The Tongkuangyu Cu Deposit, Trans-North China Orogen: A Metamorphosed Paleoproterozoic Porphyry Cu Deposit

2020 ◽  
Vol 115 (1) ◽  
pp. 51-77
Author(s):  
Xuyang Meng ◽  
Jeremy Richards ◽  
Jingwen Mao ◽  
Huishou Ye ◽  
S. Andrew DuFrane ◽  
...  
Keyword(s):  
North China ◽  
Porphyry Copper ◽  
Volcanic Rocks ◽  
Copper Deposit ◽  
Granitic Rocks ◽  
Weighted Mean ◽  
Porphyry Cu ◽  
Copper Mineralization ◽  
Biotite Schist ◽  
Granodiorite Porphyry

Abstract The Tongkuangyu copper deposit in the Zhongtiaoshan region, southern Trans-North China orogen, is hosted by a poorly constrained sequence of Paleoproterozoic volcano-sedimentary (quartz-sericite schist and biotite schist) and granitic rocks that have been metamorphosed to lower greenschist facies and variably deformed. The deposit has previously been proposed to be either a porphyry-type or a sediment-hosted stratiform Cu deposit, and its age of formation has been debated. The quartz-sericite schist is interpreted to be a felsic crystal tuff and consists of angular quartz crystals in a fine-grained sericite-altered matrix. Two quartz-sericite schist samples yielded zircon U-Pb upper concordia intercept ages of 2512 ± 12 (2σ, mean square of weighted deviates [MSWD] = 0.19) and 2335 ± 16 Ma (2σ, MSWD = 0.80). Biotite schist, which is interleaved locally with the quartz-sericite schist and is interpreted to be a basaltic-andesitic sill, yielded a younger zircon U-Pb upper concordia intercept age of 2191 ± 10 Ma (2σ, MSWD = 1.7). Five samples of granodiorite and granodiorite porphyry that intruded the schist sequence yielded similar zircon U-Pb ages, with a weighted mean upper concordia intercept age of 2182 ± 7 Ma (2σ, MSWD = 1.3). These results suggest that the volcanic sequence was deposited between ∼2.5 and 2.3 Ga and was intruded by basaltic-andesitic sills and a suite of granodiorite and granodiorite porphyry intrusions at ∼2.19 to 2.18 Ga. Two stages of copper mineralization are interpreted to have formed after pervasive sericite alteration of the felsic volcanic rocks. Stage 1 mineralization includes disseminated and deformed quartz veinlets containing chalcopyrite ± pyrite ± magnetite ± molybdenite associated with biotite ± K-feldspar alteration in granodiorite porphyry and schist. Stage 2 comprises undeformed quartz-chlorite-carbonate veins with bornite ± chalcopyrite ± magnetite associated with local chlorite and silicic alteration. Allanite crystals intergrown with chalcopyrite in the granodiorite porphyry yielded an approximate concordia U-Pb age of 2115 ± 31 Ma (2σ, MSWD = 2.3). Two molybdenite samples in a deformed quartz-chalcopyrite-molybdenite vein yielded Re-Os model ages of 2106 ± 9 and 2089 ± 9 Ma (2σ), consistent with previously published results. Hydrothermal monazite grains with Cu-Fe sulfide inclusions in the granodiorite porphyry, quartz-sericite schist, and undeformed chlorite-bornite-quartz veins yielded much younger U-Pb upper concordia intercept ages of 1832 ± 16 (2σ, MSWD = 0.48), 1810 ± 14 (2σ, MSWD = 0.92), and 1809 ± 12 Ma (2σ, MSWD = 0.38), respectively. The results are in agreement with four Re-Os model ages for pyrite mineral separates from undeformed quartz-sulfide veins, which yielded a weighted mean age of 1807 ± 4 Ma (2σ, n = 4, MSWD = 0.42). In contrast, hydrothermal rutile crystals in the quartz-sericite schist and biotite schist yielded a range of roughly concordant ages between 2.1 and 1.8 Ga, reflecting isotopic disturbance. We interpret these results to indicate original copper mineralization at ∼2.1 Ga that is significantly later than the granodiorite (∼2.18 Ga) and schists (∼2.5–2.2 Ga), followed by hydrothermal remobilization and metamorphism at ∼1.8 Ga. The metavolcanic and granodiorite porphyry host rocks, alteration styles, and disseminated and veinlet form of the earlier mineralization are strongly reminiscent of porphyry Cu deposits, and ages of ∼2.1 Ga have been reported for one intrusion and three volcanic rock samples from the district. The Tongkuangyu, therefore, represents one of the oldest known porphyry copper deposits. Remobilization of copper occurred at ∼1.8 Ga during the Zhongtiao orogeny.

HYPOGENE ALUNITE FROM THE EL SALVADOR DISTRICT, CHILE, INDICATES POTENTIAL FOR A BLIND PORPHYRY COPPER CENTER

2020 ◽  
Vol 115 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Jeffrey W. Hedenquist ◽  
Yasushi Watanabe ◽  
Antonio Arribas
Keyword(s):  
El Salvador ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Hydrothermal Activity ◽  
Porphyry Copper Deposits ◽  
Copper Ore ◽  
Copper Mineralization ◽  
Alteration Minerals ◽  
Porphyry Copper Mineralization ◽  
Granodiorite Porphyry

Abstract Surface samples of hypogene alunite that cement late breccia bodies from the El Salvador porphyry copper district of Chile were recently dated. One alunite sample over the principal Turquoise Gulch porphyry deposit has a 40Ar/39Ar total gas age of 40.64 ± 1.04 Ma, overlapping the age of a late latite intrusion. Two other samples associated with quartz-alunite replacement of rhyolite, ~750 m southwest of the collapse zone over the block cave of the porphyry copper deposit, are distinctly younger, at 38.12 ± 0.66 and 38.04 ± 0.22 Ma (averages of duplicate analyses, with ±2σ errors). Previously reported U/Pb ages of zircons from 15 Eocene-age diorite, granodiorite, and granite porphyry intrusions have weighted mean ages that range from about 44 to 41 Ma, with peak magmatic flux interpreted at 44 to 43 Ma. Porphyry copper ores in the El Salvador district formed at about the same time as porphyry intrusions, with intrusive centers that migrated in a south-southwest direction, from the small deposits at Cerro Pelado (~44.2 Ma), to Old Camp (~43.6 Ma) and M Gulch-Copper Hill (~43.5–43.1 Ma), to the main ore deposit at Turquoise Gulch (~42 Ma). The granodiorite porphyry intrusions at Turquoise Gulch are associated with ~80% of the known copper ore of the district; they record waning stages of magmatism at 42.5 to 42.0 Ma, followed by weakly altered latite dikes at 41.6 Ma. Molybdenite in quartz veins returned Re-Os ages of 41.8 to 41.2 Ma. The two alunite samples from our study with coincident dates of ~38 Ma provide evidence for magmatic-hydrothermal activity younger than any recognized to date, consistent with the alteration overprint of quartz-alunite on older muscovite after erosion. This younger activity must have been associated with a blind intrusion, likely located south of the Turquoise Gulch deposit, based on the distribution of alteration minerals, and offset from the zoning associated with the Turquoise Gulch center. Stable isotope values (δ34S, δ18O, δD) of the ~38 Ma alunite indicate a high-temperature hypogene origin, consistent with formation in a lithocap environment that typically is located at shallow levels over and on the shoulders of porphyry copper deposits. Both observations—alteration overprint and markedly younger age of alunite—indicate the potential for porphyry copper mineralization south of Granite Gulch, as much as 1,000 m below the level of the coeval outcropping quartz-alunite replacement, perhaps near ~2,000-m elevation; this is hundreds of meters deeper than the known copper ore of Turquoise Gulch.

scholarly journals Geological and Chronological Constraints on the Long-Lived Eocene Yulong Porphyry Cu-Mo Deposit, Eastern Tibet: Implications for the Lifespan of Giant Porphyry Cu Deposits

2017 ◽  
Vol 112 (7) ◽  
pp. 1719-1746 ◽  
Author(s):  
Jia Chang ◽  
Jian-Wei Li ◽  
David Selby ◽  
Jia-Cheng Liu ◽  
Xiao-Dong Deng
Keyword(s):  
Early Stage ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Granite Porphyry ◽  
Radiometric Dating ◽  
Time Interval ◽  
Porphyry Cu ◽  
Economic Significance ◽  
Vein Formation ◽  
Porphyry Cu Deposit

Abstract The Yulong porphyry Cu-Mo deposit, the third largest porphyry Cu deposit in China, contains proven reserves of > 6.5 million metric tons (Mt) Cu and 0.4 Mt Mo. Previous radiometric dating studies have provided numerous ages for this deposit, but the timing and duration of the process governing the deposition of Cu and Mo remains not well constrained. In this paper, we first document multiple stages of mineralization and hydrothermal alteration associated with distinct magmatic pulses at Yulong by field and textural relationships, and then present high-precision molybdenite Re-Os ages of 14 quartz-molybdenite ± chalcopyrite veins representing these stages to precisely constrain the timing and duration of Cu-Mo mineralization. The ore-hosting Yulong composite stock consists of three successive porphyry intrusions: (1) monzonitic granite porphyry (MGP), (2) K-feldspar granite porphyry (KGP), and (3) quartz albite porphyry (QAP). The vein formation, Cu-Mo mineralization, and ore-related alteration are grouped into early, transitional, and late stages with respect to the intrusive history. The first two porphyry intrusions are followed by cyclical sequences of veining that are mainly associated with potassic alteration and have formed (1) ME vein/USTT, (2) EBE/T veins, (3) A1E/T veins, (4) A2E/BT veins, and (5) A3E/T veins. A2E/BT and A3E/T veins of the early and transitional stages are dominated by quartz and chalcopyrite ± pyrite, respectively, and represent the main Cu-Mo mineralization events. More than 80% of Cu and Mo at Yulong were deposited in the early stage with the remainder being formed in the transitional stage. The late-stage pyrite-quartz veins (DL), which are characterized by sericitic alteration halos, postdate the intrusion of QAP dikes and have no economic significance. Molybdenite Re-Os ages of A2E and BT veins indicate that sulfide deposition at Yulong was episodic over a prolonged history lasting over 5.13 ± 0.23 m.y. (1σ). However, the bulk Cu-Mo ores formed in a shorter time interval of 1.36 ± 0.24 m.y. (1σ) with most Cu precipitated in a more restricted timespan of 0.82 ± 0.24 m.y. (1σ) in the early stage. These results, combined with geochronologic data from porphyry copper deposits elsewhere, confirm that multiple magmatic-hydrothermal pulses with a lifespan of tens to hundreds of thousands of years are sufficient to form a giant porphyry copper deposit. Factors such as metal concentration, volume, and focusing efficiency of ore-forming fluids could have played important roles in producing a giant porphyry Cu deposit regardless of a short- or long-lived magmatic-hydrothermal system.

scholarly journals Mapping Hydrothermal Zoning Pattern of Porphyry Cu Deposit Using Absorption Feature Parameters Calculated from ASTER Data

2019 ◽  
Vol 11 (14) ◽  
pp. 1729 ◽  
Author(s):  
Mengjuan Wu ◽  
Kefa Zhou ◽  
Quan Wang ◽  
Jinlin Wang
Keyword(s):  
Thermal Emission ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Geological Mapping ◽  
Systematic Sampling ◽  
Small Scale ◽  
Absorption Feature ◽  
Porphyry Cu ◽  
Feature Parameters ◽  
Porphyry Cu Deposit

Identifying hydrothermal zoning pattern associated with porphyry copper deposit is important for indicating its economic potential. Traditional approaches like systematic sampling and conventional geological mapping are time-consuming and labor extensive, and with limitations for providing small scale information. Recent developments suggest that remote sensing is a powerful tool for mapping and interpreting the spatial pattern of porphyry Cu deposit. In this study, we integrated in situ spectral measurement taken at the Yudai copper deposit in the Kalatag district, northwestern China, information obtained by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), as well as the spectra of samples (hand-specimen) measured using an Analytical Spectral Device (ASD) FieldSpec4 high-resolution spectrometer in laboratory, to map the hydrothermal zoning pattern of the copper deposit. Results proved that the common statistical approaches, such as relative band depth and Principle Component Analysis (PCA), were unable to identify the pattern accurately. To address the difficulty, we introduced a curve-fitting technique for ASTER shortwave infrared data to simulate Al(OH)-bearing, Fe/Mg(OH)-bearing, and carbonate minerals absorption features, respectively. The results indicate that the absorption feature parameters can effectively locate the ore body inside the research region, suggesting the absorption feature parameters have great potentials to delineate hydrothermal zoning pattern of porphyry Cu deposit. We foresee the method being widely used in the future.

Geochronology of mid-Cretaceous to Eocene magmatism, Babine porphyry copper district, central British Columbia

2001 ◽  
Vol 38 (4) ◽  
pp. 639-655 ◽  
Author(s):  
D G MacIntyre ◽  
M E Villeneuve
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Porphyry Copper ◽  
Volcanic Rocks ◽  
Porphyry Copper Deposits ◽  
Isotopic Dating ◽  
Plate Convergence ◽  
Copper Mineralization ◽  
Porphyry Copper Mineralization ◽  
Magmatic Event

New U/Pb and 40Ar/39Ar isotopic dating in the Babine porphyry copper district of central British Columbia documents three distinct magmatic events at 107–104, 85–78, and 54–50 Ma. The earliest event involved emplacement of rhyolite domes into submarine volcanic rocks of the Rocky Ridge Formation. The rhyolite domes and related dacitic to basaltic volcanic rocks gave a U–Pb age of 107.9 ± 0.2 Ma and an 40Ar/39Ar age of 104.8 ± 1.2 Ma. The rhyolites, which were previously mapped as Eocene, are reinterpreted to be part of a previously unrecognized mid-Cretaceous cauldron subsidence complex. The regionally extensive Late Cretaceous magmatic event is also recognized in the Babine district and is represented by 40Ar/39Ar ages of 85.2 ± 2.8 and 78.3 ± 0.8 Ma on two Bulkley intrusions, one of which has associated porphyry copper mineralization. The final magmatic event is the most widespread and involved emplacement of the Babine intrusions and formation of numerous porphyry copper deposits including the Bell and Granisle past producers. Twenty-one new 40Ar/39Ar isotopic ages for these intrusions and coeval andesites of the Newman Formation have a narrow range from 53.6 ± 0.9 to 49.9 ± 0.6 Ma, whereas previous K–Ar isotopic dating had a possible range of 15 Ma. The mid-Cretaceous, Late Cretaceous, and Eocene magmatic suites in the Babine district are interpreted to be part of a long-lived volcano-plutonic complex that was the site of periodic magmatism and porphyry copper mineralization over a 60 Ma time period. This complex may have evolved within a zone of extension (pull-apart basins) situated between dextral strike-slip faults that were active during periods of rapid oblique plate convergence.

scholarly journals Using Whole Rock and Zircon Geochemistry to Assess Porphyry Copper Potential of the Tonggou Copper Deposit, Eastern Tianshan

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 584
Author(s):  
Xue-Bing Zhang ◽  
Feng-Mei Chai ◽  
Chuan Chen ◽  
Hong-Yan Quan ◽  
Ke-Yong Wang ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Middle Part ◽  
Orogenic Belt ◽  
Geochemical Data ◽  
Eastern Tianshan ◽  
Porphyry Cu ◽  
Central Asian ◽  
Geochemical Analyses

Eastern Tianshan hosts a number of porphyry Cu deposits. However, these mainly formed in the Jueluotage Belt, in the middle part of Eastern Tianshan. The Tonggou porphyry Cu mineralization is an exception to this, since it is located in the Bogda Orogenic Belt, north of Eastern Tianshan. We obtained new zircon U-Pb ages, whole-rock geochemical data, zircon Hf isotope data, and zircon trace element compositions. LA-ICP-MS zircon U-Pb dating indicates a crystallization age of 302.2–303.0 Ma for the Tonggou mineralized granodiorite (TMG), which suggests that the Tonggou porphyry Cu mineralization formed in the Late Carboniferous period. εHf (t) data (1.8–14.1) for TMG suggests it was sourced from juvenile crustal melts, mixed with some mantle materials. TMG displays low ΣREE, compatible elements (Ba, Sr, Zr, and Hf), Zr/Hf and Nb/Ta ratios, as well as clearly negative Eu anomalies in whole rocks analyses. In addition, TMG is enriched in P, Hf and Th/U ratios in zircon, and has lower crystallization temperatures (734 to 735 °C) than the Daheyan barren granodiorite (DBG) (753 to 802 °C). Whole rock and zircon geochemical analyses show that the TMG was formed by fractional crystallization to a greater extent than the DBG in the Bogda Orogenic Belt. Moreover, zircon grains of the TMG show high Ce4+/Ce3+ ratios (159–286), which are consistent with related values from large porphyry deposits of the Central Asian Orogenic Belt (CAOB). High Ce4+/Ce3+ ratios reflect oxidizing magmas as a result of fractional crystallization, which indicates that the Tonggou deposit has potential to host a large porphyry Cu deposit.

scholarly journals Zircon U-Pb, Molybdenite Re-Os and Quartz Vein Rb-Sr Geochronology of the Luobuzhen Au-Ag and Hongshan Cu Deposits, Tibet, China: Implications for the Oligocene-Miocene Porphyry–Epithermal Metallogenic System

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 476
Author(s):  
Hanxiao Huang ◽  
Hong Liu ◽  
Guangming Li ◽  
Linkui Zhang ◽  
Huawen Cao ◽  
...  
Keyword(s):  
Quartz Vein ◽  
Porphyry Copper ◽  
Western China ◽  
Geochronological Data ◽  
Porphyry Cu ◽  
Metallogenic Belt ◽  
Granodiorite Porphyry ◽  
Epithermal Au ◽  
New Discovery ◽  
Metallogenic System

The Gangdese metallogenic belt in Tibet is an important copper and iron polymetallic, metallogenic belt in western China. The Luobuzhen epithermal Au-Ag and Hongshan porphyry Cu deposits, as two new discovery deposits in the last few years, are located in the western Gangdese metallogenic belt. In this paper, we present quartz vein Rb-Sr isochron, zircon U-Pb and molybdenite Re-Os ages for a better understanding of the minerallogenetic epoch of the deposits. Geochronological data show that the Rb-Sr isochron age of a quartz vein in a Luobuzhen Au-Ag deposit is 21.1 ± 1.8 Ma (MSWD (mean standard weighted deviation) = 0.19), zircon U-Pb ages from diorite and granodiorite porphyry in Hongshan Cu deposit are 50.0 ± 0.4 Ma (MSWD = 0.94) and 23.7 ± 0.1 Ma (MSWD = 0.73), respectively, and a Re-Os isochron age of molybdenite in Hongshan Cu deposit is 23.0 ± 2.0 Ma (MSWD = 0.014). These data suggest that the Luobuzhen epithermal Au-Ag and Hongshan porphyry Cu deposits formed at ca. 23–21 Ma, which were controlled by the same magmatic hydrothermal events. Formation of both the Luobuzhen and Hongshan deposits were obviously earlier than the Miocene porphyry metallogenetic events in the Gangdese porphyry copper belt.

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