Interaction Between Mafic Dike Rocks and Salt Deposits in the Rhine Graben, Southwest Germany

2021 ◽  
Author(s):  
Simon Braunger ◽  
Manuel Scharrer ◽  
Michael A.W. Marks ◽  
Thomas Wenzel ◽  
Gregor Markl
Keyword(s):  
Direct Contact ◽  
Rock Interaction ◽  
Salt Layer ◽  
Potash Salt ◽  
Mineral Assemblages ◽  
Bituminous Shale ◽  
Fast Cooling ◽  
Salt Deposits ◽  
Host Rocks ◽  
Mineralogical Evidence

ABSTRACT Dikes of primitive olivine melilitites and monchiquites intruded into an Oligocene (Rupelian) potash salt deposit near Buggingen (SW Germany). Ocelli and amygdules reveal distinct mineral assemblages depending on whether the dike rocks are in direct contact with the potash layer or with bituminous shales (Fish Shale). Samples in contact with the potash salt layer show roundish textures that contain smectite ± talc ± chlorite, calcite, and in cases anhydrite and halite, while those close to the bituminous shale mainly comprise smectite, calcite, zeolite group minerals, and analcime. No textural or mineralogical evidence for high-temperature (magmatic) interaction between the dike rocks and the evaporites was observed. This is presumably related to (1) a very low magmatic water activity in the magma, which prevented exsolution of aqueous fluids and appreciable dissolution of the salt, and (2) fast cooling of the magmas, inhibiting melting of the salt deposits and potential liquid mingling and/or assimilation processes. Halite formation in the dike rocks is, rather, related to later, post-magmatic hydrothermal fluids that previously interacted with the salt-rich host rocks. Alteration of the initially glassy groundmass to smectites and zeolites caused an enrichment of Na in the residual fluid, but halite saturation was not attained, as indicated by the absence of groundmass halite. Only fluid–rock interaction in millimeter-sized vugs caused halite precipitation via desiccation by swelling of previously formed clay minerals. Locally, the boron silicate datolite formed in pseudomorphs after olivine. Its precipitation was controlled by the Si and B supply provided by the breakdown of serpentine and smectite.

scholarly journals New orogenic type gold occurrences in the Uyanga ore knot (Central Mongolia)

2018 ◽  
pp. 22-36
Author(s):  
Ariunbileg Sodov ◽  
Olga Gaskova ◽  
Altansukh Gankhuyag ◽  
Dagva-Ochir Lkhagvasuren ◽  
Otgonbaatar Dorjsuren ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Gold Deposits ◽  
Gold Content ◽  
Rock Interaction ◽  
Central Mongolia ◽  
Quartz Veins ◽  
Mineral Assemblages ◽  
Metallogenic Zone ◽  
Host Rocks

The Uyanga ore knot district of the Khangay metallogenic zone are hosted by the lower-middle Devonian volcanogenic-sedimentary Erdenetsogt formation. About 40 samples were collected from the host rocks, veins and quartz veins in the Uyanga ore knot district in 2016. The new Burgetei, Ult and Senjit gold occurrences were studied. The quartz-sulfide, gold-arsenic and gold-antimony-mercury mineralization are determined in the berecitization, silicification, limonitization and glauconization altered metasomatic zones within the Uyanga ore knot districts. The rocks of the Erdenetsogt formation have an irregular gold content: 0.96 g/t Au is determined in quartz vein taken from trench of the Burgetei occurrence (BG-7/16), Au content is highest up to 3.5 g/t in the quartzite-jasper (Ult-7/16 and Ult-9/16) cut by quartz veins in the Ult occurrence. The Senjit occurrence represents Au-Hg-Sb epizonal level of orogenic gold deposits structure with highest Hg content up to 851 ppm. This year no sulfide minerals were found in the siltstone of this occurrence. The Au content of arsenical pyrite of the Burgetei and Ult is below the detection limit by electron microprobe analysis. The Au content of arsenopyrite of the Ult occurrence is highest (up to 238 ppm). Therefore, the ore-mineral assemblages in the gold occurrences reflect the differences between the three explored sites, formed in the course of fluid evolution during the fluid-rock interaction. Variable concentrations of indicative elements (As, Te, Sb, Hg) and their ratios confirm this fact. The geodynamic position, the type of the hydrothermal alteration of both igneous and sedimentary rocks, textures and mineral assemblages, the mineralization sequences are consistent with orogenic classification for the Burgetei, Ult and Senjit gold occurrences.

Paragenesis of veins of the Duck Pond tin prospect, Meguma Group, East Kemptville, Nova Scotia

1989 ◽  
Vol 26 (10) ◽  
pp. 2032-2043 ◽  
Author(s):  
Christian V. Pitre ◽  
Jean M. Richardson
Keyword(s):  
Nova Scotia ◽  
Manganese Oxides ◽  
Open Pit ◽  
Granitic Magma ◽  
Sulphide Minerals ◽  
Main Indicator ◽  
Argillic Alteration ◽  
Mineral Assemblages ◽  
Indicator Mineral ◽  
Host Rocks

The Duck Pond tin prospect is a vein- and strata-bound cassiterite prospect that is located 2 km west of the East Kemptville open-pit tin mine in southwestern Nova Scotia. The host rocks of the Duck Pond prospect are interbedded metawacke and meta-argillite that belong to the transition unit of the Meguma Group. These rocks contain quartz, sericite, chlorite, hematite, rutile, manganese oxides, feldspar, and porphyroblastic garnet, but not detrital cassiterite. The prospect is structurally controlled and contains several cross-cutting vein sets that have alkalic, chloritic, or argillic alteration assemblages. Muscovite is the main indicator mineral for alkalic alteration and occurs in veins that contain anorthoclase or quartz. Cassiterite is associated with chloritic alteration and occurs as subhedral to euhedral grains, acicular needles, and colloform layers in veins in meta-argillite and as strata-bound disseminations in metawacke. Most cassiterite precipitated under externally buffered conditions with respect to oxygen. Fe, Cu, Zn, and As sulphide minerals and quartz were deposited during argillic alteration. Late-stage processes such as recrystallization, sulphidation, and oxidation also occurred. Chalcopyrite is replaced by bornite and covellite; pyrite is replaced by marcasite.Unlike the F-rich East Kemptville deposit, fluorine-rich and tin-sulphide minerals are not present in the Duck Pond prospect. Trace tourmaline, absent at East Kemptville, is found at Duck Pond. However, the source of tin-mineralizing fluids at Duck Pond and East Kemptville was likely the granitic magma of the Davis Lake complex, which also hosts the East Kemptville deposit. From the mineral assemblages and textural relationships, it appears that as the temperature dropped from 425–405 °C to less than 200 °C at Duck Pond, the pH dropped from 5.2 to no lower than 3. Log [Formula: see text] dropped from at least −19 to −43. Log [Formula: see text] rose from < −15 to > −10. Cassiterite precipitated at the higher ends of the temperature and pH ranges and the lower end of the log [Formula: see text] range.

MAPPING THE MINERAL ZONATION AT THE ERNEST HENRY IRON OXIDE COPPER-GOLD DEPOSIT: VECTORING TO Cu-Au MINERALIZATION USING MODAL MINERALOGY

2022 ◽  
Vol 117 (2) ◽  
pp. 485-494
Author(s):  
Tobias U. Schlegel ◽  
Renee Birchall ◽  
Tina D. Shelton ◽  
James R. Austin
Keyword(s):  
Iron Oxide ◽  
Gamma Ray ◽  
Geochemical Data ◽  
Iocg Deposits ◽  
Mineral Mapping ◽  
Gamma Ray Spectrometer ◽  
Mineral Assemblages ◽  
Copper Gold ◽  
Host Rocks ◽  
Acid Alteration

Abstract Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.

scholarly journals New orogenic type gold occurrences in the Uyanga ore knot (Central Mongolia)

2019 ◽  
Vol 98 ◽  
pp. 08020
Author(s):  
Ariunbileg Sodov ◽  
Olga Gaskova ◽  
Altansukh Gankhuyag ◽  
Dagva-Ochir Lkhagvasuren ◽  
Otgonbaatar Dorjsuren ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Gold Deposits ◽  
Gold Content ◽  
Rock Interaction ◽  
Central Mongolia ◽  
Quartz Veins ◽  
Central Asian ◽  
Mineral Assemblages ◽  
Metallogenic Zone ◽  
Water Rock Interaction

The Khangay-Khentey belt is located in central Mongolia (Central Asian Orogenic Belt). The Uyanga ore knot district of the Khangay metallogenic zone are hosted by the lower-middle Devonian volcanogenic-sedimentary Erdenetsogt formation. The new Burgetei, Ult and Senjit gold occurrences were studied. The rocks of the Erdenetsogt formation have an irregular gold content: 0.96 g/t Au is determined in quartz vein (BG-7/16), Au content is highest up to 3.5 g/t in the quartzite-jasper (Ult-7/16 and Ult-9/16) cut by quartz veins in the Ult occurrence. The Senjit occurrence represents Au-Hg-Sb epizonal level of orogenic gold deposits structure with highest Hgand Sb content up to 8.5 ppm and 39 ppm respectively. The Au content of arsenic pyrite of the Burgetei and Ult is below the detection limit by electron microprobe analysis. The Au content of arsenopyrite of the Ult occurrence is highest (up to 238 ppm). The ore-mineral assemblages in the new gold occurrences reflect the differences between three explored sites, formed in the course of fluid evolution during the water-rock interaction. Variable concentrations of indicative elements (As, Te, Sb, Hg) and their ratios confirm this fact.

Mineralogical and Isotopic Characteristics of Sodic-Calcic Alteration in the Highland Valley Copper District, British Columbia, Canada: Implications for Fluid Sources in Porphyry Cu Systems

2020 ◽  
Vol 115 (4) ◽  
pp. 841-870 ◽  
Author(s):  
Kevin Byrne ◽  
Robert B. Trumbull ◽  
Guillaume Lesage ◽  
Sarah A. Gleeson ◽  
John Ryan ◽  
...  
Keyword(s):  
Water Source ◽  
White Mica ◽  
Late Triassic ◽  
Supporting Evidence ◽  
Fine Grained ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Alteration Minerals ◽  
External Water ◽  
Host Rocks

Abstract The Highland Valley Copper porphyry Cu (±Mo) district is hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera. Fracture-controlled sodic-calcic alteration is important because it forms a large footprint (34 km2) outside of the porphyry Cu centers. This alteration consists of epidote ± actinolite ± tourmaline veins with halos of K-feldspar–destructive albite (1–20 XAn) ± fine-grained white mica ± epidote. The distribution of sodic-calcic alteration is strongly influenced by near-orthogonal NE- and SE-trending fracture sets and by proximity to granodiorite stocks and porphyry dikes. Multiple stages of sodic-calcic alteration occurred in the district, which both pre- and postdate Cu mineralization at the porphyry centers. The mineral assemblages and chemical composition of alteration minerals suggest that the fluid that caused sodic-calcic alteration in the Guichon Creek batholith was Cl bearing, at near-neutral pH, and oxidized, and had high activities of Na, Ca, and Mg relative to propylitic and fresh-rock assemblages. The metasomatic exchange of K for Na, localized removal of Fe and Cu, and a paucity of secondary quartz suggest that the fluid was thermally prograding in response to magmatic heating. Calculated δ18Ofluid and δDfluid values of mineral pairs in isotopic equilibrium from the sodic-calcic veins and alteration range from 4 to 8‰ and −20 to −9‰, respectively, which contrasts with the whole-rock values for least altered magmatic host rocks (δ18O = 6.4–9.4‰ and δD = −99 to −75‰). The whole-rock values are suggested to reflect residual magma values after D loss by magma degassing, while the range of hydrothermal minerals requires a mixed-fluid origin with a contribution of magmatic water and an external water source. The O-H isotope results favor seawater as the source but could also reflect the ingress of Late Triassic meteoric water. The 87Sr/86Srinital values of strongly Na-Ca–altered rocks range from 0.703416 to 0.703508, which is only slightly higher than the values of fresh and potassic-altered rocks. Modeling of those data suggests the Sr is derived predominantly from a magmatic source, but the system may contain up to 3% seawater Sr. Supporting evidence for a seawater-derived fluid entrained in the porphyry Cu systems comes from boron isotope data. The calculated tourmaline δ11Bfluid values from the sodic-calcic domains reach 18.3‰, which is consistent with a seawater-derived fluid source. Lower tourmaline δ11Bfluid values from the other alteration facies (4–10‰) suggest mixing between magmatic and seawater-derived fluids in and around the porphyry centers. These results imply that seawater-derived fluids can infiltrate batholiths and porphyry systems at deep levels (4–5 km) in the crust. Sodic ± calcic alteration may be more common in rocks peripheral to porphyry Cu systems hosted in island-arc terranes and submarine rocks than currently recognized.

Gold–copper–bismuth mineralization in hedenbergitic skarn, Tombstone Mountains, Yukon

1987 ◽  
Vol 24 (12) ◽  
pp. 2362-2372 ◽  
Author(s):  
Isobel J. Brown ◽  
Bruce E. Nesbitt
Keyword(s):  
Large Scale ◽  
Small Volume ◽  
Gold Mineralization ◽  
Rock Interaction ◽  
The North ◽  
Mineral Assemblages ◽  
Intrusive Rocks ◽  
Porosity And Permeability ◽  
Relationship Of ◽  
The Relationship

Gold mineralization on the Marn property, Yukon, occurs in two pyroxene skarn bodies, which are adjacent to the Mount Brenner Stock in the Ogilvie Mountains. The skarns are separated by a 600 m wide monzonite intrusion and show contrasting mineralogical and geochemical characteristics in addition to quite different metal values. Significant but uneconomic Au, Ag, W, and Cu mineralization is found in skarn on the north side of the intrusion, while very low Au grades (0.052 g/t) occur at the southern contact. The mineral assemblages of both skarns are dominated by iron-rich pyroxenes. The iron content of the pyroxenes varies between Hd40 and Hd80 in the northern location and Hd80 and Hd100 in the southern skarn. A well-developed sequence of retrograde alteration affected only the northern skarn. This was probably the result of porosity and permeability differences in the early, high-temperature pyroxene skarn, which permitted greater fluid–rock interaction in the northern skarn during cooling. A small volume of diopsidic, aluminous, wollastonite-bearing skarn occurs in both the northern and southern localities. The relationship of this type of skarn to the hedenbergitic skarn is ambiguous, since there is no large-scale mineralogical zoning. The Marn is similar to hedenbergitic, auriferous skarns of Japan, where the oxidation state of the intrusive rocks is believed to be the controlling factor in the development of skarn mineralogy.

scholarly journals Rhenium - rich molybdenites in Thracian porphyry Mo±Cu occurrences, NE - Greece

2001 ◽  
Vol 34 (3) ◽  
pp. 1015 ◽  
Author(s):  
Β. ΜΕΛΦΟΣ ◽  
Π. ΒΟΥΔΟΥΡΗΣ ◽  
Κ. ΑΡΙΚΑΣ ◽  
Μ. ΒΑΒΕΛΙΔΗΣ
Keyword(s):  
Chemical Composition ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Mineral Chemistry ◽  
Rare Element ◽  
Alteration Zones ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Host Rocks

The present study correlates both the mineralogy of the hydrothermal alteration and the mineral chemistry of molybdenites from three porphyry Mo ± Cu occurrences in Thrace: Melitena, Pagoni Rachi/Kirki and Ktismata/ Maronia. The mineralisations are genetically related to calcalkaline, subvolcanic bodies of Tertiary age. According to their mineralogical and chemical composition the host rocks are characterized as dacite (Melitena), dacitic andésite (Pagoni Rachi) and porphyry microgranite (Ktismata/Maronia). The molybdenites occur in disseminated form, as fracture fillings, as well within quartz stockworks crosscuting the central alteration zones of the intrusives. They are accompanied by the following mineral assemblages: quartz, sericite, pyrophyllite, diaspore, Ca-Ba-rich alunite, pyrite (Melitena); quartz, albite/K-feldspar, biotite, actinolite, magnetite (Pagoni Rachi); and sericite, kaolinite, pyrophyllite, chlorite (Ktismata). Preliminary microthermometric results showed homogenisation temperatures from 352° to 390 °C for Pagoni Rachi area and from 295° to 363 °C for Melitena area. The salinities range between 4.5 and 6.1 wt% eq. NaCl and between 2.7 and 3.4 wt% eq. NaCl, respectively. Detailed study on over 400 fluid inclusions from the porphyry Cu-Mo deposit in Maronia area revealed formation temperatures from 300° to 420 °C, whereas salinities are distincted in two different groups from 6 to 16 wt% eq. NaCl and from 28 to 55 wt% eq. NaCl. The chemical composition of the molybdenites from the three porphyry Mo±Cu deposits in Thrace was studied with 155 microprobe analyses. The results revealed unusual high and variable Re concentrations in the studied molybdenites. Re content in molybdenite from Melitena area vary from 0.21 to 1.74 wt%, 0.79 wt% on average. The highest values were measured in samples from Pagoni Rachi (0.45-4.21 wt%, 1.98 wt% on average). Finally, microprobe analyses from molybdenite in Ktismata/Maronia showed Re content between 0.12 and 2.88 wt% (0.76 wt% on average). Rhenium is a very rare element with many definite uses, and is mainly associated with molybdenite in porphyry type deposits. According to the data published so far the Re content in molybdenite reaches up to 0.42 wt%. It is obvious therefore that such high Re concentrations (0.12 to 4.22 wt%) from the studied molybdenites in Thrace, are very ineresting for a possible future exploitation.

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