scholarly journals Transport-controlled hydrothermal replacement of calcite by Mg-carbonates

Geology ◽  
2015 ◽  
Vol 43 (9) ◽  
pp. 779-782 ◽  
Author(s):  
Laura Jonas ◽  
Thomas Müller ◽  
Ralf Dohmen ◽  
Lukas Baumgartner ◽  
Benita Putlitz
Keyword(s):  
Hydrothermal Replacement

Hydrothermal replacement of feldspars in igneous enclaves of the Velay granite and the genesis of myrmekites

1996 ◽  
Vol 8 (4) ◽  
pp. 703-718 ◽  
Author(s):  
Daniel Garcia ◽  
Marie-Lola Pascal ◽  
Jacques Roux
Keyword(s):  
Hydrothermal Replacement

F, Cl content of Hydrothermal Biotite as a Geochemical Indicator Vectoring to Ore: Constrain on Niaz Cu-Mo porphyry Deposit, NW Iran

2020 ◽  
Author(s):  
Kamal Siahcheshm ◽  
Christiane Wagner ◽  
Beate Orberger ◽  
Michel Fialin ◽  
Nicolas Rividi
Keyword(s):  
Outer Part ◽  
Chemical Effect ◽  
Magmatic Fluid ◽  
Positive Correlation ◽  
Alteration Zones ◽  
Nw Iran ◽  
Metallogenic Belt ◽  
Argillic Alteration ◽  
Hydrothermal Replacement ◽  
Moderate Range

<p>The Niaz porphyry Cu-Mo deposit in the Arasbaran metallogenic belt of NW Iran exhibits extensive hydrothermal alteration developed in three temporally and spatially overlapping zones:   early potassic, transitional phyllic and intermediate argillic, and late advanced argillic. The early and transitional zones contain biotite, either of magmatic (re-equilibrated) or hydrothermal (replacement and/or neoformed) origin. This study aims to understand the petrography and chemistry of the hydrothermal biotite for evaluating the fluid compositional changes during alteration processes. Selected samples from the different alteration zones were studied for petrography crossing from inner to outer parts of the Niaz deposit. Electron microprobe analyses (Cameca SX100) including halogens (F and Cl) were performed on the hydrothermal micas at the Centre CAMPARIS, Institut des Sciences de la Terre de Paris (ISTeP), Sorbonne University, France. The biotite composition displays an increase in Al<sub>2</sub>O<sub>3</sub>, FeO and Cl, but a decrease in TiO<sub>2</sub>, MgO and F, from the potassic to the transitional phyllic and intermediate argillic alteration zones. The hydrothermal biotite with high Mg (X<sub>Mg</sub> = 0.61-0.72) inside potassic zone tends to incorporate more F and less Cl compared to the biotite with lower Mg; a crystal-chemical effect referred to as “Fe-F and Mg-Cl avoidance rules”. The biotite from the potassic zone possesses  a moderate range of F content (0.24 to 0.91wt. %) that is significantly higher than in the phyllic (0.45 to 0.62 wt. %) and argillic (0.19 to 0.37 wt. %) zones, exhibiting a positive correlation with X<sub>Mg</sub> and a negative correlation with Cl. However, the biotite from transitional phyllic as well as intermediate argillic alteration zones shows a scattered relationship.</p><p>The biotite from the central potassic to transitional phyllic and intermediate argillic alteration zones have average log (X<sub>F</sub>/X<sub>OH</sub>) values of ‑1.16, ‑1.19, and ‑1.44, respectively. The log (X<sub>Cl</sub>/X<sub>OH</sub>) values are ‑2.10, ‑1.97, and ‑1.98, whereas log (X<sub>Cl</sub>/X<sub>F</sub>) val­ues vary from 0.95, 0.78 to 0.54. The systematic variation of the logarithmic ratios reflects a sys­tematic variation of the F content in biotite associated with these alteration zones.</p><p>Microthermometric data of fluid inclusions show a decrease in temperature from potassic through phyllic to intermediate argillic zones (420, 360 and 280 °C, respectively). The log (fH<sub>2</sub>O/fHF) and log (fH<sub>2</sub>O/fHCl) values calculated for fluids equilibrated with biotite increase progressively outward in these alteration zones (6.04, 6.42 and 7.39, respectively). The decrease in halogen content of hydrothermal fluids toward outer parts of the deposits reflects an increase in the degree of mixing between magmatic fluid and meteoric water.</p><p>The F content of biotite decreases systematically toward the outer part of the deposit, while the Cl content shows unsystematic variations crossing the alteration zones. This finding suggests that the Cl content cannot be used as exploration tool for vectoring the mineralization. However, the positive correlation between the F content in biotite and bulk concentration of Cu in the different alteration zones may provide a possible geochemical tool to vectoring the Cu mineralization in porphyry deposits.</p>

Solute chemistry of inclusion fluids from sparry dolomites and magnesites in Middle Cambrian carbonate rocks of the southern Canadian Rocky Mountains

1998 ◽  
Vol 35 (5) ◽  
pp. 546-555 ◽  
Author(s):  
Bruce E Nesbitt ◽  
Walter Prochaska
Keyword(s):  
Rocky Mountains ◽  
Carbonate Rocks ◽  
Open Space ◽  
Mississippi Valley ◽  
Canadian Rocky Mountains ◽  
Middle Cambrian ◽  
Solute Chemistry ◽  
Hydrothermal Replacement ◽  
D Values ◽  
Total Salinity

Middle Cambrian carbonate rocks of the southern Canadian Rocky Mountains are host to widespread units of white, sparry, hydrothermal, replacement, and open-space filling dolomite. Contained within the dolomites are occurrences of talc and Mississippi Valley type Pb-Zn (the former Kicking Horse and Monarch mines) mineralization and economic concentrations of magnesite (Mount Brussilof mine). Results of studies of solute chemistry of saline (18-25 equivalent wt.% NaCl) inclusion fluids reveal distinctly low Na/Br (55-220) and Cl/Br (95-340) values. These values indicate that the brines which formed the dolomite originated from seawater that had deposited large amounts of halite in an evaporitic environment. Low I/Br ratios for the dolomite-magnesite inclusion fluids are consistent with their derivation from seawater and contrast sharply with the high I/Br ratios of Laramide-age fluids, which formed veins throughout the Rocky Mountains. Variations in F/Br ratios between texturally early and late magnesites indicate the involvement of a second fluid in the formation of the late magnesites. Results of the study of solute chemistry of inclusion fluids from hydrothermal dolomites, magnesites, and associated mineralization are consistent with a model of the pre-Laramide formation of these materials from seawater that had undergone extensive evaporation and halite deposition. Distinct differences in I/Br, total salinity, and delta D values between the dolomite-magnesite depositing fluids and Laramide-age vein-forming fluids clearly indicate the lack of the involvement of Laramide-age fluids in the genesis of the dolomites, magnesites, and associated mineralization.

scholarly journals Mechanism and kinetics of hydrothermal replacement of magnetite by hematite

2019 ◽  
Vol 10 (1) ◽  
pp. 29-41 ◽  
Author(s):  
Jing Zhao ◽  
Joël Brugger ◽  
Allan Pring
Keyword(s):  
Mechanism And Kinetics ◽  
Hydrothermal Replacement ◽  
Kinetics Of

scholarly journals Supergene destruction of a hydrothermal replacement alunite deposit at Big Rock Candy Mountain, Utah: mineralogy, spectroscopic remote sensing, stable-isotope, and argon-age evidences

2005 ◽  
Vol 215 (1-4) ◽  
pp. 317-337 ◽  
Author(s):  
Charles G. Cunningham ◽  
Robert O. Rye ◽  
Barnaby W. Rockwell ◽  
Michael J. Kunk ◽  
Terry B. Councell
Keyword(s):  
Remote Sensing ◽  
Stable Isotope ◽  
Hydrothermal Replacement

scholarly journals Niobium and rare earth minerals from the Virulundo carbonatite, Namibe, Angola

2012 ◽  
Vol 76 (2) ◽  
pp. 393-409 ◽  
Author(s):  
L. Torró ◽  
C. Villanova ◽  
M. Castillo ◽  
M. Campeny ◽  
A. O. Gonçalves ◽  
...  
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Second Generation ◽  
Accessory Mineral ◽  
Vein Formation ◽  
Rare Earth Minerals ◽  
Late Generation ◽  
Alteration Processes ◽  
Hydrothermal Replacement ◽  
First And Second Generation

AbstractThe Virulundo carbonatite in Angola is one of the largest in the world and contains pyrochlore as an accessory mineral in all of the carbonatite units (calciocarbonatites, ferrocarbonatites, carbonatite breccias and trachytoids). The primary magmatic pyrochlore is fluorine dominant and typically contains about equal molar quantities of Ca and Na at the A site. High-temperature hydrothermal processes have resulted in the pseudomorphic replacement of the primary pyrochlore by a second generation of pyrochlore with less F and Na. Low-temperature hydrothermal replacement of the first and second generation pyrochlore, associated with quartz-carbonate-fluorite vein formation in the carbonatite, has produced a third generation of pyrochlore, with a high Sr content. The Sr appears to have been released by low-temperature hydrothermal replacement of the primary magmatic carbonates. Finally, supergene alteration processes have produced late-stage carbonates, goethite, hollandite and rare earth element (REE) minerals (mainly synchysite-(Ce), britholite-(Ce), britholite-(La), cerite-(Ce)). Cerium separated from the other REE s in oxidizing conditions and Ce4+ was incorporated into a late generation of supergene pyrochlore, which is strongly enriched in Ba and strongly depleted in Ca and Na.

Hydrothermal replacement in deep seated iron ore deposits of the Lake Superior region

1943 ◽  
Vol 38 (1) ◽  
pp. 1-24 ◽  
Author(s):  
Hugh Marine Roberts ◽  
Melville William Bartley
Keyword(s):  
Iron Ore ◽  
Lake Superior ◽  
Ore Deposits ◽  
Iron Ore Deposits ◽  
Hydrothermal Replacement
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