本文選題：揚(yáng)子陸塊 + 南沱組　； 參考：《地球科學(xué)》2016年10期

【摘要】：揚(yáng)子陸塊新元古代地層發(fā)育完整并廣泛分布,三峽地區(qū)南沱組冰磧巖是揚(yáng)子北部南華紀(jì)的冰成雜礫巖,不整合地覆蓋在新元古代黃陵花崗巖之上.南沱組冰磧巖成分復(fù)雜,分選性差,缺乏可對(duì)比的標(biāo)志,其沉積時(shí)代和物源組成研究較少且存在爭(zhēng)議.對(duì)南沱組冰磧巖開(kāi)展鋯石U-Pb定年工作,得到最年輕的鋯石年齡為706±7 Ma,印證了南沱組沉積時(shí)代應(yīng)不早于700Ma的說(shuō)法,并可與Marinoan冰期對(duì)應(yīng).所獲得鋯石U-Pb年齡譜峰值主要分為~3.0Ga,2.5~2.3Ga,2.05~1.95Ga和900~700Ma,反映了揚(yáng)子陸塊4次地殼再造事件,其中古元古代和太古代年齡與崆嶺雜巖相似,900~800Ma和800~700Ma的鋯石年齡與附近黃陵花崗巖和揚(yáng)子北緣巖體一致.冰磧砂巖的微量元素和同位素組成分異明顯,可能是揚(yáng)子北緣巖體、黃陵花崗巖和崆嶺雜巖不同程度混合的結(jié)果.南沱組冰磧巖中包裹的花崗質(zhì)礫石表現(xiàn)出不同的微量元素特征,具有偏低的稀土含量和虧損的重稀土組成,結(jié)合其鋯石U-Pb年齡和Sr-Nd同位素特征,這些花崗質(zhì)礫石主體可能來(lái)自于附近黃陵花崗巖和崆嶺巖基.南沱組冰磧巖的物質(zhì)組成特征反映了新元古時(shí)期,揚(yáng)子地區(qū)強(qiáng)烈的裂谷巖漿作用所導(dǎo)致的北高南低的地勢(shì)環(huán)境.
[Abstract]:The Neoproterozoic strata of the Yangtze block are well developed and widely distributed. The moraine rock of Nantuo formation in the three Gorges area is an ice conglomerate of the Nanhua period in the northern part of Yangzi, which is unconformably covered on the neoproterozoic Huangling granite. The moraine rocks of Nantuo formation are complex in composition, poor in sorting and lack of comparable markers, and there are few researches on sedimentary age and provenance composition in Nantuo formation. Zircon U-Pb dating was carried out for the moraine rocks of Nantuo formation, and the youngest zircon age was 706 鹵7 Ma, which confirmed that the sedimentary age of Nantuo formation should not be earlier than 700Ma, and could correspond to Marinoan glacial age. The peak values of zircon U-Pb age spectrum are mainly divided into 3. 0 Ga, 2. 5, 2. 3, 2. 05 and 1. 95 Ga and 900, 700 Ma, which reflect the 4 crustal reconstruction events in the Yangtze continent block. The zircon ages of Gu Yuan and Archean are similar to those of the Kongling complex and the zircon ages of 800~700Ma and Huangling granites are consistent with those of the nearby Huangling granites and the northern margin of Yangtze. The trace elements and isotopic compositions of moraine sandstone are distinct, which may be the result of the mixing of the northern Yangtze margin, Huangling granite and Kongling complex to different degrees. The granitic gravels in the moraine rocks of the Nantuo formation show different trace element characteristics, with low rare earth content and depleted heavy rare earth composition, combined with the zircon U-Pb age and Sr-Nd isotopic characteristics. These granitic gravel bodies may be derived from nearby Huangling granite and Kongling rock bases. The material composition characteristics of moraine rocks in Nantuo formation reflect the strong rift magmatism in Yangzi area in the Neoproterozoic.
【作者單位】： 中國(guó)科學(xué)技術(shù)大學(xué)地球和空間科學(xué)學(xué)院;中國(guó)地質(zhì)大學(xué)地球科學(xué)學(xué)院;
【基金】：國(guó)家自然科學(xué)基金項(xiàng)目(Nos.40973042;41090372) 中央高�；究蒲袠I(yè)務(wù)費(fèi)專項(xiàng)資金
【分類號(hào)】：P597.3;P588.2

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