Late-kinematic gold mineralisation during regional uplift and the role of nitrogen: an example from the La Codosera area, W. Spain

1993 ◽  
Vol 57 (388) ◽  
pp. 437-450 ◽  
Author(s):  
S. J. Dee ◽  
S. Roberts
Keyword(s):  
Fluid Inclusion ◽  
Aqueous Fluid ◽  
Ductile Deformation ◽  
Ammonium Ion ◽  
Rock Interaction ◽  
Fluid Inclusion Data ◽  
Quartz Veins ◽  
Vein Formation ◽  
Peak Metamorphism ◽  
Lowermost Part

AbstractVein formation occurred throughout a deformation sequence which involved early transpressive ductile deformation through to late-kinematic transpressive brittle structures which host a series of gold prospects. Fluid inclusion data from (S1) fabric parallel veins associated with early deformation suggest that a low-salinity aqueous fluid, with a mean salinity of 6.4 wt.%, was present during peak metamorphism, Pelite mineralogy and isochores constrain peak metamorphism to the lowermost part of the upper greenschist facies at 325 to 425°C and 1.4 to 3.4 kbar.Fluid inclusion data from auriferous and barren late-kinematic quartz veins, both containing unmixing assemblages of aqueo-carbonic inclusions with low salinities of ≈2.7 wt.% NaCl equiv., indicate unmixing occurred at 300°C and 1.5 kbar.Volatiles (CO2, N2, CH4) are observed in all the late-kinematic veins. The N2contents of veins with elevated gold grades are typically higher than those with low gold grades. N2reaches 8.7 mole% in a vein with 0.49−4.6 p.p.m. Au compared to <1 mole% in a vein with <0.05 p.p.m. Au. The CH4content of late kinematic veins is generally less than 1 mole% and shows no relative enrichment in mineralised veins. The generation of N2in the mineralising fluid most likely results from interaction of fluid with the ammonium ion, NH4+, in micas and feldspars. This interaction could take place either at source, due to metamorphic devolatisation reactions, or along those structures which acted as fluid conduits due to fluid-rock interaction.

Uraninite-albite veins from the Mistamisk Valley of the Labrador Trough, Quebec

1981 ◽  
Vol 44 (336) ◽  
pp. 471-483 ◽  
Author(s):  
L. Kish ◽  
M. Cuney
Keyword(s):  
Aqueous Solution ◽  
Fluid Inclusion ◽  
Gas Phase ◽  
Hydrothermal Solution ◽  
Hydrothermal Solutions ◽  
Fluid Inclusion Data ◽  
Vein Formation ◽  
Lower Proterozoic ◽  
Temperature And Pressure ◽  
First Time

AbstractThe uraninite-albite veins of the Mistamisk area occur in the argillite member of the Dunphy Formation, which is near the base of the slightly meta-morphosed Lower Proterozoic sequence of the central Labrador Trough. The vein minerals are albite, uraninite, dolomite, and chlorite, and minor quantities of quartz, tellurides, sulphides, gold, and organic material. Pitchblende and calcite are related to late remobilization.The veins were deposited in fractures by hydrothermal solutions, and metasomatism caused albitization of wall rocks. Fluid inclusions have an unusual composition, described here for the first time in connection with soda-metasomatism; the aqueous solution of the inclusions is oversaturated in NaCl and contains Ca2+ and Mg2+, and the gas phase mostly consists of N2, CO and CO2. The presence of hematite and absence of hydrocarbons indicates that the vein-forming solution was oxidizing.The temperature and pressure of vein formation, estimated from fluid inclusion data, was 300°–350° and 2.5 kbar respectively consistent with the composition of the phengite which is a common metamorphic mineral of the host rock. Vein emplacement occurred in the waning stages of the Hudsonian Orogeny, the hydrothermal solution possibly originating by metamorphism of sodic schists of the Mistamisk area, which are possibly of evaporitic origin.

scholarly journals Transport and Evolution of Supercritical Fluids During the Formation of the Erdenet Cu–Mo Deposit, Mongolia

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 201 ◽  
Author(s):  
Geri Agroli ◽  
Atsushi Okamoto ◽  
Masaoki Uno ◽  
Noriyoshi Tsuchiya
Keyword(s):  
Fluid Inclusion ◽  
Supercritical Fluids ◽  
Hydrothermal System ◽  
Host Rock ◽  
Fluid Injection ◽  
Sector Collapse ◽  
Fluid Inclusion Data ◽  
Multiple Generations ◽  
Quartz Veins

Petrological and fluid inclusion data were used to characterize multiple generations of veins within the Erdenet Cu–Mo deposit, Mongolia, and constrain the evolution of fluids within the magmatic–hydrothermal system. Three types of veins are present (from early to late): quartz–molybdenite, quartz–pyrite, and quartz. The host rock was emplaced at temperatures of 700–750 °C, the first quartz was precipitated from magma-derived supercritical fluids at 650–700 °C, quartz–molybdenite and quartz–pyrite veins were formed at ~600 °C, and the quartz veins were precipitated in response to retrograde silica solubility caused by decreasing temperatures at <500 °C. We infer that over-pressured fluid beneath the cupola caused localized fluid injection, or that accumulated stress caused ruptures and earthquakes related to sector collapse; these events disrupted impermeable layers and allowed fluids to percolate through weakened zones.

Fluid-rock interaction in the geothermal field of Chipilapa (El Salvador): contribution of fluid-inclusion data

1996 ◽  
Vol 8 (3) ◽  
pp. 515-532 ◽  
Author(s):  
Hubert Bril ◽  
Photinie Papapanagiotout ◽  
Patricia Patrier ◽  
Jean-Françοis Lenain ◽  
Daniel Beaufort
Keyword(s):  
Fluid Inclusion ◽  
El Salvador ◽  
Geothermal Field ◽  
Rock Interaction ◽  
Fluid Inclusion Data

Formation of emeralds at pegmatite-ultramafic contacts based on fluid inclusions in Kianjavato emerald, Mananjary deposits, Madagascar

2006 ◽  
Vol 70 (2) ◽  
pp. 141-158 ◽  
Author(s):  
Ye. Vapnik ◽  
I. Moroz ◽  
M. Roth ◽  
I. Eliezri
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
East Coast ◽  
Fluid Inclusion Data ◽  
Pan African ◽  
Probe Analysis ◽  
Raman Probe

AbstractKianjavato emerald (Mananjary deposits, East coast of Madagascar) was formed during metasomatic processes at the contact between pegmatites and hornblendites. The metasomatic exchange was related to a Pan-African tectonometamorphic event.Fluid inclusions in the Kianjavato emerald and quartz were studied by means of microthermometry and Raman probe analysis. Three main types of inclusions were revealed: CO2-rich, CH4-rich and aqueous-rich, with a salinity of ∼2 wt.% NaCl equiv. The inclusions occurred along the same primary and pseudosecondary trails and were considered to be formed simultaneously. Based on fluid-inclusion data, the conditions of emerald growth were 250°C < T < 450°C and P = 1.5 kbar.The fluid inclusion data for Kianjavato emerald were compared to the data for another Madagascar emerald, Ianapera. The latter is of similar age, but its genesis was determined by a shearing event. Our fluid inclusion data suggested that shearing was also important as a mechanism of introducing CO2-rich fluid for the genesis of the Kianjavato emerald.

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