邱燕, 陈国能, 刘方兰. 南海西南海盆花岗岩的发现及其构造意义[J]. 地质通报, 2008, 27(12): 2104-2107.
    引用本文: 邱燕, 陈国能, 刘方兰. 南海西南海盆花岗岩的发现及其构造意义[J]. 地质通报, 2008, 27(12): 2104-2107.
    QIU Yan, CHEN Guo-neng, LIU Fang-lan. Discovery of granite and its tectonic significance in southwestern basin, south China Sea[J]. Geological Bulletin of China, 2008, 27(12): 2104-2107.
    Citation: QIU Yan, CHEN Guo-neng, LIU Fang-lan. Discovery of granite and its tectonic significance in southwestern basin, south China Sea[J]. Geological Bulletin of China, 2008, 27(12): 2104-2107.

    南海西南海盆花岗岩的发现及其构造意义

    Discovery of granite and its tectonic significance in southwestern basin, south China Sea

    • 摘要: 在水深约2800m~4000m、地壳厚度大致为8-10km的南海西南海盆,广州海洋地质调查局1:100万海洋区域地质调查在3个测站拖网获得花岗岩和沉积-变质岩样品。经显微构造分析与鉴定,这3个测站的样品分别为细粒黑云母花岗岩、石英变沉积岩和花岗闪长岩。全岩Ar-Ar 和K-Ar同位素年龄测定1yDG测站细粒黑云母花岗岩年龄为109.7 Ma和114.2Ma,离子探针测出其锆石年龄为120Ma,证实该花岗岩石形成于早白垩世晚期,因而极有可能属于华南东部中生代花岗岩带的元素。以往有诸多学者认为南海西南海盆的形成是海底扩张所引起的,地壳性质属于洋壳。花岗岩的发现使西南海盆地壳属洋壳的认识受到严重挑战。

       

      Abstract: The samples of granite and metamorphic-sediment rock have been obtained at three spots with the water depth of 2800m-4000m in Xinan Sea-basin of the South China Sea, where the crust thickness is about 8-10 kilometres calculated by gravitational and magnetic data and taken for oceanic crust by some tectonic geologists. These samples were dragged by Guangzhou Marine Geological Survey when they were doing the project of offshore mapping with 1:1000000 scale there. The three samples are respectively fine granitite, quartz metamorphic-sediment and granodioite by microstructure analysis. The isotopic age of the fine granitite is 109.7Ma and 114.2Ma measured by Ar-Ar and K-Ar methods and the zircon age is 120Ma, by ion microprobe. These realities are made sure that the granites formed in the late of early Cretaceous, and therefore they belong to a part of Mesozoic granite zone of the South China quite possibly. The discovery above strongly challenges the idea that the crust of Xinan Sea-basin in the South China Sea is oceanic crust due to seafloor spreading, which is considered, up to the present.

       

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