Granodiorite Porphyry Research Articles

The magma evolution sequence and geodynamic setting in the Qibaoshan ore area, Wulian County, Shandong Province, China

The Qibaoshan ore area is located in Wulian town, Shandong Province, which is an important polymetallic metallogenic zone containing gold, copper, lead, and zinc. The polymetallic mineralization is mostly related to the Qibaoshan complex. The Qibaoshan complex is composed mainly of pyroxene diorite, andesitic porphyrite, pyroxene andesite porphyrite, amphibole andesite porphyrite, diorite porphyrite, and granodiorite porphyry, among which granodiorite–porphyry is the main wall rock of gold and copper ore body, whereas lead and zinc mineralization is closely related to diorite porphyrite. A combined study of laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating and geochemical analyses (major and trace elements) for 5 Mesozoic plutons from the Qibaoshan complex was carried out to determine their ages, petrogenesis, and tectonic setting. The U–Pb zircon ages measured by laser ablation–inductively coupled plasma–mass spectrometry indicate that the Qibaoshan complex was emplaced in 3 stages, represented by the ~175 Ma pyroxene diorite, ~129 Ma andesitic porphyrite/ porphyrite, ~125 Ma granodiorite‐porphyry, and ~112 Ma diorite porphyrite. Systematic diagenetic chronology and rock geochemistry show that formation of ~175 Ma pyroxene diorite in Qibaoshan ore‐concentrated area is possibly related to the transformation environment from compression to extension of the Sulu orogenic belt and/or of the subduction of the Pacific Plate, whereas the formation of the Early Cretaceous subvolcanic rock has a volcanic arc affinity related to subduction of the Pacific Plate. Based on the previous studies, this paper argues that the metallogenic age of Qibaoshan polymetallic ore‐concentrated area is 125–105 Ma, which is formed in the volcanic arc dynamics environment of the Pacific Plate subduction in the Late Yanshanian. In addition, a small amount of 610–799 Ma and 1.8 Ga was developed in the samples of the pyroxene diorite and andesitic porphyrite, suggesting their source may have great affinities with South China.

Late Carboniferous adakitic porphyries in the Huangliangzi pluton, West Junggar (Xinjiang), NW China: Petrogenesis and their tectonic implications

Late Carboniferous to Early Permian granitic rocks are widely distributed in the Western Junggar (Xinjiang, NW China), but their petrogenesis and tectonic contexts remain controversial. In this paper, we present new zircon U–Pb age, major element, trace element data for the Huangliangzi pluton from the southern West Junggar. The pluton mainly consists of granodiorite porphyry, biotite monzonitic granite porphyry, and quartz monzonite diorite porphyry. Laser‐ablation inductively‐coupled mass‐spectrometry (LA‐ICP‐MS) zircon U–Pb obtained the age of 321.7 ± 1.3 Ma, indicating the granodiorite porphyry was emplaced in the early Late Carboniferous, coeval with abundant magmatic rocks in the region. Geochemically, these rocks are moderately peraluminous high‐K calc‐alkalic and characterized by relatively high SiO2 (64.31–66.69 wt.%), Al2O3 (15.82–16.73 wt.%), and Sr (379–489 ppm) contents and low MgO (1.08–2.46 wt.%; Mg# = 39–55), Y (7.61–9.64 ppm), and Yb (0.95–1.23 ppm) contents, along with positive Eu anomalies (Eu/Eu* = 1.01–1.34) and high Sr/Y (47.7–57.1) ratios. These are compositional features of adakites that are commonly assumed to have been produced through partial melting of subducted oceanic crust. In addition, the adakitic rocks are relatively enriched in light rare‐earth elements (LREEs), large ion lithophile elements (LILEs: e.g., Rb, Ba, Sr, and K), and depleted in high‐field‐strength elements (HFSEs: e.g., Nb, Ta, and Ti) and are also characterized by high εNd(t) value and low initial (87Sr/86Sr)i ratio. The most plausible mechanism for the Huangliangzi adakitic porphyries is the partial melting of subducted oceanic crust interacting with a mantle wedge. Combined with the geological setting and previous studies, therefore, we suggest that the southern West Junggar was in a subduction‐dominated island‐arc setting in the early Late Carboniferous, and multistage subduction–accretionary orogeny may be the main mechanism for the difference between the north and the south subduction duration in the Western Junggar.

Zircon U-Pb geochronology, Hf isotopes and geochemistry of intrusive rocks in the Simorgh prospecting area, Lut Block, eastern Iran: petrogenesis and geological implications

The Simorgh prospecting area is located in the central part of the Lut Block in eastern Iran. The Lut Block, the eastern part of the Central Iranian Microcontinent (CIM), has a complex tectonic evolution and is characterized by extensive magmatic activities with a range of geochemical signatures. The Simorgh intrusions have features typical of calc-alkaline to high-K calc-alkaline rocks, metaluminous to slightly peraluminous and formed in a volcanic arc setting. Mineralization in the area is believed to be related to these intrusions. To better understand the petrogenesis of these intrusions, we report zircon U-Pb dating and Hf isotopes and whole rock geochemistry of two granites and one diorite. Age dating using Zircon U-Pb method on pyroxene diorite porphyry stock and two granite porphyry dikes revealed 24.85 ± 0.51 Ma, 25.37 ± 0.56 Ma and 25.94 ± 0.76 Ma ages respectively (late Oligocene, Chattian). Field observations and U-Pb dating indicate that there are at least two stages of emplacement: pre-mineralization intrusions (diorite porphyry) and syn-mineralization intrusions (granite porphyry, granodiorite porphyry and pyroxene diorite porphyry). Mantle-normalized, trace-element spider diagrams display enrichment in large ion lithophile elements (LILE) and light rare earth elements ((La/Yb)N = 9.26–14.48), and depletion in high field strength elements (HFSE) and heavy rare earth elements, as well as negative Eu anomalies (Eu/Eu* = 0.49–0.91). Zircon Hf isotope data from the Simorgh intrusive rocks show largely positive eHf(t) (average = 3.6 ± 2.0). Hf model ages are ranging from 720 to 1320 Ma, indicating its derivation from a relatively juvenile source. The presence of zircon xenocrysts may prove its contamination by older continental crust (Siderian).

Partial melting of subducted Southern Qiangtang crust in northern Tibet: evidence from the geochemistry and geochronology of the Riwanchaka granodiorite porphyry in Central Qiangtang

ABSTRACTThis article presents new zircon U–Pb geochronology, Hf isotopic, and whole-rock major- and trace-element geochemical data that provide insights into the petrogenesis and tectonic history of the Riwanchaka granodiorite porphyries of Central Qiangtang, Tibet. Zircon U–Pb ages of 236–230 Ma indicate an early Late Triassic age of emplacement of the porphyries, and zircon Hf isotopic data yield εHf(t) values of – 7.0 to – 1.5 and ancient zircon Hf crustal model ages (TDMC) of 1524–1220 Ma. The granodiorite porphyries are characterized by low K2O contents, high Mg# values, and relatively high Cr and Ni contents. They are classified as I-type calc-alkaline granite and are considered to have formed through the anatexis of ancient mafic crustal rocks with contributions from mantle-derived components. The geochemistry and isotopic compositions of all samples are similar to those of magmatic rocks that originated in the South Qiangtang crust. However, field observations indicate that the pluton intrudes the North Qiangtang crust, and we propose that the granodiorite porphyries were derived by partial melting of subducted continental crust of the South Qiangtang terrane. These new data have been integrated with data from previous studies to construct a new model of slab rollback during northward subduction of the Southern Qiangtang continental crust at ca. 245–226 Ma, thereby improving our understanding of magmatic processes involved in continental subduction in collision settings.

Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet

Ore-forming fluid exsolution in a shallow magma chamber is a critical step in the formation of porphyry Cu ± Mo ± Au deposits but one for which direct evidence is rarely found. Here, Cl abundance, major-trace element content and H isotope analysis of amphibole in diorite and barren granodiorite porphyry samples from the Duolong porphyry-epithermal Cu-Au district are presented in order to reveal processes associated with fluid exsolution and magma evolution. Low-Al Mg-hornblende formed in ore-bearing diorite at ∼750–860 °C and ∼80–200 MPa. On primitive mantle-normalized diagrams, these low-Al amphibole grains have slightly convex upward REE patterns with distinctly negative Eu anomalies and negative anomalies in Pb, Sr, Eu, Zr, Hf, and Ti anomalies, suggesting crystallization from the same arc magma after plagioclase and magnetite crystallization. A large variation in estimated melt H2O (∼6 to 3 wt%) and Cl content (0.09–0.38 wt%), as well as low δD values (−103 to −113‰) indicate that the magma underwent large-scale fluid exsolution, contributing to the formation of Duolong Cu-Au mineralization. Additionally, amphibole from a barren granodiorite porphyry shows two distinct populations, distinguished by their Al content. This intrusion has low-Al amphibole (Mg-hornblende) which formed at similar conditions to low-Al amphiboles in the diorite (∼790–870 °C and ∼100–230 MPa), whereas high-Al amphibole (tschermakite) formed at ∼880–970 °C and ∼210–400 MPa. Some high-Al amphibole phenocrysts have slightly convex REE patterns with no negative Eu anomalies, a depletion in Nb, Zr, and Hf, and positive Sr, Ba, and Pb anomalies, likely consistent with amphibole crystallization from more mafic basaltic-andesitic melts. Low-Al amphibole in the granodiorite porphyry shows different compositional trends compared to those in the diorite, suggesting that they crystallized from different magmas. Considering the evidence for mafic magma replenishment suggested by the positive correlation between AlIV and Mg# values in high-Al amphibole, the low-Al amphibole in the barren granodiorite porphyry likely crystallized from a new hybrid magma with mafic to intermediate-felsic magma compositions. Meanwhile, smaller variations in Cl content (0.08–0.24 wt%) in low-Al amphibole was dominantly controlled by magma evolution (shown by variable Mg#) rather than fluid exsolution. Thus, the low δD values (−102 to −122‰) were likely inherited from evolved dioritic magmas that underwent fluid exsolution. Importantly, the Cl compositional variation of amphibole has a potential application as a powerful tool to identify ore-bearing and barren intrusions within porphyry Cu ± Mo ± Au deposits.

Petrogenesis of the Pulang porphyry complex, southwestern China: Implications for porphyry copper metallogenesis and subduction of the Paleo-Tethys Oceanic lithosphere

The Pulang complex is located in the southern segment of the Yidun Arc in the Sanjiang Tethys belt, southwestern China. It is composed of quartz diorite, quartz monzonite and granodiorite porphyries, and hosts the super-large Pulang deposit. This study presents new U-Pb geochronological, major-trace elemental and Sr-Nd-Hf isotopic data to constrain the petrogenesis of the Pulang complex and to evaluate its significances for porphyric mineralization and tectonic evolution of the Paleo-Tethys Ocean. The zircon U-Pb dating yields ages ranging from 208Ma to 214Ma. Geochemically, the Pulang complex has high Sr and MgO contents, and high Sr/Y and La/Yb ratios, but low Yb and Y contents, displaying adakitic affinities. However, it has moderate Sr/Y and La/Yb ratios, and high Rb contents (32 to 202ppm). The Pulang samples plot into the transitional field between adakites and normal arc rocks, differing from typical adakites. It is attributed to the assimilation of 10–15% crustal components. The zircon εHf(t) (−4.6 to −2.5), whole-rock (87Sr/86Sr)i (0.7052 to 0.7102), εNd(t) (−0.62 to 2.12) values and adakitic affinities suggest that the Pulang complex was derived from a basaltic slab-melt source and reacted with peridotite during ascending through an enriched asthenospheric mantle wedge. The basaltic slab-melts likely resulted from the westward subduction of the Ganzi-Litang oceanic plate (a branch of the Paleo-Tethys). As far as the metallogenesis concerned, three factors in mineralization are proposed in this paper. The country rock, quartz diorite porphyry, has higher Cu contents than the mantle (average 30ppm), suggesting that ore-forming magma was derived from a Cu-enriched source, which is a crucial contribution to the late mineralization to form the super-large Pulang deposit. In addition, the barren quartz diorite, granodiorite, and ore-bearing quartz monzonite porphyries are all characterized by high oxygen fugacity, which is another important factor for the mineralization. Moreover, the separation/exsolution of the quartz monzonite from the quartz diorite is vital to the enrichment of Cu in the Pulang deposit. The emplacement of the Pulang pluton, posterior to the closure of the Jiangshajiang Ocean (a branch of the paleo-Tethys), is consistent with the igneous rocks associated with the westward subduction of the Ganzi-Litang oceanic plate during late Triassic Time. The Zhongdian Arc in the southern segment of the Yidun Arc was close to the arc front that was conducive to Cu mineralization in the porphyry system.

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

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

Evolution of Middle-Late Triassic granitic intrusions from the Badaguan Cu-Mo deposit, Inner Mongolia: Constraints from zircon U-Pb dating, geochemistry and Hf isotopes

The Great Xing’an Range in the eastern part of the Central Orogenic Belt is one of the major polymetallic metallogenic belts in China. The Badaguan Cu-Mo deposit, in the Erguna massif forms part of this belt and is a typical porphyry deposit associated with multiple granitic intrusions, which are temporally and genetically related to the formation of this deposit. In this paper, we present new zircon U–Pb ages, Hf isotopic data, and whole-rock major and trace element geochemistry on the Badaguan granitoids. Zircon U–Pb data indicate that the intrusions formed during two major phases: ca. 244–237 Ma and ca. 232–229 Ma. The Middle Triassic (ca. 244–237 Ma) phase is represented by a suite of medium-K calc-alkaline granite, K-feldspar granite, biotite granite, and porphyritic granite with I-type affinities. In general, they are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high field strength elements (HFSEs). Their zircon εHf (t) values and two-stage model ages (TDM2) range from −1.5 to +8.5 (with a mean value of +4.9) and from 732 to 1366 Ma (with a mean value of 959 Ma), respectively. In contrast, the Late Triassic (ca. 232–229 Ma) intrusions dominantly comprise a suite of high-K calc-alkaline I-type granite porphyry and granodiorite porphyry. These rocks are enriched in LILEs and LREEs but depleted in HREEs and HFSEs, such as Nb, Ta and Ti. Their εHf (t) and TDM2 values range from +3.4 to +6.2 (with a mean value of +5.0) and from 865 to 1047 Ma (with a mean value of 942 Ma), respectively. These results suggest that the primary magmas of the Middle and Late Triassic intrusive rocks were co-magmatic and were mainly derived from the partial melting of juvenile thickened lower crust. In addition, the primary magma forming the Middle Triassic complex also assimilated a small amount of ancient crustal material and experienced a remarkable degree of fractional crystallization prior to its emplacement. In contrast, the source magma of the Late Triassic complex probably underwent interaction between of minor mantle-derived melt and crustal components prior to emplacement. The Cu in Badaguan deposit was likely sourced from the mantle-derived melt, whereas the Mo was contributed by the host rocks with high Mo contents.

Geochemistry, U-Pb geochronology and Sr-Nd isotopes of the Neogene igneous rocks, at the Iju porphyry copper deposit, NW Shahr-e-Babak, Iran

The Iju porphyry copper deposit is located in the Kerman copper belt in the northwest of Shahr-e-Babak city within the southern extension of the Urumieh-Dokhtar magmatic arc. Based on a cut-off grade of 0.15%, the deposit contains 24 million tonnes (Mt) of ore with an average grade of 0.4 wt% Cu. The igneous rocks at the Iju deposit are primarily made up of Upper Miocene sub-volcanic and volcanic sequences that intruded Eocene volcanic rocks. Sub-volcanic rocks comprise barren quartz-monzonite porphyry and syn-mineralized granodiorite porphyry along with andesitic volcanic rocks. Geochemical evidences show that they are co-genetic, medium- to high-potassium calc-alkaline, and likely part of a subduction zone I-type granitoid magma. These rocks are characterized by enrichment in LREEs relative to HREEs with negative Nb–Ta anomalies similar to subduction zone magmatism. All samples exhibit enriched uniform chondrite-normalized REE patterns without noticeable Eu anomalies similar to magnetite-series granitoids. The igneous rocks of the Iju deposit exhibit geochemical features similar to adakites. The U-Pb zircon dating shows 9.33 ± 0.19 Ma (Tortonian stage) for quartz-monzonite (oldest unit), 9.01 ± 0.20 Ma for granodiorite and 8.83 ± 0.19 Ma for andesite (youngest unit) unit. The initial 87Sr/86Sr and 143Nd/144Nd ratios and εNd(t) values for the quartz-monzonites are 0.704234, 0.512819 and 3.75, respectively, similar to the values for the granodiorite, which are 0.704278, 0.512813 and 3.64, respectively. In most discrimination diagrams, the Iju samples show characteristics of both oceanic slab-derived and delaminated/collisional thickened lower crust-derived adakites. The geochronological, geochemical and isotopic data for the igneous rocks of the Iju deposit indicate that after long term subduction of the Neo-Tethys oceanic crust beneath the central Iranian plate, continental collision between the Arabian and Eurasian plates during the Miocene-Pliocene led to crustal thickening, breaking-off of a subducted slab and development of an asthenospheric window, thereby facilitating partial melting of the subduction-contaminated sub-continental lithospheric mantle and thickened lower crust and generating the Cu-bearing adakites in the Iju region.

Zircon U-Pb age, trace element and Hf isotope composition of Sepon Au-Cu deposit, Laos: tectonic and metallogenic implications

ABSTRACT The Truong Son Fold Belt, located at the northeastern margin of the Indochina Block, is considered to be tectonically linked to the subduction of the Paleotethys Ocean and subsequent collision. Sepon is one of the most important super large deposits of the Truong Son Fold Belt. Our LA-ICP-MS zircon U-Pb dating results show that granodiorite porphyry samples from the Sepon deposit have ages of 302.1±2.9 Ma, which is a crucial phase for magmatic-tectonical activities from the Late Carboniferous to Early Permian and has avital influence on the mineralization of copper and gold. Zircon from granodiorite porphyry yields eHf (t) values of 4.32 to 9.64, and TDM2 has an average age of 914 Ma, suggesting that the source of the granodiorite porphyry in the region were mainly mantle components but underwent mixing and contamination of crust materials. The Ce4+/Ce3+ value of zircon in the granodiorite porphyry varys greatly from 2.4 to 1438.29, which shows magma mixing might occur. Considering the characteristics of trace elements in the zircon and the whole rock geochemical characteristics of intrusion rocks as well as the characteristics of regional volcanic-sedimentary association, it is indicated that the tectonic setting may be the continental arc environment. The Sepon Au-Cu deposit is derived from emplacement of calc-alkaline intermediate-acid magma with coming from deep sources in the subduction process of the Paleotethys Ocean, forming porphyry Mo-Cu, skarn Cu-Au mineralization and a hydrothermal sedimentary-hosted Au mineralization in the wall rocks.

Geochronological Constraints on the Haftcheshmeh Porphyry Cu‐Mo‐Au Ore Deposit, Central Qaradagh Batholith, Arasbaran Metallogenic Belt, Northwest Iran

AbstractThe Haftcheshmeh porphyry Cu‐Mo‐Au deposit in the Arasbaran metallogenic belt (AMB) of NW Iran contains more than 185 Mt of ore, with a grade ranging from 0.3% to 0.4%. It is hosted within a porphyritic diorite to granodiorite intruded into an older gabbro ‐ diorite intrusion. 40Ar/39Ar analyses of primary magmatic hornblende from the granodiorite porphyry and gabbro ‐ diorite show plateau ages of 26.41 ± 0.59 Ma, with an inverse isochron age of 25.9 ± 1.0 Ma and a plateau age of 27.47 ± 0.17 Ma, with an inverse isochron age of 27.48 ± 0.35 Ma for these two rock types, respectively. Comparing these new age data with those from the nearby Sungun (20.69 ± 0.35 Ma) and Kighal porphyry deposits defines a northwest‐southeast Cu‐Mo‐Au mineralization zone extending for 20 km over the time span of ∼27 to 20 Ma. Geochemically, Haftcheshmeh rocks are calc‐alkaline with high potassium affinities with tectonic setting in relation to volcanic arc setting. Large ion lithophile elements (LILE) such as Th, U and K show enrichment on a primitive mantle normalized diagram (specially Pb), and are depleted in high field strength elements (HFSE) such as Ti and Nb, pointing to a mantle magma source contamination with crustal materials by subducted oceanic crust.

Indo–Chinese Magmatic Activity in the Duobaoshan District of Heilongjiang Province and Its Geological Significance

AbstractThe Duobaoshan ore concentration area, located in Nenjiang County of Heilongjiang Province, is an important porphyry Cu‐Mo ore concentration area in China, which is characterized by complex magmatic activities and multi‐phase overprinting metallogenesis. On the basis of field geological observation, systematic sampling, in‐lab analysis and the metallogenic regularity in the Xiang'an‐Mongolian metallogenic belt, this work carried out high‐precision dating and geochemical analysis on the Yuejin, 173‐kilometer and Wolihedingzi rock bodies. These rock bodies are renamed monzonitic granite and their consistent age (238 Ma) show that they were formed not in Variscan but in Indosinian. Therefore, it is inferred that the ore spots formed in the potassium silicate and sericite alteration zones of the rock mass also belong to Indosinian. In addition, we collected granodiorite from the Tongshan mining pit, and its zircon age is 223.1±2.8 Ma and the Cu content of the sample is high. The Tongshan mineralization is inferred to undergo the superimposition of Indosinian diagenetic mineralization. The age of the granodiorite porphyry related to copper‐molybdenum mineralization in the Xiaoduobaoshan area is 222.1±5.5 Ma, and the earlier age of granodiorite is 471.8±7.4 Ma, indicating that the initial magmatic activities belong to the Duobaoshan porphyry system in the Caledonian period. The geochemical characteristics of the Indosinian rock samples show continental arc features, with reference to tectonic‐magmatic activities of the whole Daxing'anling area. We consider that the magmatic activities and mineralization of the Indosinian period are affected by the southward subduction of Okhotsk Ocean since Late Permian. By combining the mineralization rules of Daxinganling area and the structural systems of Duobaoshan ore concentration area, we divide two rock‐mineralization belts in this area including the Yuejin‐Duobaoshan‐Tongshan belt and 173‐kilometer‐Xiaoduobaoshan‐Wolihedingzi belt, which are distributed nearly parallel along the NW‐trending fractures and show similar geotectonic settings and the timing of the magmatic activities. It is favorable for discovering porphyry Cu‐Mo deposits in these two metallogenic belts, especially in the Yuejin, 173‐kilometer and Wolihedingzi areas where less research work has been made.

Palaeozoic Magmatism Associated with Gold-Antimony-Tin-Tungsten-Lead-Zinc and Silver Mineralization in the Neighbouring of Porto, Northern Portugal

In the studied area there are evidences of Palaeozoic magmatism along the stratigraphic succession from Cambrian to Carboniferous. Igneous, volcanic and sub-volcanic rocks occur along and around a significant Variscan structure, the Valongo Anticline, an asymmetrical antiform anticline, trending NW-SE, located in Central Iberian Zone in the neighbourhood of Porto (Northern Portugal). Mineralizations of gold-antimony-tin-tungsten-lead-zinc and silver occur in the area. Magmatism related to acid and basic subvolcanic and volcanic rocks occurs interbedded in Montalto Formation metasediments (conglomerates, quartzite, wakes and slates) of Cambrian age. In the transition Cambrian-Ordovician (Tremadocian?) underlying the Lower Ordovician massive quartzite of Santa Justa Formation (Floian age), volcanic rocks show bimodal composition and occur interbedded in a lithologic association mainly composed of conglomerate and quartzite with minor slate and wake intercalations. The acid volcanism consists of interbedded volcanoclastic rocks of rhyolitic affinities and black and green cherts in thick layers represent the basic volcanism. To the top of this basal Early Ordovician volcano-sedimentary succession, overlaying Floian massive quartzites, a succession of interbedded quartzite’s, wackes and slates, enriched in ironstones in the normal limb, and bearing prints of volcanic origin occur. Sub-concordant quartz veins (exhalative-origin) interbedded in the ironstones were interpreted as volcanic layers recrystallized during the circulation of hydrothermal mineralizing fluids. The presence of igneous rocks in Palaeozoic Carboniferous metasediments around Porto is known since middle of nineteen century. Granodioritic porphyry intrusion occurs interbedded in carboniferous metasediments. Metasedimentary country rocks are surrounded by pre- to post-orogenic Variscan granites with no direct spatial relationship with mineralization but hidden granitic apexes suggest an indirect genetic relationship with Sb-Au veins. Chemical analyses were performed on some of the rocks evidencing their origin. Some of them are related to mineralizations. Earlier the main Variscan Au-Sb metallogenic hydrothermal event, metallic preconcentrations (Au, Sb, Pb) occurred during the Palaeozoic, often related to magmatic events.

Oxygen fugacity, temperature and pressure estimation from mineral chemistry of the granodiorite porphyry from the Jilongshan Au-Cu deposit and the Baiguoshu prospecting area in SE Hubei Province: A guide for mineral exploration

The Jilongshan Au-Cu deposit is located in the Jiurui district of the Middle-Lower Yangtze River Metallogenic Belt in the south-eastern part of Hubei Province and close to the northern border of Jiangxi Province. This study focuses on mineral chemistry of biotite, amphibole and plagioclase in the ore-related granodiorite porphyry at the Jilongshan deposit and similar porphyry rock from the nearby Baiguoshu prospect, in an attempt to investigate the mineralization potential in the Baiguoshu area. The biotites from the Jilongshan and Baiguoshu granodiorite porphyries all belong to magnesian-biotite but the Jilongshan contains higher Mg. The calculation of Fe3+ and Fe2+ of the biotites indicated that the Jilongshan pluton shows higher oxygen fugacity that is favorable for Cu-Au mineralization, whereas the Baiguoshu pluton shows lower fO2. The Jilongshan amphiboles show higher Mg/(Mg+Fe) and lower Si which mainly belong to magnesiohornblende, whereas the Baiguoshu accommodates mainly the tschermakite. The plagioclases of the Jilongshan and Baiguoshu plutons show no compositional difference and both belong to andesine. The calculated temperatures and pressures by the coexisting amphibole-plagioclase pairs indicate that average crystallization temperature of the Jilongshan pluton is 624–736°C and the pressure is low at 0.5–0.9kbar, in contrast the Baiguoshu pluton shows higher temperature of 724–832°C and higher pressure of 3.2–6.3kbar. These data suggest that the Baiguoshu pluton has less mineralization potential than the Jilongshan pluton, therefore the Baiguoshu prospect shows less economic importance and further exploration should be carried out at depth in the Jilongshan area.

Constraints on the Genesis of the Jiande Polymetallic Copper Deposit in South China Using Fluid Inclusion and O-H-Pb Isotopes

ABSTRACT The Jiande copper deposit is located in the Qin-Hang metallogenic belt, South China. The deposit is dominated by “stratiform-like” ores, which are hosted in the dolomite of the Upper Carboniferous Huanglong Formation. These ore bodies were previously proposed to be Carboniferous sedimentary exhalative (Sedex) style mineralization, but they also appear to be related to the Late Mesozoic granodiorite porphyry at Jiande. Three stages of mineralization can be observed. The prograde skarn minerals garnet and diopside were formed in the pre-ore stage. The “stratiform-like” ores, with minor quartz-polymetallic veins, were formed in the main mineralization stage. The post-ore stage is characterized by quartz-calcite ± pyrite veins. Fluid inclusions in quartz from the pre-ore skarn, the main stage of mineralization, and post-ore quartz–calcite ± pyrite veins were studied. Fluid inclusion petrography shows that two-phase liquid-rich (Type I), two-phase vapor-rich (Type II), and halite-bearing (Type III) fluid inclusions can be identified in the studied hydrothermal quartz samples. Primary Type II and Type III fluid inclusions only occur in quartz from the the main stage, whereas Type I fluid inclusions are present in all three stages of hydrothermal quartz. Type I fluid inclusions in pre-ore stage have homogenization temperatures of 290-368°C and salinities of 2.6-8.8 wt.% NaCl equiv. Type II and coexisting Type III fluid inclusions in the main stage share similar homogenization temperatures of 293 to 334 °C and 290 to 326 °C,but have two contrasting salinity ranges of 1.2 to 2.2 wt.% and 31.87 to 38.16 wt.% NaCl equiv, respectively. The coexistence of Type II and Type III fluid inclusions and their similar homogenization temperatures but contrasting salinities suggest that fluid boiling processes occurred. Type I fluid inclusions in the post-ore quartz–calcite veins have homogenization temperatures of 202-278 °C and salinities of 0.2-6.5 wt.% NaCl equiv. The hydrogen and oxygen isotopes (δD ranges from -78 ‰ to -61 ‰, δ18OH2O calculated from quartz are from 8.1 ‰ to 10.6 ‰) of fluid inclusions in quartz imply that ore fluids were principally derived from magmatic water. The lead isotopes of sulfide from the ores are close to the orogenic Pb evolution curve and are also similar to those of the Jiande Jurassic igneous rocks, suggesting that the metals were sourced mostly from the Jurassic igneous rocks. The skarn alteration, inferred boiling fluid inclusion assemblages, stable isotopic features of magmatic fluids, and metal source imply that the main stages of mineralization in the Jiande polymetallic copper deposit is of skarn-type, related to Jurassic granodiorites.

Characteristics of Cu–Mo Mineralization in the Chatree Mining Area, Central Thailand

AbstractCu–Mo mineralization occurs in southern part of the Chatree Au–Ag deposit, central Thailand. Quartz veins of Cu–Mo mineralization are divided into five types: Types A, B, C, D and E. Quartz veins of Types A, B and C are hosted in altered granodiorite porphyry, and quartz veins of Types D and E occur in altered andesite lava. Mineral assemblages of Types A, B and C quartz veins are composed of qz–chl–ilt–mol–py–ccp, qz–chl–ilt–ccp–py and qz–chl–ilt–ccp–py–sp–po, respectively. Types D and E quartz veins consist of qz–chl–py–ccp–sp–po and qz–ep, respectively. Fluid inclusions of quartz veins are divided into liquid‐rich two‐phases fluid inclusion, vapor‐rich two‐phases fluid inclusion and multiphase solid‐bearing fluid inclusion. Coexistence of a halite‐bearing fluid inclusion having salinity of 37 equiv. wt.% NaCl and a vapor‐rich two‐phases fluid inclusion having salinity of 1 equiv. wt.% NaCl suggests that the Cu–Mo‐bearing quartz veins were formed at temperature of 450°C and pressure of 250 bars (depth of approximately 1.5 km from the paleosurface). Based on the formation temperature of 450°C of quartz veins and the δ18O values of quartz of the quartz veins, the δ18O value of fluid responsible for the Cu–Mo‐bearing quartz vein is estimated to be +9.9‰. The origin of fluid forming the Cu–Mo‐bearing quartz veins in the N prospect of the Chatree mining area would be magmatic water. Based on the characteristics of geology, age, mineral assemblage and the formation environment, Cu–Mo mineralization would be different from the epithermal Au–Ag mineralization of the Chatree mining area.

Zircon U–Pb and Hf–O isotopes trace the architecture of polymetallic deposits: A case study of the Jurassic ore-forming porphyries in the Qin–Hang metallogenic belt, China

The Qin–Hang intra-continental porphyry–skarn Cu polymetallic belt (QHMB) is among the economically important metallogenic belts in South China. The significant differences in the size and metal assemblage of the Jurassic magmatic–hydrothermal ore deposits in this belt remain as an enigma. Here we employ zircon U–Pb and Hf–O isotopes of the Tongshanling and Baoshan Cu–Pb–Zn deposits in the central part of the QHMB to investigate the contrasting metallogenic architecture. Our SIMS zircon U–Pb data indicate that the Tongshanling and Baoshan granodiorite formed at ~160Ma. These rocks show high Mg# values, and negative zircon εHf(t) and high δ18O values suggesting that the magmas of the granodiorite porphyries were mainly generated through the anatexis of older crustal components triggered by the input of mantle-derived magma. The minor content of amphibole phenocrysts, low Sr/Y ratios, negative Eu anomaly, and low zircon Ce4+/Ce3+ ratios indicate that the porphyries are relatively less oxidized with less water content compared with the ore-bearing porphyries in the Dexing and Yuanzhuding porphyry Cu deposits in the northern and southern part of the QHMB, suggesting that high magmatic water content and oxidation state are important prerequisites for the formation of large size porphyry–skarn copper deposits in the QHMB. The positive correlation between zircon εHf(t) values with the Cu reserves, as well as zircon δ18O values with the Cu/(Cu+Pb+Zn) ratios of the deposits indicate that the magmatic sources exerted a first-order control on the volume and metal assemblage of deposits in the QHMB. The Hf and Nd isotope contour maps indicate that the central part of the QHMB has high potential for Pb–Zn-dominated magmatic–hydrothermal deposits, whereas the northern and southern part of the QHMB are prospective for large Cu deposits. Our results have important implications in formulating regional exploration strategies for Jurassic porphyry–skarn Cu–Pb–Zn deposits in the Qin–Hang belt.

Early Jurassic porphyry copper mineralization in NE China: A case study of the Yanghuidongzi deposit

The Yanghuidongzi Cu deposit is located in the southeastern part of Heilongjiang Province in NE China and represents one of the few known Early Jurassic porphyry Cu deposits within the eastern edge of the Xing’an–Mongolia Orogenic Belt. Here we present new whole-rock major and trace element and Sr–Nd isotopic data, zircon U–Pb and Hf isotopic data, and molybdenite Re–Os data for units associated with the deposit. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) dating of zircons from the granodiorite porphyry in the study area yielded ages of 191.0±1.1 and 191.2±1.0Ma that are interpreted to be the emplacement age of this intrusion. The molybdenite Re–Os dating undertaken during this study yielded model ages of 192.7–187.0Ma, an isochron age of 188.2±3.8Ma, and a weighted mean model age of 190.2±2.6Ma, representing the timing of formation of the Cu mineralization in this area. The Yanghuidongzi granodiorite porphyry contains relatively high concentrations of SiO2 (68.88–72.49wt%), Al2O3 (15.37–16.31wt%), and Sr (230–479ppm), but relatively low concentrations of Y (7.97–9.87ppm) and Yb (0.72–0.85ppm), suggesting that this intrusion has an adakitic affinity. Combining this with the positive εNd (t) (0.7–1.1) and εHf(t) values (4.0–6.9), low Mg# values (41–50), and the low concentrations of MgO (0.86–1.22wt%), Cr (3.17–4.37ppm), and Ni (2.11–4.20ppm) within this intrusion suggests it formed from a magma generated by the partial melting of juvenile lower crustal material during the Early Jurassic subduction of the Paleo-Pacific Plate.

Geochronological and Geochemical Constraints on the Petrogenesis and Geodynamic Setting of the Daheishan Porphyry Mo Deposit, Northeast China

AbstractThe Daheishan Mo deposit of the Lesser Xing'an–Zhangguangcai Range metallogenic belt in northeast China is a super‐large molybdenum deposit with Mo reserves of 1.09 Mt. The Mo mineralization occurs mainly in a granodiorite porphyry. Zircon SIMS U–Pb dating yields a crystallization age of 168.3 ± 1.4 Ma for the granodiorite porphyry. Molybdenite Re–Os dating indicates that Mo mineralization occurred at 169.2 ± 1.2 Ma. These geochronological data indicate that these magmatic and hydrothermal activities occurred during the Middle Jurassic. The granodiorite porphyry can be classified as high‐K calc‐alkaline series, and the rare earth elements (REE) are characterized by a significant fractionation between light REE (LREE) and heavy REE (HREE) with slightly positive Eu anomalies (Eu/Eu* = 1.08–1.12). Large ion lithophile elements (e.g., Rb, U, K, and Pb) are enriched, whereas high field strength elements (e.g., Nb, Ta, Ti, HREEs, and Yb) are strongly depleted. The granodiorite porphyry is also characterized by initial strontium isotope ratios (87Sr/86Sr)i of 0.70460–0.70482 and magmatic zircon δ18O values of 5.2–6.5 ‰ that are similar to those of the mantle. Zircon ɛHf(t) and whole‐rock εNd(t) values range from 5.6 to 9.9 and 0.8 to 1.1, respectively. The two‐stage Nd model ages (TDM2) are in the range of 868–894 Ma, similar to Hf model ages, indicating that the parent magma has a uniform source and primarily originated from a juvenile crustal source. Combined with the regional geological history, geochemistry of the Daheishan granodiorite porphyry, and new isotopic age data, we propose that the formation of the Daheishan porphyry Mo deposit is likely related to the subduction of the Paleo‐Pacific Plate.

Geochemistry and fluid inclusions of scheelite-mineralized granodiorite porphyries from southern Anhui Province, China

We report petrological, cathodoluminescence (CL), major and trace element analyses and fluid inclusion studies on scheelite (W)-mineralized granodiorite porphyries from Dongyuan and Zhuxiling, southern Anhui Province (China). In Dongyuan, the larger part of the granodiorite porphyry body is mineralized with W concentrations up to 1140g/t (total WO3 reserves >140 000 tonnes), whereas in Zhuxiling mineralization is spatially more limited. All mineralized rocks are strongly altered, containing abundant calcite and no fresh plagioclase. W-mineralized rocks show higher K, Pb and lower Na, Sr, Ti contents compared to the non-mineralized ones. Co-variations between mobile elements (K, Na, Pb, Sr, Rb, etc.) and W, combined with petrological observations, demonstrate that fluid alteration must have controlled the mineralization. In quartz from both deposits 4 types of fluid inclusions have been recognized, i.e., aqueous-carbonic (WC-type), aqueous (W-type, subdivided into Wm-type containing minor detected CO2 and Wn containing no CO2), carbonic (pure CO2, C-type) and late secondary aqueous inclusions (LW-type). WC- and LW-type inclusions represent the original magmatic fluids and meteoric waters, respectively. The other inclusions represent evolved magmatic fluids which are closely related to alteration and mineralization. WC-, Wm- and Wn-type inclusions show higher salinity and lower homogenization temperatures, indicating fluid immiscibility with CO2 effervescence. Additionally, during plagioclase alteration and precipitation of K-feldspar and sericite the K/Na ratio is lowered and Ca released. The precipitation of scheelite must have been promoted by increasing Ca contents in the fluid and also by increasing pH due to CO2 loss. The present study demonstrates that for granitic rocks without calcareous wall rock, plagioclase breakdown must have been the key factor for scheelite mineralization. The presence of CO2-rich fluid indicates that both deposits formed in the same intracontinental extension setting as those in the Nanling region. Thus, the Yanshanian granites from southern Anhui Province may have a great potential for W mineralization, especially the blind ones in deep levels.