Giant Porphyry Mo Deposit Research Articles

A 2D seismic reflection dataset of the Caosiyao giant porphyry Mo deposit in the shallow coverage area in Jining, Inner Mongolia, China

AbstractProspecting for and exploiting buried mineral deposits is currently challenging. Given their high precision and resolution, reflection seismic methods might be useful in such applications involving deep mineral deposits. However, there are few open seismic datasets available from mineral deposit exploration, especially in hardrock environments. The world‐class Caosiyao porphyry Molybdenum deposit (1.76 Mt) in the Jining area of Inner Mongolia, China, is largely covered by loess layers, which poses challenges to its exploration. Seismic reflection surveys were conducted to help delineate the deep granite porphyry intrusions and associated orebodies. This paper presents the raw seismic reflection dataset from three profiles on the Caosiyao deposit area, which can be used as a standard dataset for reflection seismic processing in shallow coverage and hardrock areas. Situated at the juxtaposition of the Khondalite Belt and the Trans‐North China Orogen in the northern North China Craton, the Jining region hosts considerable known porphyry Mo deposits. As such, this open dataset can assist in research on deep geological structures and hence increase prospecting efficiency in geologically similar areas.

Mantle contribution to the generation of the giant Jinduicheng porphyry Mo deposit, Central China: New insights from combined in-situ element and isotope compositions of zircon and apatite

Identifying crust–mantle interaction is important for understanding the genesis of granite-hosted mineral deposits in post-collisional or intracontinental settings. We have used combined zircon-apatite trace element compositions, zircon HfO isotopes and apatite SrNd isotopes, which were all acquired by in-situ techniques, to evaluate the mantle contribution to the formation of a giant porphyry Mo deposit, the Jinduicheng deposit in the East Qinling–Dabie orogenic belt, Central China. Zircons from the host granites yielded a UPb age of ∼139 Ma, suggesting a post-collisional setting for the ore-related intrusion. Most magmatic zircons from the granites have Ti-in-zircon temperatures lower than 830 °C, moderate Zr/Hf ratios (25–55), and mantle-like δ18O values (peaking at ∼5.6‰), similar to typical I-type granites worldwide. The magmatic zircons have variable εHf(t) values (−26.7 to −7.2) and Ti-in-zircon temperatures (646–894 °C, peaking at ∼740 °C). The coexisting igneous apatites have initial 87Sr/86Sr ratios of 0.70694–0.71027, and variable εNd(t) values (−16.0 to −9.3), Sr contents (132–663 ppm), and Eu/Eu* values (0.12–0.47). The Sr–Nd–Hf isotopes of the apatites and zircons, along with the positive correlations between apatite Sr contents, Eu/Eu* values, and εNd(t) values, a positive correlation between Ti-in-zircon temperatures and zircon εHf(t) values, as well as mixing modeling using SrNd isotopes, suggest that at least two end-member melts were involved in the formation of the host granites: one is the ancient lower crust-derived melt, and the other is the metasomatized lithospheric mantle-derived melt, which have relatively enriched and depleted Sr–Nd–Hf isotopic compositions, respectively. We suggest that the post-collisional lithospheric thinning, asthenospheric upwelling and underplating of the mantle-derived mafic magmas may have triggered the crustal melting, magma mixing, and generation of the host granites of the Jinduicheng deposit. We postulate that, besides the heat, the metasomatized lithospheric mantle-derived magmas likely supplied additional volatiles (e.g., Cl, S), facilitating the porphyry Mo formation. Our study highlights that, combined in-situ element and isotope compositions of accessory minerals can provide multidimensional insights into petrogenetic tracing, and enhance the genetic interpretations of granites and related mineral deposits.

Apatite and zircon geochemistry for discriminating ore-forming intrusions in the Luming giant porphyry Mo deposit, Northeastern China

The Luming giant porphyry Mo deposit in NE China host >0.89Mt Mo, but which intrusion induced the Mo mineralization is still in debated. In this study, apatite and zircon geochemistry from three mentioned ore-forming granites, namely monzogranitic porphyry (MGP), granodiorite (GD) and monzogranite (MG) in Luming ore district are presented in order to constrain the real ore-forming granite. Apatite and zircon U-Pb dating of the MGP, GD and MG yield a crystallization age of ca. 177 Ma, ca. 187 Ma and ca. 186 Ma, respectively. Whole-rock geochemistry, in-situ apatite Sr-Nd and zircon Hf isotopic compositions suggest that these granites formed by partial melting of juvenile lower crust with different depth. Both the MGP and GD have adakitic affinities and the depth of their magma source is > 45 km with garnet as residual phase, whereas the source depths for the MG was < 33 km with plagioclase as residue. Apatite and zircon geochemical features indicated that the magma of MGP and GD have higher oxygen fugacity, water contents and lower Ti-in-zircon temperatures than these of the MG, which make the MGP and GD are more favorable for Mo mineralization, but the less volume of GD limited its metallogenic potential. Decoupled Nd-Hf isotopes of the MGP, GD and MG could be induced by recycled ocean sediment added in their source region, and the addition of recycled sediments could be account for Mo concentrate in the source and regional Mo mineralization.

Trace element and isotopic (S, Pb) constraints on the formation of the giant Chalukou porphyry Mo deposit, NE China

Abstract Porphyry-type Mo deposits have supplied most of the Mo to the world. However, the source of the Mo and the controls on its enrichment in such deposits is still a matter of great debate. In this study, we present in situ trace element and isotopic data for a giant porphyry Mo deposit (the Chalukou Mo deposit in NE China) and use these data to address these issues. Three primary paragenetic stages of mineralization were recognized at Chalukou: (Stage I) K-feldspar + quartz + minor pyrite (Py-I) + minor molybdenite (Mol-I); (Stage II) quartz + sericite + molybdenite (Mol-II) + pyrite (Py-II); (Stage III) quartz + chlorite + epidote + fluorite + pyrite (Py-III) + galena + sphalerite + minor chalcopyrite. The bulk of the molybdenite was deposited in Stage II. In situ S isotope analyses of the sulfide ores show that the δ34S values vary from –5.2 to +7.8‰ (mean = +2.9‰) and correspond to δ34SH2S values from –2.4 to +3.3‰ (mean = +1.1‰). These values are consistent with a magmatic source for the sulfur. In situ Pb isotope compositions of the sulfide ores are almost identical to those of the local Mesozoic granites and other magmatic-hydrothermal ore deposits in this region, suggesting a close genetic association between the Mo mineralization and felsic magmatism. Pyrite from the three stages of mineralization differs significantly in its trace element composition. The first generation, Py-I, has a high Cu content (8.7 ± 49.6 ppm; where the first value is the median and the second is the standard deviation) and Mo content (6.9 ± 3.8 ppm). Pyrite-II has the lowest Cu concentration (1.3 ± 2.1 ppm) and a relatively high Mo concentration (5 ± 128 ppm), and Py-III has a high Cu content (8.7 ± 37.1 ppm) but the lowest Mo content (0.05 ± 5.7 ppm). From this, we infer that pyrite recorded the chemical evolution in the Mo/Cu ratio of the ore fluid and that this ratio reached a maximum in Stage II, coinciding with the widespread saturation of the fluid in molybdenite. The evolution of the Mo/Cu ratio in pyrite implies that the fluid was undersaturated in chalcopyrite at the high temperature of Stage I, despite the Cu concentration of the fluid apparently being at its high level, and chalcopyrite only saturated later, at a lower temperature. Molybdenite, however, because of its lower solubility, saturated early (Stage I) and in the subsequent stage (Stage II) was supersaturated in the fluid. There is a significant enrichment of Mo in the syn-ore intrusions at Chalukou compared to the pre-ore monzogranite. The very low Sr/Y ratios for the Chalukou syn-ore intrusions, which are in sharp contrast to the high Sr/Y ratios of the pre-ore monzogranite and those of porphyries related to Cu deposits, suggest that fractional crystallization of plagioclase may have been a key factor in generating the syn-ore magmas. Molybdenum is a highly incompatible metal and will concentrate in the crust, and assimilation of old continental crust, therefore, may explain the Mo enrichment of the syn-ore intrusions and ultimately the formation of the giant Chalukou deposit.

Multiple tectonic-magmatic Mo-enrichment events in Yuleken porphyry Cu-Mo deposit, NW China and its’ implications for the formation of giant porphyry Mo deposit

The Yuleken porphyry Cu-Mo deposit located in the Chinese Altay-East Junggar, a section of the Central Asian Orogenic Belt, the world's largest Phanerozoic subduction-accretionary orogen, witnessed the multistage tectonic-magmatic evolution and mineralization from arc to syn- and post-collision environment over a time span of about 52 Ma. Four types of molybdenite have been distinguished: (1) primary magmatic-hydrothermal, undeformed molybdenite in porphyry, (2) recrystallized molybdenite associated with ductile deformation, (3) recrystallized, intrafoliational molybdenite, and (4) fracture-related hydrothermal molybdenite, and these are characterized by decreasing Re abundances from magmatic to hydrothermal conditions. Individual molybdenite types are non-stoichiometric and exhibit the following negative correlation between the Mo and Re contents:Re (apfu) = −0.0026 Mo (apfu) + 0.00268.This trend reflects successive stages of tectonic-hydrothermal events from a magmatic island-arc to a post-collisional setting. These repetitive mineralization events produced Mo enrichment and higher overall Mo grade of the Yuleken deposit, and are recorded in progressively decreasing Re concentrations in molybdenite. Statistical evaluation of Mo and Re abundances in giant to small porphyry deposits worldwide also indicates that decreasing Re in molybdenite will lead to lower overall Re resource (in a single deposit) and to greater overall Mo resource (in the same deposit). Multiple mineralization processes related to repetitive tectonomagmatic episodes in large porphyry Mo deposits that display Re depletion in molybdenite suggest that reworking of mantle-derived porphyry systems by successive events of crustal growth may be the responsible for Mo enrichment and higher overall Mo ore grade, and eventually produce giant porphyry molybdenum deposits.

Constraints on the Formation of the Giant Daheishan Porphyry Mo Deposit (NE China) from Whole-Rock and Accessory Mineral Geochemistry

AbstractThere are more than 80 porphyry (or skarn) Mo deposits in northeastern China with Jurassic or Cretaceous ages. These are thought to have formed mainly in a continental arc setting related to the subduction of the Paleo-Pacific oceanic plate in the Jurassic and subsequent slab rollback in the early Cretaceous. The Jurassic Daheishan porphyry Mo deposit is one of the largest Mo deposits in NE China, which contains 1·09 Mt Mo with an average Mo grade of 0·07 %. To better understand the factors that could have controlled Mo mineralization at Daheishan, and potentially in other similar porphyry Mo deposits in NE China, the geochemical and isotopic compositions of the ore-related granite porphyry and biotite granodiorite, and the magmatic accessory minerals apatite, titanite and zircon from the Daheishan intrusions, were investigated so as to evaluate the potential roles that magma oxidation states, water contents, sulfur and metal concentrations could have played in the formation of the deposit. Magmatic apatite and titanite from the causative intrusions show similar εNd(t) values from –1·1 to 1·4, corresponding to TDM2 ages ranging from 1040 to 840 Ma, which could be accounted for by a mixing model through the interaction of mantle-derived basaltic melts with the Precambrian lower crust. The Ce and Eu anomalies of the magmatic accessory minerals have been used as proxies for magma redox state, and the results suggest that the ore-forming magmas are highly oxidized, with an estimated ΔFMQ range of +1·8 to +4·1 (+2·7 on average). This is also consistent with the high whole-rock Fe2O3/FeO ratios (1·3–26·4). The Daheishan intrusions display negligible Eu anomalies (Eu/Eu* = 0·7–1·1) and have relatively high Sr/Y ratios (40–94) with adakitic signatures; they also have relatively high Sr/Y ratios in apatite and titanite. These suggest that the fractionation of amphibole rather than plagioclase is dominant during the crystallization of the ore-related magmas, which further indicates a high magmatic water content (e.g. &amp;gt;5 wt%). The magmatic sulfur concentrations were calculated using available partitioning models for apatite from granitoids, and the results (9–125 ppm) are indistinguishable from those for other mineralized, subeconomic and barren intrusions. Furthermore, Monte Carlo modelling has been conducted to simulate the magmatic processes associated with the formation of the Daheishan Mo deposit, and the result reveals that a magma volume of ∼280 km3 with ∼10 ppm Mo was required to form the Mo ores containing 1·09 Mt Mo in Daheishan. The present study suggests that a relatively large volume of parental magmas with high oxygen fugacities and high water contents is essential for the generation of a giant porphyry Mo deposit such as Daheishan, whereas a specific magma composition (e.g. with unusually high Mo and/or S concentrations) might be less critical.

Incursion of meteoric water triggers molybdenite precipitation in porphyry Mo deposits: A case study of the Chalukou giant Mo deposit

There has been a long-term debate about the timing of the incursion of meteoric water into porphyry systems and whether it plays an important role in ore precipitation. To evaluate the role of meteoric water in the mineralization in porphyry Mo deposits, typical hydrothermal veins of different stages from the Chalukou giant porphyry Mo deposit are selected for combined scanning electron microscope cathodoluminescence (SEM-CL), fluid inclusion microthermometry and high-resolution secondary ion mass spectroscopy (SIMS) oxygen isotope analyses. Multiple generations of quartz are identified in almost all of the veins. The barren quartz veins and quartz-magnetite veins of the early Mo mineralization stage are dominated by granular CL-bright quartz (EMQ1), which usually shows dissolution and re-deposition textures and are overprinted by CL-dark quartz (EMQ2)-filled healed fractures. The molybdenite precipitation in the quartz-molybdenite veins of the main Mo mineralization stage is synchronous with small volumes (<15%) of CL-dark quartz (MMQ2) and postdates the large volume (>85%) of CL-bright quartz (MMQ1). Similar to the quartz-molybdenite veins, the precipitation of pyrite in the quartz-pyrite veins during the transitional stage and sphalerite in the quartz-sphalerite-pyrite veins during the Zn-Pb mineralization stage are also directly associated with CL-dark quartz (TSQ2, ZPQ2). The SIMS oxygen isotopic values of EMQ1 and MMQ1 fall into the range of 5.42–9.79‰ with calculated equilibrium fluid compositions of 2.07–6.45‰, indicating a magma-dominated fluid composition, whereas MMQ2, TSQ2 and ZPQ2 have very low oxygen isotopic values from −4.68 to 4.29‰ with corresponding fluid compositions of −13.64 to −5.94‰, implying that the fluid formed by the mixing of magmatic water and a large proportion of meteoric water. The contrasting SEM-CL features and oxygen isotopic compositions of the two generations of quartz in the quartz-molybdenite veins demonstrate that the incursion of meteoric water into the hydrothermal system occurred earlier than the molybdenite precipitation. Based on these results and the crosscutting relationships and spatial distribution of the veins, we reconstructed the quartz evolutionary sequence during the vein development process. After the early precipitation of barren quartz, the reduction in fluid pressure from lithostatic to hydrostatic conditions allowed the incursion of convecting cool meteoric water into the relatively hot hydrothermal system, and the temperature of the evolved Mo-rich fluid decreased rapidly from >500 °C to <400 °C, leading to concentrated molybdenite precipitation with small volumes of quartz. Fluid cooling resulting from the incursion of meteoric water may have played a greater role in the metal precipitation in the Chalukou Mo deposit than wallrock interactions and fluid boiling. Moreover, this process may have also occurred in other porphyry Mo deposits.

The formation of the Caosiyao giant porphyry Mo deposit on the northern margin of the North China Craton: Constraints from U―Pb and Re―Os geochronology, whole‐rock geochemistry, Hf isotopes, and oxygen fugacity of the magma

The Caosiyao giant porphyry Mo deposit (1.76 Mt), which is the third largest such deposit in China, is located on the northern margin of the North China Craton and associated with the Caosiyao intrusive complex that was emplaced in Archaean metamorphic rocks. The intrusive complex consists of monzogranite and coarse‐, medium‐, and fine‐grained granite porphyries that yield U―Pb ages of 148.5 ± 1.2, 146.4 ± 1.0, 144.6 ± 1.0, and 142.8 ± 3.2 Ma, respectively. Four molybdenite Re―Os model ages range from 143.1 ± 2.4 to 145.3 ± 2.1 Ma, which are consistent with the U―Pb ages for the igneous complex. The geochronological data indicate that the multistage magmatic‐hydrothermal processes were important in the formation of the Caosiyao giant deposit. The rocks of the Caosiyao granitic complex have high contents of silica (SiO2 = 71.7–75.6 wt.%) and total alkalis (mostly K2O + Na2O &gt; 8 wt.%), low contents of CaO and MgO, and exhibit peraluminous high‐K calc‐alkaline to shoshonitic affinities. They are enriched in large‐ion lithophile elements (e.g., K, Rb, U, and Th) and light REEs and depleted in Eu, Ba, Sr, Nb, P, and Ti. The geochemical characteristics indicate advanced fractional crystallization and that the rocks are strongly fractionated I‐type granites. The negative Hf isotopic compositions of the granitic rocks, combined with old two‐stage Hf model ages, indicate the magmas were derived from partial melting of the ancient lower crust of the North China Craton. All the intrusive rocks in the complex have relatively high Ce4+/Ce3+ ratios and oxygen fugacity, which would have facilitated Mo extraction into the melts owing to the much higher solubility of S as sulphate (SO42−) than sulphide (S2−). The magma crystallization temperatures decreased from 882°C to 770°C as the magma evolved. The multistage magmatic‐hydrothermal processes, and the prolonged fractional crystallization, combined with high magma oxygen fugacity are the key factors to form the Caosiyao giant Mo deposit. The tectonic setting of deposit formation was one of extension related to rollback of the subducting Palaeo‐Pacific Plate during the Late Jurassic to Early Cretaceous.

The Mesozoic Caosiyao giant porphyry Mo deposit in Inner Mongolia, North China and Paleo-Pacific subduction-related magmatism in the northern North China Craton

The Caosiyao giant porphyry Mo deposit is located in the Wulanchabu area of Inner Mongolia, within the northern North China Craton (NCC). It contains more than 2385Mt of ore with an average grade of 0.075% Mo. In the Caosiyao mining district, Mo mineralization occurs mainly in a Mesozoic granite porphyry as disseminations and stockworks, with some Mo distributed in Archean metamorphic rocks and diabase as stockworks and veins. The host granite porphyry is composed of two different phases that can be distinguished based on mineral assemblages and textures: one phase contains large and abundant phenocrysts (coarse-grained), while the other phase is characterized by fewer and smaller phenocrysts (medium-grained). Zircon U–Pb–Hf analyses of the former phase yielded a concordant 206Pb/238U age of 149.8±2.4Ma with a 206Pb/238U weighted mean age of 149.9±2.4Ma and εHf(t) values ranging from −12.2 to 18.3, while the latter phase gave a concordant 206Pb/238U age of 149.0±2.2Ma with a 206Pb/238U weighted mean age of 149.0±2.1Ma and εHf(t) values ranging from −13.1 to 17.7. Five samples of disseminated molybdenite have a 187Re–187Os isochron age of 149.5±5.3Ma with a weighted average age of 149.0±1.8Ma, whereas six veinlet-type molybdenite samples have a well-constrained 187Re–187Os isochron age of 146.9±3.1Ma and a weighted average age of 146.5±0.8Ma. Thus, it is suggested that the Mo mineralization of the Caosiyao deposit occurred during the Late Jurassic (ca. 147–149Ma), almost coeval with the emplacement of the host granite porphyry (ca. 149–150Ma). The host granite porphyry is characterized by high silica (SiO2=71.52–74.10wt%), relatively high levels of oxidation (Fe2O3/FeO=0.32–0.94wt%) and high alkali element concentrations (Na2O+K2O=8.21–8.76wt%). The host granite porphyry also shows enrichments in U and K, and depletion in Ba, Sr, P, Eu, and Ti, suggesting strong fractional crystallization of plagioclase, biotite, and accessory minerals. These observations, together with high SiO2 contents and a high differentiation index (DI=89.04–92.44), indicate a strong differentiation of the granite magma.Based on geological, geochronological, isotope systematics, and geochemical studies, we propose, for the first time, a genetic model for the Caosiyao porphyry Mo deposit. Under a regional extensional setting caused by far-field tectonics related to the Paleo-Pacific subduction during the Late Jurassic, a series of geodynamic, magmatic, and ore-forming processes took place, including formation of multi-directional and multi-phase faults, emplacement of the granitic host rocks, and Mo mineralization. Highly silicic, highly oxidized, and alkali-rich granitic magma, derived from partial melting of old lower crust, intruded into the country rocks. This highly differentiated granitic magma and the exsolved ore-forming fluids, enriched in Mo, migrated upward and interacted with the wall rocks. Eventually, ore minerals precipitated in fractures, resulting in the extensive deposition of molybdenite.

Ore genesis and fluid evolution of the Daheishan giant porphyry molybdenum deposit, NE China

The Daheishan giant porphyry Mo deposit is located at the eastern segment of the CAOB, NE China. The ore-bearing intrusion of Daheishan deposit is a Jurassic granitic complex that includes Changgangling biotite granodiorite, Qiancuoluo seriate granodiorite, and Qiancuoluo granodioritic porphyry. Mineralization consists of disseminated, breccia and veined types. The hydrothermal fluids show significant magmatic signatures, as evidenced by the hydrogen and oxygen isotopic compositions of quartz and sulfur isotopic characteristics of ores. Consistence of lead isotopic compositions of the sulfides and the Daheishan intrusive complex further indicate a close relationship between the mineralization and magma. The fluid inclusions in quartz comprise of predominant aqueous two-phase as well as gas-rich fluid inclusions and a small number of daughter mineral-bearing inclusions. The gas species in the fluid inclusions are H2O, CO2, N2, CH4, C2H6, Ar∗ and minor H2S; the liquid compositions are SO42−, Cl−, Na+, K+, Ca2+ and Mg2+. Raman spectroscopy on individual fluid inclusions reveals a main gaseous composition of H2O, minor H2S and CO2. The fluid system in Daheishan Mo deposit can be described as NaCl–KCl–H2O type. Fluid inclusion microthermometry reveals subsolidus homogenization temperatures for fluid inclusions in the magmatic quartz phenocrysts (Th=400–450°C, salinities=∼21eq. wt.%), suggesting an obliteration of higher temperature history of the porphyry system by the superimposed processes. Most of the mineralization occurred at temperature range of 220–360°C, or higher. The temperature and salinity decreased to 100–170°C and 0–15eq. wt.%, respectively, when the hydrothermal fluid activities were gradually ending. No distinct evolution pattern based on the homogenization temperature or stable isotopic analyses is observed among the different mineralization stages. Mineralization was supposed to be related to the multi-phased boiling of fluids, instead of the gradual cooling of fluids. Pressure may be more critical than temperature in controlling the precipitation of molybdenite.

Geochemical signature of the granitoids in the Chalukou giant porphyry Mo deposit in the Heilongjiang Province, NE China

The Chalukou porphyry Mo deposit, located in the northern Great Xing'an Range, is the largest Mo deposit in the Xing'an–Mongolia orogenic belt. Its ore bodies are mainly hosted in the intermediate-felsic complex and Jurassic volcanic sedimentary rocks, of which Late Jurassic granite porphyry, quartz porphyry and fine-grained granite are closely associated with Mo mineralization. The Middle Jurassic monzogranite belongs to shoshonite series, with SiO2 and Al2O3 contents of 69.48 to 74.98% and 12.35 to 14.48%, respectively. The total alkali (K2O+Na2O) content ranges from 7.67 to 10.42%, with K2O/Na2O ratios between 1.07 and 2.81. These rocks are strongly enriched in Rb and K but are depleted in Ta, Nb, P and Ti, with negative Eu anomalies and positive εHf(t). The Late Jurassic granite porphyry, quartz porphyry and fine-grained granite are shoshonite or high-K calc-alkaline series. Their SiO2 and Al2O3 contents range from 73.87 to 78.95% and 10.35 to 13.47%, respectively. The total alkali (K2O+Na2O) contents range from 8.06 to 10.02%, with K2O/Na2O ratios from 1.03 to 8.20. These rocks are strongly enriched in Rb, K and Th, but are depleted in P, Ti, Ba and Sr, indicating clear negative Eu anomalies and positive εHf(t). The Middle–Late Jurassic granitoids in the Chalukou deposit are highly fractionated I-type granitoids, and derived from juvenile lower crust materials that originated from the Neoproterozoic depleted mantle. These granitoids formed in the extension tectonic setting of the post-collision stage of the Mongol–Okhotsk orogenic belt, probably superposed by the back-arc extension related to the subduction of the Paleo-Pacific Plate.

Ore geology and fluid inclusion study of the Donggebi giant porphyry Mo deposit, Eastern Tianshan, NW China

The Donggebi giant porphyry Mo deposit in Hami city, Xinjiang Province, NW China, was formed in the Triassic in the Jueluotage metallogenic belt of Eastern Tianshan. Mo mineralization is associated with the Donggebi porphyritic granite, occurring as numerous stockworks in the altered wall rocks. The hydrothermal ore‐forming process can be divided into four stages, from early to late, characterized by veinlets composed of (1) quartz + K‐feldspar ± beryl ± pyrite ± tourmaline; (2) quartz + molybdenite ± K‐feldspar ± tourmaline ± fluorite ± beryl; (3) quartz + polymetallic sulphides ± fluorite; and (4) quartz + calcite ± fluorite. Three types of fluid inclusions (FIs) are distinguished in this study based on petrographic and microthermometric criteria, i.e. carbonic (C‐type), aqueous (W‐type) and solid‐bearing fluid inclusions (S‐type). All three types of FIs can be observed in the quartz, beryl and fluorite formed in stages 1, 2 and 3, while the stage 4 minerals only contain aqueous inclusions. The FIs in minerals of stages 1, 2, 3 and 4 yield homogenization temperatures of 261–443, 210–385, 152–304 and 159–263 °C, respectively, and salinities of ≤9.3 wt.% NaCl equiv., without consideration of the contribution from daughter minerals. The maximum estimated pressure decrease from 193 MPa in stage 1, through 182 MPa in stage 2, to 129 MPa in stage 3, suggesting the maximum mineralizing depths decreased from 8.4, through 7.9, to 5.6 km, and possibly occurred at 5.6–7.9 km. Therefore, the ore‐forming fluids at Donggebi are characterized by high‐temperature, CO2‐bearing and NaCl‐poor and then progressively evolved to CO2‐poor and lower‐temperature. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Geochronology of magmatism and mineralization of the Daheishan giant porphyry molybdenum deposit, Jilin Province, Northeast China: constraints on ore genesis and implications for geodynamic setting

Daheishan giant porphyry Mo deposit is located in the Lesser Xing’an–Zhangguangcai Ranges, Jilin Province, NE China. Mineralization is closely related to the Daheishan intrusive complex, which can be divided into Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry. Four stages of mineralization are distinguished, based on the cross-cutting relationships of mineralized veins. LA-ICPMS zircon U-Pb analysis yields 206Pb/238U ages of 177.9 ± 2.3 Ma for the Changganglin biotite granodiorite, 169.9 ± 2.3 Ma for the Qiancuoluo biotite granodiorite, and 166.6 ± 4.0 Ma for the Qiancuoluo granodioritic porphyry. Hydrothermal fluids responsible for mineralization evolved from different magmas. Six molybdenite samples yield Re-Os model ages of ~167 Ma. Muscovite from the last mineralization stage gives a 40Ar/39Ar plateau age of 163.6 ± 0.9 Ma. Geochronology data indicate that the entire magmatic system lasted for about 10 million years, and the total duration of hydrothermal activity was less than 4 million years. The εHf(t) values of zircons obtained from the Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry range from 4.5 to 9.1, 5.7 to 10.9, and 4.4 to 7.1, respectively, indicating that they were mainly derived from the depleted mantle, although contaminated by crustal materials to a greater or lesser extent. The formation of the Daheishan porphyry Mo deposit was temporally and spatially related to the amalgamation of Jiamusi Massif and Songliao terrane in the Palaeo-Pacific Ocean regime. Regional Hf isotopic compositions of zircon suggest an episode of crustal growth in the Phanerozoic in the Lesser Xing’an–Zhangguangcai Ranges. Regional Mo mineralization ages suggest a peak of porphyry Mo mineralization in the Jurassic in the Lesser Xing’an-Zhangguangcai Ranges.

Fluid inclusions and H–O–S–Pb isotope systematics of the Chalukou giant porphyry Mo deposit, Heilongjiang Province, China

The Chalukou giant porphyry Mo deposit, located in the northern Great Xing'an Range, is the largest Mo deposit in the Xing'an–Mongolia orogenic belt. This deposit's ore bodies are mainly hosted in an intermediate–felsic complex and Jurassic volcanic sedimentary rocks, of which Late Jurassic granite porphyry, quartz porphyry and fine grained granite are closely associated with the Mo mineralization. Three types of fluid inclusions (FIs) are present in the quartz associated with oxide and sulphide minerals, i.e., liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs. The FIs in the quartz phenocrysts of the granite porphyry contain liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs. The homogenization temperatures vary from 230°C to 440°C and 470°C to 510°C, and their salinities vary from 0.7% to 53.7% NaCl eq. and 6.2% to 61.3% NaCl eq., respectively. The FIs of K-feldspar–quartz–magnetite veins of the early stage are composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs with homogenization temperatures and salinities of 320°C to 440°C and 4.2% to 52.3% NaCl eq., respectively. The FIs of quartz–molybdenite veins and breccia of the middle stage are composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase FIs with homogenization temperatures and salinities of 260°C to 410°C and 0.4% to 52.3% NaCl eq., respectively. FIs of quartz–fluorite–galena–sphalerite veins of the late stage are liquid-rich two-phase FIs with homogenization temperatures and salinities of 170°C to 320°C and 0.5% to 11.1% NaCl eq., respectively. The ore-forming fluids of the Chalukou deposit are characterised by high temperature, high salinity and high oxygen fugacity, belonging to an F-rich H2O–NaCl±CO2 system. The δ18OW values vary from −4.5‰ to 3.2‰, and the δDW values vary from −138‰ to −122‰, indicating that the ore-forming fluids were a mixture of magmatic and meteoric water. The δ34S values range from −1.9‰ to +3.6‰ with an average of +1.6‰. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of the metallic minerals are in the ranges of 18.269–18.501, 15.524–15.567 and 38.079–38.264, respectively. Both the S and Pb isotopic systems indicate that the ore metals and fluids came primarily from a deep-seated magma source from the juvenile lower crust. The Mo mineralization in the Chalukou deposit occurred at a depth of 0.5 to 1.3km, and multiple stages of phase separation or immiscibility of ore-forming fluid was critical for the formation of the Chalukou deposit.

Zircon U–Pb and molybdenite Re–Os dating of the Chalukou porphyry Mo deposit in the northern Great Xing’an Range, China and its geological significance

The newly discovered Chalukou giant porphyry Mo deposit, located in the northern Great Xing’an Range, is the biggest Mo deposit in northeast China. The Chalukou Mo deposit occurs in an intermediate-acid complex and Jurassic volcano-sedimentary rocks, of which granite porphyry, quartz porphyry, and fine-grained granite are closely associated with Mo mineralization. However, the ages of the igneous rocks and Mo mineralization are poorly constrained. In this paper, we report precise in situ LA-ICP-MS zircon U–Pb dates for the monzogranite, granite porphyry, quartz porphyry, fine grained granite, rhyolite porphyry, diorite porphyry, and andesite porphyry in the Chalukou deposit, corresponding with ages of 162±2Ma, 149±5Ma, 148±2Ma, 148±1Ma, 137±3Ma, 133±2Ma, and 132±2Ma, respectively. Analyses of six molybdenite samples yielded a Re–Os isochron age of 148±1Ma. These data indicate that the sequence of the magmatic activity in the Chalukou deposit ranges from Jurassic volcano-sedimentary rocks and monzogranite, through late Jurassic granite porphyry, quartz porphyry, and fine-grained granite, to early Cretaceous rhyolite porphyry, diorite porphyry, and andesite porphyry. The Chalukou porphyry Mo deposit was formed in the late Jurassic, and occurred in a transitional tectonic setting from compression to extension caused by subduction of the Paleo-Pacific oceanic plate.

Fluid inclusion and isotope geochemistry of the Qian'echong giant porphyry Mo deposit, Dabie Shan, China: A case of NaCl-poor, CO2-rich fluid systems

The Qian'echong Mo deposit in Guangshan county, Henan Province, China, is a giant porphyry Mo deposit formed in Early Cretaceous in the Dabie Shan. Mo mineralization is associated with the Qian'echong granite porphyry, mainly presenting as numerous veinlets in the altered wallrocks, with potassic, phyllic, argillic and propylitic alteration developed. The hydrothermal ore-forming process can be divided into four stages: quartz+potassic feldspar+magnetite stage 1, quartz+molybdenite stage 2, quartz+carbonate+polymetal sulfide stage 3 and quartz+carbonate+fluorite stage 4. Fluid inclusions (FIs) can be distinguished between pure carbonic, carbonic, aqueous and solid-bearing types, but only the stage 1 quartz contains all the four types of FIs. The stage 2 quartz has three of the four types of FIs, with exception of PC-type. The stage 3 minerals are developed with the aqueous FIs with or without daughter minerals, but short of any kinds of CO2-bearing FIs. In stage 4 minerals, only the W-type FIs can be observed. The FIs in minerals of stages 1, 2 and 3 are mainly homogenized at temperatures of 260−400°C, 200−340°C and 160−300°C, with salinities of 2.00−11.58wt.% NaCl.eqv, 1.06−10.98wt.% NaCl.eqv and 0.53−9.47wt.% NaCl.eqv, respectively. The estimated minimum trapping pressures are up to 100MPa in stage 1 and to 62MPa in stage 2, respectively, corresponding to an initial mineralization depth of no less than 4km. The quartz separates from veinlets yield δ18O values of 7.1−10.2‰, corresponding to δ18OH2O values of −1.4−5.7‰, and the δDH2O values of fluid inclusions of −55−−72‰, suggesting that the ore-fluids evolved from magmatic to meteoric in sources. Therefore, the initial fluids forming the Qian'echong deposit, compared to those forming the porphyry systems in volcanic arcs, are characterized by relatively high temperature, high salinity, high fO2, CO2-rich, and NaCl-poor, considering that no halite has been observed in S-type FIs. We suggest that the “CO2-rich fluid” is a distinctive feature of porphyry systems developed in continental collision regime.