Petrogenesis, Ore Mineralogy, and Fluid Inclusion Studies of the Tagu Sn–W Deposit, Myeik, Southern Myanmar

Abstract

Most of the granite-related Sn-W deposits in Myanmar are located in the Western Granitoid Province (WGP) of Southeast Asia. The Tagu deposit in the southern part of the WGP is a granite related Sn-W deposit. The biotite granite is composed of quartz, feldspars (plagioclase, orthoclase, and microcline), and micas (muscovite and biotite) and belongs to S-type peraluminous granite. Abundances of large-ion lithophile elements (LILEs), such as Rb, K, and Pb, coupled with the deficiency of high-field-strength elements (HFSEs), such as Nb, P, and Ti, indicate that the parental magma for the Tagu granite was derived from the lower continental crust at syn-collisional setting. Mineralized veins consist of early-formed oxide ore minerals, such as cassiterite and wolframite, which were followed by the formation of sulfide minerals. Three main types of fluid inclusions were distinguished from the mineralized quartz veins hosted by granite and metasedimentary rocks: Type-A-two phases, liquid (L) + vapor (V) aqueous inclusions; Type-B-two phases, vapor (V) + liquid (L) vapor-rich inclusions; And type-C-three phases, liquid + CO 2 -liquid + CO 2 -vapor inclusions. Quartz in the veins hosted in granite corresponding with earlier deposition contains type-A, type-B, and type-C fluid inclusions, whereas that in the veins hosted in metasedimentary rocks corresponding with later deposition contains only type-A fluid inclusions. The homogenization temperatures of type-A inclusions range from 140 • C to 330 • C (mode at 230 • C), with corresponding salinities from 1.1 wt.% to 8.9 wt.% NaCl equivalent for quartz veins hosted in metasedimentary rocks, and from 230 • C to 370 • C (mode at 280 • C), with corresponding salinities from 2.9 wt.% to 10.6 wt.% NaCl equivalents for quartz veins hosted in granite. The homogenization temperatures of type-B vapor-rich inclusions in quartz veins in granite range from 310 • C to 390 • C (mode at 350 • C), with corresponding salinities from 6.7 wt.% to 12.2 wt.% NaCl equivalent. The homogenization temperatures of type-C H 2 O-CO 2 -NaCl inclusions vary from 270 • C to 405 • C (mode at 330 • C), with corresponding salinities from 1.8 wt.% to 5.6 wt.% NaCl equivalent. The original ascending ore fluid was probably CO 2 -bearing fluid which evolved into two phase fluid by immiscibility due to pressure drop in the mineralization channels. Furthermore, the temperature and salinities of two-phase aqueous fluids were later most likely decreased by the mixing with meteoric water. The salinities of the type-B vapor-rich inclusions are higher than those of the type-C CO 2 -rich inclusions, which may have resulted from CO 2 separation from the fluids. The escape of gases can lead to an increase in the salinity of the residual fluids. Therefore, the main ore-forming mechanisms of the Tagu Sn-W deposit are characterized by fluid immiscibility during an early stage, and fluid mixing with meteoric water in the late stage at a lower temperature.

Timing and tectonic setting of tin mineralization in southern Myanmar: constraints from cassiterite and wolframite U–Pb ages

“…The principal tin-producing areas are located around Dawei and Myeik towns, with much of the historical production from placers (Htun et al 2017). This tin metallogenic district is also rich in tungsten that is commonly found spatially associated with tin as wolframite and rare scheelite (Htun et al 2019).…”

The Occurrence of Primary REE Minerals and Their Para genesis within S-Type Granite and Quartz Vein, South Bangka, Bangka Belitung Islands, Indonesia

“…The FIs have VCO2/( LH2O+LCO2+VCO2)=10-20 vol%, LCO2/( LH2O+LCO2+VCO2)=10-20 vol% and LH2O/( LH2O+LCO2+VCO2) = 6070 vol%. Its eutectic temperature is -76 , disappeared clathrate temperature +8.0 , partial homogenization temperature +26.8 , and final homogenization temperature 317 .Using equation wt.% NaCl = 15.52022 -1.02342T -0.95286T2 , T : final clathrate melting temperature (Htun et al, 2019), salinity were calculated to be 3.96 wt.%NaCl (Table 7).…”