Generation of Late Mesozoic Qianlishan A2-type granite in Nanling Range, South China: Implications for Shizhuyuan W-Sn mineralization and tectonic evolution
Generation of Late Mesozoic Qianlishan A2-type granite in Nanling Range, South China: Implications for Shizhuyuan W-Sn mineralization and tectonic evolution
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南岭晚中生代千里山A(2)型花岗岩的生成：对柿竹园钨锡成矿及构造演化的启示
DOI：
10.1016/j.lithos.2016.10.010
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发表时间：
2016-12-01
期刊：
影响因子：
3.5
通讯作者：
Xu, Deru
中科院分区：
文献类型：
--
作者：
Chen, Yuxiao;Li, He;Xu, Deru
南岭西段晚中生代千里山花岗杂岩体与柿竹园巨型钨锡钼铋多金属存款矿床共生。主要由P-1斑状黑云母花岗岩、P-2等粒黑云母花岗岩和P-3花岗斑岩三期侵入岩组成。花岗岩的三相均含有石英、斜长石、钾长石和富铁黑云母。它们具有A型花岗岩的地球化学亲合性，高的FeOT/（FeOT + MgO）比（0.84-0.99），总碱（Na 2 O + K 2 O，7.50- 9.04wt.%），高Ga/Al比（10，000 × Ga/Al > 2.6）和高Zr + Nb + Y + Ce浓度（>350 ppm）。高Y/Nb比值（>1.2）表明千里山杂岩属A（2）型花岗岩。P1、P2和P3花岗岩的锆石U-Pb年龄分别为158-157 Ma、158-155 Ma和154 Ma。这些年龄与柿竹园钨多金属存款矿床的成矿年龄相似，误差在一定范围内。千里山花岗岩形成于低氧逸度条件下，锆石Ce ~（4+）/Ce ~（3+）比值较低（1.53 ~ 198），磷灰石中Eu负异常显著（Eu-N/Eu-N ~*，0.03-0.13）。P-3花岗岩的新锆石Hf（t）值为-13.0 ~-4.4，与P-1和P-2花岗岩的结果相似。花岗岩和磷灰石颗粒的特点是高F，但低Cl浓度，表明高F/CI组分的流入。特别是P-2花岗岩具有较高的F（1840-8690 ppm）、W（7-158 ppm）和Sn（6-51 ppm）含量，具有较强的演化特征。千里山杂岩体中F与W、Sn的正相关趋势表明，高F源是W、Sn成矿的关键。我们认为，岩石圈地幔源区在俯冲带的远端被俯冲流体交代，形成千里山花岗岩的A（2）特征，氟是通过大洋板片中多硅白云母的裂解引入的。岩石圈地幔的部分熔融是由软流圈地幔上涌引起的，软流圈地幔上涌是板片回滚的结果。钨、锡在还原花岗质岩浆中通过高F含量的强化分馏作用而富集，形成巨型多金属矿床。(C)2016由Elsevier B. V.出版
The Late Mesozoic Qianlishan granitic complex in the western Nanling Range, South China is associated with the Shizhuyuan giant W-Sn-Mo-Bi polymetallic deposit. It mainly consists of three phases of intrusions, P-1 porphyritic biotite granite, P-2 equigranular biotite granite and P-3 granite porphyry. All three phases of granite contain quartz, plagioclase, K-feldspar and Fe-rich biotite. They have geochemical affinities of A-type granites, e.g., high FeOT/(FeOT + MgO) ratios (0.84-0.99), total alkali (Na2O + K2O, 7.50-9.04 wt.%), high Ga/AI ratios (10,000*Ga/Al > 2.6) and high Zr + Nb + Y + Ce concentrations (>350 ppm). High Y/Nb ratios (>1.2) suggest that the Qianlishan complex belongs to A(2)-type granite. Zircon U-Pb ages indicate a short age interval decreasing from 158-157 Ma, to 158-155 Ma and to 154 Ma for the P-1, P-2 and P-3 granites, respectively. These ages are similar to the mineralization age of the Shizhuyuan tungsten polymetallic deposit, within error. The Qianlishan granites were generated at low oxygen fugacity conditions based on the low values of zircon Ce4+/Ce3+ ratios (1.53-198) and significantly negative Eu anomalies (Eu-N/Eu-N*, 0.03-0.13) in apatite. New zircon epsilon Hf(t) values for the P-3 granite range from -13.0 to -4.4, similar to those previously obtained for the P-1 and P-2 granites. Both the granite and apatite grains therein are characterized by high F but low Cl concentrations, suggesting the influx of a high F/CI component. The P-2 granites especially contain higher F contents (1840-8690 ppm) and W (7-158 ppm) and Sn (6-51 ppm) concentrations and with stronger evolution features. Positive trends between F and W and Sn of Qianlishan complex indicate that high F source is crucial for mineralization of W and Sn. We consider that the lithospheric mantle source may have been metasomatized by subduction fluids in the far end of subduction zones to produce the A(2) feature of the Qianlishan granite and the fluorine was introduced through breakdown of phengite in the oceanic slab. Partial melting of the lithospheric mantle was induced by upwelling of the asthenospheric mantle as a consequence of slab rollback. Tungsten and tin have been enriched in reduced granitic magmas through fractionation enhanced by high F contents, forming the giant polymetallic deposits. (C) 2016 Published by Elsevier B.V.