發(fā)布時(shí)間：2018-06-05 07:05

  本文選題：南海 + 西沙��； 參考：《中國(guó)科學(xué):地球科學(xué)》2017年12期

【摘要】：基底年齡對(duì)重建海洋區(qū)域的構(gòu)造演化歷史具有重要意義.南海西沙隆起盆地基底方面的研究主要局限在重磁和地震資料以及20世紀(jì)70年代西永一井的分析資料上,長(zhǎng)期沒(méi)有新的突破.本文針對(duì)新獲取的西科一井兩個(gè)基底樣品開展了巖石學(xué)分析和鋯石U-Pb同位素測(cè)年,來(lái)研究西沙群島基底的形成時(shí)間及構(gòu)造屬性.結(jié)果表明,基底成分為晚侏羅世角閃斜長(zhǎng)片麻巖,鋯石~(206)Pb/~(238)U平均年齡為(152.9±1.7)Ma,但是最年輕年齡為(137±1)Ma,說(shuō)明變質(zhì)作用結(jié)束時(shí)間大致在早白堊世.變質(zhì)巖底部與二長(zhǎng)花崗巖突變接觸,為早白堊世晚期((107.8±3.6)Ma)巖漿侵入的結(jié)果,與西永一井早期測(cè)得的前寒武紀(jì)基底年齡(全巖Rb-Sr法,627Ma)明顯不同,西科一井的基底鋯石都屬于晚中生代巖漿活動(dòng)的產(chǎn)物.晚侏羅世-早白堊世的區(qū)域變質(zhì)作用和花崗質(zhì)巖漿侵入不僅出現(xiàn)于西沙,在南海的珠江口盆地和南沙群島等區(qū)域都有報(bào)道,與東亞陸緣受到古太平洋板塊大規(guī)模、長(zhǎng)時(shí)間的俯沖密切相關(guān),其可能導(dǎo)致了中特提斯洋在南海的關(guān)閉.對(duì)于南海是否發(fā)育有統(tǒng)一的前寒武紀(jì)變質(zhì)結(jié)晶基底仍存在爭(zhēng)議,但是可以肯定的是,中生代板塊俯沖擠壓與新生代裂陷拉張已經(jīng)顯著改造了南海地區(qū)的原始基底
[Abstract]:The basement age is of great significance for the reconstruction of the tectonic evolution history of the marine area. The research on the basement of Xisha uplift basin in the South China Sea is mainly confined to the gravity and magnetic data and seismic data and the analysis data of Xiyong Yiyi well in the 1970s. There has been no new breakthrough for a long time. In this paper, petrological analysis and zircon U-Pb isotopic dating have been carried out for two basement samples obtained from Xichiyi well to study the formation time and tectonic properties of the basement of Xisha Islands. The results show that the basement composition is a late Jurassic hornblende gneiss with an average age of 152.9 鹵1.7 Ma for zircon Zircon 206Pb / L / 238U, but the youngest age is 137 鹵1 Ma, indicating that the end time of metamorphism was probably in the early Cretaceous. The metamorphic rock bottom is in contact with the monzomorphic granite, which is the result of magmatic intrusion in late early Cretaceous (107.8 鹵3.6 Ma), which is obviously different from the Precambrian basement age (whole-rock Rb-Sr method 627Ma), which was obtained in the early stage of Xiyong first well. The basement zircon of Xiceyi well is the product of late Mesozoic magmatic activity. The late Jurassic-early Cretaceous regional metamorphism and granitic magmatic intrusion occurred not only in Xisha, but also in the Pearl River mouth basin and Nansha Islands in the South China Sea. Long-term subduction may have led to the closure of the Middle Tethys in the South China Sea. It is still controversial whether there is a unified Precambrian metamorphic crystalline basement in the South China Sea, but it is certain that the Mesozoic plate subduction and Cenozoic rift extension have significantly altered the primitive basement in the South China Sea.
【作者單位】： 同濟(jì)大學(xué)海洋地質(zhì)國(guó)家重點(diǎn)實(shí)驗(yàn)室;中國(guó)地質(zhì)大學(xué)構(gòu)造與油氣資源教育部重點(diǎn)實(shí)驗(yàn)室;中海石油中國(guó)有限公司湛江分公司;西北大學(xué)地質(zhì)學(xué)系;
【基金】：國(guó)家科技重大專項(xiàng)項(xiàng)目(編號(hào):2017ZX05-26-005) 國(guó)家自然科學(xué)基金項(xiàng)目(批準(zhǔn)號(hào):91128207、41576059)資助
【分類號(hào)】：P736.1
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本文編號(hào)：1981092