CAJ | 학술논문

对鄂东南地区位于毛铺-两剑桥断裂带上的铜鼓山岩体进行了野外地质及镜下显微研究及岩石化学分析,重点分析了其中锆石U-Pb年龄和Hf同位素组成。结果表明铜鼓山岩体为石英闪长玢岩,岩体形成于(147±2.6) Ma,属晚侏罗世-早白垩世,与鄂东南地区其它岩体年龄具有一致性。铜鼓山岩体中存在的大量继承锆石。分析的4个继承锆石形成于古元古代晚期1798~1888 Ma。继承锆石具有高的Th/U比值和极其相似的Lu-Hf同位素组成,表明它们捕获于同一火成岩。这表明鄂东南地区存在古元古代基底。这些古元古代继承锆石低的εHf(t)值和冥太古代的 Hf 同位素两阶段模式年代暗示古元古代克拉通化是在太古宙基底上发展的。鄂东南地区和扬子陆块其它众多地区一样存在古元古代-太古宙基底。扬子陆块古元古代-太古宙基底极可能从四川盆地、鄂西崆岭和郧西地区东延至鄂东南地区。
대악동남지구위우모포-량검교단렬대상적동고산암체진행료야외지질급경하현미연구급암석화학분석,중점분석료기중고석U-Pb년령화Hf동위소조성。결과표명동고산암체위석영섬장분암,암체형성우(147±2.6) Ma,속만주라세-조백성세,여악동남지구기타암체년령구유일치성。동고산암체중존재적대량계승고석。분석적4개계승고석형성우고원고대만기1798~1888 Ma。계승고석구유고적Th/U비치화겁기상사적Lu-Hf동위소조성,표명타문포획우동일화성암。저표명악동남지구존재고원고대기저。저사고원고대계승고석저적εHf(t)치화명태고대적 Hf 동위소량계단모식년대암시고원고대극랍통화시재태고주기저상발전적。악동남지구화양자륙괴기타음다지구일양존재고원고대-태고주기저。양자륙괴고원고대-태고주기저겁가능종사천분지、악서공령화운서지구동연지악동남지구。
This paper has reported the integrated study of zircon U-Pb age and Lu-Hf isotope composition in zircons from the Tonggushan pluton, southeast Hubei Province. Tonggushan pluton is composed of quartz diorite porphyry. The 206Pb/238U mean age of magmatic zircon is (147±2.6) Ma, indicating that Tonggushan pluton was formed in the Late Jurassic-Early Cretaceous, which is consistent with the formation time of other plutons in this area. A large number of inherited zircons, formed in 1798~2888 Ma, exist in Tonggushan pluton. The Paleoproterozoic zircons are of magmatic origin and have similar 176Hf/177Hf and 176Lu/177Hf ratios, suggesting that they were probably derived from the same igneous basement rock. The Paleoproterozoic zircons have low Hf-isotope compositions and characteristics of crustal source. Hf model ages of these zircons and the presence of older inherited cores within them suggest that the source of Paleoproterozoic magma was Neoarchaean crust, implying the existence of an unexposed old basement beneath southeast Hubei Province and the whole Yangtze block. These data supply new clue to the study of the Precambrian basement evolution of Yangtze block. The Paleoproterozoic-Archean basement of the Yangtze Block most likely spreads from the Sichuan Basin through western Huebei Province to southeastern Hubei Province.