The effect of H 2 O on sulfide melting temperatures has been
investigated in the FeS-PbS-ZnS system at 1.5 GPa, revealing that the
addition of H 2 O results in a 35°C drop in melting temperature
from 900° to 865°C. In addition to the melting point depression, the
solubility of H 2 O is confirmed by the presence of vesicles in the
quenched melt. No oxide phases were present in any of the run products,
ruling out oxidation as a cause of the melting point depression.
Confirmation of the solubility of H 2 O in sulfide melts is
consistent with the recent suggestion by Mungall and Brenan (2003) of a
magmatic origin for halogen-rich alteration associated with magmatic sulfide
ore deposits, as the hydrous component of the alteration may similarly
originate in the fractionating sulfide melt. Anatectic sulfide melts could
be expected to contain more H 2 O than magmatic sulfide melts,
owing to the lack of a parental silicate melt that buffers the H 2 O
content of magmatic sulfide melts. Fluids expelled from the cooling
anatectic melts, such as that present during granulite facies metamorphism
of sulfide deposits at Broken Hill, Australia, may have been responsible for
associated retrograde hydrothermal alteration.
Black opal, the most unique and economically important opal in the world, is only found at Lightning Ridge in northern New South Wales. Only a handful of studies have been published on black opal, all of which suggest that black opal formed in the Cretaceous and Early Tertiary (Darragh et al. 1965, Watkins 1984, Pecover 1996, Behr 2001, Behr et al. 2000, Townsend 2001). Determining the origin of black opal is important for our understanding of sedimentation and regolith evolution, silica transport pathways and to improve the value of the mineral resource economy of New South Wales. This study aims to determine the age and origin of Lightning Ridge black opal. All of the significant opal deposits in Australia occur within sedimentary deposits above or near the Great Artesian Basin. Vegetation, soil and geological environments are similar for all opal deposits. North of Lightning Ridge at Hebal, precious boulder opal is mined and, as the name suggests, it is found on the surface of Quaternary gravels. The mining area of Lightning Ridge is extremely flat with slight ridges consisting of outcropping Cretaceous sediments. It is below these ridges that the precious black opal is mined. The town is 150 m above sea level with the mining area ranging from 137 m to 162 m above sea level. The area is structurally undeformed with little outcrop Several conceptual models have been suggested to explain black opal formation: 1. weathering; 2. syntectonic; and 3. Cretaceous microbes. We have established an alternative model for black opal formation based on the use of stable isotopes ( 13 C, deuterium and 18 O), major and trace elements in sediments, ground water analysis and radiocarbon dating. METHODS Fieldwork was conducted during two one-week trips in March and June 2002. 13 mines were visited and sampled to study the similarities or differences of the opal in mines of the Lightning Ridge area. Ironstone, silcrete, sandstone, claystone, potch and opal (where possible) were sampled. Ground-water samples were collected from 4 sites; pH, alkalinity, electrical conductivity and dissolved oxygen were measured on site, and anions, cations 13 C, deuterium and 18 O were analysed in appropriate laboratories. Opal and sediment thin-sections were analysed for biological evidence and mineralogical compositions. The thin-sections were analysed using transmitted, reflected and scanning electron microscopy. X-Ray Fluorescence was used to determine the bulk major element composition of the Lightning Ridge sediments. Opal and sediment stable isotopes of 13 C, 18 O and deuterium were analysed by mass spectrometry. Trace elements were analysed in situ using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LAICP-MS) at the Research School of Earth Sciences (RSES) at the Australian National University. The opals were 13 C dated using the mass spectrometer at Research School of Physics (RSPhys), Australian National University.
Research Article| March 01, 2019 Geology and Genesis of the Giant Pulang Porphyry Cu-Au District, Yunnan, Southwest China Kang Cao; Kang Cao 1State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Resources, China University of Geosciences, Wuhan 430074, China2Key Laboratory of Deep-Earth Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China Search for other works by this author on: GSW Google Scholar Zhi-Ming Yang; Zhi-Ming Yang 2Key Laboratory of Deep-Earth Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China †Corresponding author: e-mail, zm.yang@hotmail.com Search for other works by this author on: GSW Google Scholar John Mavrogenes; John Mavrogenes 3Research School of Earth Sciences, Australian National University, Acton, ACT 2601, Australia Search for other works by this author on: GSW Google Scholar Noel C. White; Noel C. White 4 Centre for Ore Deposit and Earth Sciences (CODES), University of Tasmania, Private Bag 79, Hobart, Tasmania 7001, Australia5Ore Deposits and Exploration Center, Hefei University of Technology, Hefei 230009, China Search for other works by this author on: GSW Google Scholar Ji-Feng Xu; Ji-Feng Xu 6State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Yang Li; Yang Li 7Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06511, United States Search for other works by this author on: GSW Google Scholar Wei-Kai Li Wei-Kai Li 2Key Laboratory of Deep-Earth Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China Search for other works by this author on: GSW Google Scholar Economic Geology (2019) 114 (2): 275–301. https://doi.org/10.5382/econgeo.2019.4631 Article history accepted: 10 Feb 2019 first online: 27 Mar 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kang Cao, Zhi-Ming Yang, John Mavrogenes, Noel C. White, Ji-Feng Xu, Yang Li, Wei-Kai Li; Geology and Genesis of the Giant Pulang Porphyry Cu-Au District, Yunnan, Southwest China. Economic Geology 2019;; 114 (2): 275–301. doi: https://doi.org/10.5382/econgeo.2019.4631 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract The giant Pulang porphyry Cu-Au district (446.8 million tonnes at 0.52% Cu and 0.18 g/tonne Au) is in the southern segment of the Yidun arc (Zhongdian arc), part of the Sanjiang Tethyan orogenic belt in southwest China. The district consists of three deposits: South Pulang (~96% of the total ore reserves) and the smaller East and North Pulang deposits. Four intrusive phases host the three Pulang deposits, which are, in order of emplacement, premineralization fine-grained quartz diorite and coarse-grained quartz diorite, intermineralization quartz monzonite, and late-mineralization diorite porphyry. The complex intruded carbonaceous rocks of the Late Triassic Tumugou slates. Zircon U-Pb laser ablation-inductively coupled plasma-mass spectrometry dating shows that intrusive activity occurred at about 216 ± 2 Ma.Hydrothermal alteration of the intrusions at Pulang includes five main types: K-silicate, epidote-chlorite, chlorite-illite, quartz-illite, and clay alteration. K-silicate alteration, subdivided into early K-feldspar alteration and late biotite alteration (dominant), mainly affected the central quartz monzonite and adjacent coarse-grained quartz diorite and fine-grained quartz diorite. Epidote-chlorite alteration, the most widespread alteration in the district, extends from the deposit core outward and has overprinted K-silicate alteration at South and North Pulang. Late chlorite-illite, quartz-illite, and clay alteration have overprinted preexisting K-silicate and epidotechlorite alteration assemblages and are locally developed in all four intrusive phases. Copper and gold are positively correlated and are mainly (90%) associated with epidote-chlorite alteration and, to a lesser degree, with K-silicate and chlorite-illite alteration. Hypogene pyrrhotite is intergrown with chalcopyrite and mainly occurs in chlorite-illite– and quartz-illite–altered, coarse-grained quartz diorite at East Pulang. Molybdenite Re-Os dating shows that mineralization in the district occurred at 216.54 ± 0.87 to 216.13 ± 0.86 Ma.The sequence of intrusion emplacement, alteration and veining, and sulfide associations at the three deposits suggests that South and North Pulang are two separate porphyry Cu-Au deposits, whereas East Pulang is probably a distal part of South Pulang. The dominance of primary magnetite over ilmenite and the assemblage titanite + magnetite + quartz in the causative quartz monzonite, and the abundant hydrothermal anhydrite veins associated with early K-silicate and main-mineralization epidote-chlorite alteration indicate the oxidized nature of the felsic intrusion and resultant early hydrothermal fluids. The pyrrhotite related to late chlorite-illite and quartz-illite alteration suggests local reduction due to interaction with the carbonaceous Tumugou slates. The atypical association of epidote-chlorite alteration and Cu mineralization at Pulang either is due to fluids from another porphyry deposit nearby overprinting epidote-chlorite alteration onto preexisting copper mineralization and K-silicate alteration at Pulang or is the result of collapse of epidote-chlorite–stable fluids into the K-silicate-altered core during waning hydrothermal activity. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
One waste product in recycling of Al is salt cake, a mixture of Al, salts, and residue oxides. Several methods have been proposed to recycle salt cake, one involving high-temperature leaching of salts from the salt cake. The salt composition can be approximated as a mixture predominantly of NaCl and KCl salts, with lesser amounts of Mg chloride. In order to better assess the feasibility of recycling salt cake, an experimental study was conducted of phase equilibria in the system H{sub 2}O-NaCl-KCl-MgCl{sub 2} at pressure (P), temperature (T), and composition conditions appropriate for high- temperature salt cake recycling. These experiments were designed to evaluate the effect of small amounts (2-10 wt%) of MgCl{sub 2} on solubilities of halite (NaCl) and sylvite (KCl) in saturated solutions (30-50 wt% NaCl+KCl; NaCl:KCl = 1:1 and 3:1) at elevated P and T.
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