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.

scholarly journals Prediction of Mississippi-Valley type ore fluid metal concentrations from solid solution metal concentrations in ore-stage minerals

2017 ◽  
Author(s):  
◽  
Sarah Smith
Keyword(s):  
Solid Solution ◽  
Fluid Inclusion ◽  
Distribution Coefficient ◽  
Fluid Inclusions ◽  
Mississippi Valley ◽  
Carbonate Minerals ◽  
Metal Concentrations ◽  
Fluid Inclusion Data ◽  
Mvt Deposits ◽  
Mississippi Valley Type

Mississippi-Valley-type (MVT) deposits have some of the greatest enrichments of Pb, Zn, Ba, and F in the Earth's crust. Fundamental to understanding how these elements were transported and precipitated to form MVT deposits is knowledge of their concentrations in the ore fluids. Recent research aimed at determining the concentrations of Pb, Zn, and Ba in the ore fluids that formed the MVT deposits of the U.S. midcontinent, the type examples for the MVT deposit class, has focused on using LA-ICPMS to analyze fluid inclusions. This research has shown U.S. mid-continent MVT ore fluids to have Ba concentrations on the order of 10's of ppm. However, LA-ICP-MS results for Pb and Zn concentrations are equivocal due to interferences from Zn and Pb in the host mineral matrix and uncertainties about whether the measured Pb and Zn signals represent aqueous solute or "accidentals", i.e. Pb or Zn solid particulates entrained within the fluid inclusions. In light of these limitations, this study sought to determine metal concentrations in MVT ore fluids instead by calculating them theoretically based on their solid solution concentrations in the ore-stage minerals calcite and galena. Using experimental partition coefficients from Rimstidt et al. (1998) at ore stage temperatures and measured compositions of ore-stage calcite from the Illinois-Kentucky and Central Tennessee MVT districts, concentrations of Mg, Mn, Fe, Zn, Sr, Ba, and Pb in the ore fluid were predicted. The predicted ore fluid concentrations of Mg and Mn, which form carbonate minerals (magnesite and rhodochrosite) with the calcite structure, were in good agreement with available fluid inclusion data for these elements. Thus, the predicted ore fluid concentrations of Zn and Fe, which also form carbonate minerals (smithsonite and siderite) with the calcite structure, 10s of ppm Zn and 1s to 10s of ppm Fe in Illinois-Kentucky and a maximum of 10s of ppm Zn and 1s to 10s of ppm Fe in Central Tennessee , are likely to be accurate. These Zn concentrations are typical of modern sedimentary brines and high enough to allow efficient Zn ore formation. In contrast, the predicted ore fluid concentrations of Sr and Ba, which form carbonate minerals (strontianite and witherite) with the aragonite structure, were in poor agreement with available fluid inclusion data for these elements. Thus, the predicted 1s of ppm ore fluid concentration of Pb, which also forms a carbonate mineral (cerussite) with the aragonite structure, is unlikely to be accurate. Using predicted thermodynamic data (Sverjensky, 1985) for ZnS with the galena structure, a thermodynamic distribution coefficient for Zn between aqueous solution and solid solution in galena was calculated. This distribution coefficient was used in combination with Zn concentrations measured in solid solution in galena from the Central Missouri, Central Tennessee, Illinois-Kentucky, Northern Arkansas, Tri-State, and Southeast Missouri MVT districts to predict Zn/Pb ratios for the ore fluids. The Zn/Pb ratios do not agree with the ore Zn/Pb ratios of the districts and appear to be an artifact of the temperature used in the calculations. Therefore the predicted ore fluid Zn/Pb ratios are unlikely to be correct.

Fluid inclusions in thenardite from northern Mali: experimental stretching and microthermometric investigations

1990 ◽  
Vol 54 (375) ◽  
pp. 305-309 ◽  
Author(s):  
A. Canals-Sabate ◽  
J. C. Touray ◽  
J. Fabre
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Eutectic Temperature ◽  
List Type ◽  
Formation Temperature ◽  
Heating Rates ◽  
Fluid Inclusion Data ◽  
Primary Fluid ◽  
Homogenization Temperatures ◽  
Underground Brines

AbstractLarge thenardite crystals have been sampled at New Agorgott, in the Taoudenni area of northern Mali. They are still in equilibrium with a pressurized NaCl saturated brine capped by a halite layer. Clays located about 1 m above the thenardite occurrence have been dated at 6760 y.BP. The crystals contain numerous, large, brine and solid inclusions. Microcryscopic studies show that the fluids can be explained by the addition of MgCl2 to the Na2SO4-NaCl-H2O system (eutectic temperature: −31 to −35°C; possible bloedite Na2Mg(SO4)2.4H2O formed after freezing). The homogenization temperatures of primary fluid inclusions are in the range 28 to 50°C. In order to understand the significance of the highest Th values, overheating experiments under 1 bar pressure were performed at different heating rates up to 170°C. The results are as follows:(i)When the temperature of stretching (TOh) is higher than about 10°C, overheating is recorded and fossilized (identical Th after some hours, several days or 8 months storage at 5°C).(ii)The lowest Th values (28°C) are probably near the formation temperature of thenardite; the highest ones reflect stretching under present desert conditions.(iii)With TOh lower than about 60°C, a fair correlation is observed between Th and TOh.Finally, taking into account recent natural overheating, the fluid inclusion data are compatible with the formation of thenardite from underground brines later than the beginning of desert conditions in the Taoudenni area (i.e. about 3000 y.BP).

scholarly journals Contribution to Understanding of Ore Fluids in the Zletovo Mine Based on Fluid Inclusion Data

2019 ◽  
Vol 66 (2) ◽  
pp. 75-86
Author(s):  
Goran Tasev ◽  
Todor Serafimovski ◽  
Matej Dolenec ◽  
Nastja Rogan Šmuc
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Hydrothermal Solutions ◽  
Volcanic Centre ◽  
Fluid Inclusion Data ◽  
Phase Density ◽  
Lead Zinc ◽  
Quartz Grains

AbstractThe Zletovo is lead–zinc (Pb–Zn) deposit, adjacent to the Plavica volcanic centre (R. Macedonia) with high-sulphidation and porphyry mineralisation. The analysis of fluid inclusions showed homogenisation temperatures in the range 335–145°C, which reflects phases of pulsation of hydrothermal solutions and defined into four groups from the lowest to the highest temperatures. The frequency of the homogenisation temperatures ranged from 265 to 125°C and with the most dominant from 245 to 225°C, from 225 to 205°C and from 145 to 125°C. Also, it was confirmed that hydrothermal ore-bearing solutions were defined as NaCl-type with range from 4.4 to 8.6 wt% NaCl equivalent. The latest stage salinities ranged from 3 to 12 wt% NaCl equivalent, where those from 10 to 12 wt% and from 6 to 8 wt% NaCl equivalent, prevailed. This suggests that hydrothermal solutions within analysed quartz grains were at final mineralizing phase. Density of fluid inclusions ranged from 0.7 to 0.95g/cm3. Calculated pressures and paleo-depths of mineralisation ranged from 14 to 130 bar and from 0.6 to 0.8 km.

scholarly journals Fluid Evolution of Fuzishan Skarn Cu-Mo Deposit from the Edong District in the Middle-Lower Yangtze River Metallogenic Belt of China: Evidence from Petrography, Mineral Assemblages, and Fluid Inclusions

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-25
Author(s):  
Lu Zhang ◽  
Shao-Yong Jiang ◽  
Suo-Fei Xiong ◽  
Deng-Fei Duan
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Yangtze River ◽  
Homogenization Temperature ◽  
Lithostatic Pressure ◽  
Lower Permian ◽  
Fluid Evolution ◽  
Metallogenic Belt ◽  
Lower Yangtze ◽  
Vapor Liquid

The Fuzishan Cu-Mo deposit is located in the Edong district of the Middle-Lower Yangtze River Metallogenic Belt, China. The orebodies mainly occurred as lenticular and bedded shapes in the skarn zone between the Lower Permian Qixia Formation carbonate rocks and the quartz diorite. Four paragenetic stages have been recognized based on petrographic observations: (1) prograde skarn stage, (2) retrograde skarn stage, (3) quartz-sulfide stage, and (4) carbonate stage. Six fluid inclusion types were recognized: S1(vapor + liquid + halite ± other daughter minerals), S2(vapor + liquid + daughter minerals except halite), LV(rich liquid + vapor), VL(rich vapor + liquid), V (vapor), and L (liquid) types. Fluid inclusion studies show distinct variations in composition, final homogenization temperature, and salinity in four stages. Daughter minerals of the primary fluid inclusions include chalcopyrite, molybdenite, hematite, anhydrite, calcite, and halite in the prograde skarn stage and hematite, calcite, and sulfide (?) in the retrograde skarn stage. No daughter minerals occurred in the quartz-sulfide and carbonate stages. Final homogenization temperatures recorded in these stages are from 405 to >550°C, from 212 to 498°C, from 150 to 485°C, and from 89 to 223°C, respectively, while salinities are from 3.7 to 42.5, from 2.6 to 18.5, from 2.2 to 17.9, and from 0.2 to 11.5 wt.% NaCl equivalent, respectively. The coexisting VLand S1type fluid inclusions show similar homogenization temperature of 550 to about 650°C in the prograde skarn stage, indicating that immiscibility occurred at lithostatic pressure of 700 bars to perhaps 1000 bars, corresponding to a depth of 2.6 km to about 3.7 km. The coeval VLand LVtypes fluid inclusions with homogenization temperature of 350 to 400°C in the late retrograde skarn and quartz-sulfide stages suggest that boiling occurred under hydrostatic pressure of 150 to 280 bars, equivalent to a depth of 1.5 to 2.8 km. Mo mineralization in the retrograde stage predated Cu mineralization which mainly occurred in the quartz-sulfide stage. Fluid compositions indicate that ore-forming fluid has highfO2and rich Cu and Mo concentration in the early stage, while relatively lowerfO2and poor Cu and Mo concentration in the middle to late stages. Microthermometric data show a decreasing trend in temperature and salinity in the fluid evolution process. Decreasing temperature and boiling event may be the main factors that control the ore precipitation.

scholarly journals Mineralogical and Fluid Inclusions Study of Epithermal Type Veins Intruding the Volcanic Rocks of the Kornofolia Area, Evros, NE Greece.

2019 ◽  
Vol 55 (1) ◽  
pp. 202
Author(s):  
Foteini Aravani ◽  
Lambrini Papadopoulou ◽  
Vasileios Melfos ◽  
Triantafillos Soldatos ◽  
Triantafillia Zorba ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fluid Inclusion ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Volcanic Rocks ◽  
The Other ◽  
Calc Alkaline ◽  
Ft Ir ◽  
Host Rocks

The volcanic rocks of Kornofolia area, Evros, host a number of epithermal-type veins. The host rocks are Oligocene calc-alkaline andesites to rhyo-dacites. The andesites form hydrothermal breccias and show hydrothermal alteration. The veins comprise mainly silica polymorphs such as quartz, chalcedony and three types of opal (milky white, transparent and green). Amethyst also forms in veins at the same area. Apart from the silica polymorphs, the veins are accompanied by calcite and zeolites. The main aim of this study is the characterization of the silica polymorphs. Using FT-IR analyses, variations in the crystal structure of the three opals were recognized. The green opal is found to be more amorphous than the other two types. Fluid-inclusion measurements were performed in calcite and were compared with amethyst from previous studies. The Th is between 121-175 °C and the Te between -22.9 and -22.4 °C. The salinities range from 0.9 to 4.5 wt % NaCl equiv.

A new occurrence of lazulite from the Main Central Thrust in Kumaun Himalaya, India: fluid inclusion, EPMA and Raman spectroscopy focusing on lazulite in a highly tectonized zone

2019 ◽  
Vol 481 (1) ◽  
pp. 211-230 ◽  
Author(s):  
Dinesh S. Chauhan ◽  
Rajesh Sharma ◽  
D. R. Rao
Keyword(s):  
Raman Spectroscopy ◽  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Structural Formula ◽  
Stability Field ◽  
Adjacent Area ◽  
Structural Level ◽  
Main Central Thrust ◽  
Kumaun Himalaya ◽  
D Values

AbstractThe present study reports and investigates ‘lazulite’ occurring in the vicinity of a highly tectonized zone of the Main Central Thrust (MCT) in the Himalaya. The azure blue lazulite, hosted in quartz veins, occurs in fractured Berinag quartzite, which forms the footwall of the MCT near Sobla village in NE Kumaun Himalaya, India. Lazulite was investigated using SEM-EDX, micro Raman spectroscopy, fluid inclusion microthermometry and electron probe microanalysis (EPMA). Lazulite contains inclusions of rutile and hematite and has Mg/(Mg+Fe) ratios of 0.86 to 0.90. The phosphorus in lazulite shows a negative trend with Mg+Al contents. This lazulite is an intermediate solid solution near the lazulite end-member with a cationic composition in the structural formula: Mg0.81–0.89Fe0.10–0.13 Al1.88–1.98P2.00–2.07. Its composition in the lazulite–scorzalite stability field points to a higher temperature of its formation. Fluids trapped as inclusions in lazulite and the associated quartz are generally C–O–H fluid. The fluid inclusion isochors for lazulite, together with the temperature calculated for metamorphism of the equivalent structural level in the adjacent area suggest 500–600°C and 7.25 to 9.25 kbar, which match the peak metamorphic temperature–pressure derived elsewhere for the Higher Himalayan Crystallines. Moderately enriched δD‰ values and H2O–CO2–low NaCl fluid suggest that water from a deep reservoir, more likely a metamorphic fluid, participated in lazulite formation. Classic sigmoidal fluid inclusions in lazulite reveal their development during MCT shearing, whereas the overpressured fluid inclusions suggest a post-lazulite uplift. The MCT lazulite is interpreted to have formed during Himalayan shearing and concurrent metamorphism. The present study also implies that this refractory mineral can sustain fluid inclusions within it against intense deformation conditions, such as in the MCT.

New chemical, isotopic, and fluid inclusion data from zinc-lead-copper veins, Shawangunk Mountains, New York

1990 ◽  
Vol 85 (1) ◽  
pp. 182-196 ◽  
Author(s):  
J. Scott Wilber ◽  
Felix E. Mutschler ◽  
Jules D. Friedman ◽  
Robert E. Zartman
Keyword(s):  
New York ◽  
Fluid Inclusion ◽  
Fluid Inclusion Data
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