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.

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.

scholarly journals Linking Mineralogy to Lithogeochemistry in the Highland Valley Copper District: Implications for Porphyry Copper Footprints

2020 ◽  
Vol 115 (4) ◽  
pp. 871-901 ◽  
Author(s):  
Kevin Byrne ◽  
Guillaume Lesage ◽  
Sarah A. Gleeson ◽  
Stephen J. Piercey ◽  
Philip Lypaczewski ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
White Mica ◽  
Coarse Grained ◽  
Late Triassic ◽  
Material Transfer ◽  
Rock Composition ◽  
Porphyry Cu ◽  
Propylitic Alteration ◽  
Shortwave Infrared ◽  
Pathfinder Elements

Abstract The Highland Valley Copper porphyry deposits, hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera, are unusual in that some of them formed at depths of at least 4 to 5 km in cogenetic host rocks. Enrichments in ore and pathfinder elements are generally limited to a few hundred meters beyond the pit areas, and the peripheral alteration is restricted to narrow (1–3 cm) halos around a low density of prehnite and/or epidote veinlets. It is, therefore, challenging to recognize the alteration footprint peripheral to the porphyry Cu systems. Here, we document a workflow to maximize the use of lithogeochemical data in measuring changes in mineralogy and material transfer related to porphyry formation by linking whole-rock analyses to observed alteration mineralogy at the hand specimen and deposit scale. Alteration facies and domains were determined from mapping, feldspar staining, and shortwave infrared imaging and include (1) K-feldspar halos (potassic alteration), (2) epidote veins with K-feldspar–destructive albite halos (sodic-calcic alteration), (3) quartz and coarse-grained muscovite veins and halos and fine-grained white-mica–chlorite veins and halos (white-mica–chlorite alteration), and two subfacies of propylitic alteration comprising (4) prehnite veinlets with white-mica–chlorite-prehnite halos, and (5) veins of epidote ± prehnite with halos of chlorite and patchy K-feldspar. Well-developed, feldspar-destructive, white-mica alteration is indicated by (2[Ca-C] + N + K)/Al values <0.85, depletion in CaO and Na2O, enrichment in K2O, and localized SiO2 addition and is spatially limited to within ~200 m of porphyry Cu mineralization. Localized K2O, Fe2O3, and depletion in Cu, and some enrichment in Na2O and CaO, occurs in sodic-calcic domains that form a large (~34 km2) nonconcentric footprint outboard of well-mineralized and proximal zones enriched in K. Water and magmatic CO2-rich propylitic and sodic-calcic–altered rocks form the largest lithogeochemical footprint to the mineralization in the Highland Valley Copper district (~60 km2). Calcite in the footprint is interpreted to have formed via phase separation of CO2 from a late-stage magmatic volatile phase. Several observations from this study are transferable to other porphyry systems and have implications for porphyry Cu exploration. Feldspar staining and shortwave infrared imaging highlight weak and cryptic alteration that did not cause sufficient material transfer to be confidently distinguished from protolith lithogeochemical compositions. Prehnite can be a key mineral phase in propylitic alteration related to porphyry genesis, and its presence can be predicted based on host-rock composition. Sodic-calcic alteration depletes the protolith in Fe (and magnetite) and, therefore, will impact petrophysical and geophysical characteristics of the system. Whole-rock loss on ignition and C and S analyses can be used to map enrichment in water and CO2 in altered rocks, and together these form a large porphyry footprint that extends beyond domains of enrichment in ore and pathfinder elements and of pronounced alkali metasomatism.

Protracted Magmatism and Mineralized Hydrothermal Activity at the Gibraltar Porphyry Copper-Molybdenum Deposit, British Columbia

2020 ◽  
Vol 115 (5) ◽  
pp. 1119-1136 ◽  
Author(s):  
Christopher Kobylinski ◽  
Keiko Hattori ◽  
Scott Smith ◽  
Alain Plouffe
Keyword(s):  
Mineral Exploration ◽  
Porphyry Copper ◽  
Hydrothermal Activity ◽  
White Mica ◽  
Late Triassic ◽  
American Continent ◽  
North American Continent ◽  
Porphyry Cu ◽  
The North ◽  
Molybdenum Deposit

Abstract The Gibraltar Cu-Mo deposit, with a total tonnage of 3.2 million tons (Mt) Cu, is located in the Canadian Cordillera and hosted by the Late Triassic Granite Mountain batholith. The batholith formed through multiple intrusions of tonalitic rocks over a period of ~25 m.y. beginning at 229.2 ± 4.4 Ma in the Quesnel island arc before the accretion of the arc to the North American continent. Late in its evolution, Cu fertile magmas intruded in the center of the batholith, during at least three events from 218.9 ± 3.1 to 205.8 ± 2.1 Ma. The fertile magmas were hotter and more mafic than older barren magmas. They generated magmatic-hydrothermal activity, forming potassic alteration and white mica alteration, and produced Cu mineralization as chalcopyrite-quartz veinlets and disseminated chalcopyrite. Zircon in the Cu-bearing tonalite intrusion (218.9 ± 3.1 Ma) shows high Ce4+/Ce3+ (681 ± 286 [2σ], n =15) compared to those from older barren intrusions (129 ± 56 [2σ], n = 118). Oxidation conditions for parental magmas are calculated using the compositions of zircon and amphibole. The magmas for Cu-bearing intrusions have an average of fayalite-magnetite-quartz buffer (FMQ) +1.7 ± 0.7 (2σ, n = 73), whereas those for older barren intrusions have slightly lower fO2 (avg FMQ +1.3 ± 0.5 [2σ], n = 108), although the values are overlapping for the two. The bulk rocks of Cu-bearing tonalite intrusions in the Granite Mountain batholith have low Sr/Y ratios (<22) independent of the degrees of alteration. The low ratios are also reflected by low Sr/Y in zircon, suggesting that the low Sr/Y ratios of bulk rocks represent those of unaltered rocks. The values are low compared to those associated with many other porphyry Cu deposits globally. The data suggest that igneous rocks elsewhere with low Sr/Y in bulk rocks may have a potential to host economic Cu deposits. Ratios of Ce/Nd and Ce/Ce* (=Ce/((NdN)2SmN)) in zircon are positively correlated with the Ce4+/Ce3+ in zircon from the Granite Mountain batholith. Since the former two ratios can be obtained solely from zircon composition, these ratios from detrital zircon may be useful in evaluating the occurrences of oxidized intrusions in regional mineral exploration.

LATE EOCENE BIOSTRATIGRAPHIC AGE FOR ANDESITIC VOLCANIC HOST ROCKS FORMED IN AN ISLAND ENVIRONMENT AT THE COBRE PANAMA PORPHYRY Cu-Mo-Au-Ag DEPOSIT, PANAMA

2020 ◽  
Author(s):  
Stewart D. Redwood ◽  
Jonathan R. Bryan ◽  
David M. Buchs ◽  
Colin Burge
Keyword(s):  
Late Eocene ◽  
Volcanic Center ◽  
Volcanic Front ◽  
Fine Grained ◽  
Porphyry Cu ◽  
Volcanic Sequence ◽  
Macroscopic Observation ◽  
Arc Setting ◽  
Large Foraminifera ◽  
Host Rocks

Abstract The giant Cobre Panama porphyry Cu-Mo-Au-Ag deposit in western Panama is hosted by an undated andesitic volcanic sequence, the Petaquilla batholith (32.20 ± 0.76–28.28 ± 0.61 Ma), and porphyry stocks (28.96 ± 0.62–27.48 ± 0.68 Ma). Here we present a biostratigraphic age for the volcanic sequence based on stratigraphically diagnostic large foraminifera from thin limestone beds within kilometer-thick andesitic rocks. These yield a late middle to late Eocene biostratigraphic age (41.2–33.9 Ma), with a probable late Eocene age (Priabonian stage, 37.8–33.9 Ma), which is slightly older than the age of the batholith and porphyry intrusions. The volcanic sequence is dominated by fine-grained, massive basalt to andesite lavas with subordinate volcaniclastic deposits. A preliminary description of volcanic textures based on macroscopic observation of drill core and quarry/road exposures supports the occurrence of lavas, fallout tuffs, volcanic breccias, and possible pyroclastic density current deposits. Rare polymictic conglomerates with well-rounded clasts of igneous rocks attest to minor sedimentary reworking from a nearby subaerial volcanic environment. The dated limestone that is interbedded with the submarine volcanic sequence was deposited in an estimated water depth of 50 to 80 m, probably in a middle- to outer-shelf large foraminiferal shoal. These results support deposition on the flank of an active volcanic island during early shallowing of the Isthmus of Panama. The Cobre Panama volcanic center is interpreted to have formed in the final stages of the latest Cretaceous-Eocene volcanic arc before, or possibly during, the 175-km sinistral offset of the Panama volcanic front in the late Eocene-Oligocene. However, it remains unclear whether the volcanic center formed on the western continuation of the San Blas-Chagres arc segment or the eastern termination of the Azuero-Soná arc segment and whether it was emplaced during broadening of the pre-Oligocene volcanic front or in a back-arc setting.

Pressure – temperature and tectonic evolution of Triassic lawsonite – aragonite blueschists from Pinchi Lake, British Columbia

1996 ◽  
Vol 33 (5) ◽  
pp. 800-810 ◽  
Author(s):  
Edward D. Ghent ◽  
Philippe Erdmer ◽  
Douglas A. Archibald ◽  
Mavis Z. Stout
Keyword(s):  
Tectonic Evolution ◽  
Plate Boundary ◽  
White Mica ◽  
Strike Slip ◽  
Late Triassic ◽  
North American Cordillera ◽  
The North ◽  
Early Mesozoic ◽  
Mineral Assemblages

A blueschist and eclogite terrane is associated with one of the largest faults in the Canadian Cordilleran Orogen, the Pinchi fault. Blueschists (in situ) and retrogressed eclogite blocks occur along the Pinchi fault zone near 54°30'N and 124°W. Critical blueschist facies mineral assemblages include lawsonite–glaucophane, jadeite–lawsonite–glaucophane–quartz, and aragonite. White mica 40Ar/39Ar spectra on blueschist and eclogite yield ages in the range 221.8 ± 1.9 to 223.5 ± 1.7 Ma, establishing a direct link between the blueschists and eclogites. Preservation of aragonite sets rigid constraints on the pressure–temperature–fluid–time conditions of unroofing. K–Ar dates indicate that this is some of the oldest documented metamorphic aragonite. Comparison with computed petrogenetic grids suggests that metamorphic temperatures were in the range 200–300 °C, with pressures greater than 8–10 kbar (1 kbar = 100 MPa). Unroofing likely occurred during collision of the Cache Creek terrane with Quesnellia in the Late Triassic to Middle Jurassic. The fault was initiated as a plate boundary and was active as late as Eocene time as a strike-slip zone. The Pinchi blueschist terrane is similar to others in the North American Cordillera and highlights a tectonic regime of repeated blueschist metamorphism and rapid unroofing along many parts of the western margin of North America in the early Mesozoic.

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.

Evidence for hibbingite–kempite solid solution

1998 ◽  
Vol 62 (2) ◽  
pp. 251-255 ◽  
Author(s):  
Bernhardt Saini-Eidukat ◽  
Nikolai S. Rudashevsky ◽  
Alexander G. Polozov
Keyword(s):  
Solid Solution ◽  
Siberian Platform ◽  
Lower Paleozoic ◽  
Fine Grained ◽  
Platinum Group Minerals ◽  
Mineral Assemblages ◽  
Native Silver ◽  
Chalcopyrite Ore ◽  
Silver Grains ◽  
New Occurrences

AbstractNew occurrences of hibbingite, γ-Fe2(OH)3Cl, have been found associated with platinum-group minerals in the Noril'sk Complex, and with the Korshunovskoye iron ores of the southern Siberian platform. The Norils'k grains, which are up to 0. 6 mm in diameter, are associated with the platinumgroup minerals froodite, cabriite, urvantsevite and with native silver in massive pentlandite–cubanite– chalcopyrite ore. The Korshunovskoye iron ore sample in which hibbingite was found is composed of fine-grained magnetite ore associated with halite. Hibbingite, hematite and silver grains are found in cavities in halite; the reddish-brown hibbingite grains usually occur as encrustations in the cavities. The size of hibbingite and hematite grains is up to 100 µm.Hibbingite from the Noril'sk Complex contains a significant kempite (Mn2(OH)3Cl) component; in some cases it contains over 50 mol. % Mn. These data suggest that at least a partial solid solution series exists between hibbingite and kempite. All known occurrences of hibbingite represent paragenetically late mineral assemblages. In the case of the Korshunovskoye deposits, the occurrences are associated with highly concentrated hydrothermal brines derived from the Lower Paleozoic saline sediments of the Siberian Platform cover.

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.

Leka Ophiolite Complex as analogy to the serpentinization-carbonation system on Mars.

2021 ◽  
Author(s):  
benjamin bultel ◽  
Agata M. Krzesinska ◽  
Damien Loizeau ◽  
François Poulet ◽  
Håkon O. Astrheim ◽  
...  
Keyword(s):  
Near Infrared ◽  
Nir Spectroscopy ◽  
Ground Truth ◽  
Ultramafic Rocks ◽  
Ophiolite Complex ◽  
Spectral Parameters ◽  
Thin Sections ◽  
Accessory Minerals ◽  
Mineral Assemblages ◽  
Alteration Minerals

&lt;p&gt;Serpentinization and carbonation have affected ultramafic rocks on Noachian Mars in several places called here serpentinization-carbonation systems (SCS). Among the most prominent SCS revealing mineral assemblages characteristic of serpentinization/carbonation is the Nili Fossae region [1]. Jezero crater &amp;#8211; the target of the Mars 2020 rover &amp;#8211;hosted a paleolake which constitutes a sink for sediments from Nili Fossae [1]. Thanks to the near infrared spectrometer onboard Mars2020 [2], the mission has the potential to offer ground truth measurement for other putative serpentinization/carbonation system documented on Mars. Several important aspects that may be addressed are: Do carbonates result from primary alteration of olivine-rich lithologies or are they derived by reprocessing of previous alteration minerals [3]? What is the composition? and nature of the protolith, which appear to be constituted of considerable amounts of olivine [4]? To reveal critical information regarding the conditions of serpentinization/carbonation, accessory minerals need detailed studies [1; 5]. In case of Jezero Crater, and serpentinization on Mars in general, the main alteration minerals are identified, but little is known about the accessory minerals.&lt;/p&gt; &lt;p&gt;The Nili Fossae-Jezero system has potential analogues in terrestrial serpentinized and carbonated rocks, such as the Leka Ophiolite Complex, Norway (PTAL collection, https://www.ptal.eu). Here, distinct mineral assemblages record different stages of hydration and carbonation of ultramafic rocks [6].&lt;/p&gt; &lt;p&gt;We perform petrological and mineralogical analyses on thin sections to characterize the major and trace minerals and combine with Near Infrared (NIR) spectroscopy measurements. A set of spectral parameters are defined and compare to spectral parameters previously used on CRISM and OMEGA data [1, 4, 7, 8]. We study the significance of the mineralogical assemblages including nature of accessory minerals. Effect of the presence of accessory minerals on the NIR signal is investigated and their potential incidence on the amount of H&lt;sub&gt;2&lt;/sub&gt;/CH&lt;sub&gt;4&lt;/sub&gt; production in mafic or ultramafic system is discussed [5].&lt;/p&gt; &lt;p&gt;We started to apply the newly defined spectral parameters on several SCS on Mars. Results confirm local carbonation of earlier serpentinized rocks and suggest that different protoliths could have led to diversity of mineralogical associations in SCS on Mars. Multiple detection of brucite are also suggested for the first time on Mars. Altogether our results help to better describe key geochemical conditions of the SCS on Mars for habitability potential of the martian crust and Mars&amp;#8217;s evolution.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;References:&lt;/p&gt; &lt;ul&gt; &lt;li&gt;Brown, A. J., et al.&amp;#160;&lt;em&gt;EPSL&lt;/em&gt;1-2 (2010): 174-182.&lt;/li&gt; &lt;li&gt;Wiens, R.C.,&amp;#160;et al.&amp;#160;&amp;#160;&lt;em&gt;Space Sci Rev&lt;/em&gt;&lt;strong&gt;217,&amp;#160;&lt;/strong&gt;4 (2021).&lt;/li&gt; &lt;li&gt;Horgan, B., et al.&amp;#160;&lt;em&gt;Second International Mars Sample Return&lt;/em&gt;. Vol. 2071. 2018.&lt;/li&gt; &lt;li&gt;Ody, A., et al.&amp;#160;&lt;em&gt;JGR: Planets&lt;/em&gt;2 (2013): 234-262.&lt;/li&gt; &lt;li&gt;Klein, F., et al. &lt;em&gt;Lithos&lt;/em&gt;178 (2013): 55-69.&lt;/li&gt; &lt;li&gt;Bjerga, A., et al.&amp;#160;&lt;em&gt;Lithos&lt;/em&gt;227 (2015): 21-36.&lt;/li&gt; &lt;li&gt;Viviano-Beck et al, &lt;em&gt;JGR: Planets 11&lt;/em&gt;8.9 (2013)&lt;/li&gt; &lt;li&gt;Viviano-Beck et al, &lt;em&gt;JGR: Planets 119.6&lt;/em&gt;&amp;#160;(2014)&lt;/li&gt; &lt;/ul&gt;

The Giant Chalukou Porphyry Mo Deposit, Northeast China: The Product of a Short-Lived, High Flux Mineralizing Event

2021 ◽  
Author(s):  
Qingqing Zhao ◽  
Degao Zhai ◽  
Ryan Mathur ◽  
Jiajun Liu ◽  
David Selby ◽  
...  
Keyword(s):  
High Precision ◽  
Inductively Coupled Plasma ◽  
Hydrothermal Activity ◽  
Ore Deposits ◽  
Ionization Mass ◽  
Inductively Coupled ◽  
Fine Grained ◽  
Porphyry Cu ◽  
Icp Ms ◽  
Porphyry Mo Deposit

Abstract Whether giant porphyry ore deposits are the products of single, short-lived magmatic-hydrothermal events or multiple events over a prolonged interval is a topic of considerable debate. Previous studies, however, have all been devoted to porphyry Cu and Cu-Mo deposits. In this paper, we report high-precision isotope dilution-negative-thermal ionization mass spectrometric (ID-N-TIMS) molybdenite Re-Os ages for the newly discovered, world-class Chalukou porphyry Mo deposit (reserves of 2.46 Mt @ 0.087 wt % Mo) in NE China. Samples were selected based on a careful evaluation of the relative timing of the different vein types (i.e., A, B, and D veins), thereby ensuring that the suite of samples analyzed could be used to reliably determine the age and duration of mineralization. The molybdenite Re-Os geochronology reveals that hydrothermal activity at Chalukou involved two magmatic-hydrothermal events spanning an interval of 6.92 ± 0.16 m.y. The first event (153.96 ± 0.08/0.63/0.79 Ma, molybdenite ID-N-TIMS Re-Os age) was associated with the emplacement of a granite porphyry dated at 152.1 ± 2.2 Ma (zircon laser ablation-inductively coupled plasma-microscopic [LA-ICP-MS] U-Pb ages), and led to only minor Mo mineralization, accounting for &lt;10% of the overall Mo budget. The bulk of the Mo (&gt;90%) was deposited in less than 650 kyr, between 147.67 ± 0.10/0.60/0.76 and 147.04 ± 0.12/0.72/0.86 Ma (molybdenite ID-N-TIMS Re-Os ages), coincident with the emplacement of a fine-grained porphyry at 148.1 ± 2.6 Ma (zircon LA-ICP-MS U-Pb ages). The high-precision Re-Os age determinations presented here show, contrary to the finding of a number of studies of porphyry Cu and Cu-Mo systems, that the giant Chalukou porphyry Mo deposit primarily formed in a single, short-lived (&lt;650 kyr) hydrothermal event, suggesting that this may also have been the case for other giant porphyry Mo deposits.

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