关键词: 铁质花岗岩；花岗岩产铀潜力；印支晚期桃金洞花岗岩；诸广山南体

Abstract:

In this paper, geochronology and petrogeochemistry and Sr-Nd isotopic geochemistry of Taojindong granite are studied and
compared with those of other Indosinian granites in the eastern part of the southern Zhuguangshan composite pluton. LA-ICP-MS
zircon U-Pb dating for Taojindong granite yields an age of 204 ± 2.1 Ma, suggesting its intrusion in the late Indosinian period.
Chemically, this granite is peraluminou, and shows relatively high contents of silica（SiO2=69.7%~75.0%）, alkali（K2O+Na2O=7.74%~
9.08%）and FeOT, and low abundance of magnesium. Thus, the Taojindong granite is characterized as calc-alkalic- to alkali-calcic,
peraluminous, and ferroan. The rock samples display high total REE contents（ΣREE=226~272×10-6）, with LREE/HREE ratios of
6.27~11.4 and（La/Yb）N ratios of 4.01~15.0, and a negative Eu anomaly（δEu=0.15~0.42）. This granite is enriched in Rb, Th and U,

and depleted in Ba, Sr, Ti and Eu, showing characteristics of a typical low Ba and Sr granite. Isotope geochemical analysis reveals high
and variable initial 87Sr/86Sr ratios（0.71922~0.72040）, yet low and constant εNd（t）values（-10.0~-10.2）with two stage model age of
1.80~1.82 Ga. All these features suggest that the Taojindong granite is a typical crust-derived granite. The granitic magma may have
been derived from low-intermediate degree partial melting in a crustal extension-thinning tectonic environment in the late Indosinian
period, of metagreywackes rocks whose origin was crust rocks separated from the mantle in the Paleoproterozoic. In the southern
Zhuguangshan composite pluton, compared with non-uranium-mineralization-bearing granites, the uranium-mineralization- bearing
granites experienced stronger hydrothermal alterations, and show wider variations in FeOT（/ FeOT + MgO）ratios, higher uranium
concentration, more depletion in CaO, Ba, Sr, Ti and Eu, lower εNd（t） values and more ancient two stage model ages. The
non-uranium-mineralization-bearing granites were derived from metagreywackes and relatively depleted in U. Taojindong granites have
not experienced significant hydrothermal alteration and have no characteristics of intense alteration like uranium-mineralizationbearing
granites. The geochemical features of the Taojindong granites are similar to those of the Indosinian non-uranium-mineralizationbearing
granites in the southern part of the Zhuguangshan composite pluton, and its uranium potential is slight.

Key words: ferroan granite, uranium mineralization potential of granite, late Indosinian Taojindong granites, Zhuguangshan composite pluton