Granodiorite Porphyry Research Articles

Zircon and cassiterite U-Pb dating identifies the first Early Cretaceous Sn deposit in Fujian: Implication for tin mineralization potential in the southeastern coastal belt of South China

The Xiayi Sn deposit, located in the Sanming city, southeast China, is the largest Sn deposit in Fujian province. The mineralization mainly consists of cassiterite-bearing veinlets and stockworks, and it is spatially associated with the granodiorite porphyry. Despite its economic significance, few studies have been carried out, and the mineralization age remains unknown. In this paper, we present the first geochronological data on the cassiterite and the associated granodiorite porphyry, Hf isotope of the zircon, and trace element compositions of cassiterite from the Xiayi Sn deposit. These data give precise age of the Sn mineralization and constrain its relationship with the granitic intrusion. Zircon U-Pb dating of the ore-related granodiorite porphyry yielded the age of 138.3 ± 1.8 Ma, which agreed well with the cassiterite U-Pb age of 136.5 ± 1.4 Ma, documenting the genetic link between the Sn mineralization and granitic magmatism. Zircon εHf(t) ranged from −4.5 to −1.8 with a weighted mean of −3.4 and the Hf model ages (TDM2) vary from 1.31 to 1.47 Ga with a mean value of 1.40 Ga. These data indicate that the granodiorite porphyry originates from the partial melting of the crustal materials of Mesoproterozoic basement and show the addition of mantle-derived materials, similar to typical Sn mineralized granite in the southeastern coastal tin belt and Nanling tungsten-tin belt. Besides, cassiterite from Xiayi deposit show clear CL-bright and CL-dark sector zonation in the cathodoluminescence images. LA-ICP-MS trace element analyses of cassiterites indicate a high Ti and Fe but low Nb and Ta contents in both CL-bright and CL-dark sector zones, while the W content is significantly high in the CL-dark zone and low in the CL-bright zone. Cassiterite trace element compositions together with the mineralization pattern and alteration assemblages indicate that Xiayi is a porphyry tin deposit. These results provide proof of the extension of the southeastern coastal Sn metallogenic belt and offer potential breakthroughs in tin deposit exploration in southwestern Fujian Province.

Ore genesis of the Bayanbaolege Ag-Pb-Zn deposit, NE China: Constraints on LA-ICP-MS studies of cadmium and related trace elements in sulfides

The newly discovered Bayanbaolege Ag-Pb-Zn deposit is located in the Southern Great Hinggan Range metallogenic belt, northeastern China, with 1440 t Ag, 380000 t Zn, 50000 t Pb, and a beneficial component of Cd (806 t Cd) and Ga (211 t Ga). The orebodies of this deposit occur as veins and are hosted mainly by a contact zone between the Permian silty slate and the granite intrusion, and have a closely spatio-temporal relationship with the early Cretaceous granodiorite porphyry intrusion.The mineralization process of the Bayanbaolege deposit can be divided into three mineralization stages including arsenopyrite-pyrite-quartz stage (stage I), pyrite-pyrrhotite-chalcopyrite stage (stage II) and galena-sphalerite-argentite -pyrite-calcite stage (stage III). LA-ICP-MS trace element mapping and spot analyses were conducted on the sphalerite and pyrite in stage III at the Bayanbaolege deposit.LA-ICP-MS trace element mapping and spot analyses were conducted on the stage III sphalerite and pyrite selected from the Bayanbaolege deposit in order to identify the occurrence form and distribution characteristics of critical metal elements, constrain the possible controls on the variation of trace elements, reveal the physicochemical condition of mineralization and provide new insights into the ore genesis. The results show that Ga, Ge, In, Cd, Mn, Cu, Ag and Co concentrations in sphalerite, and pyrite is the preferential host for Ge, As and Ni. The occurrence of Ga, Ge, In and Cd in sphalerite are mainly deposited in form of isomorphism. Physicochemical condition studies suggest that sphalerite precipitated from a medium-temperature hydrothermal system with the range from 190 °C to 291 °C (average at 230 °C) and accompanied with the intermediate fS2. Trace element concentrations of sphalerite are different from that of the MVT, VMS, SEDEX and skarn deposits. The results of this study, combined with the previous geological and physicochemical evidence, indicate that the Bayanbaolege Ag-Pb-Zn deposit deposit is an intrusion-related mesothermal hydrothermal vein-type deposit.

Unveiling an early Paleozoic porphyry-epithermal gold system in Songshunangou district, North Qilian, northwest China: Geological and geochronological constraints

The Songshunangou district is located in the central part of the North Qilian orogenic belt and hosts both the Eastern and Western deposits. The Western deposit is a porphyry-Au deposit, characterized by concentrated high-grade Au mineralization within a quartz-dioritic porphyry and occurs along the contact to basaltic andesite. Alteration is concentric with potassic alteration associated with high-grade Au mineralization in the core zone, while surrounding propylitic alteration is associated with an only lower-grade Au mineralization. Barren sericite-chlorite alteration is restricted to shallow zones above or partially overprinted the potassic alteration. Mineralization, including chalcopyrite, bornite, pyrite, magnetite, native gold with minor galena, sphalerite, hematite, and covellite, is observed as quartz-sulfide stockworks and fine-grained disseminations in different alteration zones. LA-ICP-MS zircon U–Pb dating of samples from the ore-bearing quartz-dioritic porphyry, the post-mineralization dioritic porphyry and the granodioritic porphyry in the Western deposit yield mean 206Pb/238U ages of 456.3 ± 2.0 Ma to 454.9 ± 2.4 Ma, and 449.5 ± 4.5 Ma to 448.3 ± 1.4 Ma, respectively. Pyrite from quartz – chalcopyrite – bornite veinlets in the Western deposit yields a Re-Os isochron age of 454.6 ± 3.7 Ma. In the Eastern deposit, which is an intermediate-sulfidation epithermal deposit hosted in basaltic andesite, sericite-chlorite alteration is associated with the mineralization. The mineralization is predominantly found within veins and disseminated, primarily composed of galena, sphalerite, native gold, tetrahedrite, and minor chalcopyrite, pyrite, and covellite. The alteration mineral assemblage comprises sericite, chlorite, Mn-calcite, quartz, calcite, and minor epidote. A Mn-calcite – quartz – polymetallic vein from the Eastern deposit yields a calcite Sm-Nd isochron age of 453.2 ± 5.8 Ma, suggesting that intermediate-sulfidation mineralization was coeval with the emplacement of the ore-bearing quartz-dioritic porphyry and the porphyry mineralization in the Western deposit. Based on these geologic features and geochronological data, we conclude that an early Paleozoic porphyry-epithermal Au system developed in the Songshunangou district, which formed in an arc setting associated with the northward subduction of the North Qilian Ocean beneath the North Qilian orogenic belt. The occurrence of an early Paleozoic porphyry-epithermal Au system in the North Qilian orogenic belt provides new insights for regional mineral exploration.

Deep epithermal Au mineralization at Tuanjiegou, northeast China

To better understand the physicochemical features of deeply mineralized intervals of low-sulfidation (LS) Au deposits, the Early Cretaceous Tuanjiegou Au deposit in northeastern China was characterized as it comprises alteration and mineralization styles that reflect deeper portions of the mineralizing system. From shallow to deeper portions of the Tuanjiegou deposit, the mineralization is zoned from sulfide-poor quartz bands through hydrothermal breccia to deep pyrite–marcasite-rich veinlets that occur along hydrofractures within a granodiorite porphyry stock. The zoned alteration halo is centred on the ore zones, and comprises an inner phyllic alteration zone (illite + quartz + muscovite) and an outer intermediate argillic alteration zone (illite ± smectite), with propylitic alteration being limited. Given that apatite fission track ages are extremely sensitive to the ambient temperatures of 60–120 °C, the overlap in the closure dates of magmatic apatite (108.1 ± 3.8 Ma) and zircon (108.2 ± 1.2 Ma) from the granodiorite porphyry is indicative of shallow emplacement of the granodiorite porphyry, likely at depths slightly >0.7 km. A similar paleodepth (900 ± 188 m) was estimated from homogenization temperatures (291 ± 14 °C) of boiling fluids. Preservation of the deep portions of the Tuanjiegou ore system may imply that the productive ore intervals of poorly explored LS epithermal deposits globally are underestimated. Given the evidence for a magmatic origin of the ore-forming fluids at Tuanjiegou, we highlighted that ore-forming fluids are released initially from a water-saturated, oxidizing felsic melt under low-pressure (∼4 km) conditions.

Texture and trace element characteristics of quartz in the Dongyuan porphyry W deposit, eastern China

Most W mineralization in the world is genetically related with highly fractionated granites, but little is known about ore-forming fluid evolution of W mineralization associated with weakly fractionated granites. To reveal the ore-forming fluid evolution of W mineralization related to the weakly fractionated granites, a combined study of field and petrographic observations, mineralogical, morphological, and in-situ geochemical data of different-type quartz from Dongyuan porphyry W deposit in the world-class Jiangnan W belt, China, was carried out. The petrographic observation and cathodoluminescence (CL) imaging revealed the quartz in the Dongyuan W deposit can be divided into hydrothermal quartz (Qz1 with core-edge structure, and Qz2 with oscillating zone) in the mineralized alteration zone, and magmatic quartz (Qz3 with inherited core) in granodiorite porphyry. The LA-ICP-MS results of the Dongyuan quartz samples show that Al may enter the quartz structure with trivalent Al3+ instead of Si4+, monovalent alkali metals and bivalent (Ge2+, Sr2+) cations is mainly of charge compensators in quartz, while Ti possibly is in the form of microinclusions of titanium-containing minerals in quartz. The integrated interpretation of the trace element compositions (e.g., Al and Ti contents, Al/Na ratios) and CL texture of quartz indicate high temperature (>400 °C) and uniform Al-rich acidic fluid are conducive to W precipitation of the Dongyuan deposit. Furthermore, trace element compositions (e.g., Ge, Al) and micro-textures of quartz have the potential for distinguishing magmatic and hydrothermal quartz in the Dongyuan W deposit.

Earlier stage, higher temperature, and deeper space facilitate indium precipitation in a skarn system, as exemplified by the Baoshan Pb-Zn polymetallic deposit, South China

Indium (In), one of the strategic critical metal elements, is preferred to be enriched in the skarn system, but the enrichment regularity in terms of temporal and spatial distribution in a specific skarn Pb-Zn deposit remains unclear. To address the problem, we conducted a systematic geological, mineralogical, and trace element geochemical investigation on the Baoshan In-rich Pb-Zn polymetallic deposit, Hunan Province. This deposit is situated in the central part of the famous Nanling W-Sn-Pb-Zn polymetallic metallogeny belt, South China. Three ore districts in the Baoshan deposit with distinct economic element associations are divided, including the Central District (dominated by Cu-Mo), West District (dominated by Pb-Zn), and North District (dominated by Pb-Zn). They comprise a typical skarn system, including the outcropped granodiorite porphyry, typical skarn mineral assemblages, and Pb-Zn-hosting Carboniferous limestone. We systematically sampled the representative Pb-Zn ores in two ore districts (West and North) and three underground levels (-270 m, −230 m, and −190 m). Four types of sphalerites with different mineral associations and mineralogical characteristics were identified, that is, Sp1a and Sp1b (formed in the early sulfide stage), as well as Sp2a and Sp2b (formed in the late sulfide stage). Our EPMA (Electron Probe Micro-Analyzer) and LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometer) analyses reveal the four types of sphalerite have distinct chemical compositions. Such as, the mean value of indium is 3524 ppm for Sp1a, 142 ppm for Sp1b, 48.03 ppm for Sp2a, and 87.98 ppm for Sp2b in a decreasing order, and a similar trend of calculated temperatures ranging from 336 to 135 °C using GGIMFis thermometers can be obtained. Further LA-ICP-MS trace elements mapping show that the core of Sp1a is relatively enriched in more In, Cu, Sn, and Ag contents. Spatially, the sphalerites in the deep contain a higher indium content (mean = 1581 ppm) than those in the shallow (107.20 ppm) in the vertical profile. In the planar, indium is more enriched in the West District (mean = 1090 ppm) than in the North District (60.92 ppm). The indium distribution regularity reflects that the metals-carrying magmatic hydrothermal fluids flow from Central District, through the West District, to the North District. Collectively, we conclude that indium prefers to be enriched in the earlier stages, higher temperature, and deeper space during the sphalerite crystallization in the Baoshan skarn system, and therefore highlight the deep space of Baoshan West District is a promising target for indium exploration. This new finding maybe shed light on the scientific understanding on indium enrichment and associated exploration strategies in the similar skarn Pb-Zn metallogenic systems.

Genetic relationship between skarn and porphyry mineralization at the Saibo copper deposit, West Tianshan, NW China: Constraints from fluid inclusions, H–O–C–S–Pb isotopes, and geochronology

The Saibo skarn–porphyry deposit, located in West Tianshan, NW China, is a large copper deposit discovered recently; however, information regarding the differences and connections between skarn and porphyry mineralization remains limited. Thus, this study aimed to investigate fluid inclusions (FIs), H–O–C–S–Pb isotopes, and U–Pb, and Re–Os geochronology to unravel the origin and evolution of the entire hydrothermal system. Skarn mineralization occurs as stratiform and lenticular in the contact zone between the granodiorite porphyry and Kusongmuqieke Group limestone. We identified four mineralization stages: prograde skarn stage (IS), retrograde skarn stage (IIS), quartz–pyrrhotite–chalcopyrite stage (IIIS), and calcite–quartz–pyrite stage (IVS), and four types of FIs: CH4-rich (C-type), halite-bearing (S-type), vapor-rich (V-type), and liquid-rich (L-type) FIs. The homogenization temperatures (Th) of FIs from stages IS, IIIS, and IVS were 366–419, 271–315, and 174–235 °C, respectively, with salinities of 1.7–46.0, 2.2–9.6, and 4.5–7.7 wt% NaCl eqv., respectively. Porphyry mineralization occurs as veinlet-disseminated ores in the granodiorite porphyry. We identified three mineralization stages: quartz–molybdenite–pyrite stage (IP), quartz–chalcopyrite–pyrite stage (IIP), and calcite–quartz–galena stage (IIIP). Unlike skarn mineralization, only the S-, V-, and L-type FIs were identified, with Th of 332–379, 263–315, and 169–233 °C from stages IP, IIP, and IIIP, respectively, and salinities of 1.9–42.3, 2.2–9.6, and 4.2–6.9 wt% NaCl eqv., respectively. The H–O isotope data indicate that the ore-forming fluids were initially derived from magmatic water and gradually diluted by meteoric water during fluid migration. According to C isotope data and the presence of C-type FIs, fluids from skarn mineralization contained more organic carbon than those from porphyry mineralization. The S–Pb isotope data of sulfides suggest that ore-forming materials are derived from both granodiorite porphyry and the Kusongmuqieke Group, although the latter contributed more to skarn mineralization. Pyrites from porphyry mineralization yielded a Re–Os isochron age of 376.0 ± 7.9 Ma, which was slightly younger than the chalcopyrite Re–Os ages of skarn mineralization (>379 Ma). The granodiorite porphyry, which is considered the ore-causative intrusion, yielded a U–Pb age of 380.8 ± 1.8 Ma. Our results indicate that two styles of mineralization were formed successively at different spatial locations during the emplacement of the granodiorite porphyry in a southward subduction setting of the North Tianshan Ocean. The proposed metallogenic model provides a better understanding of the Saibo skarn–porphyry metallogenic system and is expected to assist in the exploration of similar deposits in the West Tianshan orogenic belt.

Mantle contributions to granitoids associated with Sn mineralization: Geochemical and isotopic evidence from the giant Dachang deposit, South China

Major Sn deposits are commonly linked to crust-derived and highly evolved granites, with magma generation aided by mantle heating. However, whether and how the mantle components contribute to Sn polymetallic mineralization remains unclear. In this study, in combination with a compilation of equivalent data in the region, we provide new constraints on this issue based on detailed investigations on the petrogenesis and metallogenic significance of granitoids including the causative batholith and later granodiorite porphyry dike in the giant Dachang Sn deposit from South China. The former has zircon U-Pb ages of 93–91 Ma and belongs to highly evolved S-type biotite granite, which experienced fractionation of massive feldspar. The latter shows zircon U-Pb ages of 90 Ma and displays I-type granite features. The batholith was mainly derived from the dehydration melting of biotite in the metasedimentary sources, as revealed by the relatively low whole-rock Pb contents (<30 ppm) and high Ba/Pb ratios (2.71–17.1) and initial T(ti-zr) of 790 ℃. Compared with the adjacent crust-derived S-type granites (−24.8 – −5.1) and I-type granites (−11.0 to −5.2), the Dachang S-type biotite granites present higher zircon εHf(t) values (−9.1 to −2.1). Furthermore, the low magmatic zircon δ18O values (6.2 ‰) and higher apatite LREE (3277–4114 ppm) and Sr (1137–1357 ppm) contents than of arc-type basic rocks were discerned. These characteristics jointly hint the contributions of mantle components. The higher initial T(ti-zr) (>850 °C), whole-rock Mg# (52 to 58), apatite εNd(t) (−9.2 to −6.5) and zircon εHf(t) (−7.6 to 2.5) values but lower zircon δ18O values (6.33 to 8.30 ‰) of the later granodiorite porphyry dike than those of the batholith also suggest that mantle material was involved in the generation of the dikes, which is evident by the variational features of zircon and apatite trace elements. In addition, at the zircon Hf <12000 ppm and Eu/Eu* > 0.05, the higher zircon ΔFMQ values (mostly from −1.8 to 2.0) and H2O contents (100–1100 ppm) of the Dachang granitoids than the pure crust-derived S-type granites (ΔFMQ = mostly from −3.7 to −1.5; H2O < 100 ppm) imply that mantle materials involved are relatively rich in water and oxidized. These suggest that the addition of mantle components is conducive to the extraction of Sn from metasedimentary sources, and moderately facilitates the increase of oxygen fugacity which still maintains the incompatibility of Sn in magmas with ΔFMQ < 2. Also, the involvement of mantle components upgrades the H2O contents in S-type magmas, favoring the migration of ore-forming elements from magmas to hydrothermal fluids. The sediment-derived causative granites displayed higher εHf(t) and εNd(t) values with greater Sn tonnages of their associated world-class Sn polymetallic deposits, supporting the opinion that the contributions of mantle components play an important role in the generation of giant Sn deposits.

Origin of the Saibo-Lamasu Skarn Cu deposit, Western Tianshan, Xinjiang, NW China: Evidence from geology, mineral chemistry, fluid inclusions, stable isotopes, and organic geochemistry

The Saibo-Lamasu Cu deposit is the largest skarn Cu deposit in Western Tianshan, Xinjiang, NW China. The Cu orebodies are predominantly hosted in the contact zone between the oxidized granodiorite porphyry (lg fO2 = FMQ + 1.4 to 4.4) and reduced carbonaceous limestones (effective source rocks, TOC = 0.19 to 0.32 %). Three hydrothermal stages have been recognized: (1) The pre-ore stage skarn minerals in the proximal locations are dominated by andradite (And84Gro15Pyr1) and diopside (Di76-81Hd17-23Jo1-2), while that in the distal locations are mainly wollastonite, grossular (And15Gro83Pyr2), and hedenbergite (Di31-35Hd64-68Jo1-2). The coexistence of halite-bearing multiphase and vapor-rich fluid inclusions have similar total homogenization temperatures (Th) indicating that fluid boiling happened during this stage. (2) The syn-ore stage is typified by abundant sulfides and quartz. The coexistence of fluid inclusions representing trapped vapor (vapor-rich fluid inclusions) and liquid phases (liquid-rich fluid inclusions) showing similar Th implies the occurrence of a later boiling. (3) The non-boiling fluid inclusions in post-ore stage calcite are dominated by the liquid-rich fluid inclusions that have variable Th and relatively consistent salinities. The hydrothermal fluids are mainly magmatic water, the positive δ34S values of sulfides could reflect magmatic sulfur influenced by the interaction with wall rocks. The CH4 generated by the thermal pyrolysis of organic matter in carbonaceous limestones was dissolved in oxidized magmatic fluids that contributed to the change of skarn mineral assemblage and fluid characteristics on the temporal and spatial scales at the Saibo-Lamasu skarn Cu deposit.

Zircon U-Pb Ages, Petrogenesis, and Tectono-Magmatic Evolution of Late Jurassic–Early Cretaceous S-Type Granitoid in Wujinshan Area of Northwestern Zhejiang, South China

Northwest Zhejiang area (NWZJ) is one of the important parts of the large Qingzhou-Hangzhou mineralized belt in South China formed during the Late Jurassic–Early Cretaceous period. Through the study of zircon LA-ICPMS U-Pb dating, whole-rock geochemistry, and Sr-Nd isotopes for the Wujinshan granitoid in NWZJ, two distinct S-type granitic rocks of porphyry type granodiorite and granite were identified, and the two ages of 146.4 ± 1.5 Ma for granodiorite porphyry and 141.9 ± 1.4 Ma for granite porphyries were obtained. These rocks exhibited a geochemical affinity for S-type granitoid, and the two magmatic ages indicate that these rocks were intruded in two magmatic pulses. The Late Jurassic granodiorite porphyry showed moderate SiO2 (64.38–67.89 wt.%) with higher K2O + Na2O (6.22–6.78 wt.%), lower K2O/Na2O (0.57–0.96), moderate Zr (170–215 ppm), high Sr (302–475 ppm), and low Mg# (31–32) contents. The Early Cretaceous granite porphyries contained high SiO2 (69.68–74.85 wt.%), variable K2O + Na2O (4.60–6.99), high K2O/Na2O (1.72–23.53), slightly higher Zr (160–255 ppm), variable Sr (25–412 ppm), and very low to intermediate Mg# (13–44). The granodiorites had intermediate ∑REE (149–177 ppm), while granite samples showed moderate to high ∑REE content (147–271 ppm), and both rocks showed negative Eu anomalies (0.18–0.29). We propose that these two rocks were predominantly generated by the partial melting of Mesoproterozoic metamorphic basement and underwent variable degrees of fractionation and evolution. The Late Jurassic granodiorite porphyry was formed by the partial melting of Mesoproterozoic metamorphic basement with slab-derived melts or basaltic lower crust input following fractional crystallization, while the Early Cretaceous granite porphyries were generated by the partial melting of Mesoproterozoic metamorphic basement and crystal fractionation with variable magma mixing and assimilation in the upper crust. Tectonically, the Wujinshan granitoid formed in a volcanic arc setting largely affected by the subduction and slab rollback of the paleo-Pacific Plate.

Genesis of the Jinying gold deposit, southern Jilin Province, NE China: Constraints from geochronology and isotope geochemistry

AbstractThe Jinying gold deposit is located in southern Jilin Province in northeast China and is representative of the large Early Cretaceous gold deposits in this area. To better understand ore genesis of this deposit, a multi-isotope integrated analysis of U–Pb–Rb–Sr–He–Ar–S has been carried out. Laser ablation inductively coupled plasma–mass spectrometry (LA–ICP–MS) dating of zircons from the granodiorite porphyry and dioritic porphyrite in the study area yields ages of 172.1 ± 1.2 Ma and 122.5 ± 0.8 Ma, suggesting that corresponding intrusion occurred in the Middle Jurassic and the Early Cretaceous. Rb–Sr dating of the pyrite yields an isochron age of 120 ± 3 Ma, suggesting that gold mineralization occurred in the Early Cretaceous. The fluid inclusions in pyrite yield 3He/4He ratios clustered within a small range from 0.08 to 0.13 Ra, 40Ar/36Ar ratios between 331.6 and 351.3, and mantle He in the range of 1.0–1.6%, indicating that the ore-forming fluids originated from a mixed crustal and mantle source. The in situ S isotopic values of pyrite vary between + 0.1 ‰ and + 2.8 ‰, suggesting that the ore-related sulphur came from the deep magmatic source. Combined with the geological history of the study area, it can be concluded that the gold mineralization was possibly related to the extensional setting associated with the rollback of the Palaeo-Pacific Plate.

The formation of a giant post-collision porphyry copper system: A case study of the Jiama deposit, Tibet

The large magma reservoirs underlying world-class porphyry deposits are one of the key factors in their formation, which thus led to the present study focusing on the unmineralized intrusive rocks underlying the porphyry molybdenum-copper orebody of the post-collisional Jiama porphyry-skarn copper-polymetallic deposit in southern Tibet. The Jiama porphyry intrusion comprises intermediate-silica quartz diorite, monzogranite, and granodiorite porphyries, as well a high-silica granite porphyry. The intrusive rocks suite exhibits similar whole-rock Sr-Nd isotopic compositions [εNd(t) = −3.9 to −0.8], suggesting a common, non-radiogenic magma source. Yet, these rocks have distinct geochemical characteristics. The intermediate-silica rocks are relatively enriched in Ba and Sr with minor Eu anomalies, and show adakite-like geochemical characteristics. In contrast, the high-silica granite porphyry is strongly depleted in Ba, Sr, and Eu, and lacks adakite-like geochemical characteristics. We propose that the high-silica granite porphyry represents highly fractionated melt extracted from a silicic mush reservoir (crystallinity of ∼40%−65%), and that the monzogranite and granodiorite porphyries constitute the complementary residual silicic cumulates. High crystallinity facilitates the formation of connected fluid pathways, allowing the efficient removal of volatiles from the remaining silicic melt and a rapid flux of the ore-forming fluids toward the apical parts of the large magma reservoir. Less-evolved mafic melt is believed to have repeatedly intruded the base of the magma reservoir, thereby releasing volatiles and water into the silicic mush systems. The volatiles migrated upward through the fluid channels and accumulated in the apical part of the magma reservoir, subsequently, as a result of the overpressure in the roof zone, ore-forming fluids and successive batches of magma were expelled together, thereby forming the Jiama porphyry-skarn deposit.

Genesis of the Kuh-Panj porphyry copper deposit, Kerman, Iran: Constraints from mineralization, geochemistry, fluid inclusion, and zircon U[sbnd]Pb isotope systematics

The Miocene Kuh-Panj porphyry copper deposit, with reserve estimated at about 100 Mt. at 0.21 % Cu, is located 120 km SW of Kerman in the southern part of the Urumieh-Dokhtar magmatic arc. The Eocene host rocks consist of tuff, lithic tuff, breccia tuff, and lava flows, ranging in composition from rhyodacite to andesite. A late Miocene granodiorite porphyry stock (8.57 ± 0.49 Ma, U/Pb zircon) intruded into the Eocene sequence. Subvolcanic dykes cut the Eocene rocks and porphyry stock. The Kuh-Panj porphyry system has an extensive and typical hydrothermal alteration zoning pattern, which is comprised of potassic, phyllic, argillic, and propylitic alteration types from inner proximal to outer distal zones. Copper mineralization occurs in potassic and to some extent in phyllic zones. Mineralization is mostly observed as disseminated, stockwork, and vein-veinlets forms in the porphyry stock. Vein paragenesis includes barren quartz, M-type (magnetite+biotite), A1-type (quartz+magnetite+chalcopyrite±chlorite±biotite), A2-type (quartz+chalcopyrite±pyrite), D-type (quartz+pyrite±chalcopyrite), and L-type (galena+sphalerite±chalcopyrite±pyrite) veins. The I-type granitoids with calc-alkaline affinity have enrichments of LILE (Pb, K, U, Sr, and Cs), depletion of HFSE (P, Nb, Ta, Zr, and Ti), and enrichment in LREE displaying geochemical similarity to arc-related magmatic rocks. The high SiO2 (ave. 68.9 wt%), high Al2O3 (ave. 14.5 wt%), low MgO (ave. 1.3 wt%), low P2O5 (< 0.2 wt%), high Sr (ave. 365 ppm), high Sr/Y (ave. 45), relatively high LaN/YbN (ave. 28), relatively high Th (ave. 8 ppm), low Y (ave. 8 ppm), and low Yb (0.5 ppm) contents are similar to those of fertile porphyries and lower crust-derived adakites. The most dominant type of fluid inclusions in quartz from mineralized veins are liquid-vapor-halite-solid (LVHS), liquid-vapor-halite (LVH), liquid-vapor (LV), and vapor-liquid (VL) fluids. Homogenization temperatures of LVHS, LVH, LV, and VL fluids range from 306 to 574 °C, 141–566 °C, 215–422°, and 349–571 °C, respectively. Salinities of LVHS, LVH, LV, and VL fluid inclusions range from 30 to 69, 29.0–65.5, 0.35–22.0, and 0.7–13.0 wt% NaCl eq., respectively. The extreme variations in salinities of fluid inclusions represent the combined effects of varying salinity of the magmatic fluid, aqueous fluid-phase immiscibility (boiling), and mixing with lower salinity meteoric water later in the cooling history of the porphyry system. Normal cooling, water-rock interaction, surface fluid dilution, and boiling are dominant factors that control both the distribution and abundance of mineralization. Zircon from the Kuh-Panj system has high Th/U (0.53 to 0.83), low Dy/Yb (<0.3) ratios, positive Eu/Eu* (1.28–1.85), strong positive Ce/Ce* (1.36 to 197) reflecting high Ce4+/Ce3+ ratios, and enrichment in HREEs relative to LREEs, which indicate the magmatic origin of zircon, oxidized, and hydrous conditions of the primary magma. This magma with adakitic affinities is favorable for producing fertile porphyry systems. Based on these multidisciplinary studies, the Kuh-Panj deposit is classified as a continental arc-related porphyry copper system hosted predominantly at the transition zone between potassic and phyllic alteration zones due to decreasing temperature, boiling, and fluid-rock reaction that all enhance CuFe sulfide saturation.

Geology, geochemistry, and geochronology of the Zegulangbei deposit in the Jiama ore district: Implications for a polycentric, complex porphyry mineralization system model

Jiama is a typical giant-scale collisional-type porphyry mineralization system of in the Gangdese metallogenic belt, Tibet. The Zegulangbei deposit is located in the northern part of the ore district, which was a recent discovery. In the Zegulangbei deposit, intrusions have developed in multiple stages and led to the formation of complex porphyry intrusions (2# porphyries), of which granodiorite porphyry and Ⅱ-quartz diorite porphyry occurred related to mineralization. Hydrothermal alteration surrounding the 2# porphyries is characterized by potassic, phyllic, and chlorite–sericite alteration, with minor propylitization, argillization and tourmalinization. Furthermore, veinlet-disseminated copper and molybdenum mineralization mainly occurred within the potassic and phyllic alteration zones. Partial copper mineralization developed within the chlorite–sericite alteration zone. The mineralization is comprised of porphyry Cu–Mo, hornfels Cu–Mo and skarn Cu–polymetallic ore bodies. Hydrothermal vein system developed well, including 5-staged veins (M-, A-, B-, C-, and D-type vein). The similar ages of intrusive rocks (15.8–14.5 Ma, U–Pb), biotite and sericite alteration minerals (15.04–15.02 Ma, 40Ar–39Ar), and molybdenite (14.9 Ma, Re–Os) indicate that the intermediate–felsic magmatic rock emplacement triggered the hydrothermal alteration and mineralization in the Zegulangbei deposit. Geochemistry and Sr–Nd–Pb isotopes of the intrusions in Zegulangbei are consistent with those of the intrusions in the Main deposit (1# porphyries) and the Miocene adakites that developed in the eastern Gangdese belt, implying they were generated from the partial melting of the thickened phlogopite-bearing juvenile crust that had been reworked by diapirs of the arc magma during subduction. The evidence presented in this study suggests that Zegulangbei developed a complete porphyry Cu–polymetallic mineralization system, which was related to the same magma chamber in the upper crust that caused the mineralization in the Main deposit.

The role of magma chamber depth on porphyry mineralization: Insights from the late Jurassic Gutian porphyry Cu-Mo deposit in coastal SE China

Porphyry deposits (less than5 km) contain the world’s major Cu and Mo reserves, as well as a significant amount of Au, and are genetically linked to porphyries originated from deep (8–15 km depth) upper crust magma chambers. The role of magma chamber depth in the porphyry ore formation remains an unresolved key issue. Here, we analyzed various rock-forming minerals to constrain the magmatic physicochemical conditions of three coeval and cogenetic intrusions which are difference in fertility for porphyry Cu-Mo formation from the Gutian porphyry Cu-Mo deposit. Our results show that the barren granodiorite, barren granodiorite porphyry (P1), and fertile granodiorite porphyry (P2) have similar crystallization temperatures, oxygen fugacities, and water and sulfur contents, and are water saturated. However, only the P2 intrusion that sourced from a deep magma chamber (8.6–11.4 km) generated porphyry Cu-Mo mineralization. It indicates that magma chamber depth exerted a major control on porphyry Cu-Mo formation. Moreover, the emplacement depth of the fertile P2 intrusion is similar to that of the barren granodiorite and P1 intrusion (i.e., 3.7 ± 0.5 km), indicating significant decompression during the emplacement of P2 magma. This dramatic pressure drop is recorded by the plagioclase XAn (mole fraction of anorthite [An]) value, triggering fluid exsolution and rapid mineral crystallization, as supported by the micro-/crypto-crystalline groundmass of the P2 intrusion. Our results highlight that deep magma chambers can accumulate a larger volume of magma (and thus metals) to provide sufficient ore-forming materials and can promote fluid exsolution that extracts metals from the magma.

Insights from apatite and zircon geochemistry into peraluminous I-type granitoid: A case study of granodiorite porphyry and lamprophyre in Baoshan, China

Granitoids are the most important component of continental crust, yet there has been debate regarding the classification and petrogenesis of peraluminous I- and S-type. As a result of fractional crystallizing and crustal contamination, whole-rock geochemistry sometimes fails to accurately reflect the type of primitive magma. Recent studies, however, suggest that the accessory mineral compositions can shed light on the character and petrogenesis of their primitive magma. In this contribution, we use apatite and zircon as indicators to explore the distinctions between peraluminous I- and S-type granitoids, and the petrogenesis of typical peraluminous I-type granitoids (Baoshan granitoids). Apatite trace elements indicate that their initial magma was mafic I-type, even though whole-rock compositions appear to be the hybrids of I- and S-type granitoids. Additionally, we propose that the assimilation and fractional crystallization processes are responsible for the decoupling between the compositions of whole-rock and accessory minerals. The compositions and isotopes of zircon can also reveal the components of the magma source region. The zircons εHf(t) values of the Baoshan granodiorite porphyry and lamprophyre have comparable Hf(t) values (−9.5 to −6.2 and −12.5 to −6.2, respectively). Based on the spotting of ~900 Ma inherited zircons and enriched εHf(t) values, we propose that the granitoids were formed by the partial melting of felsic Paleoproterozoic crust and a little of Neoproterozoic mafic juvenile crust, while lamprophyre was generated by the cooling of upwelling magma from the same source region as granitoids. According to the apatite trace element ratios (Sr/Th vs. La/Sm), the source region of the Baoshan intrusion is identified to been metasomatized by slab-derived fluid. Our data, in conjunction with previous studies, suggest that the paleo-Pacific slab roll-back triggered the high-temperature asthenosphere mantle upwelling, while the assimilation and fractional crystallization occurring along with the rising melts in route to the surface.

Superimposed mineralization and emplacement paleodepth of the Laozuoshan Cu-Au deposit in the Jiamusi block: Evidence from garnet U-Pb geochronology and mineral geochemistry

The Laozuoshan deposit is a large superimposed Cu-Au deposit composed of three ore zones (eastern, middle, and western). A large number of studies have revealed that the middle zone and eastern zone are skarn gold deposits formed by the contact metasomatism between a Late Paleozoic granodioritic magma and Mashan Group carbonate strata, while the western zone is a porphyry copper-gold deposit related to the hypabyssal emplacement of an Early Cretaceous dioritic-granodioritic magma. Therefore, is there mineralization related to this Early Cretaceous dioritic-granodioritic magmatism in the middle and eastern zones? To determine whether there was Early Cretaceous magmatism in the middle and eastern zones, diorite, diorite porphyrite and granodiorite porphyry, which are closely related to the skarn copper-gold mineralization in the eastern zone, were selected for study in this paper. Accurate garnet U-Pb isotope dating and chemical analysis of minerals reveal the following: (1) The formation age of the skarn copper-gold mineralization (104 Ma) is basically consistent with the emplacement time of the dioritic magma (103–106 Ma), which occurred in the Early Cretaceous. (2) The high temperature (722–802 °C), weak oxidation–reduction conditions (Δ FMQ = −4.82 ∼+0.24; log(ƒO2) = −21.2 ∼ −19.0), high water content (5.69–7.13 wt%) and shallow emplacement characteristics of the Early Cretaceous dioritic magma indicate that this magma had the potential to provide thermogenic minerals. (3) The geochemical characteristics of the skarn minerals reveal that the Early Cretaceous mineralization of the Laozuoshan deposit represents a calcareous reducing skarn copper-gold metallogenic system. Combining the mineralization and alteration characteristics of the three zones and previous work, this study further concludes that the Laozuoshan deposit is a superimposed metallogenic system involving a Late Permian skarn Au metallogenic system (eastern zone and middle zone) and an Early Cretaceous porphyry (western zone)-skarn (eastern zone and middle zone) Cu-Au system. The deep part of the mining area has the potential for searching for porphyry Cu-Au deposits.

Genesis of Makeng-type Fe-polymetallic deposits in SE China: New constraints by geochronological and isotopic data from the Dapai–Makeng metallogenic system

The southwestern Fujian depression belt (SFDB) is an economically important Mesozoic Fe metallogenic belt in South China and is renowned for its Makeng-type Fe deposits, in which stratified skarn Fe orebodies generally occur in or near the contact zone between late Paleozoic carbonate sequences and Mesozoic granites. However, the genesis and geodynamic setting of these deposits remain unclear because the characteristics of the widely distributed Pb–Zn–Cu and Mo orebodies in these deposits and the temporal, spatial, and genetic relationships between magmatism and mineralization are poorly defined. The Dapai Fe polymetallic deposit in the SFDB is a typical example of Makeng-type Fe deposits but also has regional significance, whereby the stratified skarn Fe orebodies have overprinted the stratabound Pb–Zn–Cu mineralization followed by final fissure-filling by vein-disseminated Mo mineralization. A detailed geological investigation suggests that episodic magmatic–hydrothermal events were involved in the formation process of the Dapai Fe polymetallic deposit.Pyrite and sphalerite from the Pb–Zn–Cu orebodies yield an Rb–Sr isochron age of 175.5 ± 3.3 Ma, which is regarded as the timing of Pb–Zn–Cu mineralization. Zircon grains from Fe-mineralized granodiorite porphyry and Mo-mineralized monzogranite yield weighted-mean 206Pb/238U ages of 146.3 ± 0.9 Ma and 131.7 ± 0.4 Ma, interpreted as the timings of Fe and Mo mineralization, respectively. Six zircons from granodiorite also yield a 206Pb/238U model age cluster of ∼184 Ma, which coincides reasonably with the timing of Pb–Zn–Cu mineralization and implies the existence of an unidentified ore-related intrusion in the Dapai deposit. Five further zircons from the porphyritic granodiorite yield an age cluster of ∼150 Ma, consistent with the timing of Fe mineralization. Galena, pyrite, and sphalerite from the Dapai and Makeng deposits have similar S–Pb isotopic compositions and suggest a magmatic source. Combining our results with published isotopic data for the SFDB, we suggest that the Pb–Zn–Cu mineralization in this area was derived from crustal magmas that mixed with mantle-derived magma prior to emplacement. The δ56Fe and δ57Fe values of magnetite from Dapai and Makeng are both slightly lower than those of the ore-related granites, suggesting that Fe in the initial fluid in both deposits was derived mainly from coeval granitic rocks. The Fe isotopic variation between intrusions and skarn Fe orebodies is interpreted as resulting from mass fractionation that occurred during fluid exsolution from melt. Contents of Re in molybdenite from published data for the SFDB indicate crust–mantle mixed sources of Mo and Re. The Makeng-type Fe polymetallic deposits formed as a result of three magmatic–hydrothermal episodes, generating Pb–Zn–Cu mineralization at 185–160 Ma, Fe–Mo mineralization at 150–140 Ma, and Mo–Fe mineralization at 135–130 Ma. The different metal associations formed during multiple stages of magmatism caused by ongoing subduction and rollback and/or retreat of the paleo-Pacific Plate.

Petrogenesis of the Ore-Related Intrusions of the Aikengdelesite Mo (–Cu) and Halongxiuma Mo Deposits: Implication for Geodynamic Evolution and Mineralization in the East Kunlun Orogen, Northwest China

The East Kunlun Orogenic Belt (EKOB) is the most important Triassic polymetallic metallogenic belt in China. A study about the petrogenesis of the ore-related intrusions is of great significance to the geodynamic evolution of orogenic belts. In this study, analysis of U–Pb zircon dating, whole-rock major and trace element compositions, and zircon Hf isotopes for the granitoids hosting the Aikengdelesite Mo (–Cu) and Halongxiuma Mo deposits in the EKOB are studied to determine their chronology and petrogenesis. Zircon date results show that the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry formed at 244.2 ± 1.7 Ma and 230.0 ± 1.0 Ma respectively. All samples of the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry which have high SiO2 and K2O contents, and low MgO and Cr, belong to the high-K calc-alkaline series. The Aikengdelesite granite porphyry samples show I-type geochemical affinities, whereas the Halongxiuma granodiorite porphyry samples are A-type granitoids. They all show negative zircon εHf(t) values (−7.4 to −3.3 and −3.7 to −2.5). We suggest that the Aikengdelesite granite porphyry may have been derived from the lower continental crust. While the Halongxiuma granodiorite porphyry could have formed by partial melting of basic lower crustal materials. By combining the results of this study with previous data, two magmatic and mineralization peak periods (278–237 Ma and 230–210 Ma) were observed in the Paleo-Tethys of the EKOB. Porphyry–skarn deposits occurring in the first episode were formed in the setting of an active continental margin related to the Paleo-Tethys Ocean plate subduction (e.g., Aikengdelesite porphyry deposit), while deposits occurring in the second episode were formed in a post-collisional setting (e.g., Halongxiuma porphyry deposit).

Contrasting apatite geochemistry between ore-bearing and ore-barren intrusions of the giant Kalmakyr gold-rich porphyry Cu deposit, Tien Shan, Uzbekistan

The Kalmakyr deposit in Uzbekistan is one of the world’s largest gold-rich porphyry Cu deposits, and mineralization was proposed to be closely associated with the emplacement of the latest intrusive phases, that is, granodiorite porphyry. However, it is still unclear which features of these ore-bearing intrusions are crucial for the enormous metal enrichment and how they correlate with magmatic fertility. In this study, we address these questions by comparing the petrological and in situ major and trace element geochemistry of apatite for the ore-bearing and ore-barren intrusions. Magmatic apatite from the ore-bearing granodiorite porphyry has higher Eu/Eu* (0.50–0.58), Sr/Y (1.09–1.64), and La/Yb (36.19–53.42) ratios than the ore-barren quartz porphyry (0.01–0.02, 0.02–0.03, and 2.01–3.75, respectively) and monzonite (0.20–0.11, 0.36–1.12, and 19.71–56.32, respectively). Moreover, the ore-bearing granodioritic magma has higher S (average of 111 ppm) and Cl (average of 8602 ppm) contents than the magma of quartz porphyry (S contents average of 9 ppm; Cl contents average of 2652 ppm) and monzonite (S contents average of 9 ppm; Cl contents average of 8483 ppm). These features collectively suggest that the ore-bearing granodiorite porphyry has relatively high oxygen fugacity, H2O, Cl, and S contents compared to those from the ore-barren intrusions. By comparing our data with the published dataset from porphyry Cu–Mo and Mo-only deposits in the world, we suggest that the high Cl content and low F/Cl ratio in magmatic apatite might be an important indicator to prospect for gold-rich porphyry Cu deposits.