Magmatic sulfides in high-potassium calc-alkaline to shoshonitic and alkaline rocks

Abstract

Abstract. We investigate the occurrence and chemistry of magmatic sulfides and their chalcophile metal cargo behaviour during the evolution of compositionally different magmas from diverse geodynamic settings both in mineralised and barren systems. The investigated areas are the following: (a) the Miocene Konya magmatic province (hosting the Doğanbey Cu–Mo porphyry and Inlice Au epithermal deposits, representing post-subduction) and (b) the Miocene Usak basin (Elmadag, Itecektepe, and Beydagi volcanoes, the latter associated with the Kişladağ Au porphyry in western Turkey, representing post-subduction). For comparison we also investigate (c) the barren intraplate Plio-Quaternary Kula volcanic field west of Usak. Finally, we discuss and compare all the above areas with the already studied (d) Quaternary Ecuadorian volcanic arc (host to the Miocene Llurimagua Cu–Mo and Cascabel Cu–Au porphyry deposits, representing subduction). The volcanism of the newly studied areas ranges from basalts to andesites–dacites and from high-K calc-alkaline to shoshonitic series. Multiphase magmatic sulfides occur in different amounts in rocks of all investigated areas, and, based on textural and compositional differences, they can be classified into different types according to their crystallisation at different stages of magma evolution (early versus late saturation). Our results suggest that independently of the magma composition, geodynamic setting, and association with an ore deposit, sulfide saturation occurred in all investigated magmatic systems. Those systems present similar initial metal contents of the magmas. However, not all studied areas present all sulfide types, and the sulfide composition depends on the nature of the host mineral. A decrease in the sulfide Ni∕Cu (a proxy for the monosulfide solid solution (mss) to intermediate solid solution (iss) ratio) is noted with magmatic evolution. At an early stage, Ni-richer, Cu-poorer sulfides are hosted by early crystallising minerals, e.g. olivine–pyroxene, whereas, at a later stage, Cu-rich sulfides are hosted by magnetite. The most common sulfide type in the early saturation stage is composed of a Cu-poor, Ni-rich (pyrrhotite mss) phase and one to two Cu-rich (cubanite, chalcopyrite iss) phases, making up ∼84 and ∼16 area % of the sulfide, respectively. Sulfides resulting from the late stage, consisting of Cu-rich phases (chalcopyrite, bornite, digenite iss), are hosted exclusively by magnetite and are found only in evolved rocks (andesites and dacites) of magmatic provinces associated with porphyry Cu (Konya and Ecuador) and porphyry Au (Beydagi) deposits.

Gold in Mineralized Volcanic Systems from the Lesser Khingan Range (Russian Far East): Textural Types, Composition and Possible Origins

“…Gold, in particular, exhibits chalcophile behavior during partial melting and magmatic crystallization and is strongly affected by presence or absence of sulfide phases during these processes [16,[30][31][32][33][51][52][53]. Since sulfides are common minerals both in the mantle [31][32][33][118][119][120] and in various primitive and evolved silicate melts [51,102,[121][122][123][124], gold is effectively scavenged by sulfide liquids during the course of magmatic evolution [16,49,53,55,116,122]. Further liberation of gold and formation of native gold particles or gold-bearing intermetallic compounds may follow several different scenarios.…”

Benefits of combining GPS and GLONASS for measuring ocean tide loading displacement

“…Farrell 1972;Baker 1984), require a separate computation procedure. We input the FES2014b ocean tide model (Carrère et al 2016), and an elastic Earth response Green's function computed from the Preliminary Reference Earth Model (PREM) (Dziewonski and Anderson 1981) by Wang et al (2020), to the NLOADF (SPOTL) software (Agnew 1997;2012) to compute a priori OTL displacements. These are then applied in the GNSS processing via the hardisp program of the IERS Conventions 2010.…”

“…as well as fulfilling the GNSS data criteria described above. As stated above, we used an elastic Green's function based on PREM for all of our computations, and at our 49 stations, the M2 constituent height component displacements differ by only 0.16 mm RMS from when the anelastic Green's function of Wang et al (2020) is used. Ocean tide model variations caused 0.7-0.8 mm RMS inter-model agreement for the predicted M2 OTL height displacements at OHI2, TOW2, TRO1, VARS and WARK (labelled in Fig.…”

Deep to Shallow Sulfide Saturation at Nisyros Active Volcano

“…Image analysis software (ImageJ © 1.38 software) was used to obtain modal abundances in Table S2 of Supporting Information S2. Bulk major and trace element analysis of 20 host lava samples and nine enclaves was conducted with X-ray fluorescence-XRF (PANalytical Axiom AX spectrometer) and laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS; Agilent 7700) on fused glass beads at the University of Lausanne (see Georgatou & Chiaradia, 2020). For trace element measurements by LA-ICP-MS, 70 s of background measurement was followed by three cycles of ∼50 s of sample measurement, on different parts of the sample, with 15 s of wash-out in between.…”