REE and C‐O Isotopic Geochemistry of Calcites from the World‐class Huize Pb‐Zn Deposits, Yunnan, China: Implications for the Ore Genesis

Abstract

The world‐class Huize Pb‐Zn deposits of Yunnan province, in southwestern China, located in the center of the Sichuan‐Yunnan‐Guizhou Pb‐Zn polymetallic metallogenic province, has Pb+Zn reserves of more than 5 million tons at Pb+Zn grade of higher than 25% and contains abundant associated metals, such as Ag, Ge, Cd, and Ga. The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield. Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types, namely lumpy, patch and vein calcites in accordance with their occurrence. There is not intercalated contact between calcite and ore minerals and among the three types of calcite, indicating that they are the same ore‐forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element (REE) and C‐O isotopic compositions of calcites in the Huize Pb‐Zn deposits. From lumpy to patch to vein calcites, REE contents decrease as LREE/HREE ratios increase. The chondrite‐normalized REE patterns of the three types of calcites are characterized by LREE‐rich shaped, in which the lumpy calcite shows (La)N < (Ce)N < (Pr)N≈ (Nd)N with Eu/Eu* < 1, the patch calcite has (La)N < (Ce)N < (Pr)N≈ (Nd)N with Eu/Eu* > 1, and the vein calcite displays (La)N > (Ce)N > (Pr)N > (Nd)N with Eu/Eu* > 1. The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield. The δ13CPDB and δ18OSMOW values of the three types of calcites vary from −3.5‰ to −2.1‰ and 16.7‰ to 18.6‰, respectively, falling within a small field between primary mantle and marine carbonate in the δ13CPDB vs δ18OSMOW diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages. The ore‐forming fluids of the deposits resulted from crustal‐mantle mixing processes, in which the mantle‐derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts, and the crustal fluid was mainly provided by carbonate strata in the orefield. The ore‐forming fluids in the deposits were homogenized before mineralization, and the ore‐forming environment varied from relatively reducing to oxidizing.

Geological, rare earth elemental and isotopic constraints on the origin of the Banbanqiao Zn–Pb deposit, southwest China

“…These deposits distribute in a large triangular area of 170,000 km 2 in SW Sichuan, NE Yunnan and NW Guizhou provinces Xu et al, 2014;Zhang et al, 2015). This triangular area forms the famous SYG Pb-Zn metallogenic province (e.g., Liu and Lin, 1999;Zhou et al, 2001;Han et al, 2007;Huang et al, 2010;Zhou et al, 2013aZhou et al, , 2014a. Among these deposits, the Huize world-class Zn-Pb-Ge deposit (Fig.…”

“…In the northern part of the Yangtze Block, sparse metamorphic rocks represent crystalline basement (Qiu et al, 2000;Hu and Zhou, 2012), whereas the Meso-to Neo-Proterozoic volcanic-sedimentary sequence represents folded basement in the western part (Yan et al, 2003;Sun et al, 2009;Zhao et al, 2010). The cover sequence of the western Yangtze Block consists mainly of Paleozoic and lower Mesozoic shallow marine sedimentary rocks, and Jurassic to Cenozoic terrestrial sediments (Liu and Lin, 1999;Yan et al, 2003;Huang et al, 2010). In the western Yangtze Block, the Permian mantle plume-derived Emeishan large igneous province (ca.…”

“…Tectonically, this province is located on the western Yangtze Block, southwest China (Fig. 1A;Zheng and Wang, 1991;Cromie et al, 1996;Zhou et al, 2001;Han et al, 2007;Huang et al, 2010), where multiple orogenic events occurred (e.g., Zaw et al, 2007;Hu and Zhou, 2012;Pirajno, 2013). Studies have demonstrated that the Pb-Zn deposits in the SYG province have some similar features, including: (i) host in carbonate rocks of Sinian (Neoproterozoic Ediacaran) to Permian, (ii) occur within thrust fault and/or fold structures, (iii) high grade of Pb + Zn (>15 wt.%), (iv) spatially associated with the Permian Emeishan flood basalts (ca.…”

“…On the other hand, although the most of these Pb-Zn deposits in the SYG province are clearly epigenetic, different opinions have been proposed on the ore genesis of them. These hypotheses include: (i) the Mississippi Valley-type (MVT) deposit related to basin brine (Zheng and Wang, 1991;Zhou et al, 2001;Wu et al, 2013;Zhang et al, 2015), (ii) the Permian Emeishan mantle plume-related deposit (Xie, 1963;Huang et al, 2003Huang et al, , 2010Xu et al, 2014), and (iii) the unique SYG-type deposit that are different from the typical MVT deposit Zhou et al, 2013aZhou et al, -c, 2014b. Recently, studies of Cd, Ge and Zn isotopes Zhou et al, 2014a,b;Meng et al, 2015), and in situ trace elements of sphalerite (Ye et al, 2011) have indicated that the ore genesis of these Pb-Zn deposits in the SYG province is Zhou et al, 2013a).…”

Identification of Two Types of Metallogenic Fluids in the Ultra-Large Huize Pb–Zn Deposit, SW China

“…(1) Fluid mixing: based on C-O isotopic analysis, Huang et al [8,[33][34][35] believe that the mixing of crust and mantle fluids is the key to metallogenesis; Luo et al [36] proposed that mixing between fluids is the primary mechanism of precipitation, based on their summation of previous studies on fluid inclusions; Zhang et al [37][38][39][40] believe that the processes of fluid mixing and boiling are the primary causes of sulfide precipitation, based on the results of studies on strontium isotopes and fluid inclusions. (2) Fluid boiling: Han et al [12,13,23] performed a detailed study of the geological characteristics and fluid inclusions and came to the conclusion that fluid boiling is the primary mechanism of mineral enrichment and metallogenesis.…”