岩石成因和找矿前景,采用区域地质填图、LA-ICP-MS锆石U-Pb定年和全岩地球化学特征分析等方法进行研究。野外地质接触关系厘定唐舍复式岩体的成岩序列为中粒二长花岗岩、中粗粒正长花岗岩、粗中粒斑状正长花岗岩和细粒正长花岗岩,锆石U-Pb年代学显示成岩时代分别为(140.4±3.3)、(131.7±3.2)、(132.2±1.6)和(125.0±2.0)Ma。各类岩石均具有高Si、富碱、低P、低Ti的特征,为准铝质—弱过铝质、高钾钙碱系列的I型花岗岩; 岩石的轻、重稀土元素分异程度较强,球粒陨石标准化稀土元素配分模式右倾,富集Rb、Th、U、K等,亏损Ba、Nb、Ta、Sr、P、Ti等,呈中等—强负Eu异常。总体上,唐舍复式岩体从早到晚岩浆演化具有SiO₂含量、K₂O含量、K₂O/Na₂O值、A/CNK值逐渐增高,TiO₂、Al₂O₃、TFeO、MgO、CaO、P₂O₅含量逐渐降低,负Eu异常逐渐增强,分异程度逐渐增高的趋势,为古太平洋板块俯冲-碰撞造山后陆内拉张环境下的下地壳物质重融,经结晶分异作用沿唐舍背斜构造侵位的产物。唐舍复式岩体侵入接触带由内向外矿化类型及矿种具有钨→银铅锌→锑/萤石的分带性,形成了一个矽卡岩型-热液脉型矿化系统,具有较好的找矿前景。

Diagenetic Sequence,Petrogenesis and Prospecting Prospect of Tangshe Complex Pluton in the Northeastern Margin of Jiangnan Orogenic Belt,China

In order to understand the diagenetic sequence, petrogenesis and prospecting prospect of Tangshe complex pluton in the northeastern margin of Jiangnan orogenic belt, the regional geological mapping, LA-ICP-MS zircon U-Pb age, and all-rock geochemical analysis were studied. According to the geological contact relationship, the diagenetic sequence of Tangshe complex pluton from early to late is determined as medium grained monzonitic granite, medium-coarse grained syenogranite, coarse-medium grained porphyritic syenogranite and fine grained syenogranite, respectively, and the diagenetic ages are(140.4±3.3),(131.7±3.2),(132.2±1.6), and(125.0±2.0)Ma.The rocks have the characteristics of high Si and alkali, low P and Ti, being metaluminum-weak peraluminous and high-K calc-alkaline series, which belong to I-type granites. In addition, the light and heavy rare earth elements are highly differentiated, and the chrondrite-normalized REE pattern leans to right with the enrichment of Rb, Th, U, and K, the depletion of Ba, Nb, Ta, Sr, P, and Ti, and the medium-strong negative Eu anomaly. Generally, the magmatic evolution from early to late shows that the contents of SiO₂ and K₂O, the ratio of K₂O/Na₂O, and A/CNK gradually increase, the contents of TiO₂, Al₂O₃, TFeO, MgO, CaO, P₂O₅ gradually decrease, negative Eu anomaly gradually increases, and the degree of differentiation gradually increases. Tangshe complex pluton is the product of anticline tectonic emplacement after crystal-separation of the remelting of lower crustal material in the inland tension environment after the subduction-collision orogenic of paleo-Pacific plate.Types of mineralization and minerals in the contact zone of Tangshe complex pluton are characterized by W→Ag-Pb-Zn→Sb/fluorite zoning from inside to outside, which form a skarn-hydrothermal vein-type mineralization system with a good prospecting prospect.