The Research On The Petrological Geochemistry And Genesis Of The Mo Tianling And YuanBaoshan Granites In The Northwest Of GuangXi

The research area is located at the Yangtze plate and South China plate margin. The Neoproterozoic large-area igneous rocks widely spread in Yangtze block of South China. Particularly, the Neoproterozoic granites and associated mafic-ultramafic rocks are widely developed in northern area of Guangxi. There are close links of time and space between mafic rocks and gabbro-intrusions. The northern area of Guangxi are ideal sites of studying relationship between mafic-ultramafic rocks and granitic magmatism. This paper discuss tectonic environment and petrological geochemistry characteristics of igneous rocks and sedimentary rocks from the northern area of Guangxi on the basis of a large number of field geological work and the studies of major elements, trace elements and zircon age.Due to the the Mesoproterozoic and Neoproterozoic subduction of"the Small Inter- continental Sea Basin"from southestern Guangxi. "Sibao Arc" and " Longsheng Arc" are formed in southern Yangtze plate successively. Limited subduction happens when the small ocean basin closes, and then intracontinental subduction orogeny take palce. Diagrams of major elements and trace elements of mafic- ultramafic rocks, granites and metamorphic rocks show characteristics of the arc genesis and granites have also syn- collisional granite characteristics.According to the same characteristics of major elements, REE and trace elements among mafic-ultramafic rocks, granites and metamorphic rocks, magmatic melt experiences intensely fractional crystallization. So the igneous rocks may undergo crustal(Sibao Group) contamination, Magma of Mafic-ultramafic rocks and granites show the homology of resource.In terms of the intrusive relationship, petrological geochemistry characteristics , composition between rock-forming minerals and accessory minerals of igneous rocks, successions of igneous rocks as followed is indicated: Mafic-ultramafic rocks ??→granodiorites ??→biotite granitesREE and tace elements Pattern for Danzhou Group and igneous rocks are same.∑REE of Danzhou Group is higher than that of igneous rocks. According to the CL images and zircon age of Danzhou Group, Inference is reached, mafic-ultramafic rocks, granodiorites and biotite granites may be the source regional rocks. The lowermost sedimentary age of Danzhou Group is no higher than 766.0±4.4Ma.