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1.
The Halasu porphyry copper belt situated in the East Junggar is one of the major porphyry copper belts in Xinjiang Uygur Autonomous Region, northwest China. Copper and molybdenum mineralization occurs as disseminated sulfides or veinlets mainly in granodiorite porphyry and diorite porphyry, with the intense development of zoned alteration from potassic, through sericitic to an outer zone of propylitic alteration.New LA–ICP-MS zircon U–Pb dating reveals that magmatism in the belt can be divided into three periods during the Middle Devonian and Early Carboniferous, namely the pre-mineralization stage of 390 Ma, syn-mineralization stage of 382–372 Ma, and post-mineralization stage of 350–320 Ma. The syn-mineralization intrusions are calc-alkaline, whereas pre- and post-mineralization intrusions are shoshonitic and high-K calc-alkaline. The syn-mineralization intrusions are enriched in highly incompatible trace elements but depleted in Nb, Ta, Hf and Ti relative to the pre- and post-mineralization intrusions.Zircon trace elements analyses demonstrate a negative correlation between Ti-in-zircon temperatures and oxygen fugacity. Ore-bearing syn-mineralization granitoids are characterized by higher water content, oxygen fugacity and low temperatures with higher mineralization potential than pre- and post-mineralization ones. These characteristics, together with the geochemical signature of the intrusions, suggest that the ore-bearing porphyries are derived from relative high ƒH2O magma reservoir. The remarkably homogeneous Hf isotopic compositions (εHf(t) = 8 to 13) from syn-mineralization intrusions span over 10 m.y., suggesting the existence of a long-lived reservoir beneath Halasu belt during the Middle Devonian. All the intrusions have low initial 87Sr/86Sr values (0.703935 to 0.707172), high εNd(t) values (4.7 to 5.5) and young crustal model ages (650 to 750 Ma). Combined with the mantle-derived Pb isotope characteristics, the Sr–Nd–Hf data suggest that the parental magma was probably derived from flat subduction triggered partial melting of juvenile crust generated during subduction–accretionary process with no significant input of old crust, whereas pre-mineralization and post-mineralization intrusions are supposed to emplaced in immature island arc setting and post-orogenic setting, respectively.  相似文献   

2.
The Chalukou deposit is located in the North Great Xing’an Range of the Xing’an-Mongolia Orogen bordering and to the northeast of the North China Craton. The deposit is a high-F-type porphyry Mo deposit hosted by the Chalukou composite igneous body containing small intrusive bodies genetically related to Mo mineralization. The composite igneous body includes pre-mineralization dolerite, monzogranite and syenogranite, syn-mineralization rhyolitic porphyry, granitic porphyry and fine-grained monzogranite, and post-mineralization rhyolitic porphyry, quartz porphyry, dioritic porphyry and andesitic porphyry. Detailed laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon dating of the igneous components of the composite igneous body was carried out to determine the temporal framework for magmatism in the Chalukou region. The new LA-ICP-MS U-Pb ages constraint documented here, together with the published ages, indicate that there was a protracted porphyry Mo ore-forming event of approximately 7 million years between ca. 152 when the ore related rhyolitic porphyry was emplaced and ca.145 Ma when molybdenite ceased being deposited. The dating reveals that the mineralization is a part of relatively long-lived magmatic cycle involving the emplacement of small doleritic stocks at ca. 165 Ma that progressively evolved into extensive granitic intrusions at ca. 164 Ma, and then diminished with the emplacement of mineralization-related porphyries to ca. 152 Ma. The emplacement of barren Early Cretaceous magmatism, represented by volcanic units in the ca. 136 Ma Guanghua Formation and porphyries, followed the mineralized magmatism.The syn-mineralization porphyry units associated with Mo contain zircons assaying ∼15 times higher in U and Th than the pre-mineralization magmatic phases. This indicates that there was a significant enrichment of Mo, U and Th in the magma, and directly associated with ore fluid exsolution. The return to their normal levels in the three elements in the post-mineralization magmatic phases indicates that they were exhausted from the magma chamber in the later phases. A genetic model is proposed for the enormous introduction of ore metals and enrichment at the Chalukou deposit. The protracted and multiphase igneous activity during the long-lived magmatism reflects a multistage enrichment of metal, and may play a crucial role in the formation of a volatile-enriched, fertile and large-volume magma chamber beneath the Chalukou deposit. Such a chamber is envisaged to be required for the formation of porphyry Mo deposits in general.  相似文献   

3.
黑龙江省岔路口超大型斑岩钼矿床位于大兴安岭北部,是目前我国东北地区最大的钼矿床,矿体赋存于中酸性杂岩体及侏罗系火山-沉积岩内,其中花岗斑岩、石英斑岩、细粒花岗岩与钼矿化关系密切.本文采用LA-ICP-MS锆石U-Pb定年方法,获得了矿区内二长花岗岩、花岗斑岩、石英斑岩、细粒花岗岩、流纹斑岩、闪长玢岩及安山斑岩的结晶年龄分别为162±1.6 Ma、149±4.6 Ma、148±1.6 Ma、148±1.2 Ma、137±3.3 Ma、133±1.7Ma和132±1.6 Ma.岔路口矿区内至少存在3期岩浆活动,其顺序为侏罗纪火山-沉积岩、二长花岗岩→晚侏罗世花岗斑岩、石英斑岩、细粒花岗岩→早白垩世流纹斑岩、闪长玢岩、安山斑岩.岔路口矿床成矿时代为晚侏罗世,是东北亚大陆内部构造-岩浆活化的产物,形成于古太平洋板块俯冲作用引起的挤压向伸展构造体制转折背景,与我国东部大规模钼矿化爆发期相对应.  相似文献   

4.
The newly discovered Chalukou giant porphyry Mo deposit, located in the northern Great Xing’an Range, is the biggest Mo deposit in northeast China. The Chalukou Mo deposit occurs in an intermediate-acid complex and Jurassic volcano-sedimentary rocks, of which granite porphyry, quartz porphyry, and fine-grained granite are closely associated with Mo mineralization. However, the ages of the igneous rocks and Mo mineralization are poorly constrained. In this paper, we report precise in situ LA-ICP-MS zircon U–Pb dates for the monzogranite, granite porphyry, quartz porphyry, fine grained granite, rhyolite porphyry, diorite porphyry, and andesite porphyry in the Chalukou deposit, corresponding with ages of 162 ± 2 Ma, 149 ± 5 Ma, 148 ± 2 Ma, 148 ± 1 Ma, 137 ± 3 Ma, 133 ± 2 Ma, and 132 ± 2 Ma, respectively. Analyses of six molybdenite samples yielded a Re–Os isochron age of 148 ± 1 Ma. These data indicate that the sequence of the magmatic activity in the Chalukou deposit ranges from Jurassic volcano-sedimentary rocks and monzogranite, through late Jurassic granite porphyry, quartz porphyry, and fine-grained granite, to early Cretaceous rhyolite porphyry, diorite porphyry, and andesite porphyry. The Chalukou porphyry Mo deposit was formed in the late Jurassic, and occurred in a transitional tectonic setting from compression to extension caused by subduction of the Paleo-Pacific oceanic plate.  相似文献   

5.
The Yuchiling Mo deposit is a recently discovered giant porphyry system in the East Qinling Mo belt, China. Its apparent causative intrusion, i.e., the Yuchiling granite porphyry, is the youngest intrusion (phase 4) of the Heyu multiphase granite batholith, which was emplaced between 143 and 135 Ma. New robust constraints on the formation of the Yuchiling porphyry Mo system are provided by combined zircon U–Pb, biotite 40Ar/39Ar, and molybdenite Re–Os dating. Zircon grains from the Mo-mineralized granite porphyry yield weighted 206Pb/238U age of 134.0?±?1.4 Ma (n?=?19, 2σ error, MSWD?=?0.30). Magmatic biotite from the same sample yield a 40Ar/39Ar plateau age of 135.1?±?1.4 Ma (2σ error), and an inverse isochron age of 135.6?±?2.0 Ma (n?=?7, 2σ error, MSWD?=?10.8), which are effectively coincident with the zircon U–Pb age within analytical error. Three pulses of mineralization can be deduced from the molybdenite Re–Os ages, namely: ～141, ～137, and ～134 Ma, which agree well with the zircon U–Pb ages of granitic phases 1, 2, and the Yuchiling porphyry (phase 4), respectively. These well-constrained temporal correlations indicate that Mo mineralization was caused by pulses of granitic magmatism, and that the ore-forming magmatic-hydrothermal activity responsible for the Yuchiling porphyry Mo system lasted about 8 Ma. The Yuchiling Mo deposit represents a unique style of porphyry Mo system formed in a post-collision setting, and associated with F-rich, high-K calc-alkaline intrusions, which differ from convergent margin-associated porphyry Mo deposits.  相似文献   

6.
The Wunugetushan porphyry Cu–Mo deposit is located in northeastern China. The deposit lies within the Mongolia–Erguna metallogenic belt, which is associated with the evolution of the Mongol–Okhotsk Ocean. The multiple episodes of magmatism in the ore district, occurred from 206 to 173 Ma, can be divided into pre-mineralization stage (biotite granite), mineralization stage (monzogranitic porphyry and rhyolitic porphyry), and post-mineralization stage (andesitic porphyry). The biotite granite has (87Sr/86Sr)i values of 0.704105–0.704706, εNd(t) values of ?0.67 to ?0.07, and εHf(t) values of ?0.4 to 2.8, yielding Hf two-stage model ages (TDM2) 1250–1067 Ma, and Nd model ages of 1.04–0.96 Ga, indicating that the pre-mineralization magmas were generated by the remelting of Neoproterozoic juvenile crustal material. The monzogranitic porphyry has (87Sr/86Sr)i values of 0.704707–0.706134, εNd(t) values of 0.29–1.33, and εHf(t) values of 1.0–2.9, yielding TDM2 model ages of 1173–1047 Ma. The rhyolitic porphyry has (87Sr/86Sr)i ratio of 0.702129, εNd(t) value of ?0.21, and εHf(t) values of ?0.5 to 7.1, TDM2 model ages from 1269 to 782 Ma. These results show that the magmas of mineralization stage were generated by the partial melting of juvenile crust mixed with mantle-derived components. The andesitic porphyry has (87Sr/86Sr)i ratio of 0.705284, εNd(t) value of 0.82, and εHf(t) values from 4.1 to 7.4, indicating that the post-mineralization magma source contained more mantle-derived material. The Mesozoic Cu–Mo deposits which genetically related to Mongol–Okhotsk Ocean were temporally distributed in Middle to Late Triassic (240–230 Ma), Early Jurassic (200–180 Ma), and Later Jurassic (160–150 Ma) period. The Middle Triassic to Early Jurassic Cu–Mo mineralization was dominated by Mongol–Okhotsk oceanic plate southeast-directed subducted beneath the Erguna massif. The Later Jurassic Cu–Mo mineralization was controlled by the continent–continent collision between Siberia plate and Erguna massif.  相似文献   

7.
The Jiguanshan porphyry Mo deposit is located in the southern part of Xilamulun metallogenic belt at the northern margin of the North China Craton (NCC). In the Jiguanshan mining district, two stages of granitoids intrusions have been recognized: a pre-ore granite porphyry with stockworks and veins of Mo mineralization, and a granite porphyry with disseminated Mo mineralization. Zircon U–Pb data and Hf isotope analyses show that the dissemination-mineralized granite porphyry yielded a weighted mean 206Pb/238U age of 156.0 ± 1.3 Ma, with a crustal εHf(t) values from − 5.6 to + 0.2, and that the main group of magmatic zircons from the pre-ore granite porphyry have a weighted mean 206Pb/238U age of 167.7 ± 1.7 Ma with εHf(t) values from − 3.2 to + 1.0. Combined with groundmass Ar–Ar age data of the granite porphyry and molybdenite Re–Os age, it is suggested that the Mo mineralization of Jiguanshan deposit was formed in the late Jurassic (153 ~ 155 Ma) during tectonic and magmatic events that affected northeast China. The Mo mineralization was a little bit later than the host granite porphyry. Besides disseminated in the host granite porphyry, Mo mineralization also presents in middle Jurassic pre-ore granite porphyry, Jurassic fine-grained diabase, Triassic quartz porphyry, and in rhyolitic volcanic rocks as well as syenite of Devonian age.The Jiguanshan mining district was affected by the tectonic events associated with the Paleo-Asian Ocean closure, and later by far-field tectonism, related to subduction of the Paleo-Pacific plate (Izanagi) in the Jurassic-Cretaceous. The tectonic and thermal events linked with the latter are commonly referred to as Yanshanian tectono-thermal event, and consists of a series of geodynamic, magmatic and ore-forming processes, which in the mining district area included the intrusion of the pre-ore granite porphyry, the host granite porphyry, Mo mineralization, and fine-grained diabase. Major and trace element analyses show that the host granite porphyry is characterized by high silica abundances (SiO2 = 77.16 to 77.51%), high Rb/Sr ratios (13.57 to 14.83), high oxidation (Fe2O3/FeO = 34.25 to 62.00) and high alkalies (Na2O + K2O = 8.21 to 8.38%). Petrographic and microthermometry studies of the fluid inclusions from Mo mineralized veins, characterized by plenty of daughter mineral-bearing inclusions, showed that the predominant homogenization temperatures range from 250 to 440 °C. Combined with Laser Raman analysis of the fluid inclusions, it is indicated that Mo mineralization is related to a high-temperature, hypersaline and high-oxygen fugacity H2O–NaCl fluid system, with high F contents.Based on geology, geochronology, isotope systematics, geochemistry and fluid inclusion studies as well as regional geology, we propose, for the first time, a genetic model for the Jiguanshan porphyry Mo deposit. During the Jurassic geodynamic evolution of northeast China, high silicic, high oxidized and alkaline-rich granitic magma probably derived from partial melting of the lower crust, episodically intruded along faults into the country rocks. This fluid system, fractionating from the highly differentiated granitic magma and bearing Mo with minor Cu metals, migrated upwards and interacted with the older wall rocks and associated fractures, in which the ore minerals precipitated, resulting in the development of what we refer to as the “Jiguanshan-type” porphyry Mo deposit.  相似文献   

8.
The Suyunhe large porphyry Mo deposit (∼0.57 Mt molybdenum), located in the West Junggar, NW China, is the largest known porphyry Mo deposit in Xinjiang. Granitoids in this deposit are mainly characterized by three closely spaced intrusive centers (known as stocks I, II and III respectively). The stocks I and III mainly consist of barren granodiorite porphyry and tonalite porphyry, whereas the stock II is mainly composed of fertile monzonitic granite porphyry and granite porphyry. Based on detailed major and trace element, and Sr–Nd isotopic analyses, two distinct compositional groups can be identified. The first group of high-silica end-members (HSE) is characterized by high SiO2 (mostly >75 wt%), low MgO (0.07–0.69 wt%) and Mg# (0.19–0.36), significant Eu depletion in the chondrite-normalized diagram, and low Sr/Y and La/Yb, as well as noticeably negative anomalies of Ba, Sr, P and Ti in the primitive mantle-normalized diagram. The second group of low-silica end-members (LSE), however, displays adakite-like features with lower SiO2 (<75 wt%), higher MgO (0.52–1.32 wt%) and Mg# (0.32–0.52; mostly >0.4), and higher Sr/Y (mostly >20) and La/Yb (>8). The depleted Sr–Nd isotopic characteristics (εNd(T) = 3.5–6.4 and Isr = 0.7026–0.7055) and young two-stage model ages of HSE and LSE indicate that they were both derived from partial melting of juvenile lower crust that might be triggered by asthenosphere upwelling subsequent to a slab rollback event. However, the depths of initial melting might be different. The current evidence demonstrates that HSE in the Suyunhe deposit formed by partial melting of juvenile crust at depths of less than ∼33 km with a plagioclase residue, whereas that for LSE occurred at depths of >40 km where a garnet residue existed and the crust was thickened. The lower source depth, as well as subsequently strong plagioclase fractionation, results in the absence of adakite-like characteristics in HSE.The Ce4+/Ce3+and EuN/EuN1 ratios in zircons of HSE are much lower than ore-forming intrusions from porphyry Cu deposits in the Central Asian Orogenic Belt, but noticeably higher than barren intrusions from the Lachlan fold belt and ore-bearing intrusions from small-intermediate porphyry Mo deposits from the East Qinling–Dabie and the Nanling metallogenic belts, China, indicating that neither too high nor too low oxygen fugacities are favorable for large porphyry Mo deposits. Based on previous studies of adakitic rocks in the world, adakite-like LSE in the Suyunhe deposit are believed to have higher oxygen fugacities, and thus be less fertile than HSE. We finally suggest that adakites and adakite-like rocks are unproductive for porphyry Mo deposits.  相似文献   

9.
《Resource Geology》2018,68(1):1-21
The 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 ε Nd(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.  相似文献   

10.
The Taoxihu deposit (eastern Guangdong, SE China) is a newly discovered Sn polymetallic deposit. Zircon U-Pb dating yielded 141.8 ± 1.0 Ma for the Sn-bearing granite porphyry and 145.5 ± 1.6 Ma for the biotite granite batholith it intruded. The age of the granite porphyry is consistent (within error) with the molybdenite Re–Os isochron age (139.0 ± 1.1 Ma) of the Sn mineralization, indicating a temporal link between the two. Geochemical data show that the granite porphyry is weakly peraluminous, contain high Si, Na and K, low Fe, Mg, Ca and P, and relatively high Rb/Sr and low K/Rb values. The rocks are enriched in Rb, Th, U, K, and Pb and depleted in Ba, Sr, Ti and Eu, resembling highly fractionated I-type granites. They contain bulk rock initial 87Sr/87Sr of 0.707371–0.707730 and εNd(t) of −5.17 to −4.67, and zircon εHf(t) values from −6.67 to −2.32, with late Mesoproterozoic TDM2 ages for both Nd and Hf isotopes. This suggests that the granite porphyry was likely formed by the partial melting of the crustal basement of Mesoproterozoic overall residence age with minor mantle input.δ34SCDT values of the Taoxihu chalcopyrite and pyrite range from 0.1 to 2.1‰ (average: 0.9‰), implying a dominantly magmatic sulfur source. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the Taoxihu sulfide ores are 18.497–18.669, 15.642–15.673 and 38.764–38.934, respectively, indicating a mainly upper continental crustal lead source with minor mantle contribution. The highly fractionated and reduced (low calculated zircon Ce4+/Ce3+ and EuN/EuN1 values) nature of the ore-forming granitic magma may have facilitated the Sn enrichment and played a key role in the Sn mineralization. We propose that the ore-forming fluids at Taoxihu were of magmatic-hydrothermal origin derived from the granite porphyry, and that both the granite porphyry and the Sn mineralization were likely formed in an extensional setting, possibly related to the subduction slab rollback of the Paleo-Pacific Plate.  相似文献   

11.
The Yangchang granite‐hosted Mo deposit is typical of the Xilamulun metallogenic belt, which is one of the important Mo–Pb–Zn–Ag producers in China. A combination of major and trace element, Sr, Nd and Pb isotope, and zircon U–Pb age data are reported for the Yangchang batholith to constrain its petrogenesis and Mo mineralization. Zircon LA‐ICPMS U–Pb dating yields mean ages of 138 ± 2 and 132 ± 2 Ma for monzogranite and granite porphyry, respectively. The monzogranites and granite porphyries are calc‐alkaline with K2O/Na2O ratios of 0.75–0.92 and 1.75–4.42, respectively. They are all enriched in large‐ion lithophile elements (LILEs) and depleted in high‐field‐strength elements (HFSEs) with negative Nb and Ta anomalies in primitive‐mantle‐normalized trace element diagrams. The monzogranites have relatively high Sr (380–499 ppm) and Y (14–18 ppm) concentrations, and the granite porphyries have lower Sr (31–71 ppm) and Y (5–11 ppm) concentrations than those of monzogranites. The monzogranites and granite porphyries have relatively low initial Sr isotope ratios of 0.704573–0.705627 and 0.704281, respectively, and similar 206Pb/204Pb ratios of 18.75–18.98 and 18.48–18.71, respectively. In contrast, the εNd(t) value (−3.7) of granite porphyry is lower than those of monzogranites (−1.5 to −2.7) with Nd model ages of about 1.0 Ga. These geochemical features suggest that the monzogranite and granite porphyries were derived from juvenile crustal rocks related to subduction of the Paleo‐Pacific plate under east China. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

12.
The Chalukou porphyry Mo deposit, located in the northern Great Xing'an Range, is the largest Mo deposit in the Xing'an–Mongolia orogenic belt. Its ore bodies are mainly hosted in the intermediate-felsic complex and Jurassic volcanic sedimentary rocks, of which Late Jurassic granite porphyry, quartz porphyry and fine-grained granite are closely associated with Mo mineralization. The Middle Jurassic monzogranite belongs to shoshonite series, with SiO2 and Al2O3 contents of 69.48 to 74.98% and 12.35 to 14.48%, respectively. The total alkali (K2O + Na2O) content ranges from 7.67 to 10.42%, with K2O/Na2O ratios between 1.07 and 2.81. These rocks are strongly enriched in Rb and K but are depleted in Ta, Nb, P and Ti, with negative Eu anomalies and positive εHf(t). The Late Jurassic granite porphyry, quartz porphyry and fine-grained granite are shoshonite or high-K calc-alkaline series. Their SiO2 and Al2O3 contents range from 73.87 to 78.95% and 10.35 to 13.47%, respectively. The total alkali (K2O + Na2O) contents range from 8.06 to 10.02%, with K2O/Na2O ratios from 1.03 to 8.20. These rocks are strongly enriched in Rb, K and Th, but are depleted in P, Ti, Ba and Sr, indicating clear negative Eu anomalies and positive εHf(t). The Middle–Late Jurassic granitoids in the Chalukou deposit are highly fractionated I-type granitoids, and derived from juvenile lower crust materials that originated from the Neoproterozoic depleted mantle. These granitoids formed in the extension tectonic setting of the post-collision stage of the Mongol–Okhotsk orogenic belt, probably superposed by the back-arc extension related to the subduction of the Paleo-Pacific Plate.  相似文献   

13.
The northeastern Gangdese Pb–Zn–Ag–Fe–Mo–W polymetallic belt (NGPB), characterized by skarn and porphyry deposits, is one of the most important metallogenic belts in the Himalaya–Tibetan continental orogenic system. This belt extends for nearly four hundred kilometers along the Luobadui–Milashan Fault in the central Lhasa subterrane, and contains more than 10 large ore deposits with high potential for development. Three major types of mineralization system have been identified: skarn Fe systems, skarn/breccia Pb–Zn–Ag systems, and porphyry/skarn Mo–Cu–W systems. In this study, we conducted a whole-rock geochemical, U–Pb zircon geochronological, and in situ zircon Hf isotopic study of ore-forming rocks in the NGPB, specifically the Jiangga, Jiaduopule, and Rema skarn Fe deposits, and the Yaguila Pb–Zn–Ag deposit. Although some of these deposits (porphyry Mo systems) formed during the post-collisional stage (21–14 Ma), the majority (these three systems) developed during the main (‘soft collision’) stage of the India–Asia continental collision (65–50 Ma). The skarn Fe deposits are commonly associated with granodiorites, monzogranites, and granites, and formed between 65 and 50 Ma. The ore-forming intrusions of the Pb–Zn–Ag deposits are characterized by granite, quartz porphyry, and granite porphyry, which developed in the interval of 65–55 Ma. The ore-forming porphyries in the Sharang Mo deposit, formed at 53 Ma. The rocks from Fe deposits are metaluminous, and have relatively lower SiO2, and higher CaO, MgO, FeO contents than the intrusions associated with Mo and Pb–Zn–Ag mineralization, while the Pb–Zn–Ag deposits are peraluminous, and have high SiO2 and high total alkali concentrations. They all exhibit moderately fractionated REE patterns characterized by lower contents of heavy REE relative to light REE, and they are enriched in large-ion lithophile elements and relatively depleted in high-field-strength elements. Ore-forming granites from Fe deposits display 87Sr/86Sr(i) = 0.7054–0.7074 and εNd(t) = − 4.7 to + 1.3, whereas rocks from the Yaguila Pb–Zn–Ag deposit have 87Sr/86Sr(i) = 0.7266–0.7281 and εNd(t) = − 13.5 to − 13.3. In situ Lu–Hf isotopic analyses of zircons from Fe deposits show that εHf(t) values range from − 7.3 to + 6.6, with TDM(Hf)C model ages of 712 to 1589 Ma, and Yaguila Pb–Zn–Ag deposit has εHf(t) values from − 13.9 to − 1.3 with TDM(Hf)C model ages of 1216 to 2016 Ma. Combined with existing data from the Sharang Mo deposit, we conclude that the ore-forming intrusions associated with the skarn Fe and porphyry Mo deposits were derived from partial melting of metasomatized lithospheric mantle and rejuvenated lower crust beneath the central Lhasa subterrane, respectively. Melting of the ancient continental material was critical for the development of the Pb–Zn–Ag system. Therefore, it is likely that the source rocks play an important role in determining the metal endowment of intrusions formed during the initial stage of the India–Asia continental collision.  相似文献   

14.
The Haisugou Mo deposit is located in the northern part of the Xilamulun Mo–Cu metallogenic belt in northeastern China. The Mo mineralization mainly occurs as quartz-molybdenite veins within the Haisugou granite, which was emplaced into rocks of the Early Permian Qingfengshan Formation. Zircon U–Pb dating by LA–ICP-MS of the granite yields a crystallization age of 137.6 ± 0.9 Ma, suggesting emplacement during the peak time of Mo mineralization in eastern China, broadly constrained to ca. 150–130 Ma, when tectonic stresses shifted from compression to extension. Whole-rock geochemical data suggest that the granite belongs to the high-K calc-alkaline series, and is characterized by relatively high LREE; low HREE; depletion of Ti, Ba, and Nb; and a moderate negative Eu anomaly. The zircon εHf(t) and whole-rock εNd(t) values for the intrusion range from +4.5 to +10.0 and +0.2 to +1.6, respectively, indicating that the magma originated from the juvenile lower crust source derived from depleted mantle, with some component of ancient continental crust. The granite is also characterized by initial (87Sr/86Sr)i ratios ranging from 0.7040 to 0.7074, which suggest some contamination by the upper crust during the ascent of the primitive magma. Moreover, it can be recognized from the whole-rock major and trace element data that significant fractional crystallization occurred during magmatic evolution, with the separation of plagioclase and K-feldspar. Because Mo is an incompatible element and tends to concentrate in the melt during crystallization, fractionation processes likely played an important role in the formation of the Haisugou Mo deposit.  相似文献   

15.
十二排钼矿床位于上杭-云霄断裂带与闽西南拗陷的复合部位,是紫金山铜金矿田外围新近探明的一处具有中大型远景的斑岩型钼矿床。野外地质调查显示,其钼矿化呈细脉状、网脉状主要产出于黑云母二长花岗岩和黑云母花岗斑岩中。热液蚀变具有斑岩型矿床的分带特征,由黑云母花岗斑岩向外依次发育钾硅酸盐化带、绢英岩化带和青磐岩化带,钼矿体主要赋存于绢英岩化与钾硅酸盐化构成的叠加带中。锆石U-Pb定年结果表明,黑云母二长花岗岩和黑云母花岗斑岩分别形成于(143.1±0.9)Ma和(143.5±0.4)Ma。4件辉钼矿样品的Re-Os加权平均年龄为(143.9±2.1)Ma。辉钼矿的w(Re)为1.2×10~(-6)～7.8×10~(-6),说明成矿物质可能主要来自地壳。岩石地球化学分析结果显示,十二排含矿花岗岩具有相似的主量和微量元素组成,均属于弱过铝质高钾钙碱性I型花岗岩,其中,黑云母花岗斑岩表现出高分异花岗岩特征,两者可能是古老变质基底来源的熔体经历不同程度分异结晶的产物,并混入有少量幔源物质。综合已有的资料,文章认为十二排斑岩型钼矿化与早白垩世早期花岗质岩浆活动密切相关,上杭-云霄断裂带存在古太平洋板块俯冲后撤引发构造体制转换阶段的成岩成矿响应,进一步找矿勘查工作应加强评价早白垩世早期高分异花岗岩体的钼多金属成矿潜力。  相似文献   

16.
Extensive Early Cretaceous post-collisional igneous rocks, especially the large volume of granitoids developed in the Dabie orogen. Some of these granitic rocks are spatially, temporally, and genetically associated with economically important molybdenum deposits. The Tangjiaping large-scale (> 0.1 million ton) porphyry Mo deposit is located in the northwest of the Northern Dabie Complex unit. The Mo mineralization is mainly hosted in molybdenite-bearing quartz veinlets and stockworks in the Tangjiaping granite porphyry, which intruded into Proterozoic biotite-plagioclase gneiss and amphibole-plagioclase gneiss. Two alteration zones from the porphyry centre outwards and downwards can be recognized: (1) K-silicate alteration-silicification zone; (2) silicification-phyllic alteration zone. The Tangjiaping ore-bearing granite porphyry occurs as an individual stock with an outcrop of 0.4 km2. LA-ICP-MS zircon U-Pb dating of the Tangjiaping granite porphyry yields crystallization age of 115 ± 1 Ma, which is consistent with the molybdenite Re-Os age of the deposit given by previous studies. The Tangjiaping granitic rocks are metaluminous and belong to high-K calc-alkaline and shoshonitic series. They are relatively enriched in light rare earth elements and have moderately negative Eu anomalies. Geochemical and mineralogical characteristics indicate that the Tangjiaping granite is an A-type granite and was generated by partial melting of intermediate-felsic rocks at pressures of ca. 0.4–0.8 GPa. There are high initial 87Sr/86Sr ratios ranging from 0.707367 to 0.709410 and negative εNd(t) values varying from − 15.0 to − 14.2 for the Tangjiaping granite. In situ zircon Hf isotopic analyses show that the εHf(t) values of zircons from the Tangjiaping granite porphyry vary from − 17.0 to − 6.0. The geochemical data and Sr-Nd-Hf isotopes, coupled with the Neoproterozoic inherited zircon age (652 ± 21 Ma), indicate that the Tangjiaping granite porphyry was most likely derived from partial melting of the Northern Dabie gneiss with some relatively enriched mantle materials involved. The Tangjiaping Mo ore-forming granite porphyry was formed in an extensional setting. The Early Cretaceous asthenospheric upwelling might have played an important role in the formation of the approximately coeval Mo-bearing magmas in the Dabie orogen.  相似文献   

17.
Given that the Duobuza deposit was the first porphyry Cu–Au deposit discovered in central Tibet, the mineralization and mineralized porphyry in this area have been the focus of intensive research, yet the overall porphyry sequence associated with the deposit remains poorly understood. New geological mapping, logging, and sampling of an early granodiorite porphyry, an inter-mineralization porphyry, and a late-mineralization diorite porphyry were complemented by LA–ICP–MS zircon dating, whole-rock geochemical and Sr–Nd isotopic analyses, and in situ Hf isotopic analyses for both inter- and late-mineralization porphyry intrusions. All of the porphyry intrusions are high-K and calc-alkaline, and were emplaced at ca. 120 Ma. The geochemistry of these intrusions is indicative of arc magmatism, as all three porphyry phases are enriched in light rare earth elements and large ion lithophile elements, and depleted in heavy rare earth elements and high field strength elements. These similar characteristics of the intrusions, when combined with the relatively high (87Sr/86Sr)i, negative εNd(t), and positive εHf(t) values, suggest that the magmas that formed the porphyries were derived from a common source region and shared a single magma chamber. The magmas were generated by the mixing of upwelling metasomatized mantle-wedge-derived mafic magmas and magmas generated by partial melting of amphibolite within the lower crust.The inter-mineralization porphyry has the lowest εNd(t) and highest (87Sr/86Sr)i values, suggesting that a large amount of lower-crust-derived material was incorporated into the melt and that metals such as Cu and Au from the enriched lower crust were scavenged by the parental magma. The relative mafic late-mineralization diorite porphyry phase was formed by the residual magma in the magma chamber mixing with upwelling mafic melt derived from metasomatized mantle. The magmatic–hydrothermal evolution of the magma in the chamber released ore-forming fluid that was transported mainly by the inter-mineralization porphyry phase during the mineralization stage, which ultimately formed the Duobuza porphyry Cu–Au deposit.These porphyritic intrusions of the Duobuza deposit have high Mg# and low (La/Yb)N values, and show some high LILE/HFSE ratios, indicating the magma source was enriched by interaction with slab-derived fluids. Combined with age constraints on the regional tectonic evolution, these dating and geochemical results suggest that the Duobuza porphyry Cu–Au deposit formed in a subduction setting during the final stages of the northward subduction of the Neo-Tethyan Ocean.  相似文献   

18.
Sharang is a low-fluorine, calc-alkaline porphyry Mo deposit hosted mainly in a granite porphyry of a multi-stage plutonic complex in the northern Gangdese metallogenic belt, largely with stockwork and ribbon-textured mineralization. The observed age estimates suggest that the formation of the magmatic host complex (52.9–51.6 Ma) and the ore deposit itself (52.3 Ma) occurred during the main stage of the India–Asia collision. The host rocks are characterized by lower zircon εHf(t) values than those of the pre-ore and post-ore rocks. This suggests that the Lhasa terrane basement might play an important role in the formation of Sharang ore-forming intrusions. In view of the framework of magmatic–metallogenic events we suggest that slab roll-back may have induced melting of juvenile crust and ancient continental complexes during the India–Asia collision. This proposal focuses exploration for additional molybdenum deposits on the collision zone.  相似文献   

19.
The Gaijing Pb–Zn–Mo deposit and Shapinggou Mo deposit in the Yinshan region, Jinzhai, Anhui province, China, are hosted in various granitic intrusions with 40Ar/39Ar ages obtained for biotite and hornblende of 136.8 ± 1.6 Ma (medium-grained monzogranite), 130.4 ± 1.2 Ma (fine-grained granite), and 125.4 ± 1.0 Ma (fine-grained diorite). The modes of occurrence and cross-cutting relationships among the igneous intrusions indicate that alkali quartz-syenite and quartz-syenite porphyry (cryptoexplosive breccia) formed later than the calc-alkali monzogranite, granite, and diorite. Molybdenum mineralization occurs in pipe-like bodies hosted in cryptoexplosive breccia (pipe), quartz-syenite (porphyry), monzogranite, and granite, whereas Pb–Zn mineralization occurs in veins distally from the Mo mineralization. The Re–Os isotopic model ages of molybdenite from the Gaijing Pb–Zn–Mo deposit are 112.6 ± 1.3 and 113.5 ± 1.3 Ma, consistent with the ages of other molybdenum deposits throughout the East Qinling–Dabie metallogenic belt. The geological characteristics and isotopic ages of the Gaijing Pb–Zn–Mo and Shapinggou Mo deposits indicate a genetic relationship to the emplacement of the quartz-syenite (porphyry) and to shallow-seated porphyry–cryptoexplosive breccia intrusions. The present results, combined with existing data, suggest that the Pb–Zn–Mo deposits and related igneous rocks were formed in a geodynamic setting of regional lithospheric thinning, delamination, and thermal erosion in East China. The deposits are part of the East Qinling–Dabie molybdenum belt, which in turn is part of a large-scale E–W-trending metallogenic belt in East China.  相似文献   

20.
《International Geology Review》2012,54(10):1261-1279
The eastern Qinling belt is characterized by widespread Mesozoic post-orogenic magmatism and abundant Mo–(Au–Ag) polymetallic mineralization. Most Mo deposits in this belt are genetically related to Mesozoic granitoids. The tectonic context of this close spatial and temporal relationship is still debated. This study reports U–Pb ages and Hf isotopic composition of zircons, major and trace element and Sr–Nd–Pb isotopic composition of the Donggou granite porphyry, host rock to one of the important Mesozoic Mo deposits in this orogen. Based on geochemical results, the Donggou granite porphyry is a silica-supersaturated, high-K metaluminous A-type granite showing enrichment in light REEs, depletion in middle REEs and significant negative Eu, Ba, Nb, Sr, P, and Ti anomalies. Negative initial ?Nd values of??17.0 to??13.2 for whole-rock and negative initial ?Hf values of??19.9 to??7.8 for zircon suggest that the magma was derived from a mixture of Archaean/Proterozoic crustal rocks and mantle-derived or newly added crust. Its Pb isotopic composition is similar to the lower crust of the North China block, but different from superjacent country rocks (Xiong'er and Taihua Groups). Zircon U–Pb dating yields a late Mesozoic emplacement age of 118–117 Ma, identical with the third episode of Mo mineralization in the eastern Qinling–Dabie belt. We postulate that the Donggou Mo-related porphyry granite formed by reworking of North China lower crust with significant input of juvenile material. The magmas formed in an extensional tectonic setting, induced by lithospheric thinning and asthenospheric upwelling beneath eastern China during Cretaceous time.  相似文献   

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