| The southern Zhuguangshan composite pluton (SZCP) is an important part of Taoshan-zhuguang uranium metallogenic belt, where the uranuim deposits are mainly emplaced in the its central and eastern parts, and no uranium mineralization in the west has been reported. More previous studies foucused on granites in the eastern and western parts than in the north and middle parts (Sanjiu area) of the SZCP, In this study, Four Mesozoic granites in the Sanjiu, inclding the Taojindong (TJD), Dongling (DL), Jiulong (JL) and Zhongpeng (ZP) granites, have been studied by LA-ICP-MS zircon U-Pb dating, elemental and Sr-Nd isotopic geochemistry to constrain their petrogenesis and tectonic settings. In comparison with other uranium mineralization and non-uranium-mineralization granites, this paper attempts to evaluate the mineralization Potential of these four granites.The TJD granite yields a crystallization age of 204±2.1 Ma, suggesting it was intruded in the late Indosinian. Geochemically, the TJD granite is characterized by mainly peraluminous (ASI=1.02-1.12, except one sample 0.98), enrichments in more FeOT than MgO contents belonging to calc-alkalic to alkali-calcic ferroan granite. It has relatively high REE contents (ΣREE=225.6～271.9±10-6) with enrichments of LREE (LREE/HREE=6.27～11.4) and strong negative anomalies of Eu (δEu 0.15～0.42). It also shows enrichments in Rb, Th and U, and depletions in Ba, Sr, Ti and Eu, belonging to the typical granite with low Ba and Sr. Isotopically, it exhibits higher (87Sr/86Sr)i ratios (0.71922～0.72040) and lower εNd(t) (-10.0～10.2) with paleoproterozoic two-stage Nd model ages (1.80～1.82 Ga). The TJD graniteis a typical crust-derived granite. Its granitic magma may have been derived from low-intermediate degree partial melting of Paleoproterozoic metagreywackes rocks in a crustal extension-thinning tectonic environment.The DL, JL and ZP granites were crystallized at 161.9±1.5 Ma、162.9±2.3 Ma and 148.2±1.9 Ma, respectively, suggesting they were emplaced in the earl-y Yanshanian. They are characterized by high FeOT, low MgO and peralumino-us (ASI=1.00～1.12), belonging to calc-alkalic to alkali-calcic ferroan granites. All of these three granites show high SiO2 (average 75.9%), Rb/Sr ratios (ave rage 22.2) and evident negative anomalies of Eu (0.04～0.23), suggesting that t-hey are highly fractionatedgranites, Comparison of the DL and JL granites in t-he Sanjiang area with the Changjiang granite, indicates that they have similar petrogenesis. The source rocks of the simultaneous generated DL and JL granit-es are a mix of sandy and muddy rock, their granitic magma may has been d-erived from the partial melting of Paleoproterozoic metasedimentary rocks in a extension tectonic environment. The geochemical and isotopeic characteristics of the ZP granite are similar to those of the uranium mineralization Maofeng g-ranite and W-bearing granites in Nanling. T-he ZP granite was derived from t-he partial melting of the Paleoproterozoic mu-dstone under a extension environ-mentComparative studies have shown that the alteration of uranium mineralization granites in the SZCP is relatively strong. Their FeOT/(FeOT+MgO) ratios vary widely, belonging to Fe-enriched granite which reflects the relatively reductive magmatic evironment. The uranium mineralization granites are also more depleted in CaO, Ba, Sr, Ti and Eu. Uranium in the non-uranium mineralization granites are mainly present in accessory minerals such as zircon and thorite which have not experienced significant hydrothermal alteration. The geochemical features of the TJD granite is similar to those of the Indosinian non-uranium-mineralization granites in the SZCP and its uranium metallogenic potential is limited. DL, JL and ZP granites has potential in uranium mineralization. ZP grante with a REE tetrad effect which will have more strong uranium metallogenic potential. |
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