IN SITU DATING OF HYDROTHERMAL MONAZITE AND IMPLICATIONS FOR THE GEODYNAMIC CONTROLS ON ORE FORMATION IN THE JIAODONG GOLD PROVINCE, EASTERN CHINA

2020 ◽  
Vol 115 (3) ◽  
pp. 671-685 ◽  
Author(s):  
Jun Deng ◽  
Kun-Feng Qiu ◽  
Qing-Fei Wang ◽  
Richard Goldfarb ◽  
Li-Qiang Yang ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Eastern China ◽  
Analytical Techniques ◽  
Gold Deposits ◽  
Ore Formation ◽  
Transient Event ◽  
Late Mesozoic ◽  
Gold Producer

Abstract The Jiaodong gold province, the largest gold producer in China, formed in a setting dominated by a 30-m.y. episode of Izanagi plate rollback and widespread extension, concomitant with late Mesozoic craton destruction. This study presents new high precision in situ sensitive high-resolution ion microprobe (SHRIMP) U-Th-Pb and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb ages for hydrothermal monazite from the largest of the Jiaodong gold deposits, which were previously dated as indicating ore formation over a few tens of millions of years when applying sericite Ar-Ar, zircon U-Pb, and less robust analytical techniques. Our U-Pb dating on monazite from the Jiaojia and Linglong deposits in western Jiaodong yielded consistent ages at ca. 120 Ma. The new geochronologic results, coupled with recently reported in situ monazite dates from smaller deposits in western Jiaodong, reveal that the deposits that host most of the ≥4,000-t Au resource formed during a relatively brief period at ca. 120 Ma. In eastern Jiaodong, the much smaller resource may have formed about 5 m.y. later, recorded by 114.2 ± 1.5 Ma gold mineralization at the Rushan deposit. The postsubduction opening of a slab gap at ca. 120 Ma is the most likely cause of the extensive gold mineralization in Jiaodong. The gap induced a local and rapid devolatilization of the hydrated mantle wedge at submelt temperatures. The transient event included release of a major volume of gold-transporting aqueous-carbonic fluid that was stored in the wedge into major NNE-trending structures in the overlying lithosphere.

PRECISE AGES FOR LODE GOLD MINERALIZATION IN THE XIAOQINLING GOLD FIELD, SOUTHERN MARGIN OF THE NORTH CHINA CRATON: NEW CONSTRAINTS FROM IN SITU U-Pb DATING OF HYDROTHERMAL MONAZITE AND RUTILE

2020 ◽  
Author(s):  
Junchen Liu ◽  
Yitian Wang ◽  
Jingwen Mao ◽  
Wei Jian ◽  
Shikang Huang ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Gold Mineralization ◽  
Late Mesozoic ◽  
The North ◽  
Southern Margin ◽  
Lithospheric Extension ◽  
Gold Producer ◽  
Gold Bearing

Abstract The Xiaoqinling gold field, located along the southern margin of the North China craton, is the second largest gold producer in China, which comprises more than 1,200 auriferous quartz veins with a proven gold reserve of at least 800 tons. Previously, the absolute age of the gold metallogenesis in this area has not been well defined due to the lack of suitable dating minerals. This study presents new in situ laser ablation-inductively coupled plasma-mass spectrometry U-Pb ages of coexisting hydrothermal monazite and rutile for the Fancha gold deposit in this area, which yielded 206Pb/238U ages of 127.5 ± 0.7 Ma (n = 65, mean square of weighted deviates [MSWD] = 1.8) and 129.7 ± 4.3 Ma (n = 37, MSWD = 1.4), respectively. Both ages overlap within analytical uncertainty at the 2σ level of significance, suggesting that both gold-bearing veins were emplaced at ca. 128 Ma. Mineralogical observations indicate that the monazite and rutile precipitated simultaneously with gold from the hydrothermal fluid. Our new data, combined with recently published monazite age, define a more precise gold episode, demonstrating that the gold endowment of the Xiaoqinling area was formed during a relatively brief period at ca. 130 to 127 Ma. We suggest that auriferous fluids were generated as a result of interactions between the enriched mantle and the lower crust, which was driven by westward flat slab subduction of the Paleo-Pacific plate during the late Mesozoic. The peak of lithospheric thinning during the postsubduction may have led to the rapid release of gold from the fertilized mantle. Consequently, the large number of gold-bearing veins in the Xiaoqinling area may ultimately be related to the tectonic evolution and mantle fluid processes that occurred during Early Cretaceous lithospheric extension.

scholarly journals Oxygen Fugacity and Volatile Content of Syntectonic Magmatism in the Neoarchean Abitibi Greenstone Belt, Superior Province, Canada

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 966
Author(s):  
Baptiste Madon ◽  
Lucie Mathieu ◽  
Jeffrey H. Marsh
Keyword(s):  
Oxygen Fugacity ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Chemical Diversity ◽  
Temporal Association ◽  
Volatile Content ◽  
Abitibi Subprovince

Neoarchean syntectonic intrusions from the Chibougamau area, northeastern Abitibi Subprovince (greenstone belt), may be genetically related to intrusion related gold mineralization. These magmatic-hydrothermal systems share common features with orogenic gold deposits, such as spatial and temporal association with syntectonic magmatism. Genetic association with magmatism, however, remains controversial for many greenstone belt hosted Au deposits. To precisely identify the link between syntectonic magmas and gold mineralization in the Abitibi Subprovince, major and trace-element compositions of whole rock, zircon, apatite, and amphibole grains were measured for five intrusions in the Chibougamau area; the Anville, Saussure, Chevrillon, Opémisca, and Lac Line Plutons. The selected intrusions are representative of the chemical diversity of synvolcanic (TTG suite) and syntectonic (e.g., sanukitoid, alkaline intrusion) magmatism. Chemical data enable calculation of oxygen fugacity and volatile content, and these parameters were interpreted using data collected by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. The zircon and apatite data and associated oxygen fugacity values in magma indicate that the youngest magmas are the most oxidized. Moreover, similar oxygen fugacity and high volatile content for both the Saussure Pluton and the mineralized Lac Line intrusion may indicate a possible prospective mineralized system associated with the syntectonic Saussure intrusion.

Gold distribution in the Val-d'Or Formation and a model for the formation of the Lamaque–Sigma mines, Val-d'Or, Quebec

1991 ◽  
Vol 28 (5) ◽  
pp. 706-720 ◽  
Author(s):  
Mehmet F. Taner ◽  
Pierre Trudel
Keyword(s):  
Gold Mineralization ◽  
Regional Metamorphism ◽  
Analytical Techniques ◽  
Shear Zones ◽  
Gold Deposits ◽  
Mining District ◽  
Volcanic Complex ◽  
Geothermal Systems ◽  
Gold Mines ◽  
Geothermal Activity

Recent lithogeochemical studies by accurate analytical techniques (e.g., instrumental and radiochemical neutron-activation analyses) have been used to explore the possibility of using gold distribution in the research for new gold deposits; these show that anomalous gold distribution occurs in some parts of the Val-d'Or Formation in the Val-d'Or mining district of Quebec. Gold lithogeochemistry in the Val-d'Or Formation has shown that it is possible to distinguish: (i) background values (1.4–3.5 ppb Au); (ii) zones of primarily anomalous gold values around the Lamaque–Sigma mines (median: 15 ppb Au); (iii) enrichment halos around gold orebodies (median: 70 ppb Au); and (iv) secondary gold enrichment in shear zones. We conclude that the Val-d'Or Formation is auriferous, i.e., anomalously rich in gold at least in some of its parts and contains the Lamaque – Sigma gold mines, representing 68% of the total gold production in the district. The Val-d'Or Formation is part of a central volcanic complex within an island-arc system. The centre of this complex is located in the main Lamaque plug, and this environment may be compared to high-temperature active geothermal systems that are commonly responsible for the formation of epithermal gold deposits. Gold mineralization at Sigma and Lamaque is considered to be related to a late hydrothermal phase or a retrograde phase of regional metamorphism. For the formation of the gold deposits, two distinct and successive events are postulated: (i) a gold-rich synvolcanic geothermal activity and (ii) a late remobilisation from the host rocks followed by deposition of gold ore within favourable structures.

U-Pb Dating on Hydrothermal Rutile and Monazite from the Badu Gold Deposit Supports an Early Cretaceous Age for Carlin-Type Gold Mineralization in the Youjiang Basin, Southwestern China

2021 ◽  
Author(s):  
Wei Gao ◽  
Ruizhong Hu ◽  
Albert H. Hofstra ◽  
Qiuli Li ◽  
Jingjing Zhu ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Early Cretaceous ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Detrital Zircons ◽  
Youjiang Basin ◽  
Host Rocks ◽  
Gold Bearing ◽  
Carlin Type Gold Deposits

Abstract The Youjiang basin on the southwestern margin of the Yangtze block in southwestern China is the world’s second largest Carlin-type gold province after Nevada, USA. The lack of precise age determinations on gold deposits in this province has hindered understanding of their genesis and relation to the geodynamic setting. Although most Carlin-type gold deposits in the basin are hosted in calcareous sedimentary rocks, ~70% of the ore in the Badu Carlin-type gold deposit is hosted by altered and sulfidized dolerite. Although in most respects Badu is similar to other Carlin-type gold deposits in the province, alteration of the unusual dolerite host produced hydrothermal rutile and monazite that can be dated. Field observations show that gold mineralization is spatially associated with, but temporally later than, dolerite. In situ secondary ion mass spectrometry (SIMS) U-Pb dating on magmatic zircon from the least altered dolerite yielded a robust emplacement age of 212.2 ± 1.9 Ma (2σ, mean square of weighted deviates [MSWD] = 0.55), providing a maximum age constraint on gold mineralization. The U-Th/He ages of detrital zircons from hydrothermally mineralized sedimentary host rocks at Badu and four other Carlin-type gold deposits yielded consistent weighted mean ages of 146 to 130 Ma that record cooling from a temperature over 180° to 200°C and place a lower limit on the age of gold mineralization in the basin. Hydrothermal rutile and monazite that are coeval with gold mineralization have been identified in the mineralized dolerite. Rutile is closely associated with hydrothermal ankerite, sericite, and gold-bearing pyrite. It has high concentrations of W, Fe, V, Cr, and Nb, as well as growth zones that are variably enriched in W, Fe, Nb, and U. Monazite contains primary two-phase fluid inclusions and is intergrown with gold-bearing pyrite and hydrothermal minerals. In situ SIMS U-Pb dating of rutile yielded a Tera-Wasserburg lower intercept age of 141.7 ± 5.8 Ma (2σ, MSWD = 1.04) that is within error of the in situ SIMS Th-Pb age of 143.5 ± 1.4 Ma (2σ, MSWD = 1.5) on monazite. These ages are ~70 m.y. younger than magmatic zircons in the host dolerite and are similar to the aforementioned U-Th/He cooling ages on detrital zircons from hydrothermally mineralized sedimentary host rocks. We, therefore, conclude that the Badu Carlin-type gold deposit formed at ca. 144 Ma. The agreement of the rutile and monazite ages with the U-Th-He cooling ages of Badu and four other Carlin-type gold deposits in the Youjiang basin suggests that ca. 144 Ma is representative of a regional Early Cretaceous Carlin-type hydrothermal event formed during back-arc extension.

Uplift history of the Jiaodong Peninsula, eastern North China Craton: implications for lithosphere thinning and gold mineralization

2017 ◽  
Vol 155 (4) ◽  
pp. 979-991 ◽  
Author(s):  
RUI ZHAO ◽  
QINGFEI WANG ◽  
XUEFEI LIU ◽  
M. SANTOSH ◽  
WANMING YUAN ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Late Mesozoic ◽  
Lithosphere Thinning ◽  
Jiaodong Peninsula ◽  
History Of ◽  
Timing Of Initiation ◽  
Two Stages

AbstractThe link between lithosphere thinning and formation of world-class gold deposits is well established in the Jiaodong Peninsula within the eastern North China Craton (NCC). However, the timing of initiation and duration of the lithospheric thinning process as well as the depth of formation of the mineralization remain uncertain. Since these parameters are fundamental to formulate exploration strategies, in this study we perform fission track (FT) analysis on zircon and apatite grains in Late Mesozoic granitoid samples from the Jiaodong Peninsula and provide new constraints for the mode and duration of lithospheric evolution and mineralization depth. The zircon FT ages range from 64.3 to 90.9 Ma and those of apatite show a range of 32.8–50.9 Ma. The data collectively display age peaks at ~60–80 and ~30–50 Ma. Reverse modelling of the apatite FT results indicates rapid crustal uplift during ~30–80 Ma in the Jiaodong Peninsula. This period coincides with the timing of maximal sedimentation in the neighboring basins and voluminous basaltic eruptions in the eastern NCC. We suggest that the Jiaodong Peninsula has experienced two stages of crust uplift in the Late Cretaceous and Paleogene as a consequence of the continuing lithosphere thinning, together with the surrounding basins, forming the horst–graben system in the eastern NCC. The Late Mesozoic granitoids are the main wall rocks for gold deposits in Jiaodong, and thus the crust denudation history gathered from the FT data suggest that the gold mineralization formed at depths of c. 6–11 km.

Magnetic modeling of iron oxide copper-gold mineralization constrained by 3D multiscale integration of petrophysical and geochemical data: Cloncurry District, Australia

2013 ◽  
Vol 1 (1) ◽  
pp. T63-T84 ◽  
Author(s):  
James R. Austin ◽  
Phillip W. Schmidt ◽  
Clive A. Foss
Keyword(s):  
Iron Oxide ◽  
Gold Mineralization ◽  
Signal Amplitude ◽  
Gold Deposits ◽  
Geochemical Data ◽  
Geophysical Investigation ◽  
Structural Controls ◽  
Breccia Pipe ◽  
Copper Gold

Magnetite-rich iron oxide copper-gold deposits (IOCGs) are geologically and geochemically complex and present major challenges to geophysical investigation. They often sit beneath significant cover, exhibit magnetic remanence, and suffer from self-demagnetization effects. Because remanence in magnetite-bearing drill core samples is commonly overprinted by drilling, in situ natural remanent magnetization is difficult to measure accurately, and thus IOCGs cannot be modeled definitively using geophysics alone. We examined structural controls on a magnetite-rich IOCG in northwest Queensland and the relationships between structure, alteration, Fe oxides, and mineralization at core to deposit scale. Magnetite within the deposit has a multidomain structure, and thus it would commonly have an in situ magnetization parallel to the earth’s field. In contrast, pyrrhotite has a pseudosingle-domain structure and so it is the predominant carrier of stable remanence within the ore system. Geophysical lineament analyses are used to determine structural controls on mineralization, geophysical filters (e.g., analytic signal amplitude) are used to help define structural extent of the deposit, and basement geochemistry is used to map mineral footprints beneath cover. These techniques identified coincident anomalies at the intersection of north and northwest lineaments. Leapfrog™ interpolations of downhole magnetic susceptibility and Cu, Au, and Fe assay data were used to map the distribution of magnetite, copper, gold, and sulfur in 3D. The analysis revealed that Cu and Au mineralization were coupled with the magnetite net-vein architecture, but that Cu was locally enriched in the east–northeast-trending demagnetized zone. The results from this suite of geophysical, petrophysical, and geochemical techniques were integrated to constrain modeling of the Brumby IOCG. Brumby can be described as a breccia pipe sitting at the intersection of north-striking, east-dipping, and northwest-striking, southeast-dipping structures that plunges moderately to the south–southeast. The breccia pipe was overprinted by a relatively late net-vein magnetite breccia and crosscut by a later, magnetite-destructive, east–northeast-striking fault.

Classification of pyrite types using fractal and stepwise factor analyses in the Chah Zard gold-silver epithermal deposit, Central Iran

2020 ◽  
Vol 20 (4) ◽  
pp. 496-508
Author(s):  
Hossein Kouhestani ◽  
Majid Ghaderi ◽  
Peyman Afzal ◽  
Khin Zaw
Keyword(s):  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Study Data ◽  
Gold Deposits ◽  
Central Iran ◽  
Factor Analyses ◽  
Icp Ms ◽  
Gold Silver ◽  
Log Ratio

The major target of this research is the classification of pyrite types using fractal and stepwise factor analyses in the Chah Zard ore deposit, Central Iran. The ore occurs within a breccia/vein type and the major ore mineral hosting gold mineralization is pyrite. In this study, data were selected using optical, scanning electron microscopy (SEM) and backscattered electron observations as well as laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP–MS) analysis. Conventional interpretations represent four gold-bearing pyrite types of various textures including fractured and porous Py1, oscillatory-rimmed and simple-zoned Py2, colloform Py3 and inclusion-rich Py4. The stepwise factor process was performed on the centred log ratio (clr) transformed data in two phases and Au was grouped with As, Te, Ni and Co in the second factor from the second stage (F2-2). Also, C-N fractal modelling was performed on the As, Au, Te and F2-2 values, all of which demonstrate multifractal nature. Four populations were separated based on F2-2 values and the C-N log–log plot. The main gold mineralization starts from 32 ppm, 2.8%, 7.94 ppm and 1.26 for Au, As, Te concentrations and F2-2, respectively, based on the C-N fractal modelling. These values are correlated with inclusion-rich Py4 and simple-zoned and oscillatory-rimmed Py2. The results obtained in this study show that fractal interpretation of LA-ICP–MS data by stepwise factor analysis may provide a suitable tool for the recognition of ore mineralization in epithermal gold deposits.

scholarly journals In situ decoration of Au NPs over polydopamine encapsulated GO/Fe3O4 nanoparticles as a recyclable nanocatalyst for the reduction of nitroarenes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saba Hemmati ◽  
Majid M. Heravi ◽  
Bikash Karmakar ◽  
Hojat Veisi
Keyword(s):  
Electron Microscopy ◽  
Inductively Coupled Plasma ◽  
Analytical Techniques ◽  
Ambient Conditions ◽  
Substituted Anilines ◽  
Efficient Catalyst ◽  
Au Nps ◽  
X Ray ◽  
Inductively Coupled

AbstractA new and efficient catalyst has been designed and prepared via in situ immobilization of Au NPs fabricated polydopamine (PDA)-shelled Fe3O4 nanoparticle anchored over graphene oxide (GO) (GO/Fe3O4@PDA/Au). This novel, architecturally interesting magnetic nanocomposite was fully characterized using different analytical techniques such as Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, elemental mapping, Transmission Electron Microscopy, Fourier Transformed Infrared Spectroscopy, X-ray Diffraction and Inductively Coupled Plasma-Atomic Electron Spectroscopy. Catalytic activity of this material was successfully explored in the reduction of nitroarenes to their corresponding substituted anilines, using NaBH4 as reducing agent at ambient conditions. The most significant merits for this protocol were smooth and clean catalysis at room temperature with excellent productivity, sustainable conditions, ease of separation of catalyst from the reaction mixture by using a magnetic bar and most importantly reusability of the catalyst at least 8 times without any pre-activation, minimum loss of activity and considerable leaching.

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