scholarly journals The Schlaining quartz-stibnite deposit, Eastern Alps, Austria: constraints from conventional and infrared microthermometry and isotope and crush-leach analyses of fluid inclusions

2021 ◽  
Author(s):  
Marta Sośnicka ◽  
Stefan de Graaf ◽  
Giulio Morteani ◽  
David A. Banks ◽  
Samuel Niedermann ◽  
...  
Keyword(s):  
High Heat ◽  
Eastern Alps ◽  
Early Miocene ◽  
Fluid Migration ◽  
Rock Interaction ◽  
Two Fluids ◽  
Low Salinity ◽  
Small Vein ◽  
Ore Minerals ◽  
Ore District

AbstractStibnite was mined until the end of the twentieth century in the Schlaining ore district, Austria, near the easternmost border of the Eastern Alps where windows of Penninic ophiolites and metasediments are exposed below Austroalpine tectonic units. In Early Miocene, structurally controlled small vein and metasomatic stibnite-quartz deposits were formed in Penninic Mesozoic calcareous marbles and calcite schists. Fluid inclusion studies identified two fluids involved in the mineralization: (i) a low-salinity, low-CO2 metamorphic fluid that precipitated quartz at approximately 240 °C and (ii) a stibnite-forming ore fluid that had a meteoric origin. There is no evidence of boiling or that the fluids mixed during mineralization. The ore components Sb and H2S were leached by fluid/rock interaction from buried rock units. Stibnite mineralization occurred by cooling the ore fluid to below 300 °C, at less than 2000 m depth. Quartz precipitated at slightly lower temperatures, approximately contemporaneous with stibnite. Fluid migration and ore deposition are probably related to high heat flow during the exhumation of the Rechnitz Window in response to Neogene extension and/or shallow Early Miocene andesitic magmatism. The study emphasizes that data obtained from the analyses of gangue minerals alone cannot routinely be used to infer the origin and depositional conditions of the associated ore minerals.

Pre- to syn-folding closed paleofluid system conditions and their opening in late- to post-folding structural evolution: the case of Urgonian platform carbonates folded in the Parmelan anticline, Bornes Massif, external Western Alps

2021 ◽  
Author(s):  
Luigi Berio ◽  
Silvia Mittempergher ◽  
Fabrizio Storti ◽  
Fabrizio Balsamo ◽  
Stefano M. Bernasconi ◽  
...  
Keyword(s):  
Open System ◽  
Closed System ◽  
Fluid Migration ◽  
Fold Axis ◽  
Isotopic Data ◽  
Element Geochemistry ◽  
Secondary Porosity ◽  
Rock Interaction ◽  
Thrust Belts ◽  
The Impact

<p>Fluid systems in fold-thrust belts typically evolve from hydrologically closed to open, as a consequence of the incremental development of brittle deformation. The spatial distribution of fold-related fractures depends, among other factors, on the kinematics of folding and on the presence of inherited pre-folding structures. An improved understanding of the impact of the incremental evolution of deformation patterns on fluid migration and accumulation is crucial for industrial purposes. Here, we discuss the evolution of the fluid-rock system of the Parmelan anticline, in the Dauphinois units of the northern Subalpine Chains (Bornes Massif). We combined a detailed structural analysis in the Lower Cretaceous units (e.g. Urgonian Limestones) with the study of syn-tectonic calcite cements, by coupling stable and clumped isotope analysis with trace and major element geochemistry, radiogenic Sr isotopic data, and fluid inclusion microthermometry. The older calcite cements associated with the pre-folding structural assemblages precipitated from an <sup>18</sup>O-enriched fluid at temperatures between 90 and 115 °C. This first fluid type was thermally equilibrated with the host rock under maximum burial conditions in the Alpine Foreland and its isotopic composition has been interpreted to reflect a high degree of fluid-rock interaction in a closed system. Trace and major elements and Sr isotopes support a mixed meteoric-marine origin of this fluid, possibly trapped during subaerial platform exposure in the forebulge and then mixed with Eocene seawater. Closed system and rock-buffered conditions persisted during incipient folding whereas, during late folding, longitudinal (i.e. axial parallel) deformation structures allowed fluid circulation in an open system. Open system conditions initially occurred only in crest-limb transitional domains characterized by an higher deformation intensity. By contrast, during post-folding transpression,  the formation of a persistent vein set oblique to fold axis allowed external fluids to migrate in the anticline crest. Younger calcite cements precipitated from moderately warm (55-66 °C) <sup>18</sup>O-depleted meteoric fluids during the late- to post-folding stages. Our compositional and Sr isotopic data exclude any contribution from basement-derived ascending fluids and rule out a possible downward circulation of these meteoric fluids at basement depths. Our results indicate that, in regional anticlines of shallow crustal sectors in foreland fold-thrust belts, a significant amount of secondary porosity can be produced in the pre-folding stages when the hydromechanical stratigraphy likely preserves closed conditions and regional stratigraphic seals can prevent upward fluid migration during the entire tectonic evolution.</p>

scholarly journals Influence of basement rocks on fluid evolution during multiphase deformation: the example of the Estamariu thrust in the Pyrenean Axial Zone

2020 ◽  
Author(s):  
Daniel Muñoz-López ◽  
Gemma Alías ◽  
David Cruset ◽  
Irene Cantarero ◽  
Cédric M. Jonh ◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Normal Faults ◽  
Published Data ◽  
Fluid Migration ◽  
Rock Interaction ◽  
Fluid Chemistry ◽  
Vein Formation ◽  
Basement Rocks ◽  
Calcite Veins

Abstract. Calcite veins precipitated in the Estamariu thrust during two tectonic events decipher the temporal and spatial relationships between deformation and fluid migration in a long-lived thrust and determine the influence of basement rocks on the fluid chemistry during deformation. Structural and petrological observations constrain the timing of fluid migration and vein formation, whilst geochemical analyses (δ13C, δ18O, 87Sr/86Sr, clumped isotope thermometry and elemental composition) of the related calcite cements and host rocks indicate the fluid origin, pathways and extent of fluid-rock interaction. The first tectonic event, recorded by calcite cements Cc1a and Cc2, is related to the Alpine reactivation of the Estamariu thrust, and is characterized by the migration of meteoric fluids, heated at depth (temperatures between 56 and 98 °C) and interacted with crystalline basement rocks before upflowing through the thrust zone. During the Neogene extension, the Estamariu thrust was reactivated and normal faults and shear fractures with calcite cements Cc3, Cc4 and Cc5 developed. Cc3 and Cc4 precipitated from hydrothermal fluids (temperatures between 127 and 208 °C and between 102 and 167 °C, respectively) derived from crystalline basement rocks and expelled through fault zones during deformation. Cc5 precipitated from low temperature meteoric waters percolating from the surface through small shear fractures. The comparison between our results and already published data in other structures from the Pyrenees suggests that regardless of the origin of the fluids and the tectonic context, basement rocks have a significant influence on the fluid chemistry, particularly on the 87Sr/86Sr ratio. Accordingly, the cements precipitated from fluids interacted with crystalline basement rocks have significantly higher 87Sr/86Sr ratios (> 0.710) with respect to those precipitated from fluids that have interacted with the sedimentary cover (

Exploring the Ar isotope record of an early Miocene pseudotachylyte in an early Oligocene intrusion (Rieserferner pluton, eastern Alps)

Lithos ◽  
2019 ◽  
Vol 338-339 ◽  
pp. 1-17 ◽  
Author(s):  
Gianfranco Di Vincenzo ◽  
Giorgio Pennacchioni ◽  
Michel Bestmann
Keyword(s):  
Eastern Alps ◽  
Early Miocene ◽  
Early Oligocene ◽  
Isotope Record

Fluids in coesite-bearing rocks of the Tso Morari Complex, NW Himalaya: evidence for entrapment during peak metamorphism and subsequent uplift

2009 ◽  
Vol 146 (6) ◽  
pp. 876-889 ◽  
Author(s):  
BARUN K. MUKHERJEE ◽  
HIMANSHU K. SACHAN
Keyword(s):  
High Salinity ◽  
Granulite Facies ◽  
Ultrahigh Pressure ◽  
Nw Himalaya ◽  
Rock Interaction ◽  
Low Salinity ◽  
Ultrahigh Pressure Metamorphism ◽  
Indian Lithosphere ◽  
External Sources ◽  
Tso Morari

AbstractFluid inclusions trapped in coesite-bearing rocks provide important information on the fluid phases present during ultrahigh-pressure metamorphism. The subduction-related coesite-bearing eclogites of the Tso Morari Complex, Himalaya, contain five major types of fluids identified by microthermometry and Raman spectroscopy. These are: (1) high-salinity brine, (2) N2, (3) CH4, (4) CO2and (5) low-salinity aqueous fluids. These fluids were trapped during both deep subduction and exhumation processes. The coesite-bearing rocks are inferred to have been buried to a depth of >120 km, where they experienced ultrahigh-pressure metamorphism. The fluid–rock interaction provides direct evidence for fluid derivation during a deep subduction process as demonstrated by silica–carbonate assemblages in eclogite. High salinity brine, N2and CH4inclusions are remnants of prograde and peak metamorphic fluids, whereas CO2and low-salinity aqueous fluids appear to have been trapped late, during uplift. The high-salinity brine was possibly derived from subducted ancient metasedimentary rocks, whereas the N2and CH4fluids were likely generated through chemical breakdown of NH3-bearing K minerals and graphite. Alternatively, CH4might have been formed by a mixed fluid that was released from calcareous sediments during subduction or supplied through subducted oceanic metabasic rocks. High density CO2is associated with matrix minerals formed during granulite-facies overprinting of the ultrahigh-pressure eclogite. During retrogression to amphibolite-facies conditions, low-salinity fluids were introduced from external sources, probably the enclosing gneisses. This source enhances salinity differences as compared to primary saline inclusions. The subducting Indian lithosphere produced brines prior to achieving maximal depths of >120 km, where fluids were instead dominated by gaseous phases. Subsequently, the Indian lithosphere released CO2-rich fluids during fast exhumation and was then infiltrated by the low-salinity aqueous fluids near the surface through external sources. Elemental modelling may improve quantitative understanding of the complexity of fluids and their reactions.

scholarly journals A Trace Element Classification Tree for Chalcopyrite from Oktyabrsk Deposit, Norilsk–Talnakh Ore District, Russia: LA-ICPMS Study

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 716 ◽  
Author(s):  
Alexander E. Marfin ◽  
Alexei V. Ivanov ◽  
Vera D. Abramova ◽  
Tatiana N. Anziferova ◽  
Tatiana A. Radomskaya ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
General Feature ◽  
Classification Tree ◽  
Global Scale ◽  
Inductively Coupled ◽  
Ore Minerals ◽  
Plasma Mass Spectrometry ◽  
Ore Types ◽  
Metasomatic Replacement ◽  
Ore District

The Oktyabrsk PGE-Cu-Ni deposit is one of the largest resources in the Norilsk–Talnakh ore district, Russia, and it is viewed as an ore giant on a global scale. It contains three types of ores: massive, disseminated and veinlet-disseminated. The two former ore types were formed by a liquation process, whereas the latter was associated with fluid-induced selective metasomatic replacement of metamorphosed wall rocks. One of the major ore minerals in all ore types is chalcopyrite. In this study, we determined concentrations of trace elements in this mineral using laser ablation inductively coupled plasma mass spectrometry. It appeared that standard geochemical tools, such as plotting the data in the form of diagrams of normalized concentrations, binary and ternary plots, do not allow one to distinguish chalcopyrite from visually and genetically different ore types. In contrast, more advanced statistical methods such as cluster analysis show different groupings of elements for each ore type. Based on the element clustering, a classification tree was suggested, which allowed for the differentiation of massive, disseminated and veinlet-disseminated ore types of the Oktyabrsk deposit by Se, Te, Cd and Pb concentrations in chalcopyrite with a success rate of 86%. The general feature is that chalcopyrite of veinlet-disseminated ore is poorer in these elements compared to chalcopyrite of the two other ore types. Chalcopyrite of massive ore is poorer in Se and Te when compared to chalcopyrite of disseminated ore.

scholarly journals Selenium-Rich Ag–Au Mineralization at the Kremnica Au–Ag Epithermal Deposit, Slovak Republic

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 572 ◽  
Author(s):  
Martin Števko ◽  
Jiří Sejkora ◽  
Zdeněk Dolníček ◽  
Pavel Škácha
Keyword(s):  
Base Metal ◽  
Slovak Republic ◽  
Epithermal Deposit ◽  
Ore Minerals ◽  
Ore Mineralization ◽  
Ore Mineralogy ◽  
Chemical Trends ◽  
New Phase ◽  
Epithermal Au ◽  
Ore District

Selenium-rich Au–Ag mineralization has been discovered in the Kremnica ore district, central Slovakia. The mineralization is hosted by a single quartz–dolomite vein hosted by Neogene propyllitized andesites of the Kremnica stratovolcano. Ore mineralogy and crystal chemistry of individual ore minerals have been studied here. The early base-metal ore mineralization composed of pyrite, sphalerite, and chalcopyrite lacks selenium, whereas the superimposed Au–Ag paragenesis is Se-enriched. The Au–Ag alloys, uytenbogaardtite, minerals of the galena–clausthalite series, acanthite–naumannite series, diaphorite, miargyrite, pyrargyrite–proustite, polybasite group, minerals of the tetrahedrite group and andorite branch (andorite IV, andorite VI, Ag-excess fizélyite), freieslebenite, and rare Pb–Sb sulphosalts (scaiinite, robinsonite, plagionite) have been identified here. Besides selenides, the most Se-enriched phases are miargyrite, proustite–pyrargyrite, and polybasite–pearceite, whose Se contents are among the highest reported worldwide. In addition, one new phase has been found, corresponding to a Se-analogue of pearceite containing 2.08–3.54 apfu Se. The style of mineralization, paragenetic situation, and chemical trends observed in individual minerals are comparable to those of Au–Ag low-sulphidation epithermal Au–Ag mineralizations of the Kremnica and neighboring Štiavnica and Hodruša-Hámre ore districts. However, the pronounced enrichment in selenium is a specific feature of the studied vein only.

scholarly journals Oxygen isotopes in ophicalcites: an ever-lasting controversy?

2020 ◽  
Author(s):  
Daniel Bernoulli ◽  
Helmut Weissert
Keyword(s):  
Oxygen Isotope ◽  
Isotope Geochemistry ◽  
Regional Metamorphism ◽  
Hydrothermal Activity ◽  
Eastern Alps ◽  
Metamorphic Overprint ◽  
Rock Interaction ◽  
Sea Floor ◽  
Detachment Faults ◽  
Mid Atlantic Ridge

Abstract Tectono-sedimentary breccias, known as ophicalcites, overlie serpentinised peridotites at a Jurassic ocean–continent transition along the Penninic-Austroalpine transition in the Eastern Alps of Switzerland. Deformation of the exhumed mantle rocks and breccia formation occurred under decreasing temperatures and along low-angle detachment faults exposing the mantle rocks at the sea floor and was coupled with hydrothermal activity and carbonation of the serpentinites at shallow depth and/or at the sea floor. Carbon isotopes in the ophicalcites persistently show marine values; however, the interpretation of oxygen-isotope values remained controversial: are they related to Jurassic hydrothermal activity or do they reflect Alpine metamorphic overprint? Here we discuss recent interpretations that relate oxygen isotope values measured in ophicalcites exclusively to Jurassic hydrothermal activity; to this end we use data that we earlier obtained along a north–south profile across Graubünden (eastern Switzerland). We revisited the sites of controversial interpretation along a north–south profile in eastern Switzerland. Along this profile, oxygen isotope values in ophicalcites and overlying pelagic sediments, up to 25 my younger than the ophicalcites, show identical values and become systematically lower with increasing Alpine metamorphism; they strongly deviate from values in ophicalcites and pelagic sediments measured along the Mid-Atlantic Ridge or ancient Atlantic ocean-continent transitions as e.g. in the Iberia–Newfoundland transect. The oxygen-isotope values measured in Alpine ophicarbonates thus reflect isotopic resetting during the Alpine orogeny, related to fluid-rock interaction during regional metamorphism. Hydrothermal processes that accompanied the formation of ophicalcites are not disputed; however, they cannot be traced by oxygen isotope geochemistry.

scholarly journals Contamination risk assessment of the Transboundary Zeravshan River using chemical and isotopic studies

2019 ◽  
Vol 98 ◽  
pp. 07021
Author(s):  
Parviz Normatov ◽  
Inom Normatov
Keyword(s):  
River Water ◽  
Small Rivers ◽  
Rock Interaction ◽  
Low Salinity ◽  
Isotopic Studies ◽  
Rain Events ◽  
Isotope Analyses ◽  
Dissolution Of Minerals ◽  
Water Rock Interaction ◽  
Water Dissolution

The results of chemical and isotope analyses of water of the Zeravshan River are presented. Results show that the low salinity of the river water in the upstream reach is formed mainly by water dissolution of minerals in natural rocks, i.e. the existence of a water-rock interaction process. The detection of heavy cations in the composition of the river water is due to their transport long distances in the form of microparticles by wind and accumulation in snow cover and glaciers. During the melting of snow and glaciers, and during rain events, pollutants are carried by streams, small rivers, and finally by Zeravshan River that distributes the pollutants over long distances.

Wettability Alteration During Low-Salinity Waterflooding in a Deep Tight Carbonate Reservoirs: A Quantitative and Visual Investigation Through Spontaneous Imbibition and Zeta Potentiometric Studies

2021 ◽  
Author(s):  
N. Singh ◽  
P. H. Gopani ◽  
H. K. Sarma ◽  
F. Wu ◽  
P. S. Mattey ◽  
...  
Keyword(s):  
Contact Angle ◽  
Zeta Potential ◽  
Carbonate Reservoir ◽  
Spontaneous Imbibition ◽  
Wettability Alteration ◽  
Rock Surface ◽  
Rock Interaction ◽  
Low Salinity ◽  
Tight Carbonate ◽  
Repulsive Forces

Abstract This study focusses on the investigation of wettability alteration behavior during low salinity waterflood (LSWF) process in a tight carbonate reservoir through Zeta potential studies in conjunction with spontaneous imbibition tests and estimation of the contact angle between the wetting fluid and the rock surface. This will help in understanding the role rock-oil-brine interactions play during an LSWF process. The classical streaming potential technique were used to determine Zeta potential. Measurements were carried out with diluted brines using different rock samples of in two states: oil-saturated and brine-saturated. The experimental results imply that the value of zeta potential becomes more negative with increasing percentage of dilution (25%, 10%, and 1%). This is attributed to electrical double-layer expansion which is caused, primarily, by the reduced ionic strength. We concluded that rock saturated with oil may give an insight on oil rock interactions while the rock saturated with brine may give insight on rock-brine interactions. The dilution of water helps increase the electrostatic repulsive forces between the two interfaces, which in turns, leads to the incremental recovery during LSWF process. This observation was also confirmed by coreflooding and wettability experiments through spontaneous imbibition tests and contact angle measurements conducted using the same oil-brine-rock systems. This is an investigative study of oil-brine-rock interaction behavior during a LSWF process that is difficult to accomplish through and during a conventional coreflooding displacement test. In addition, this study also couples the relationship between the wettability alteration and oil-brine-rock interactions during an LSWF process.

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