| 南岭富重稀土花岗岩类的特征和意义 |
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| CHARACTERISTICS AND SIGNIFICANCE OF HREE-RICH GRANITOIDS OF THE NANLING MOUNTAIN AREA |
| Calca-alkaline to subalkaline HREE-rich granitoids, refering to granitic rocks with LREE/HREE ratio<1, are widely distributed in the Nanling Mountain area, South China. They occur as late or marginal phases of milti-phased intrusive complexes with ages ranging from 909 to 82 Ma, and on various tectonic backgrounds including the Jiangnan geoanticline, post-Caledonian uplifts and Hercynian-Indosinian depressions of the South China fold belt. Either hypergene, such as granitic or quartz pophyry, or hypogene diversities, including two-feldspar granite, K-feldspar granite and alkaline feldspar granite, are characterized by high silica and alkali, ;aluminia-ove-rsaturation and depletion of basic components. The main minerals are quartz, K-feldspar (orthoclase, microcline or perthitic microcline), plagioclase(An 0-30), small amounts of lepidomelane and siderophyllite, and/or muscovite.Among trace elements (ppm),Rb (340-1991) and F (340-6700) are significantly enriched, Sr (10-30) and Ba (20-70) greatly depleted, and Li varies widely from 8 to 373. REE contents range from 100 to 427 ppm, but those with strong albitization which is often related to Nb-Ta mineralization have a very low range between 35 and 50 ppm. In most cases, δEu values are <0.1, the LREE/HREE and Y/REE ratios are 0.23-0.99 and 0.3-0.6, respectively.Most of HREE-rich granites are characterized by high (87Sr/86Sr)i ratios(0.709-0.732) and enrichment of radiogenic lead isotopes for K'-feldspars, which generally cannot be discriminated from those of the early coexisting LREE-rich phases. Combined with lack of temporal and spatial constraints, HREE concentration in granitic magma is suggested as local processes including ( 1 ) fractional crystallization; ( 2 ) thermogravitational diffusion; ( 3 ) fluid metasomatism and ( 4 ) remelting, which are cotrolled by local physi-cochemical environments. |
| WU Cheng-yu,BAI Ge,HUANG Dian-hao,ZHU Zheng-shu.1992.CHARACTERISTICS AND SIGNIFICANCE OF HREE-RICH GRANITOIDS OF THE NANLING MOUNTAIN AREA[J].Acta Geoscientica Sinica,13(1):43-58. |
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