Granodiorite Porphyry Intrusions Research Articles

Relationship of copper-molybdenum and gold minering with magmatism

In the investigated deposits, a combination of skarn and hydrothermal mineralization has been identified. Specific facies within intrusive complexes align with distinct postmagmatic formations. Skarn-magnetite formations are intricately linked with the granitoid complex of the initial phase, while hydrothermal mineralization has a genetic connection to the subsequent phase of magmatism, characterized by minor intrusions of granodiorite porphyry. A distinctive zonal structure of individual facies, such as quartz-sericite-chlorite metasomatites, is observed around these granodiorite porphyry intrusions. The manifestation of rock wall metasomatism, as well as copper-molybdenum and gold ore mineralization, closely corresponds to the extent of the granodiorite-porphyry occurrences. This correlation highlights the intimate relationship between the scale of mineralization and the manifestation of granodiorite-porphyry, emphasizing the role of specific magmatic phases in the formation of skarn and hydrothermal deposits. The findings contribute to our understanding of the geological processes governing the development of diverse mineralization types within these deposits.

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

AbstractSurface 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.

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

AbstractThe 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.

High oxidation magmatic evolution in the Naruo porphyry Cu deposit, Tibet, China

The Naruo porphyry Cu deposit is the third largest deposit discovered in the Duolong metallogenic district. Previous research has focused mainly on the geochemistry of the ore-bearing granodiorite porphyry; the metallogenesis remains poorly understood. In the present work, on the basis of outcrops and drilling core geological mapping, phases of early mineralization diorite, two inter-mineralization granodiorite porphyries, and late-mineralization granodiorite porphyry have been distinguished. Furthermore, the alteration zones were outlined, and the vein sequence was identified. The diorite and three porphyry phases were subjected to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (La–ICP–MS) zircon U–Pb dating and in situ Hf isotope analyses as well as bulk major element, trace element, and Sr–Nd isotopic analyses. Molybdenite Re–Os dating was also conducted.The zircon U–Pb dating results show that the diorite and porphyry intrusions were emplaced at about 120 Ma, and the molybdenite Re–Os isochron age is 118.8 ± 1.9 Ma; this indicates that the Naruo porphyry Cu deposit was formed during a continuous magmatic–hydrothermal process. All of the diorite and granodiorite porphyry samples showed arc magmatic characteristics. Moreover, the moderate (87Sr/86Sr)i ratios and low εNd(t) and εHf(t) values of the diorite and porphyry intrusions suggest the source region of the juvenile lower crust. The lower (87Sr/86Sr)i and (143Nd/144Nd)i ratios and higher εNd(t) values and incompatible element concentrations than those in the granodiorite porphyry samples indicate a two-stage magmatic generation process for the intrusions. The early mineralization diorite has a high Cu concentration, implying that the source is enriched in Cu. However, the slightly lower Cu content of the late-mineralization granodiorite porphyry samples might imply Cu release from magmas and deposition within the metallogenic stage. The multiple stages of intrusions and subsequent volcanism within the Duolong metallogenic district, together with high Sr/Y features, indicate persistent magmatism during the metallogenic epoch, which is necessary for maintaining the activity of magmatic–hydrothermal and mineralization processes. Thus, the high Cu content in the source region, mantle-derived melt upwelling, and multiple stages of persistent magmatism were favorable for the formation of the Naruo porphyry Cu deposit.The high Fe2O3/FeO ratios of the diorite and granodiorite porphyry intrusions show very high oxidation features, which is coincident with estimated magmatic oxidation state calculated by the zircon trace element compositions. The high oxidation facilitates sulfur and chalcophile metals to be scavenged into the magmatic–hydrothermal systems, which is crucial for the metallogenesis of the Naruo porphyry Cu deposit.

Distal Au Deposits Associated with Cu-Au Skarn Mineralization in the Fengshan Area, Eastern China

Research Article| February 01, 2019 Distal Au Deposits Associated with Cu-Au Skarn Mineralization in the Fengshan Area, Eastern China Guiqing Xie; Guiqing Xie 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China2Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario P3E 2C6, Canada †Corresponding author: e-mail, xieguiqing@cags.ac.cn Search for other works by this author on: GSW Google Scholar Jingwen Mao; Jingwen Mao 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China Search for other works by this author on: GSW Google Scholar Jeremy P. Richards; Jeremy P. Richards 2Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario P3E 2C6, Canada Search for other works by this author on: GSW Google Scholar Yingxiao Han; Yingxiao Han 3School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Bin Fu Bin Fu 4Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Guiqing Xie 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China2Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario P3E 2C6, Canada Jingwen Mao 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China Jeremy P. Richards 2Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario P3E 2C6, Canada Yingxiao Han 3School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China Bin Fu 4Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia †Corresponding author: e-mail, xieguiqing@cags.ac.cn ☼Current address: Institute of Mineral Resources, Chinese Academy of Geological Sciences, No. 26 Baiwanzhuang Road, Beijing 100037, China. Publisher: Society of Economic Geologists Accepted: 23 Nov 2018 First Online: 28 Feb 2019 Online Issn: 1554-0774 Print Issn: 0361-0128 © 2019 Economic GeologyEconomic Geology Economic Geology (2019) 114 (1): 127–142. https://doi.org/10.5382/econgeo.2019.4623 Article history Accepted: 23 Nov 2018 First Online: 28 Feb 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Guiqing Xie, Jingwen Mao, Jeremy P. Richards, Yingxiao Han, Bin Fu; Distal Au Deposits Associated with Cu-Au Skarn Mineralization in the Fengshan Area, Eastern China. Economic Geology 2019;; 114 (1): 127–142. doi: https://doi.org/10.5382/econgeo.2019.4623 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 Carbonate-hosted Au deposits (12 million tonnes at 5.0 g/t Au) are located less than 1.5 km away from Cu-Au skarn deposits in the Fengshan area, Middle-Lower Yangtze River metallogenic belt, eastern China. The skarn deposits occur in the contact zones of late Mesozoic granodiorite porphyry intrusions. Bismuth tellurides and coloradoite (HgTe) occur in Cu-Au skarn and peripheral Au-As ores, respectively, whereas tellurides, including coloradoite, and lorandite (TlAsS2) are present in carbonate-hosted Au ores outside the marble front. New zircon U-Pb ages indicate that the granodiorite porphyry intrusions spatially related to both Cu-Au skarn and carbonate-hosted Au deposits were emplaced between 149.9 ± 1.3 and 145.9 ± 0.7 Ma, which overlaps with molybdenite Re-Os ages of 149.1 ± 2.1 to 145.4 ± 2.9 Ma from the Cu-Au skarn deposits. Sulfur isotope compositions of sulfide minerals from the Cu-Au skarn deposits (δ34S = –2.5 to 6.4‰) are similar to those from carbonate-hosted Au deposits (δ34S = –4.8 to 2.6‰), suggesting a similar magmatic source of sulfur. Geologic, mineralogical, and sulfur isotope evidence collectively indicate that the carbonate-hosted Au deposits are the distal product of Cu-Au skarn mineralization rather than Carlin-type Au deposits, as has been previously suggested. This study proposes a genetic model to illustrate possible linkages between oxidized Cu-Au skarn deposits (associated with oxidized magmas) and carbonate-hosted Au deposits, which may have important implications for Au deposits in the more distal parts of Cu-Au skarn systems in the Middle-Lower Yangtze River metallogenic belt and elsewhere. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Late Cretaceous tectono-magmatic activity in the Nize region, central Tibet: evidence for lithospheric delamination beneath the Qiangtang–Lhasa collision zone

ABSTRACTThe results of zircon U–Pb age dating and whole-rock geochemistry for the Late Cretaceous Nize granodiorite porphyries, combined with analysis of near-coeval structural deformation of the Lower Cretaceous Langshan Formation, provide new data to better understand the tectonic evolution of the northern Lhasa subterrane, central Tibet. Zircon U–Pb ages of 89.2 ± 0.3 Ma to 87.8 ± 0.3 Ma indicate emplacement during the Late Cretaceous. Granodiorite porphyry intrusions were contemporaneous with the development of a regional angular unconformity, overlain by the Upper Cretaceous Jingzhushan (or Abushan) Formation, within the collision zone between the South Qiangtang and Lhasa terranes. Geochemical data for Nize granodiorite porphyries indicate that they have a calc-alkaline composition enriched in large-ion lithophile elements and light rare earth elements and depleted in high-field-strength elements and heavy rare earth elements. High Al2O3 and Sr contents, low Yb and Y contents, and high Sr/Y ratios are similar to adakitic magmas.Structural analysis indicates two stages of deformation (D1 and D2), with D1 forming the focus of the present study. The D1 deformation is represented by large-scale faults and records two periods of faulting. These periods are recognized as early compressional thrust faulting and a dominant late stage characterized by normal faulting and extension, with the latter stages of D1 being near-coeval with the emplacement of the Nize granodiorite porphyries. The combination of zircon ages, geochemical data, and structural analysis indicates that the Nize granodiorite porphyries formed after collision of the South Qiangtang and Lhasa terranes. Adakitic magma derived from partial melting of the thickened lower or middle crust resulted from lithospheric delamination that may have been promoted by the convective removal of deeper lithospheric mantle.

A fluid inclusion and stable isotope study of the Pebble porphyry copper-gold-molybdenum deposit, Alaska

The hydrothermal fluid evolution in the supergiant Pebble porphyry Cu-Au-Mo deposit in southwest Alaska has been constrained using fluid inclusion and light stable isotope data. The deposit is related to ~90Ma granodiorite porphyry intrusions and mineralization occurs primarily in sodic-potassic, potassic, and advanced argillic alteration zones.Throughout the deposit vein quartz hosts intermediate-density fluid inclusion assemblages with an average salinity of 9.5wt% NaCl equivalent and homogenization temperatures of 377 to 506°C. Pressure corrections result in trapping temperatures with a maximum of 610°C. This early fluid exsolved from a crystallizing magma at depth and underwent phase separation under varying conditions during cooling and depressurization forming two distinct fluid compositions. The two fluids formed two hydrothermal alteration assemblages which have different metal signatures. In the hydrothermal core in the eastern part of the system, high-density quartz veins, potassic alteration and the most economically significant mineralization are related to ~52wt% NaCl equivalent brines that coexist with very low-density vapor. In the western part of the system peripheral to the hydrothermal core, lower quartz vein densities accompanied by sodic-potassic alteration and lower grade mineralization are associated with ~38wt% NaCl equivalent brines and low-density vapor. Sulfide mineralization precipitated late in this early alteration event at temperatures between 375 and 330°C.Fluids related to sodic-potassic alteration minerals have δ18O signatures from +6.0 to +10.5‰ VSMOW and δD values from −70 to −41‰ VSMOW, which are consistent with a magmatic fluid source. Fluids related to potassic alteration assemblages have δ18O of −1.7 to +2.3‰ VSMOW and δD of −68 to −59‰ VSMOW, which suggests that the magmatic fluids evolved to lighter oxygen isotope signatures due to quartz precipitation during alteration.Lower temperature (~280°C) sericite and illite alteration followed the high-temperature magmatic stage and formed from the rising vapor plume as it mixed with varying amounts of meteoric fluid. Sericite in quartz-sericite-pyrite alteration on the periphery of the deposit and illite from areas of illite±kaolinite alteration which overprints sodic-potassic alteration and forms quartz-illite-pyrite alteration within the deposit are related to low-salinity aqueous fluids that have a significant magmatic component (+2.1 to +4.1‰ δ18O and −76 to −67‰ δD). Illite alteration which overprints both potassic alteration and quartz-sericite-pyrite alteration formed from fluids with a large meteoric component (−9.1 to −4.8‰ δ18O and −101 to −90‰ δD). The higher vein density and therefore higher permeability in the core of the deposit facilitated ingress of larger amounts of meteoric fluid compared with the more peripheral region.Advanced argillic alteration and associated high-grade mineralization are related to a second pulse of magmatic fluid which did not intersect the two phase field during cooling and depressurization. The fluid contracted to form a 3wt% NaCl equivalent aqueous fluid that resulted in a sericite-pyrite-bornite-digenite bearing assemblage with a magmatic signature (4.6 to 6.5‰ δ18O and −108 to −102‰ δD) at 340°C. Cooling and mixing of this fluid with meteoric water resulted in a fluid that formed a pyrophyllite-quartz-sericite-chalcopyrite bearing assemblage (−8.9 to −0.6‰ δ18O and −110 to −96‰ δD) at 300°C. Compared to older potassic and sodic-potassic alteration, the advanced argillic alteration has a highly depleted δD signature which is attributed to degassing of a crystallizing intrusive fluid source.

Geochemistry, geochronology and Sr–Nd–Pb–Hf isotopic compositions of Middle to Late Jurassic syenite–granodiorites–dacite in South China: Petrogenesis and tectonic implications

In situ zircon U–Pb ages and Hf isotope data, major and trace elements and Sr–Nd–Pb isotopic compositions are reported for coeval syenite–granodiorites–dacite association in South China. The shoshonitic syenites are characterized by high K2O contents (5.9–6.1wt.%) and K2O/Na2O ratios (1.1–1.2), negative Eu anomalies (Eu/Eu*=0.65 to 0.77), enrichments of Rb, K, Nb, Ta, Zr and Hf, but depletion of Sr, P and Ti. The adakitic granodiorite and granodiorite porphyry intrusions are characterized by high Al2O3 contents (15.0–16.8wt.%), enrichment in light rare earth elements (LREEs), strongly fractionated LREEs (light rare earth elements) to HREEs (heavy rare earth elements), high Sr (438–629ppm), Sr/Y (29.2–53.6), and low Y (11.7–16.8ppm) and HREE contents (e.g., Yb=1.29–1.64ppm). The calc-alkaline dacites are characterized by LREE enrichment, absence of negative Eu anomalies, and enrichment of LILEs such as Rb, Ba, Th, U and Pb, and depletion of HFSEs such as Nb, Ta, P and Ti.Geochemical and Sr–Nd–Hf isotopic compositions of the syenites suggest that the shoshonitic magmas were differentiated from parental shoshonitic melts by fractional crystallization of olivine, clinopyroxene and feldspar. The parent magmas may have originated from partial melting of the lithospheric mantle with small amount contribution from crustal materials. The adakitic granodiorite and granodiorite porphyry have Sr–Nd–Pb isotopic compositions that are comparable to that of the mafic lower crust. They have low Mg# and MgO, Ni and Cr contents, abundant inherited zircons, low εNd(t) and εHf(t) values as well as old whole-rock Nd and zircon Hf model ages. These granodiorites were likely generated by partial melting of Triassic underplated mafic lower crust. The Hf isotopic compositions of the dacites are relatively more depleted than the Cathaysia enriched mantle, suggesting those magmas were derived from the partial melting of subduction-modified mantle sources. The coeval shoshonitic, high-K calc-alkaline and calc-alkaline rocks in Middle to Late Jurassic appear to be associated with an Andean-type subduction. This subduction could have resulted in the upwelling of the asthenosphere beneath the Cathaysia Block, which induced partial melting of the mantle as well as the mafic lower crust, and formed an arc regime in the coastal South China during Middle to Late Jurassic.

Apatite in granitoids related to polymetallic mineral deposits in southeastern Hunan Province, Shi–Hang zone, China: Implications for petrogenesis and metallogenesis

The area of southeastern Hunan Province, China, located within the southwestern part of the Shi–Hang metallogenic zone, is characterized by abundant Cu–Pb–Zn, W, and Sn polymetallic ore deposits that are closely associated with coeval late Mesozoic granodiorite porphyries and biotite granites, respectively. Here, we present new major and trace element concentrations and 87Sr/86Sr ratios of apatites from six ore-bearing granitic rocks, as determined by electron microprobe, laser ablation–inductively coupled plasma-mass spectrometry, and thermal ionization mass spectrometer, which allow us to determine the main controls on the formation of these different types of mineralization and to explore how these controls are reflected in variations in apatite chemical and isotopic compositions. The apatite data indicate that granodiorite porphyry intrusions related to Cu–Pb–Zn mineralization are oxidized and formed as a result of slab dehydration, melting of the mantle wedge overlying a subducted slab, and the partial melting of crustal material. The release of abundant Cl- and H2O-rich fluids from the slab triggered mantle melting and the extraction of metals that were precipitated within the deposits. In comparison, granites related to W and Sn deposits are moderately oxidized to reduced, and were generated by the partial melting of crustal material with only limited input from mantle-derived magmas. Granites associated with the W and Sn mineralization formed in an intra-arc rifting-related tectonic environment. The fact that these numerous polymetallic ore deposits formed in the same area during two successive periods of mineralization, the first from 180 to 160Ma and the second from 160 to 140Ma, indicates that the tectonic environment of southeastern Hunan Province evolved from a continental arc associated with the subduction of the Paleo-Pacific Plate and the formation of Cu–Pb–Zn deposits to a later intra-arc rifting environment associated with the formation of W and Sn deposits as a consequence of slab roll-back and mantle upwelling during the Late Jurassic. This study reveals that apatite compositions can be used as a proxy to reflect the differences between granitoids and their associated mineralization, and identify regional metallogeny and tectonic evolution.

Stable isotope record of hydrothermal sulfate, sulfide and silicate minerals in the Darreh-Zar porphyry copper deposit in Kerman, southeastern Iran: Implications for petrogenesis and exploration

The Darreh-Zar porphyry copper deposit is found together with other porphyries such as Sar-Cheshmeh and Sungun in the Cenozoic age Urumieh–Dokhtar magmatic belt that is related to the subduction of the Arabian plate beneath Central Iranian microcontinent. The deposit is associated with Miocene granodiorite porphyry intrusions into Eocene basaltic volcanic rocks. The principal hydrothermal facies of the area are a core zone of potassic alteration enclosed by a peripheral zone of propylitic alteration. Chlorite-sericite, sericitic, advanced argillic and intermediate argillic alteration zones cut the upper part of the potassic zone and are developed near the interface between the potassic and propylitic zones. Chalcopyrite, pyrite or local bornite, and associated anhydrite are the chief hypogene sulfide minerals, and constitute <0.1 to 0.8wt.% Cu ores. A ~50-m-thick supergene zone containing 0.8 to 1.5wt.% Cu, characterized by covellite and chalcocite, underlies an oxidized and partially leached ~20-m-thick zone containing chrysocolla, malachite and azurite.The hydrogen isotopic composition of biotite from Darreh-Zar ranges from δD of −89 to −101‰, and the calculated aqueous fluids (δD of −66 to −78‰) in equilibrium with biotite are consistent with a large component of magmatic fluid. Epidote varies from δD of −56 to −53‰, and yields calculated fluids responsible for the propylitic alteration that range from −22 to −19‰. Oxygen isotopic data for the studied quartz, biotite, anhydrite and epidote vary between δ18O of 0.8 to 9.0‰. The calculated δ18O values for aqueous fluids in equilibrium with the biotite, quartz (from barren type and A veins), anhydrite (from B veins) and epidote are 7.8±0.4, 5.1±0.6, 2.6±0.5 and −1.1±0.1‰, respectively. This marked decrease likely reflects a change from magmatic-derived fluids in central potassic zone to meteoric or sedimentary-derived fluids in the outer propylitic zone. Sulfur isotope compositions are 11.8 to 14.0‰, for anhydrite (n=3), 2.4‰ for molybdenite (n=1), 1.7 to 3.9‰ for pyrite (n=17), and 1.6 to 2.9‰ for chalcopyrite (n=2). The sulfide data, alone, suggest a conventionally ‘magmatic’ value of about 1.6 to 2.9‰ for Darreh-Zar sulfur. However, the fairly oxidized granitic parental magma shows relatively heavy bulk sulfur (δ34SΣS≈+5‰) and sulfate–sulfide sulfur isotopic fractionation is consistent with an approach to isotopic equilibrium at calculated temperatures of 520±50°C for most of the coexisting anhydrite–pyrite pairs (n=4). An exploration implication is that the identification of isotopically high sulfur isotopic compositions of gypsum from near-surface samples determines a hydrothermal system that contains deeper hypogene anhydrite, a common indicator of large porphyry Cu-Mo deposits. In contrast, isotopically low sulfur isotopic values similar to and derived from weathering of pyrite and other sulfides are common in many hydrothermal environments.

Geochemistry, and zircon U-Pb and molybdenite Re-Os geochronology of Jilongshan Cu-Au deposit, southeastern Hubei Province, China

The Jilongshan skarn Cu–Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle–Lower Yangtze River valley metallogenic belt. The region is characterized by NW-, NNW- and EW-trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO2, K2O, and Na2O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al2O3)/[n(CaO) + n(Na2O) + n(K2O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)N = 7.61–12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high-K calc-alkaline signature typical of intrusives associated with skarn and porphyry Cu–Au–Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) zircon U–Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle–Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re–Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle–crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd.

U–Pb and Re–Os geochronology of the Bainaimiao Cu–Mo–Au deposit, on the northern margin of the North China Craton, Central Asia Orogenic Belt: Implications for ore genesis and geodynamic setting

The Bainaimiao Cu–Mo–Au deposit, located at the northern margin of the North China Craton (NCC) in central Inner Mongolia, is a large Cu-dominant deposit. Orebodies are hosted in strongly deformed and metamorphosed granodiorite porphyry intrusions or in EW-trending shear zones in greenschist and sericite felsic schist of the Bainaimiao Group. Mineralization can be divided into early, middle and late stages, characterized by quartz–pyrite, polymetallic quartz–sulfides and carbonate–quartz, respectively. Hydrothermal activity led to pervasive silicification, K-feldspar, biotite and chlorite–epidote–carbonate alteration.Eight samples from Cu–Mo-bearing quartz veins and massive sulfide ores in greenschist were collected from the VIII orebody in the North ore belt and molybdenite separates were selected for Re–Os analyses. The concentrations of Re and 187Os range from 216.6 to 1051ppm and 2302 to 4913ppb, respectively. All samples give Re–Os model ages between 441.2 and 445.9Ma and yielded an isochron age of 445.0±3.4Ma (MSWD=0.26), with an initial 187Os of −4±17ppb. A granodiorite porphyry sample for SHRIMP U–Pb dating was collected from the underground of the XIII orebody of the North ore belt. Spots from 14 zircon grains have 206Pb/238U values between 426.2 and 462.9Ma and form a tight cluster on Concordia yielding a weighted mean 206Pb/238U age of 445±6Ma. This is considered to be the best estimate of crystallization age of the granodiorite porphyry. The Re–Os isochron age of the molybdenite is consistent with the SHRIMP U–Pb age of the granodiorite porphyry, which indicates that the deposit is a porphyry system of Paleozoic age.According to geodynamic setting and geological history of the northern margin of the NCC, the deposit was probably related to magmatic activity of the Middle Paleozoic Ondor Sum subduction–accretion complex-Bainaimiao arc. During the Devonian, the Bainaimiao arc was accreted to the northern margin of the NCC. Collision between the Bainaimiao arc and NCC led to regional metamorphism of the ore-hosting terrane and ore metals were remobilized in this process. Gold mineralization was probably overprinted onto the earlier Cu–Mo mineralization.

The influence on EM-anomalies of the position of the generator in a Turam loop

The Bainaimiao Cu–Mo–Au deposit, located at the northern margin of the North China Craton (NCC) in central Inner Mongolia, is a large Cu-dominant deposit. Orebodies are hosted in strongly deformed and metamorphosed granodiorite porphyry intrusions or in EW-trending shear zones in greenschist and sericite felsic schist of the Bainaimiao Group. Mineralization can be divided into early, middle and late stages, characterized by quartz–pyrite, polymetallic quartz–sulfides and carbonate–quartz, respectively. Hydrothermal activity led to pervasive silicification, K-feldspar, biotite and chlorite–epidote–carbonate alteration.Eight samples from Cu–Mo-bearing quartz veins and massive sulfide ores in greenschist were collected from the VIII orebody in the North ore belt and molybdenite separates were selected for Re–Os analyses. The concentrations of Re and 187Os range from 216.6 to 1051 ppm and 2302 to 4913 ppb, respectively. All samples give Re–Os model ages between 441.2 and 445.9 Ma and yielded an isochron age of 445.0 ± 3.4 Ma (MSWD = 0.26), with an initial 187Os of − 4 ± 17 ppb. A granodiorite porphyry sample for SHRIMP U–Pb dating was collected from the underground of the XIII orebody of the North ore belt. Spots from 14 zircon grains have 206Pb/238U values between 426.2 and 462.9 Ma and form a tight cluster on Concordia yielding a weighted mean 206Pb/238U age of 445 ± 6 Ma. This is considered to be the best estimate of crystallization age of the granodiorite porphyry. The Re–Os isochron age of the molybdenite is consistent with the SHRIMP U–Pb age of the granodiorite porphyry, which indicates that the deposit is a porphyry system of Paleozoic age.According to geodynamic setting and geological history of the northern margin of the NCC, the deposit was probably related to magmatic activity of the Middle Paleozoic Ondor Sum subduction–accretion complex-Bainaimiao arc. During the Devonian, the Bainaimiao arc was accreted to the northern margin of the NCC. Collision between the Bainaimiao arc and NCC led to regional metamorphism of the ore-hosting terrane and ore metals were remobilized in this process. Gold mineralization was probably overprinted onto the earlier Cu–Mo mineralization.

Geology of the Moonmera porphyry deposit, Queensland, Australia

The Moonmera deposit in central coastal Queensland is thus far the oldest documented porphyry deposit on the margin of the Pacific Ocean. Age of mineralization based on this investigation is 245 m.y. The deposit is associated with late-stage porphyritic differentiates of the Bouldercombe Complex, a late Permian granodioritic body of batholithic dimensions. This complex was emplaced into an east-west dilatant zone developed across the Yarrol Basin at the close of the Permo-Triassic Hunter-Bowen orogeny. The members of the intrusive complex comprise an early granodiorite porphyry, followed by an andesitic tuffisite pipe, and finally the youngest granodiorite porphyry, with associated radial and ring-dike sets. Equigranular quartz diorite of the Boulder-combe Complex forms about 95 percent of the deposit9s wall rocks.Sulfide mineralization took place during three principal episodes that are time equivalents of the three members of the Moonmera intrusive complex. Stage 1 mineralization is pyrite-chalcopyrite-molybdenite that preceded the oldest granodiorite porphyry and is volumetrically the most important mineralization at Moonmera. This mineralization which is principally in steeply dipping fractures and veins in quartz diorite has a well-developed zonation surrounding the intrusive complex. The zones are a low-grade core, a chalcopyrite-molybdenite inner halo, a chalcopyrite-pyrite intermediate halo, and a pyrite outer halo. Stage 2 mineralization occurs as very finely disseminated chalcopyrite in the matrix of the tuffisite pipe. Stage 3 mineralization is disseminated chalcopyrite either in the core of a young granodiorite porphyry pluton or in its uppermost roof zone. It also includes massive chalcopyrite and pyrite fillings of voids in breccias that mantle the roof zones of individual young intrusions.Alteration has taken place during three equivalent episodes. Alteration accompanying stage 1 mineralization is composed of a weakly developed zone of pervasive biotite which overlies a deeper zone of moderate biotite and anhydrite. Secondary orthoclase in veins, and selvages and envelopes to veins, occurs in both the shallow and deep biotite zones. Strong biotitization of the older granodiorite porphyry groundmass also occurred during this episode. Alteration accompanying stage 2 mineralization was predominantly strong biotitization of the tuffisite matrix. The episode accompanying stage 3 mineralization includes moderate to intense sericitization of the cores of the younger granodiorite porphyry intrusions and their capping breccias and propylitization of the outer margins of these intrusions.The parental magma of the Bouldercombe Complex and the Moonmera intrusive complex is believed to be derived by partial melting of oceanic lithosphere that was subducted beneath the eastern margin of Queensland during the late Permian.