郯庐断裂带南段构造演化与邻区成矿作用——从年代学资料得到的启示

The tectonic evolution of the southern segment of Tancheng-Lujiang fault zone and the metallogenesis in its adjacent region:Implications from the high precision geochronology

郯庐断裂带为我国东部北北东—北东向岩石圈深大断裂带。在其南段的邻区,分布有胶东金矿区、鲁西铁金矿区以及长江中下游的铁铜(金)成矿带和苏北油气田等矿产。从已获得大量测年资料分析,可将构造—岩浆—成矿事件分为3个阶段:1)早期(800～550 Ma):自元古宙泛古陆裂解和随之而来的加里东期古地震和局部海西期喷流作用,证实地壳运动早已拉开了它的"构造活动序幕",此阶段继承和构建了华北克拉通岩石圈先存的构造薄弱带,从成矿作用而论,此阶段可称为"成矿预备场地";2)主期(1 80～110 Ma):在三叠纪期间,扬子板块和华北板块陆—陆碰撞和中生代西太平洋板块向欧亚板块俯冲等,造就了现今郯庐断裂与分支断裂的构造格架。其中主峰形成时间为140～120 Ma±,在这个阶段广泛有钙碱性系列、富钾高锶钙碱系列、碱性系列岩浆和后期成矿热液,沿着有利构造空间剧烈活动和成矿就位。本区壳幔混熔型和壳源同熔型花岗岩,是地壳减薄和下地壳拆沉、底侵的产物,而不是单一的构造运动的结果。此阶段可称为断裂构造—岩浆活动—成矿作用的鼎盛期;3)晚期(60Ma～现代):沿东西向与北北东向(或北东向)断裂交汇处,存在橄榄玄武岩喷侵,为石油和天然气的形成提供了热源和物源,此期可称其为构造—岩浆活动的衰变期。

Tancheng-Lujiang（Tan-Lu）fault zone is a lithospheric deep fault zone with the trending of NNE-NE in eastern China. There are four concentrated mineral areas which including Au mine of Jiaodong Peninsula,Fe-Au mine of western Shangdong Province,Fe-Cu mine of the middle and lower reaches of the Yangtze River and oil and gas field of northern Jiangsu Province. Based on a large amount of high precision dating data,the tectono-magmatic-mineralization events of these areas can be classified into three phases： 1）Early phase（800～550 Ma）. In this phase,pan-paleocontinent breakup commenced in Neoproterozoic,paleo-seism occurred in Caledonian and local volcanic-sedimentary exhalative in shallow marine environments in Hercynian demonstrated that the ＂tectonic activity prelude＂ of crustal movement had been unclosed. The prior tectonic weakness belt of North China Craton lithosphere was succeeded and constructed in this phase,which can described as metallogenesis preparation period. 2）Main phase（180～110 Ma）. The present tectonic frame of Tan-Lu fault zone was accomplished by continent collision of Yangtze Plate and northern China Plate in Triassic,and dive of west Pacific Plate in Mesozoic to Eurasian Plate. Especially in around 140～120 Ma,calc-alkaline,high-K and high Sr calc-alkaline magmas as well as metallogenesis fluids in the late stages of magmatism ascent made violent activities and deposited as metallogenesis along favourite tectonic space. Crustal thinning,crust-mantle delamination and mantle-derived magma underplating led to the appearance of syntexis-type and transformation-type granites which is not due to any single tectonic movement. This phrase can be described as summit grade. 3）Late phase（60 Ma～now）. There is usually olive-basalt spouting along the junctions of EW and NNE（or NE）trending faults,which offers heat and material sources for the formation of oil and gas. This phase is the declining period of tectonic-magamatism. Pan-paleocontinental breakup,Continent-continent collision,West Pacific Plate