Gold Mineralization in the Kyaikhto District, Mon State, Southern Myanmar

Abstract

The Kyaikhto gold district is located within the Slate Belt and Mogok Metamorphic Belt of Southern Myanmar. The study area is covered by Carboniferous to Lower Permian metasedimentary rocks consisting of slate, phyllite, and schist of the Mergui Group, intruded by later igneous rocks. Four gold occurrences have been identified in the Kyaikhto district: the Kunzeik in the north, Zibyaung, and Thae Phyu Chaung in the center and Meyon in the south. Gold mineralization in the Kyaikhto district is associated with sheeted, stockwork, dissemination, and sulfide-bearing quartz veins. Ore minerals recognized include sphalerite, galena, chalcopyrite, molybdenite and pyrite with minor native gold and electrum. Two types of fluid inclusions were examined in the quartz samples of the Kunzeik and Zibyaung-Type A: aqueous carbonic fluid inclusions and Type B: aqueous fluid inclusions. At the Kunzeik, Type A fluid inclusions homogenize at temperatures from 296˚C to 376˚C with low salinities (1.6-4.6 wt% NaCl equivalent). The homogenization temperatures of Type B fluid inclusions in vein quartz range from 246˚C to 312˚C, with salinities of between 1.2 and 10.7 wt% NaCl equivalent. In the Zibyaung, the homogenization temperatures of Type A inclusions vary from 305˚C to 378˚C, with salinities from 4.6 to 9.6 wt% NaCl equivalent. The homogenization temperatures of Type B fluid inclusions mainly range from 242˚C to 298˚C, with salinities from 0.9 to 11.8 wt% NaCl equivalent. These characteristics of fluid inclusions are similar to those of orogenic gold mineralization systems.

Origin and Characteristics of the Shwetagun Deposit, Modi Taung-Nankwe Gold District and the Kunzeik and Zibyaung Deposits, Kyaikhto Gold District in Mergui Belt, Myanmar: Implications for Fluid Source and Orogenic Gold Mineralization

“…Mineralization in the Kyaikhto gold district is hosted by metasedimentary rocks of sandstone, slate, phyllite, and schist, and associated with the biotite granite and biotite granodiorite (Figure 7). The granitic rocks in this area can be correlated to the Mokpalin quartz diorite and the Kyaikhtiyo granite that have yielded the LA-ICP-MS zircon U-Pb ages of 90.8 ± 0.8 Ma and 63.3 ± 0.6 Ma, respectively (Figure 7; Mitchell et al, 2012;Myo Kyaw Hlaing et al, 2019). The metamorphic grade of the metasedimentary rocks is greenschist facies, characterized by a mineral assemblage of epidote, biotite, muscovite, and chlorite.…”

“…Forty-five thin sections and seventeen polished sections were prepared for the examination of ore and gangue minerals from Mackenzie et al, 1999;Mitchell et al, 2012;Myo Kyaw Hlaing et al, 2019). Abbreviations: Q Quaternary, P 1 -Q Lower Pliocene to Quaternary, K-Pg Cretaceous to Paleogene, Mz Mesozoic, C-P 1 Upper Carboniferous to Lower Permian, ZJ Late Proterozoic to partly Jurassic.…”

“…The Mogok Metamorphic Belt (MMB) is described as the northern part of the MMMB (Figures 1, 2). Although the local linkages between the MMB and the MB remain an open question Mitchell et al, 2004;Ye Min Swe et al, 2017;Myo Kyaw Hlaing et al, 2019), PFZ, Papun Fault Zone; TPFZ, Three Pagodas Pass Fault Zone; MMMB, Mogok-Mandalay-Mergui Belt. (Gardiner et al, 2015), they defined the MB as the southern part of the MMMB.…”

“…The metamorphic grade of the metasedimentary rocks is greenschist facies, characterized by a mineral assemblage of epidote, biotite, muscovite, and chlorite. Locally, fine-grained pyrite crystals are disseminated in the slate, phyllite, and schist (Myo Kyaw Hlaing et al, 2019).…”

“…The northern part of MB is characterized by high-grade metamorphic rocks such as gneiss, granitoid gneiss, marble, and calc-silicates associated with Late Proterozoic to Mesozoic sedimentary sequences. The southern part of MB consists of Upper Carboniferous to Lower Permian metasedimentary rocks of predominantly Mergui Group and the rocks are metamorphosed to greenschist facies with small zones of amphibolite facies along the margins of the belt, close to major shear zones and granite intrusions (Figures 1, 2; Cobbing et al, 1986Cobbing et al, , 1992Schwartz et al, 1995;Mitchell et al, 1999, Mitchell et al, 2004Khin Zaw, 1990;2017, 2019Khin Zaw et al, 2014a, 2018Ye Myint Swe et al, 2017;Mitchell, 2018;Myo Kyaw Hlaing et al, 2019).…”