Zhaoshan Chang | Colorado School of Mines (original) (raw)

Papers by Zhaoshan Chang

Life with Ore Deposits on EArth - 15th SGA Biennial Meeing, 2019

Assessing the structural evolution of the large Zaozigou gold-antimony deposit in the context of ... more Assessing the structural evolution of the large Zaozigou gold-antimony deposit in the context of the tectonic evolution of the Triassic West Qinling orogen can resolve important gaps in our understanding of the deposit formation. Porphyritic ca. 250-215 Ma dacite intrusions intruded Triassic slates along existing planar features. Reaction skarns within the compositional layers of the slates, along with the loss of macroscopic foliation and genetic textures indicate contact metamorphism caused by the intrusions. As a the slates proximal to the intrusions became increasingly brittle and notably susceptible to faulting and fracturing. Field relationships of local structures at the mine-scale indicate initial brittle faulting in a N-S orientation under a compressive regime, Shallow E-W striking faults are cut by steeply dipping ENE-striking faults, which in turn are cut by NE striking shallow faults, which are cut by a generation of NW striking shallow faults. All four fault generations are significant ore-bearing structures. The relative timing of faults in the context of the northward convergence of the South China Block relative to the North China Block suggests that the ore-hosting structures at Zaozigou evolved through progressive counterclockwise rotation of the local principal stress axis. This was facilitated by dextral strike-slip movement along the regional Xiahe-Hezuo fault.

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PacRim 2019 - Mineral Systems of the Pacific Rim, 2019

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Geochemistry: Exploration, Environment, Analysis, 2020

In the past decade, significant research efforts have been devoted to mineral chemistry studies t... more In the past decade, significant research efforts have been devoted to mineral chemistry studies to assist porphyry exploration. These activities can be divided into two major fields of research: (1) porphyry indicator minerals (PIMs), which are used to identify the presence of, or potential for, porphyry-style mineralization based on the chemistry of magmatic minerals such as zircon, plagioclase and apatite, or resistate hydrothermal minerals such as magnetite; and (2) porphyry vectoring and fertility tools (PVFTs), which use the chemical compositions of hydrothermal minerals such as epidote, chlorite and alunite to predict the likely direction and distance to mineralized centres, and the potential metal endowment of a mineral district. This new generation of exploration tools has been enabled by advances in and increased access to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), shortwave length infrared (SWIR), visible near-infrared (VNIR) and hyperspectral technologies. PIMs and PVFTs show considerable promise for exploration and are starting to be applied to the diversity of environments that host porphyry and epithermal deposits globally. Industry has consistently supported development of these tools, and in the case of PVFTs encouraged by several successful blind tests where deposit centres have successfully been predicted from distal propylitic settings. Industry adoption is steadily increasing but is restrained by a lack of the necessary analytical equipment and expertise in commercial laboratories, and also by the ongoing reliance on well-established geochemical exploration techniques (e.g. sediment, soil and rock chip sampling) that have aided the discovery of near-surface resources over many decades, but are now proving less effective in the search for deeply buried mineral resources and for those concealed under cover.

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Economic Geology, 2020

The giant, high-grade Resolution porphyry Cu-Mo deposit in the Superior district of Arizona is ho... more The giant, high-grade Resolution porphyry Cu-Mo deposit in the Superior district of Arizona is hosted in Pro-terozoic and Paleozoic basement and in an overlying Cretaceous volcaniclastic breccia and sandstone package. Resolution has a central domain of potassic alteration that extends more than 1 km outboard of the ore zone, overlapping with a propylitic halo characterized by epidote, chlorite, and pyrite that is particularly well developed in the Laramide volcaniclastic rocks and Proterozoic dolerite sills. The potassic and propylitic assemblages were overprinted in the upper parts of the deposit by intense phyllic and advanced argillic alteration. The district was disrupted by Tertiary Basin and Range extension, and the fault block containing Resolution and its Cretaceous host succession was buried under thick mid-Miocene dacitic volcanic cover, obscuring the geologic, geophysical, and geochemical footprint of the deposit. To test the potential of propylitic mineral chemistry analyses to aid in the detection of concealed porphyry deposits, a blind test was conducted using a suite of epidote-chlorite ± pyrite-altered Laramide volcaniclastic rocks and Proterozoic dolerites collected from the propylitic halo, with samples taken from two domains located to the north and south and above the Resolution ore zone. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data of epidote provided indications of deposit fertility and proximity. Competition for chalcophile elements (As, Sb, Pb) between coexisting pyrite and epidote grains led to a subdued As-Sb fertility response in epidote, consistent with epidote collected between 0.7 and 1.5 km from the center of a large porphyry deposit. Temperature-sensitive trace elements in chlorite provided coherent spatial zonation patterns, implying a heat source centered at depth between the two sample clusters, and application of chlorite proximi-tor calculations based on LA-ICP-MS analyses provided a precisely defined drill target in this location in three dimensions. Drilling of this target would have resulted in the discovery of Resolution, confirming that epidote and chlorite mineral chemistry can potentially add value to porphyry exploration under cover.

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Economic Geology, 2020

The Mt. Carlton Au-Ag-Cu deposit, northern Bowen basin, northeastern Australia, is an uncommon ex... more The Mt. Carlton Au-Ag-Cu deposit, northern Bowen basin, northeastern Australia, is an uncommon example of a sublacustrine hydrothermal system containing economic high-sulfidation epithermal mineralization. The deposit formed in the early Permian and comprises vein-and hydrothermal breccia-hosted Au-Cu mineraliza-tion within a massive rhyodacite porphyry (V2 open pit) and stratabound Ag-barite mineralization within volcano -lacustrine sedimentary rocks (A39 open pit). These orebodies are all associated with extensive advanced argillic alteration of the volcanic host rocks. Stable isotope data for disseminated alunite (δ 34 S = 6.3-29.2‰; δ 18 OSO 4 =-0.1 to 9.8‰; δ 18 OOH =-15.3 to-3.4‰; δD =-102 to-79‰) and pyrite (δ 34 S =-8.8 to-2.7‰), and void-filling anhydrite (δ 34 S = 17.2-19.2‰; δ 18 OSO 4 = 1.8-5.7‰), suggest that early advanced argillic alteration formed within a magmatic-hydrothermal system. The ascending magmatic vapor (δ 34 SSS ≈-1.3‰) was absorbed by meteoric water (~50-60% meteoric component), producing an acidic (pH ≈ 1) condensate that formed a silicic → quartz-alunite → quartz-dickite-kaolinite zoned alteration halo with increasing distance from feeder structures. The oxygen and hydrogen isotope compositions of alunite-forming fluids at Mt. Carlton are lighter than those documented at similar deposits elsewhere, probably due to the high paleolatitude (~S60°) of northeastern Australia in the early Permian. Veins of coarse-grained, banded plumose alunite (δ 34 S = 0.4-7.0‰; δ 18 OSO 4 = 2.3-6.0‰; δ 18 OOH =-10.3 to-2.9‰; δD =-106 to-93‰) formed within feeder structures during the final stages of advanced argillic alteration. Epithermal mineralization was deposited subsequently, initially as fracture-and fissure-filling, Au-Cu-rich assemblages within feeder structures at depth. As the miner-alizing fluids discharged into lakes, they produced syngenetic Ag-barite ore. Isotope data for ore-related sulfides and sulfosalts (δ 34 S =-15.0 to-3.0‰) and barite (δ 34 S = 22.3-23.8‰; δ 18 OSO 4 =-0.2 to 1.3‰), and micro-thermometric data for primary fluid inclusions in barite (Th = 116°-233°C; 0.0-1.7 wt % NaCl), are consistent with metal deposition at temperatures of ~200 ± 40°C (for Au-Cu mineralization in V2 pit) and ~150 ± 30°C (Ag mineralization in A39 pit) from a low-salinity, sulfur-and metal-rich magmatic-hydrothermal liquid that mixed with vapor-heated meteoric water. The mineralizing fluids initially had a high-sulfidation state, producing enargite-dominated ore with associated silicification of the early-altered wall rock. With time, the fluids evolved to an intermediate-sulfidation state, depositing sphalerite-and tennantite-dominated ore mineral assemblages. Void-filling massive dickite (δ 18 O =-1.1 to 2.1‰; δD =-121 to-103‰) with pyrite was deposited from an increasingly diluted magmatic-hydrothermal liquid (≥70% meteoric component) exsolved from a progressively degassed magma. Gypsum (δ 34 S = 11.4-19.2‰; δ 18 OSO 4 = 0.5-3.4‰) occurs in veins within postmineraliza-tion faults and fracture networks, likely derived from early anhydrite that was dissolved by circulating meteoric water during extensional deformation. This process may explain the apparent scarcity of hypogene anhydrite in lithocaps elsewhere. While the Mt. Carlton system is similar to those that form subaerial high-sulfidation epithermal deposits, it also shares several key characteristics with magmatic-hydrothermal systems that form base and precious metal mineralization in shallow-submarine volcanic arc and back-arc settings. The lacus-trine paleosurface features documented at Mt. Carlton may be useful as exploration indicators for concealed epithermal mineralization in similar extensional terranes elsewhere.

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Economic Geology, 2020

At the Antamina deposit, Peru, accurate classification of exoskarns and endoskarns can be problem... more At the Antamina deposit, Peru, accurate classification of exoskarns and endoskarns can be problematic when textures are mottled. In this study, we use whole-rock geochemical compositions (62 elements) of 221 samples to differentiate texturally similar endoskarns and exoskarns by comparing their compositions to least altered precursors (wall rocks and intrusive rocks). We present a simple method for discriminating these skarn types using immobile element bivariate plots. The most effective discriminators partition endoskarn and exoskarn into distinct domains defined by the composition of each precursor; these include Al2O3 versus heavy rare earth elements and some high field strength elements. Using these geochemical parameters, undifferentiated skarn samples can be more reliably classified as endoskarn or exoskarn. The effectiveness of these element pairs is attributed to their significantly different initial concentrations in wall rocks versus igneous precursors and their immobility during skarn formation. While immobile elements can differentiate the skarns, mobile element gains and losses (quantified using isocon analysis) provide insight on the bulk mineralogical and mass changes that take place during skarn formation.

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Australian Journal of Earth Sciences, 2020

The Jurassic–Cretaceous Great Artesian Basin is the most extensive, and largest volume, sedimenta... more The Jurassic–Cretaceous Great Artesian Basin is the most extensive, and largest volume, sedimentary
feature of continental Australia. The source of its mud-dominated Cretaceous infill is attributed
largely to contemporary magmatism along the continental margin to the east, but the source of
its Jurassic infill, dominated by quartz sandstone, remains unconstrained. This paper investigates
the question of a Jurassic sediment source for the northern part of the basin. Jurassic uplift and
exhumation of the continental margin crustal sector to the east provided the primary Jurassic sediment
source. (U–Th)/He data are presented for zircon and apatite from Pennsylvanian to mid
Permian granitoids of the Kennedy Igneous Association distributed within the northern
Tasmanides between the Townsville and Cairns regions and for coeval granites of the Urannha
batholith from the Mount Carlton district (N Bowen Basin), also within the northern Tasmanides.
The data from zircon indicate widespread Jurassic exhumation of a crustal tract located to the east
of the northern Great Artesian Basin and largely occupied by rocks of the Tasmanides. Detrital zircon
age spectra for samples of the Jurassic Hutton and Blantyre sandstones from the northeastern
margin of the Great Artesian Basin show their derivation to be largely from rocks of the northern
Tasmanides. In combination, the detrital age spectra and (U–Th)/He data from zircon indicate
exhumation owing to uplift generating appreciable physiographic relief along the north
Queensland continental margin during the Jurassic, shedding sediment westward into the Great
Artesian Basin during its early development. A portion of (U–Th)/He data for zircon are consistent
with late Permian–mid Triassic exhumation within the Tasmanides, attributable to the influence of
the Hunter–Bowen Orogeny. Evidence of Cretaceous and Paleocene exhumation episodes is also
indicated for some samples, mainly by apatite (U–Th)/He analysis, consistent with data previously
published from fission track studies. Overall, new data from the present study reveal that the
exhumation related to Jurassic regional uplift and the subsequent erosional reworking of the
northeast Australian continental margin is critical for the evolution and development of the northern
side of the Great Artesian Basin in eastern Australia. Apart from this, another two previously
suggested Permian–Triassic and Cretaceous exhumation and uplift episodes along the northeast
Australian continental margin are also confirmed by the dataset of this study.

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Mineralium Deposita, 2019

It has been widely accepted that magmas genetically linked to porphyry (-skarn) Cu (Mo) deposits ... more It has been widely accepted that magmas genetically linked to porphyry (-skarn) Cu (Mo) deposits are commonly oxidized. Recently, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) techniques, zircon Ce 4+ /Ce 3+ , Ce N / Ce N *, Eu N /Eu N *, and Ce/Nd ratios, and magma ΔFMQ values (departure from the fayalite-magnetite-quartz oxygen buffer) based on zircon trace element compositions, have been used as proxies to quantify magma oxidation state. Here we present the zircon trace element compositions of 13 Mesozoic porphyry (-skarn) Mo deposits in NE China of various sizes to examine the relationship between magma Mo fertility and magma oxidation state. Generally, the studied deposits with > 0.3 Mt Mo have Ce 4+ /Ce 3+ > 100, Ce N /Ce N * > 100, Ce/Nd > 10, and Eu N /Eu N * > 0.3, whereas those containing < 0.3 Mt Mo have Ce 4+ /Ce 3+ < 100, Ce N /Ce N * < 100, Ce/Nd < 10, and Eu N /Eu N * < 0.3. The calculated magma ΔFMQ values do not show significant correlation with metal tonnage, probably due to the large uncertainties of the estimated ΔFMQ data. Among these proxies, Ce 4+ / Ce 3+ and Ce N /Ce N * ratios show the strongest correlation with Mo tonnage, followed by Ce/Nd and Eu N /Eu N *. The above results confirm the previous proposal that zircon Ce and Eu anomalies can represent an intrusion's oxidation state and indicate that the Mo endowment of magmatic-hydrothermal deposits is positively correlated with the magma oxidation state. Compared with Mo-bearing intrusions, the trends for Cu-bearing intrusions are similar but are more complicated, especially for those deposits with > 10 Mt Cu. The findings in this study can be used to evaluate an intrusion's potential to produce Mo mineralization.

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Mineralium Deposita, 2020

Understanding the relationship between mineral occurrences and host granitic rocks can be controv... more Understanding the relationship between mineral occurrences and host granitic rocks can be controversial. The Zaozigou Au-Sb deposit (118 t Au, 0.12 Mt Sb), hosted in metasedimentary rocks and dacitic to granodioritic sills and dikes, is one such example of a large gold deposit argued to have formed from either magmatic or metamorphic hydrothermal processes. Two populations of monazite are identified within a mineralized dacite located along a major shear zone. Magmatic monazite commonly occurs within magmatic biotite and quartz phenocrysts and is characterized by uniform and high Th concentrations. It has a crystalli-zation age of 238.3 ± 2.6 Ma, consistent with the zircon U-Pb age of 238.0 ± 1.8 Ma from the same dacite. Hydrothermal monazite is associated with sulfides and sericite, and has a 207 Pb-corrected 206 Pb/ 238 U age of 211.1 ± 3.0 Ma. The amount of Th in hydrothermal monazite is widely variable. The low Th content of some monazite grains reflects direct precipitation from a metamorphic hydrothermal fluid. Furthermore, the elevated Th content in other hydrothermal monazite grains is likely due to the release of Th (and U) into hydrothermal fluids by dissolution of pre-existing Th-rich minerals in the country rock during ore-related alteration events. The magmatism, which overlaps Middle-Late Triassic terrane subduction-accretion in the West Qinling orogen, thus pre-dates the ore-forming event by about 30 m.y. The δ 34 S values of pyrite, arsenopyrite, stibnite, marcasite, and chalcopyrite from disseminated-and vein-type ores range from − 12.0 to − 5.5‰. Such negative values are distinct from those measured for other deposits in the northwestern part of the orogen that are genetically related to Triassic magmatism, including the Xiekeng-Jiangligou-Shuangpengxi Cu-Au-Fe-Mo skarn, Laodou reduced intrusion-related Au, and Gangcha epithermal Au ores. The Zaozigou deposit is best classified as an epizonal orogenic Au-Sb deposit. Our results demonstrate the usefulness of high-precision in situ geochronology on monazite for deciphering age relationships in ore deposits that have spatial associations with granitic rocks, thus aiding in the testing of the veracity of ore formation models.

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Economic Geology, 2021

The Watershed tungsten deposit (49.2 Mt avg 0.14% WO3) lies within the Mossman orogen, which comp... more The Watershed tungsten deposit (49.2 Mt avg 0.14% WO3) lies within the Mossman orogen, which comprises deformed Silurian-Ordovician metasedimentary rocks of the Hodgkinson Formation intruded by Carbonif-erous-Permian granites of the Kennedy Igneous Association. The Hodgkinson Formation in the Watershed area comprises skarn-altered conglomerate, psammite, and slate units that record four deformation events evolving from ductile, isoclinal, colinear folding with transposition (D1-D3) to brittle ductile shear zones (D4). Multiple felsic to intermediate dikes cut across the metasedimentary rocks at Watershed including: (1) Car-boniferous, monzonite dikes (zircon U/Pb age of 350 ± 7 Ma) emplaced during D1-2; and (2) Permian granite plutons and dikes (zircon U/Pb ages of 291 ± 6, 277 ± 6, and 274 ± 6 Ma) and diorite (zircon U/Pb age of 281 ± 5 Ma) emplaced during D4. Tungsten mineralization is largely restricted to skarn-altered conglomerate, which preserves a peak metamorphic mineralogy formed during ductile deformation and comprises garnet (Grt40-87 Alm0-35Sps1-25Adr0-16), actinolite, quartz, clinopyroxene (Di36-59Hd39-61Jhn1-5), and titanite. A first mineraliza-tion event corresponds to the crystallization of disseminated scheelite in monzonite dikes (pre-D3) and adjacent units, with scheelite grains aligned in the S1-2 fabric and affected by D3 folding. This event enriched the Hodgkinson Formation in tungsten. The bulk of the scheelite mineralization formed during a second event and is concentrated in multistaged, shear-related, quartz-oligoclase-bearing veins and vein halos (muscovite 40 Ar-39 Ar weighted average age of 276 ± 6 Ma), which were emplaced during D4. The multistage veins developed preferentially in competent, skarn-altered conglomerate units and formed synchronous with four retrograde alteration stages. The retrograde skarn minerals include clinozoisite after garnet, quartz, plagioclase, scheelite, and phlogopite with minor sodium-rich amphibole, which formed during retrograde stages 1 and 2, accompanied by later muscovite, calcite, and chlorite formed during retrograde stage 3. Retrograde stage 4 was a late-tectonic, noneconomic sulfide stage. The principal controls on scheelite mineralization at Watershed were the following: (1) early monzonite dikes enriched in scheelite; (2) D4 shear zones that acted as fluid conduits transporting tungsten from source areas to traps; (3) skarn-altered conglomerate lenses that provide a competent host to facilitate vein formation and a source for calcium to form scheelite; and (4) an extensional depo-sitional environment characterized by vein formation and normal faulting, which provide trapping structures for tungsten-bearing fluids, with decompression being a likely control on scheelite deposition. The coexistence of scheelite with oligoclase in monzonite dikes and veins suggests that tungsten was transported as NaHWO 4 0. Exploration in the area should target Carboniferous monzonite, associated with later syn-D4 shear zones cutting skarn-altered conglomerate.

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Economic Geology, 2021

The Early Permian Lizzie Creek Volcanic Group of the northern Bowen Basin, NE Queensland, Austral... more The Early Permian Lizzie Creek Volcanic Group of the northern Bowen Basin, NE Queensland, Australia, has compositions that range from basalt through andesite to rhyolite with geochemical signatures (e.g., enrichment in Cs, Rb, Ba, U, Th, and Pb, depletion in Nb and Ta) that are typical of arc lavas. In the Mount Carlton district the Lizzie Creek Volcanic Group is host to high-sulfidation epithermal Cu-Au-Ag mineralization, whereas farther to the south near Collinsville (~50 km from Mount Carlton) these volcanic sequences are barren of mag-matic-related mineralization. Here, we assess whether geochemical indicators of magma fertility (e.g., Sr/Y, La/ Yb, V/Sc) can be applied to volcanic rocks through study of coeval volcanic sequences from these two locations. The two volcanic suites share similar petrographic and major element geochemical characteristics, and both have undergone appreciable hydrothermal alteration during, or after, emplacement. Nevertheless, the two suites have distinct differences in alteration-immobile trace element (V, Sc, Zr, Ti, REE, Y) concentrations. The unmineralized suite has relatively low V/Sc and La/Yb, particularly in the high SiO2 rocks, which is related to magma evolution dominated by fractionation of clinopyroxene, plagioclase, and magnetite. By contrast, the mineralized suite has relatively high V/Sc but includes high SiO2 rocks with depleted HREE and Y contents, and hence high La/Yb. These trends are interpreted to reflect magma evolution under high magmatic H2O conditions leading to enhanced amphibole crystallization and suppressed plagioclase and magnetite crystallization. These rocks have somewhat elevated Sr/Y compared to the unmineralized suite, but as Sr is likely affected by hydrothermal mobility, Sr/Y is not considered to be a reliable indicator of magmatic conditions. Our data show that geochemical proxies such as V/Sc and La/Yb that are used to assess Cu-Au fertility of porphyry intrusions can also be applied to cogenetic volcanic sequences, provided elemental trends with frac-tionation can be assessed for a volcanic suite. These geochemical tools may aid regional-scale exploration for Cu-Au mineralization in convergent margin terranes, especially in areas that have undergone limited exhuma-tion or where epithermal and porphyry mineralization may be buried beneath cogenetic volcanic successions.

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Ore Geology Reviews, 2021

Although discriminating high temperature mineral systems, for example, magmatic-vs magmatic-hydro... more Although discriminating high temperature mineral systems, for example, magmatic-vs magmatic-hydrothermal origin Fe deposits, is challenging, the emerging Fe isotope systematics have shown good potentials to provide crucial information on resolving the problem. Here, Fe isotopes of multiple types of samples from one iron oxide-apatite (IOA) deposit and two skarn Fe deposits are measured, aiming to study their behaviors in high temperature magmatic and magmatic-hydrothermal environments. The primary observation of this study is that magnetite samples from high grade ores of magmatic origin IOA deposits has a heavier Fe isotopic signature relative to the associated igneous rocks, whereas a lighter Fe isotopic composition in magnetite samples from magmatic-hydrothermal origin skarn deposits relative to the causative intrusions. Another distinctive feature is that δ 56 Fe values of the causative intrusions in the magmatic origin IOA deposits are lighter than that of non-fertile intrusions, whereas the ore-associated intrusions of the magmatic-hydrothermal deposit are heavier in δ 56 Fe than that of non-fertile igneous rocks. The above two observed scenarios suggest that Fe isotope frac-tionation exists in both magmatic immiscibility and hydrothermal fluid exsolution processes. Magma immisci-bility leads to heavy Fe isotope enrichment in immiscible Fe-rich melt phase, and resulting light Fe enrichment in Si-rich melt phase. Hydrothermal fluid exsolution results in lighter Fe isotope enrichment in the exsolved liquid phase, with a heavy Fe isotope enrichment in the residual magma. Fe isotopes behave in different ways in magmatic and magmatic-hydrothermal mineralization processes, which makes Fe isotopes an effective tool to discriminate mineral deposits of magmatic origin from those formed by magmatic-hydrothermal processes.

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Geology, 2021

Fluid inclusion compositions obtained from laser ablation-inductively coupled plasma-mass spectro... more Fluid inclusion compositions obtained from laser ablation-inductively coupled plasma-mass spectrometry at the Haobugao Zn-Pb skarn in northeastern China provide constraints on fluid origin, evolution, and metal deposition mechanisms and an example of evaluating mineralization potential. Metal concentrations in the prograde fluids were high (up to 1.4 wt% Zn and 1.8 wt% Pb) but remained in solution, likely due to the high temperatures (440-575 °C) and salinities (35.4-45.3 wt% NaCl equivalent). Absolute concentrations of elements (e.g., Rb and Na) and mass ratios (e.g., Zn/Na and K/Na) reveal that the early, prograde fluids were magmatic, consistent with the oxygen isotope composition of fluids (δ 18 O H2O = 5.5‰-8.5‰). Later mixing with a meteoric fluid caused dilution and Zn-Pb deposition, as revealed by lowered element concentrations and Pb/(Na + K) and Zn/(Na + K) ratios in the sulfide-stage fluid inclusions. Elevated Ca/K ratios in sphalerite-hosted inclusions indicate fluid-carbonate reactions that buffered fluid pH, also facilitating Zn-Pb precipitation. Although cassiterite and molybdenite occur locally at Haobugao, mass balance calculation shows low metal endowment (maximum 2900 t Sn and 2200 t Mo) of the system. Furthermore, the generally unchanged Sn/(Na + K) and Mo/(Na + K) ratios from pre-to late-mineralization fluids suggest that the fluids were never saturated in Sn and Mo. Therefore, finding much Sn or Mo at Haobugao is unlikely. This demonstrates a potential tool for evaluating the metal endowment of a mineral prospect, which may guide exploration.

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SEG Discovery, 2020

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SEG Special Publication v.22 Mineral Deposits of China, 2019

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SEG Special Publication v.22 Mineral Deposits of China, 2019

Skarn deposits are one of the most common deposit types in China. The 386 skarns summarized in th... more Skarn deposits are one of the most common deposit types in China. The 386 skarns summarized in this review contain ~8.9 million tonnes (Mt) Sn (87% of China's Sn resources), 6.6 Mt W (71%), 42 Mt Cu (32%), 81 Mt Zn-Pb (25%), 5.4 Mt Mo (17%), 1,871 tonnes (t) Au (11%), 42,212 t Ag (10%), and ~8,500 Mt Fe ore (~9%; major source of high-grade Fe ore). Some of the largest Sn, W, Mo, and Zn-Pb skarns are world-class. The abundance of skarns in China is related to a unique tectonic evolution that resulted in extensive hydrous magmas and widespread belts of carbonate country rocks. The landmass of China is composed of multiple blocks, some with Archean basements, and oceanic terranes that have amalgamated and rifted apart several times. Subduction and collisional events generated abundant hydrous fertile magmas. The events include subduction along the Rodinian margins, closures of the Proto-Tethys, Paleo-Asian, Paleo-Tethys, and Neo-Tethys Oceans, and subduction of the Paleo-Pacific plate. Extensive carbonate platforms developed on the passive margins of the cratonic blocks during multiple periods from Neoarchean to Holocene also facilitated skarn formation. There are 231 Ca skarns replacing limestone, 15 Ca skarns replacing igneous rocks, siliciclastic sedimentary rocks, or metamorphic silicate rocks, 113 Ca-Mg skarns replacing dolomitic limestone or interlayered dolomite and limestone, and 28 Mg skarns replacing dolomite in China. The Ca and Ca-Mg skarns host all types of metals , as do Mg skarns, except for major Cu and W mineralization. Boron mineralization only occurs in Mg skarns. The skarns typically include a high-temperature prograde stage, iron oxide-rich higher-temperature retrograde stage, sulfide-rich lower-temperature retrograde stage, and a latest barren carbonate stage. The zoning of gar-net/pyroxene ratios depends on the redox state of both the causative magma and the wall rocks. In an oxidized magma-reduced wall-rock skarn system, such as is typical of Cu skarns in China, the garnet/pyroxene ratio decreases, and garnet color becomes lighter away from the intrusion. In a reduced intrusion-reduced wall-rock skarn system, such as a cassiterite-and sulfide-rich Sn skarn, the skarn is dominated by pyroxene with minor to no garnet. Manganese-rich skarn minerals may be abundant in distal skarns. Metal associations and endowment are largely controlled by the magma redox state and degree of fraction-ation and, in general, can be grouped into four categories. Within each category there is spatial zonation. The first category of deposits is associated with reduced and highly fractionated magma. They comprise (1) greisen with Sn ± W in intrusions, grading outward to (2) Sn ± Cu ± Fe at the contact zone, and farther out to (3) Sn (distal) and Zn-Pb (more distal) in veins, mantos, and chimneys. The second category is associated with oxidized and poorly to moderately fractionated magma. Ores include minor porphyry-style Mo and/or porphyry-style Cu mineralization ± Cu skarns replacing xenoliths or roof pendants inside intrusions, zoned outward to major zones of Cu and/or Fe ± Au ± Mo mineralization at the contact with and in adjacent country rocks, and farther out to local Cu (distal) + Zn-Pb (more distal) in veins, mantos, and chimneys. Oxidized and highly fractionated magma is associated with porphyry Mo or greisen W inside an intrusion, outward to Mo and/or W ± Fe ± Cu skarns at the contact zone, and farther to Mo or W ± Cu in distal veins, mantos, and chimneys. The final category is associated with reduced and poorly to moderately fractionated magma. No major skarns of this type have been recognized in China, but outside China there are many examples of such intrusions related to Au-only skarns at the contact zone. Reduced Zn-Au skarns in China are inferred to be distal parts of such systems. Tungsten and Sn do not occur together as commonly as was previously thought. The distal part of a skarn ore system may transition to carbonate replacement deposits. Distal stratabound mantos and crosscutting veins/chimneys may contain not only Zn-Pb but also major Sn, W, Cu, Mo, and Au min-eralization. The Zn-Pb mineralization may be part of either an oxidized system (e.g., Cu, Mo, Fe) or a reduced system (e.g., Sn). In China, distal Zn-Pb is more commonly related to reduced magmas. Gold and W may also be related to both oxidized and reduced magmas, although in China they are more typically related to oxidized magma. There are numerous examples of distal mantos/chimneys that continuously transition to proximal skarns at intrusion-wall-rock contact zones, and this relationship strongly supports the magmatic affiliation of such deposits and suggests that distal skarns/carbonate replacement deposits systems should be explored to find more proximal mineralization. Carbonate xenoliths or roof pendants may host the majority of mineralization in some deposits. In contact zones, skarns are better developed where the intrusion shape is complicated. The above two skarn positions imply that there may be multiple skarn bodies below drill interceptions of intrusive rocks. Many of the largest skarns for all commodities in China are related to small or subsurface intrusions (except for Sn skarns), have multiple mineralization centers, are young (<~160 Ma), and have the full system from causative intrusion(s) to distal skarns or carbonate replacement extensions discovered.
Chinese skarn deposits fall in several age groups: ~830, ~480 to 420, ~383 to 371, ~324 to 314, ~263 to 210, ~200 to 83, ~80 to 72, and ~65 to 15 Ma. They are typically associated with convergent plate boundaries, mostly in subduction settings but also in collisional settings. Seven major skarn metallogenic belts are recognized based on skarn geographic location and geodynamic background. In subduction settings, skarns may form in a belt up to 4,000 km long and 1,000 km inland, with skarns continuously forming for up to 120 m.y., e.g., the eastern China belt. In most other belts, skarns form in 5- to 20-m.y. episodes similar to the situation in South America. In collisional settings, skarns may form up to 50 m.y. after an ocean closure, and the distance to the collisional/accretionary boundary may extend to ~150 km inland. The size of collision-related skarns may be as large as the largest skarns related to oceanic crust subduction. Older suture zones may be favorable sites for younger mineralization, for example, the Triassic Paleo-Tethys suture between the North and South China blocks for the younger and largest skarn cluster of the Middle-Lower Yangtze belt in the eastern China belt, and the Triassic sutures in southwestern China for Cretaceous to Tertiary mineralization.

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European Journal of Mineralogy, 2017

Sphalerite is the most important host mineral for the recovery of indium. New techniques to study... more Sphalerite is the most important host mineral for the recovery of indium. New techniques to study the presence and distribution of this critical metal in sphalerite can therefore be of interest for scientific and technological purposes alike. In this study we use the emerging tool of hyperspectral cathodoluminescence (CL) mapping, combined with X-ray element mapping and spot analyses, to characterise the composition and CL properties of indium-bearing sphalerite from the Mt Carlton high-sulphidation epithermal deposit (NE Queensland, Australia). Mt Carlton sphalerite contains highly elevated concentrations of indium (up to 19.59 wt%) occurring within ∼1 mm thick colloform bands, which show an average composition of (Zn 0.63 Cu 0.20 In 0.15 Ga 0.01)S 0.96. Indium, Cu and Ga are interpreted to have been incorporated via the coupled substitution 2Zn 2þ ↔ Cu þ þ (In,Ga) 3þ. Hyperspectral CL mapping reveals a high-intensity CL emission directly related to In-Cu-(Ga)-rich sphalerite, centred at wavelengths between ∼500 and ∼600 nm. The CL peak is shifted to the higher-wavelength positions when the proportion of In relative to Cu increases. Our study shows that hyperspectral CL mapping is a powerful and efficient technique to study the distribution of In in sphalerite.

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Proceedings of the IAGOD symposium, 2018

Northeast Queensland of Australia is an important Sn-W-Mo-Au mineralized province in Australia, p... more Northeast Queensland of Australia is an important Sn-W-Mo-Au mineralized province in Australia, particularly for Sn and W, which includes ~10% of Australia's Economic Demonstrated Resources (EDR) of Sn and ~13% of the country's EDR of tungsten (Chang et al, 2017). Sn-dominant deposits mainly occur in three districts: the Kangaroo Hills, Herberton and Cooktown districts. The W-dominant deposits occur only in the northeast Mt Carbine-Watershed area. W-Mo deposits have been found in both the Herberton (e.g., Wolfram Camp) and Kangaroo Hill districts. To discern differences between "fertile" and "non-fertile" igneous rocks associated with Sn-W-Mo mineralization and reveal the genetic links between coeval intrusive and extrusive rocks, we integrate whole rock geochemistry, geochronology and Hf isotope signatures of igneous zircons from contemporaneous plutonic and volcanic rocks from the Herberton Sn and W-Mo mineral field. The 310-300 Ma intrusive rocks and associated intra-plutonic W-Mo mineralization formed from relatively oxidized magmas after moderate degrees of crystal fractionation. The geochemical and isotopic features of the coeval volcanic succession are best reconciled utilizing the widely-accepted volcanic-plutonic connection model, whereby the volcanic rocks represent fractionated derivatives of the intrusive rocks. The volcanic rocks of 335-310 Ma (Sn formation stage) are compositionally less evolved than the coeval intrusive rocks. In this case, we propose that the most fractionated magmas were not lost to volcanism, but instead were effectively retained at the plutonic level, which allowed further localized build-up of volatiles and lithophile metals in the plutonic environment. Given the common occurrence of volcanic and plutonic rocks associated with Sn-W-Mo mineralization worldwide, we suggest that a proper understanding of plutonic-volcanic connections can assist in assessment of regional-scale mineralization potential, which in turn can aid strategies for future ore deposit exploration. The Wolfram Camp Mine deposit is a greisen type W-Mo deposit. The host rock of the deposit is Late Carboniferous James Creek granite and which has locally intruded Hodgkinson Formation sandstone. The orebodies contain wolframite and molybdenite occur as pipe-like bodies of quartz in the roof zone of the intrusion. Alteration associated with the Wolfram Camp mineralization is mainly greisen type. The alteration can be divided into quartz-rich greisen zones, muscovite-rich greisen zones and greisenized granite zones with decreasing alteration levels. The mineralization in the study area are closely related to post-intrusive hydrothermal events and can be divided into several stages. The major ore minerals, wolframite and molybdenite, formed during the greisen stage, and base metal sulphide minerals and scheelite formed in later sulphide and calcite stages. Fluid inclusion studies was conducted on the ore bearing quartz crystals in the pipes. The homogenization temperatures of the fluid inclusions quartz containing wolframite are about 410 °C. Results from a stable isotope study suggest that the source of the hydrothermal fluid related to the formation of the wolframite, molybdenite and base metal sulphides is purely magmatic. However, the fluid responsible for the introduction of the calcite is a combination of magmatic water and meteoric water. The Mt Carbine quartz-wolframite-scheelite sheeted vein deposit is hosted in Ordovician to Devonian Hodgkinson Formation metasedimentary rocks. Field observation and drill core logging have provided evidence for a five stage paragenetic sequence of mineralization and veining, with two of the stages having significant W mineralization. Wolframite is typically euhedral and occurs in quartz veins, while scheelite occurs as (1) euhedral grains in quartz vein and, (2) pseudomorphing wolframite grains or cutting across wolframite grains as veinlets. This observation is consistent with the scheelite CL images and in-situ composition variation. The LA-ICP-MS zircon U-Pb dating results reveal the magmatic activities occurred during 300-265 Ma. Molybdenite Re-Os age and muscovite 40Ar-39Ar ages are between 285-275 Ma. Fluid inclusion studies reveal that most of the inclusion are primary and distributed in assemblages or isolated, with homogenization temperatures ranging from 290 to 210 °C. Laser Raman analysis identified CH 4 in vapour bubbles. Together with H-O-S isotopic compositions, our data indicate that both magmatic fluid and metamorphic water contributed the formation of Mt Carbine W deposit. The Watershed scheelite deposit lies within the Mossman Orogen, which comprises deformed Silurian-Ordovician metasedimentary rocks of the Hodgkinson Formation by Carboniferous and Permian granites of the Kennedy Igneous Association. Multiple felsic dykes cut cross the metasedimentary rocks at Watershed including: (a) monzonite dyke (~350 Ma); and (b) dioritic, granitic plutons and dykes (281-271 Ma). A first non-economic A | 35

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Ore Geology Reviews, 2018

In the Qarachilar Cu-Mo-Au deposit of the Ahar-Arasbaran metallogenic zone (AAMZ), northwest Iran... more In the Qarachilar Cu-Mo-Au deposit of the Ahar-Arasbaran metallogenic zone (AAMZ), northwest Iran, mi-neralization occurs as three quartz-sulfide veins that cut granodiorite-quartz monzodiorite rocks of the Qaradagh batholith (QDB). Ore formation can be divided into three stages, with chalcopyrite, molybdenite, and gold-bearing pyrite appearing mainly in the first two stages. The main wall-rock alteration is silicification, and intermediate argillic, carbonate, and propylitic alteration. Fluid inclusion microthermometry indicates trapping of medium-to high-salinity (9.2-55 wt% NaCl equiv.) fluids at Qarachilar. Fluid inclusion trapping conditions are estimated to be 190°C-530°C and 0.1-3 kbar. The variable phase ratios as well as spatial coexisting of liquid-and vapor-rich two-phase and halite-bearing multiphase fluid inclusions homogenizing over the same temperatures are consistent with fluid boiling during ore formation. Obtained δ 18 O H2O values of quartz from ore-stage veins are +5.7‰ to +9.7‰, signifying that the ore-fluid system was predominantly magmatic water. The average calculated δ 34 S H2S values are 1 ± 1‰ for pyrite, chalcopyrite and molybdenite, consistent with a magmatic source for sulfur. Combined, the fluid inclusion and stable isotope data indicate that the ore-forming fluids at Qarachilar were magmatic in origin and were subsequently cooled and diluted by meteoric water. Fluid boiling and mixing facilitated hydrothermal alteration and mineralization. Molybdenite Re-Os dating shows that mineralization occurred at 42.35 ± 0.16 Ma, coincident with formation of porphyry Cu-Mo mineralization at Agarak deposit, and Hanqasar, Aygedzor and Dastakert prospects in the Lesser Caucasus. However, Qarachilar is older than all porphyry Cu-Mo mineralization in the AAMZ and Urumieh-Dokhtar magmatic arc (UDMA), which suggests that collision between Arabia and Eurasia were oblique and thus diachronous. Our data suggest that mineralization at Qarachilar is related to collisional Eocene magmatic-hydrothermal activity related to Neo-Tethys subduction, and shares a number of similarities with the vein-type Cu-Mo-Au mineralization related to Cu-Mo porphyries.

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Ore Geology Reviews, 2018

The Aliabad-Khanchy epithermal base metal deposit is located in the Tarom-Hashtjin metallogenic b... more The Aliabad-Khanchy epithermal base metal deposit is located in the Tarom-Hashtjin metallogenic belt (THMB) of northwest Iran. The mineralization occurs as Cu-bearing brecciated quartz veins hosted by Eocene volcanic and volcaniclastic rocks of the Karaj Formation. Ore formation can be divided into five stages, with most ore minerals, such as pyrite and chalcopyrite being formed in the early stages. The main wall-rock alteration is silicification, and chlorite, argillic and propylitic alteration. Microthermometric measurements of fluid inclusion assemblages show that the ore-forming fluids have eutectic temperatures between −30 and −52°C, trapping temperatures of 150-290°C, and salinities of 6.6-12.4 wt% NaCl equiv. These data demonstrate that the ore-forming fluids were medium-to high-temperature, medium-to low-salinity, and low-density H 2 O-NaCl-CaCl 2 fluids. Calculated δ 18 O values indicate that ore-forming hydrothermal fluids had δ 18 O water ranging from +3.6‰ to +0.8‰, confirming that the ore-fluid system evolved from dominantly magmatic to dominantly meteoric. The calculated 34 S H2S values range from −8.1‰ to −5.0‰, consistent with derivation of the sulfur from either magma or possibly from local volcanic wall-rock. Combined, the fluid inclusion and stable isotope data indicate that the Aliabad-Khanchy deposit formed from magmatic-hydrothermal fluids. After rising to a depth of between 790 and 500 m, the fluid boiled and subsequent hydraulic fracturing may have led to inflow and/or mixing of early magmatic fluids with circulating groundwater causing deposition of base metals due to dilution and/or cooling. The Aliabad-Khanchy deposit is interpreted as an intermediate-sulfidation style of epithermal miner-alization. Our data suggest that the mineralization at Aliabad-Khanchy and other epithermal deposits of the THMB formed by hydrothermal activity related to shallow late Eocene magmatism. The altered Eocene volcanic and volcaniclastic rocks, especially at the intersection of subvolcanic stocks with faults were the most favorable sites for epithermal ore bodies in the THMB.

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SEG Special Publication v.22 Mineral Deposits of China, 2019

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European Journal of Mineralogy, 2017

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SEG Special Publication Number 22, 2019

SEG Special Publication Number 22

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The Watershed deposit is located in far north Queensland, about 100 km northwest of Cairns. It ha... more The Watershed deposit is located in far north Queensland, about 100 km northwest of Cairns. It has a combined JORC resource of 49.32 Mt @ 0.14% WO3 totalling 70,400 tonnes of WO3. Watershed lies within the Mossman Orogen, which comprises a folded sequence of Ordovician-Devonian metasediments intruded by Carboniferous-Permian granites of the Kennedy Province. Mineralization is hosted by a sequence of folded slates and, locally calcareous, psammites of the Hodgkinson Formation. In addition, multiple felsic dykes of the Permian S-type Whypalla Supersuite granites occur cutting the metasediments. Veining, alteration and mineralization occur in mainly five stages. Stage 0 corresponds to strongly deformed quartz-calcite-mica veins cutting slate units. Stage 1 is a widespread red-green prograde skarn in psammitic units. It is comprise mainly of grossular-spessartine-almandine garnets of up to 2 mm and hedengbergitic-diopsidic pyroxene, and is overprinted by clinozoisite, actinolite-ferroactinolite-magnesiohornblende-tourmaline-biotite-scheelite-calcite retrograde alteration.

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The Mt Carbine quartz-wolframite-scheelite sheeted vein deposit is located ~80 km NW of Cairns, N... more The Mt Carbine quartz-wolframite-scheelite sheeted vein deposit is located ~80 km NW of Cairns, Northern Queensland. It was the largest vein type W deposit in Australia and accounted for 43% of Australia's annual W production in 1986, prior to closure because of international Sn-W market crash. The hard rock resources at Mt Carbine at last review include indicated resources of 18 Mt at 0.14% WO3 and inferred resource of 29.3 Mt at 0.12% WO3 (Carbine Tungsten Limited Annual Report 2014). The vein system in Mt Carbine is hosted in Ordovician to Devonian Hodgkinson Formation metasedimentary rocks, which include turbiditic meta-sediments composed mainly of greywacke, siltstone-shale, slate, basalt, conglomerates and chert. There are at least 3 types of felsic igneous rocks in the mining district, including porphyritic biotite granite, equigranular coarse-grained biotite granite and fine-grained felsic dyke that cuts across the ore body. There is no observable contact between granite and the W veins, thus their relationship is unclear. Mineralized quartz veins and chlorite alteration occur in the porphyritic biotite granite, whereas no quartz vein and alteration are present in the fine-grained felsic dyke, indicating that the porphyritic biotite granite was earlier than mineralization and the felsic dyke later than mineralization. This observation is consistent with the latest dating results: the LA-ICP-MS zircon U/Pb age of the porphyritic biotite granite is 298 ± 3 Ma and the felsic dyke 261 ± 7 Ma, whereas the molybdenite Re-Os age from the mineralized quartz vein is 284 ± 1 Ma, and the muscovite 40 Ar-39 Ar ages are 282-277 (± 1-2) Ma. There is no overlap between the 2 muscovite 40 Ar-39 Ar ages, probably indicates there was some post-mineralization tectono-thermal activities. There are four 30-40 m wide vein zones in the open pit with different orientations, with Zones 1-3 being ~300°/80° (strike/dip), and Zone 4 270°/65°. Based on drill core logging and open pit observation, the paragenesis sequence has been established. Stage 0 is represented by the deformed curvy and discontinuous quartz-dominant vein with minor to none W mineralization. Stage I continuous quartz-dominant veins have straight and continuous margin, and are composed of wolframite ± scheelite ± K-feldspar ± biotite ± tourmailine ± apatite. Stage II veins are straight & continuous, quartz-dominant with sharp boundaries, and contain chlorite ± scheelite ± wolframite ± cassiterite ± muscovite. Stage III is represented by undeformed straight and continuous quartz ± chlorite ± muscovite ± molybdenite ± arsenopyrite ± chalcopyrite ± pyrite ± pyrrhotite ± sphalerite veins, without W mineralization. Stage IV veins are featured by the undeformed straight and continuous shape and quartz ± calcite ± fluorite mineralogy without any W mineralization. The W mineralization is mostly in stage II quartz veins, with less economic W mineralization in the other 3 stages of veins. Ore minerals are wolframite and scheelite. Wolframite is typically euhedral and occurs in quartz veins, while the occurrences of scheelite are: (1) euhedral grains in quartz vein and, (2) pseudomorphing wolframite grains or cutting across wolframite grains as veinlets.

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