scholarly journals MVT-Like Fluorite Deposits and Oligocene Magmatic-Hydrothermal Fluorite–Be–U–Mo–P–V Overprints in Northern Coahuila, Mexico

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 58
Author(s):  
Antoni Camprubí ◽  
Eduardo González-Partida ◽  
Antonin Richard ◽  
Marie-Christine Boiron ◽  
Luis González-Ruiz ◽  
...  

The formation of most fluorite deposits in northern Coahuila (NE Mexico) is explained by MVT models, and is a part of the metallogenic province of northeastern Mexico. However, fluorite skarn deposits also occur in the same region, and there is evidence for late hydrothermal manifestations with no clear origin and evolution. The latter are the main focus of this study; in particular, F–Be–U–Mo–V–P stringers in the Aguachile-Cuatro Palmas area that overprint preexisting fluorite mantos. The region experienced the emplacement of several intrusives during the Eocene and the Oligocene that are collectively grouped into the East Mexico Alkaline Province (EMAP) and postdate MVT-like deposits. Some of these intrusives have associated skarn deposits; most of them are polymetallic, but the unusual El Pilote deposit contains fluorite mineralisation that was remobilised from MVT-like deposits. The formation of the Aguachile deposit (and, collectively, part of the Cuatro Palmas deposit) has been attributed to a shallow retrograde skarn model. The Cuatro Palmas and Las Alicias fluorite deposits consist of MVT-like deposits overprinted by late hydrothermal fluorite mineralisation rich in Be–U–Mo–V–P, and the Aguachile deposit consists entirely of the latter type. The systematic fluid inclusion study of MVT-like, skarn, and late hydrothermal fluorite deposits reveals a very different distribution of temperature and salinity data that allows the discrimination of mineralising fluids for the type of deposit. MVT-like deposits were formed by fluids with temperatures of homogenisation that range between 50 °C and 152 °C and salinities between 5 and 15.5 wt.% NaCl equivalent. The El Pilote fluorite skarn was formed by fluids with temperatures of homogenisation that range between 78 °C and 394 °C and salinities between 5 and 34 wt.% NaCl equivalent, and include CaCl2-rich brines with salinities that range between 24.5 and 29.1 wt.% CaCl2. Late shallow fluorite–Be–U–Mo–V–P hydrothermal deposits were formed by fluids with temperatures of homogenisation that range between 70 °C and 180 °C and salinities between 0.9 and 3.4 wt.% NaCl equivalent; the sole exception to the above is the La Fácil deposit, with salinities that range between 7.9 and 8.8 wt.% NaCl equivalent. While temperatures of homogenisation are similar between MVT-like and late hydrothermal deposits, and both even have hydrocarbon-rich fluid inclusion associations, the salinity of late deposits is similar to that of retrograde skarn fluids, although further diluted. However, homogenisation temperatures tend to be higher in late hydrothermal than in MVT-like deposits, thus making them more similar to retrograde skarn fluids. Although this characteristic cannot solely establish a genetic link between a retrograde skarn model and late hydrothermal deposits in the study area, the characteristics of fluids associated with the latter separate these deposits from those ascribed to an MVT-like model. Assuming that mineralising fluids for late fluorite–Be–U–Mo–V–P hydrothermal deposits may correspond to a retrograde skarn (or “epithermal”) deposit, the source for fluorine may be either from (A) the dissolution of earlier formed MVT-like deposits, (B) the entrainment of remaining F-rich basinal brines, or (C) hydrothermal fluids exsolved from highly evolved magmas. Possibilities A and B are feasible due to a hypothetical situation similar to the El Pilote skarn, and due to the occurrence of hydrocarbon-rich fluid inclusions at the La Fácil deposit. Possibility C is feasible because intrusive bodies related to highly evolved magmas would have provided other highly lithophile elements like Be, U and Mo upon the exsolution of their hydrothermal fluids. Such intrusive bodies occur in both study areas, and are particularly conspicuous at the Aguachile collapse structure.

1991 ◽  
Vol 55 (381) ◽  
pp. 605-611 ◽  
Author(s):  
D. H. M. Alderton ◽  
R. S. Harmon

AbstractThe oxygen and hydrogen isotope composition of hydrothermal fluids associated with the Variscan granites of southwest England has been inferred from analysis of various silicate minerals (predominantly quartz) and by direct analysis of fluid inclusions within quartz and fluorite. These data have been combined with the results of a fluid inclusion study to develop a model for the origin and evolution of hydrothermal fluids in the region. Magmatic fluids expelled from the granites had compositions in the range δD = −65 to −15‰, and δ18O = 9 to 13‰. Respective temperature, salinity, fluid δD, and fluid δ18O values for the (i) early Sn-W mineralization, (ii) later Cu-Pb-Zn sulphide mineralization, and (iii) latest ‘crosscourse’ Pb-Zn-F mineralization are: (i) 230–400 °C, 5–15 wt.% NaCl equiv., −39 to −16‰, and 7.0 to 11.2‰, (ii) 220–300 °C mostly 2–8 wt.% NaCl equiv., −41 to −9‰, and 2.3 to 8.1‰, and (iii) 110–150 °C 22–26 wt.% NaCl equiv., −45 to +2‰, and −1.8 to +5.5‰. These data highlight the important role of both magmatic fluids exsolved from the crystallizing granite, and basinal brines circulating within restricted fracture systems.


2014 ◽  
Vol 962-965 ◽  
pp. 41-44
Author(s):  
Hao Wei ◽  
Jiu Hua Xu ◽  
Guo Rui Zhang

In this paper we use new field data, fluid inclummsions, and table isotopes (O, H, and S) to refine the roles of the hydrothermal evolution, evaluate changes in the hydrothermal fluids of Duobaoshan porphyry Cu (Mo) deposit and Sankuanggou skarn Fe-Cu deposit. Four ore-forming stages are recognized at The Duobaoshan porphyry Cu (Mo) deposit. Fluid inclusions are abundant in quartz of various stages. Estimated trapping pressures for stage I, II, III are 110-160MPa, 58-80MPa, and 8-17MPa, corresponding trapping temperatures are 375-650°C, 310-350°C, 210-290°C. The δD and δ18O values of fluids indicate a evolution process from magmtic hydrothermal fluid to a mixing magmtic and meteoric fluid. The δ34S values of sulfides mainly suggest predominantly source of deep magma chamber.


2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Toe Naing Oo ◽  
Agung Harijoko ◽  
Lucas Donny Setijadji ◽  
Kotaro YONEZU

The Shwebontha Prospect area is one of prominent epithermal Au-Ag prospects in Monywa mining district, central Myanmar, characterized by the appearance of gold-bearing and base metal quartz veins with gold grade is around 3g/t -10.4g/t. The geology of the area consists of the volcanic and volcaniclastic rocks of Upper Oligocene-Middle Miocene Magyigon Formation that served as the host rock of the ore mineralization. This research focused on fluid inclusion study is aimed to know the characteristics of hydrothermal fluids during ore mineralization as well as the possible paleo- depth and temperature of formation of gold-bearing and base metal quartz veins. The mineralization styles are gold-bearing brecciated quartz veins and chalcedonic quartz veins where sulfides are clustered as well as disseminated both in quartz gangue and volcanic host rocks. Those quartz veins include pyrite, sphalerite, galena, chalcopyrite and gold (electrum). Fluid inclusion microthermometry indicates that the ore mineralization is characterized by the values of homogenization temperature range from 158°C to 310°C and salinities range from 0.35 to 2.41wt.% NaCl equiv. This temperature is consistent with the formation temperature of 250°C to 270 °C and also their estimate paleo-depth of formation is between 440m and 640m respectively. Microthermometric data indicates that fluid mixing and dilution were significant processes during ore mineralization and evolution of hydrothermal fluids. Based on the petrography of fluid inclusion, microthermometric measurements and ore minerals assemblage as well as estimation of paleo-depth from the Shwebontha Prospect imply that forming in under shallow level epithermal environment


1989 ◽  
Vol 105 (14) ◽  
pp. 1073-1078 ◽  
Author(s):  
Osvaldo ARCE ◽  
Masateru NAMBU

1988 ◽  
Vol 111 (3) ◽  
pp. 307-319 ◽  
Author(s):  
Benedetto De Vivo ◽  
Maria Luce Frezzotti ◽  
Annamaria Lima ◽  
Raffaello Trigila

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