【摘要】：最新地質(zhì)調(diào)查發(fā)現(xiàn)鄂北大洪山地區(qū)存在晉寧期的俯沖增生雜巖,其主體以一套弧前碎屑巖(復(fù)理石)為基質(zhì),夾大量白云巖、礫巖、硅泥質(zhì)巖、輝長(zhǎng)巖、輝綠巖、玄武巖等巖塊,巖塊與基質(zhì)、巖塊與巖塊之間以斷層接觸。雜巖中大量的鎂鐵質(zhì)巖巖塊可能形成于洋中脊、洋內(nèi)弧、洋島等不同類型與洋盆演化相關(guān)的構(gòu)造環(huán)境,首次報(bào)道綠林地區(qū)雜巖中一套呈巖塊產(chǎn)出的洋島堿性玄武巖。地球化學(xué)方面,綠林地區(qū)玄武巖具低K_2O、高TiO_2、Nb/Y=0.88~1.06、輕稀土元素強(qiáng)烈富集、重稀土元素明顯虧損等特點(diǎn),整體與夏威夷洋島堿性玄武巖的地球化學(xué)特征基本一致。綠林玄武巖LA-ICP-MS鋯石U-Pb測(cè)年結(jié)果顯示,17個(gè)測(cè)點(diǎn)加權(quán)平均年齡為(817.1±7.2)Ma(MSWD=3.3),代表綠林玄武巖的形成年齡。因此綠林玄武巖可能代表晉寧期的洋島堿性玄武巖殘塊,成巖巖漿來源于富集地幔。綠林洋島堿性玄武巖與大洪山地區(qū)其他洋島玄武巖類巖石組合可能同是洋盆消減過程中的洋殼物質(zhì)殘余,不同類型洋島玄武巖的出現(xiàn)是洋盆演化階段性、復(fù)雜性的體現(xiàn),這些巖石建造的厘定為大洪山存在晉寧期縫合帶的觀點(diǎn)提供了強(qiáng)有力的證據(jù)。
[Abstract]:The latest geological investigation found that there were subducted accretive complex rocks of Jinning period in the Dahongshan area of northern Hubei Province, the main body of which was a set of pre-arc clastic rocks (clastic rocks), with a large amount of dolomite, conglomerate, sillimanite, gabbro, diabase, etc. Basalt and other rock blocks, rock and matrix, rock block to rock block contact with fault. A large number of mafic rock blocks in the complex may form different types of tectonic environments related to the evolution of oceanic basins, such as Yu Yang middle ridge, intraoceanic arc and oceanic island. It is the first time to report a set of oceanic island alkaline basalts in the complex rocks in the greenlin area. Geochemically, basalts in the Greenlin area are characterized by low K _ 2O, strong enrichment of high TiO_2,Nb/Y=0.88~1.06, light rare earth elements, and obvious depletion of heavy rare earth elements. The geochemical characteristics of alkaline basalts in the whole ocean island of Hawaii are basically consistent. The LA-ICP-MS zircon U-Pb dating results of the greenlin basalt show that the weighted mean age of 17 sites is (817.1 鹵7.2) Ma (MSWD=3.3), which represents the age of formation of the greenlin basalt. Therefore the greenlin basalt may represent the oceanic island alkaline basalt remnant in Jinning period and the diagenetic magma originated from the enriched mantle. The basalt assemblages of Lulingyang Island and other oceanic island basalts in Dahongshan area may be the remnants of oceanic crust material in the process of oceanic basin subduction, and the appearance of different types of oceanic island basalts is the embodiment of stage and complexity of oceanic basin evolution. The determination of these rock formations provides strong evidence for the existence of the Jinning suture zone in Dahongshan.
【作者單位】： 湖北省地質(zhì)調(diào)查院;
【基金】：湖北省地質(zhì)局科技項(xiàng)目(KJ2015-1) 中國(guó)地質(zhì)調(diào)查局項(xiàng)目(12120113012800;DD20160030-06)
【分類號(hào)】：P588.145

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相關(guān)期刊論文 前2條

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