Fluid inclusions and their stable isotope geochemistry of the carbonate-hosted talc deposits near the Cretaceous Muamsa Granite, South Korea

Abstract

Microthermometric and stable isotope studies of fluid inclusions were conducted for the Poongjeon talc deposit which formed as alteration products of calc-silicate minerals during the retrograde stage of contact metamorphism related to the intrusion of the Cretaceous Muamsa Granite of South Korea. Two types of quartz vein are observed in the deposit. Vein I, which occurs in marble, is characterized by both mixing and unmixing process of fluid inclusions. Repeated boiling of carbonic fluids produced high X CO2 fluids abundantly and low X CO2 or aqueous fluids a little. Occasionally mixing took place between halite ± sylvite-bearing fluids and carbonic fluids. As for vein II, which occurs typically at points of amphibolite-metapelite contact, the fluid mixing model can be applied to the coexistence of abundant CH 4 ± H 2 O, H 2 O-CO 2 -CH 4 fluids with variable CH 4 /CO 2 ratios (X CH4 > 0.1), and minor high X CO2 fluid inclusions. The CH 4 -rich inclusions seem to be derived from the reheating of C-bearing metapelite during contact metamorphism.Occurrences of halite ± sylvite-bearing inclusions along trails in both vein I and II are chronologically behind other primary inclusions and are closely related to the talc mineralization. The mineralizing fluids would have been derived directly from a water-saturated crystallizing melt and the entrapment occurred between 150 and 700 bars at 260°-390°C. The δ 13 C CO2 values, 0.1-2.4‰, of inclusion fluids of vein I seem to have resulted from the isotopic exchange of magmatic carbon with 13 C-enriched CO 2 liberated from the decarbonation for calc-silicate formation. Distinctly lower δ 13 C CO2 values, -3.5 to -1.7‰, in vein II could have originated from the strong effect of metasediment-derived fluids. Higher δ 18 O H2O values of vein I and lower δD values of vein II, both of which belong to the magmatic water range, seem to have similar evolution history as δ 13 C values. Geologic structures such as faults and contacts between different rock units seem to have promoted infiltration, mixing, and unmixing of fluids of diverse origins.

Hydrothermal fluid characteristics and genesis of Cu quartz veins in the Hwanggangri metallogenic district, Republic of Korea: Mineralogy, fluid inclusion and stable isotope studies

“…The fluid may have originated from high temperature exchange between the igneous plutons and adjacent high-δ 18 O country rocks (Taylor, 1978). The values of δ 18 O water and δD water for Pojeonri are similar to those reported by Shin and Lee (2006) for veins of the Poongjeon mine. Similar δ 18 O water and δD water values also could have resulted from boiling of hydrothermal fluids, as vapor separation results in a relative enrichment in 18 O and a relative depletion in D of the remaining aqueous fluid (Koděra et al, 2005).…”

“…3.0-7.6 (1.8-6.2) 5.0 4.5-5.1 (3.0-4.1) 2.9-6.5 (2.9-6.2) 9.0-14.5 (11.3-13.9) 5.6-9.9 (7. or local meteoric water (Choi et al, 1997;Shin and Lee, 2006;So et al, 1983;So and Yun, 1992; (Table 4). The δ 34 S values of sulfide minerals from many deposits (W-Mo, Pb-Zn, Au-Ag) in the Hwanggangri metallogenic district were present in the hydrothermal fluids mainly as reduced sulfur (H 2 S) and are interpreted to be magmatic in origin and to be derived from the local country rocks (Choi et al, 1997;Shelton et al, 1986;So et al, 1983;So and Yun, 1992;; Table 4).…”

“…These oxygen isotope data are therefore compatible with a fluid of deep crustal origin, and both mostly magmatic water and partly δ 18 O-enriched wall rock offer possible sources. Shin and Lee (2006) interpreted that most of the δ 18 O water values of quartz veins from the Hwanggangri metallogenic district relate to magmatic water, but some higher δ 18 O water values originated from δ 18 O-enriched fluids produced from decarbonation reactions. The fluid may have originated from high temperature exchange between the igneous plutons and adjacent high-δ 18 O country rocks (Taylor, 1978).…”

Sm–Nd dating and rare earth element geochemistry of the hydrothermal calcites from Guling carbonate-hosted talc mineralization in the central Guangxi province, South China

“…Abundant researches revealed that the carbonatehosted talc mineralization was formed by hydrothermal alteration of carbonates, especially dolomite, by Si-bearing hydrothermal fluids, e.g., Göpfersgrün in Germany (Hecht et al 1999), Lassing and Rebenwald in Austria (Boulvais et al 2006). This research also suggested that the Sibearing hydrothermal solutions are predominately derived from the basin brine (e.g., Puebla de Lillo in Spain; Tornos and Spiro 2000), sea water (e.g., Ruby area in the southwest Montana, USA; Brady et al 1998) and magmatic water (e.g., Hwanggangri area in South Korea; Shin and Lee 2006), respectively. Importantly, the basin brine, sea water and magmatic fluids also provide the ore-forming fluids and materials (Si and Mg) for the carbonate-hosted talc mineralization whereas the ore-bearing carbonates also could afford abundant Mg.…”

An Experimental Study of the Formation of Talc through CaMg(CO3)2–SiO2–H2O Interaction at 100–200°C and Vapor-Saturation Pressures

“…This has previously been done using several methods. These include microthermometric measurements of relevant fluid inclusions (e.g., [39,40,79]) and calculations using talc-dolomite oxygen isotope thermometry, assuming that the mineral pairs achieve oxygen isotope equilibrium [21,36]. In addition, the phase diagram of the CaO-MgO-SiO 2 -CO 2 -H 2 O system has often been referred to for evaluating the formation temperature of talc [5,35].…”