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1.
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   

2.
The recently discovered Toki cluster, which includes the Toki, Quetena, Genoveva, Miranda, and Opache porphyry Cu–Mo prospects, is located 15 km south–southwest of the Chuquicamata–Radomiro Tomic mines in northern Chile. These prospects occur in an area of 5?×?6 km and are completely covered with Neogene alluvial deposits. Inferred resources for the cluster are estimated at about 20 Mt of fine copper, with Toki and Quetena contributing ～88 % of these resources. Mineralization in these deposits is associated with tonalite porphyries that intruded andesites and dacites of the Collahuasi Group and intrusions of the Fortuna–Los Picos Granodioritic Complex. Hypogene mineralization in the Toki cluster consists mainly of chalcopyrite–bornite with minor molybdenite with mineralization grading outward to a chalcopyrite–pyrite zone and ultimately to a pyrite halo. Alteration is dominantly of the potassic type with K-feldspar and hydrothermal biotite. Sericitic alteration is relatively restricted to late quartz–pyrite veins (D-type veins). Previous K–Ar geochronology for the cluster yielded ages within a range of 34 to 40 Ma. Four new Re–Os ages for Toki indicate that molybdenite mineralization occurred in a single pulse at ～38 Ma. Re–Os ages for three different molybdenite samples from Quetena are within error of the Toki mineralization ages. These ages are concordant with a new zircon U–Pb age of 38.6?±?0.7 Ma from the tonalite porphyry in Quetena. Two Re–Os ages for Genoveva (38.1?±?0.2 and 38.0?±?0.2 Ma) are also within error of the Toki and Quetena molybdenite ages. Four Re–Os molybdenite ages for Opache range between 36.4 and 37.6 Ma. The Miranda prospect is the youngest with an age of ～36 Ma. Four new Re–Os ages for the Chuquicamata deposit range between 33 and 32 Ma, whereas nine new 40Ar/39Ar ages of biotite, muscovite, and K-feldspar range between 32 and 31 Ma. Analyzed molybdenites have Re and Os concentrations that vary between 21–3,099 ppm and 8–1,231 ppb, respectively. The highest Re and Os concentrations are found in the Toki prospect. Three new 40Ar/39Ar ages for the Toki cluster are younger than the Re–Os mineralization ages. The age spectra for these three samples show evidence of excess argon and have similar inverse isochron ages of 35 Ma that probably reflect a late hydrothermal phyllic event. The new geochronological data presented here for the Toki cluster indicate that molybdenite mineralization occurred within a very short period, probably within 2 Ma, and synchronously (at ～38 Ma) in three mineralization centers (Toki, Quetena, and Genoveva). Furthermore, mineralization at the Toki cluster preceded the emplacement of the Chuquicamata deposit (35–31 Ma) and indicates that porphyry Cu–Mo mineralization occurred episodically over a period of several million years in the Chuquicamata district.  相似文献   

3.
Jilin Province in NE China lies on the eastern edge of the Xing–Meng Orogenic Belt. Mineral exploration in this area has resulted in the discovery of numerous large, medium, and small sized Cu, Mo, Au, and Co deposits. To better understand the formation and distribution of both the porphyry and skarn types Cu deposits of the region, we examined the geological characteristics of the deposits and applied zircon U–Pb and molybdenite Re–Os isotope dating to constrain the age of the mineralization. The Binghugou Cu deposit yields a zircon U–Pb age for quartz diorite of 128.1 ± 1.6 Ma; the Chang'anpu Cu deposit yields a zircon U–Pb age for granite porphyry of 117.0 ± 1.4 Ma; the Ermi Cu deposit yields a zircon U–Pb age for granite porphyry of 96.8 ± 1.1 Ma; the Tongshan Cu deposit yields molybdenite Re–Os model ages of 128.7 to 130.2 Ma, an isochron age of 129.0 ± 1.6 Ma, and a weighted mean model age of 129.2 ± 0.7 Ma; and the Tianhexing Cu deposit yields molybdenite Re–Os model ages of 113.9 to 115.2 Ma, an isochron age of 114.7 ± 1.2 Ma, and a weighted mean model age of 114.7 ± 0.7 Ma. The new ages, combined with existing geochronology data, show that intense porphyry and skarn types Cu mineralization was coeval with Cretaceous magmatism. The geotectonic processes responsible for the genesis of the Cu mineralization were probably related to lithospheric thinning. By analyzing the accumulated molybdenite Re–Os, zircon U–Pb, and Ar–Ar ages for NE China, it is concluded that the Cu deposits formed during multiple events coinciding with periods of magmatic activity. We have identified five phases of mineralization: early Paleozoic (~476 Ma), late Paleozoic (286.5–273.6 Ma), early Mesozoic (~228.7 Ma), Jurassic (194.8–137.1 Ma), and Cretaceous (131.2–96.8 Ma). Although Cu deposits formed during each phase, most of the Cu mineralization occurred during the Cretaceous.  相似文献   

4.
《International Geology Review》2012,54(12):1481-1491
ABSTRACT

Liaoning Province in China is an area known for the occurrence of numerous copper and/or molybdenum deposits of variable size. However, the age of mineralization and tectonic setting in this region are still a subject of debate. In this study we describe the geology of these deposits and apply zircon U–Pb and molybdenite Re–Os isotopic dating to constrain their ages and define the metallogenic epochs of this province. The Huatong Cu–Mo deposit yields molybdenite Re–Os model ages of 127.6–126.3 Ma and an isochron age of 127.4 ± 0.7 Ma. The Dongbeigou Mo deposit yields molybdenite Re–Os model ages of 132.6–127.1 Ma, an isochron age of 128.1 ± 5.1 Ma, and a zircon U–Pb age of 129.4 ± 0.3 Ma for the associated monzogranite. The granodiorite associated with the Wanbaoyuan Cu–Mo deposit yields a zircon U–Pb age of 128.4 ± 1.1 Ma; the plagiogranite associated with the Yaojiagou Mo deposit yields an age of 167.5 ± 0.9 Ma; and the biotite–plagioclase gneiss from the Shujigou Cu deposit yields an age of 2549.4 ± 5.6 Ma. These results, together with previous geochronology data, show that intense Cu–Mo porphyry and skarn mineralization were coeval with Early–Middle Jurassic and Early Cretaceous granitic magmatism. The former was associated with the orogeny that followed the collision of the Siberian and North China plates and the resulting closure of the palaeo-Asian Ocean, and the latter with rifting that followed the subduction of the palaeo-Pacific Plate and associated lithospheric thinning. Volcanogenic massive sulfide Cu deposit. mineralization took place much earlier, in the late Archaean, and was related to continent–continent collision, palaeo-ocean closure, the formation of a united continental landmass, bimodal volcanism, magma emplacement, and subsequent metamorphism and deformation of syn-collisional granites.  相似文献   

5.
The Tudun deposit is a medium-sized Cu–Ni sulfide deposit, located at the westernmost edge of the Huangshan–Jing’erquan Belt in the northern part of Eastern Tianshan, NW China. Sulfide separates including pentlandite, pyrrhotite and chalcopyrite from the Tudun deposit, contain Re, common Os and 187Os ranging from 40.46 to 201.2, 0.8048 to 6.246 and 0.1709 to 0.9977 ppb, respectively. They have very low 187Os/188Os ratios of 1.224–2.352. The sulfides yield a Re–Os isochron age of 270.0 ± 7.5 Ma (MSWD = 1.3), consistent within uncertainty with the SHRIMP zircon U–Pb age for the Tudun mafic intrusion (gabbro) of 280.0 ± 3.0 Ma. The calculated initial 187Os/188Os ratio is 0.533 ± 0.022, and γOs values range from 283 to 307, with a mean of 297, indicating significant crustal contamination of the parent melt prior to sulfide saturation. The Tudun deposit shares the same age and Re–Os isotopic compositions with other orthomagmatic Cu–Ni sulfide deposits in Huangshan–Jing’erquan Belt, suggesting that they have formed in Early Permian.  相似文献   

6.
《International Geology Review》2012,54(14):1763-1785
Central Jilin Province lies along the eastern edge of the Xing–Meng orogenic belt of northeast China. At least 10 Mo deposits have been discovered in this area, making it the second-richest concentration of Mo resources in China. To better understand the formation and distribution of porphyry Mo deposits in the area, we investigated the geological characteristics of the deposits and applied zircon U–Pb and molybdenite Re–Os isotope dating to constrain the age of mineralization. Our new geochronological data show the following: the Jidetun Mo deposit yields molybdenite Re–Os model ages of 164.6–167.1 Ma, an isochron age of 168 ± 2.5 Ma, and a weighted mean model age of 165.9 ± 1.2 Ma; the Houdaomu Mo deposit yields molybdenite Re–Os model ages of 167.4–167.7 Ma, an isochron age of 168 ± 13 Ma, and a weighted mean model age of 167.5 ± 1.2 Ma; and the Chang’anpu Mo deposit yields a zircon U–Pb age for granodiorite porphyry of 166.9 ± 1.5 Ma (N = 16). These new age data, combined with existing molybdenite Re–Os dates, show that intense porphyry Mo mineralization was coeval with magmatism during the Middle Jurassic (167.8 ± 0.4 Ma, r > 0.999). The geotectonic mechanisms responsible for Mo mineralization were probably related to subduction of the Palaeo-Pacific plate beneath the Eurasian continent. Combining published molybdenite Re–Os and zircon U–Pb ages for northeast China, the Mo deposits are shown to have been formed during multiple events coinciding with periods of magmatic activity. We identified three phases of mineralization, two of which had several stages: the Caledonian (485–480 Ma); the Indosinian comprising the Early–Middle Triassic (248–236 Ma) and Late Triassic (226–208 Ma) stages; and the Yanshanian phase comprising the Early–Middle Jurassic (202–165 Ma), Late Jurassic–early Early Cretaceous (154–129 Ma), and Early Cretaceous (114–111 Ma) stages. Although Mo deposits formed during each phase/stage, most of the mineralization occurred during the Early–Middle Jurassic.  相似文献   

7.
The recently discovered Taolaituo porphyry Mo deposit and Aobaotu hydrothermal vein Pb–Zn deposit are both located in the Great Xing’an Range, Northeast China. Here we present new zircon U–Pb ages, whole-rock geochemical and Pb isotopic data, and molybdenite Re–Os ages for these two deposits. The Mo mineralization in the Taolaituo area occurred in quartz porphyry, which yields zircon U–Pb ages ranging from 138.5 ± 0.8 to 139.1 ± 0.5 Ma. Fine-grained granite representing pre-mineralization magmatic activity was formed at 145.2 ± 0.5 Ma. Molybdenite Re–Os dating indicates that Mo mineralization occurred at 133.8 ± 1.2 Ma. In the Aobaotu deposit, the ore-related granodioritic porphyry has a zircon U–Pb age of 140.0 ± 0.4 Ma. These geochronological data indicate that these magmatic and hydrothermal activities occurred during the Early Cretaceous. The mineralogical and geochemical features of the Taolaituo and Aobaotu granitoids suggest they can be classified as A1-type within-plate anorogenic granites and I-type granites, respectively. The Pb isotopic compositions suggest a mixed crust–mantle origin of the granitoids in these two deposits. The Taolaituo granitoids were formed by the partial melting of lower crust and crust–mantle interaction, with subsequent fractionation of apatite, feldspar, Ti-bearing phases and allanite or monazite. In contrast, the Aobaotu granites were derived primarily from lithospheric mantle that had been transformed or affected by the addition of subduction-related components. Combined with the regional geology, tectonic evolution and available age data from the literature, our results suggest that the Early Cretaceous (140–100 Ma) was likely to be the most important peak period for metallogenic mineralization in Northeast China. The Taolaituo and Aobaotu deposits formed under an extensional environment at an active continental margin in response to subduction of the Palaeo-Pacific oceanic plate.  相似文献   

8.
The genesis of mineralized systems across the Mountain Freegold area, in the Dawson Range Cu–Au?±?Mo Belt of the Tintina Au province was constrained using Pb and stable isotope compositions and Ar–Ar and Re–Os geochronology. Pb isotope compositions of sulfides span a wide compositional range (206Pb/204Pb, 18.669–19.861; 208Pb/204Pb, 38.400–39.238) that overlaps the compositions of the spatially associated igneous rocks, thus indicating a magmatic origin for Pb and probably the other metals. Sulfur isotopic compositions of sulfide minerals are broadly similar and their δ34S (Vienna-Canyon Diablo Troilite (V-CDT)) values range from ?1.4 to 3.6 ‰ consistent with the magmatic range, with the exception of stibnite from a Au–Sb–quartz vein, which has δ34S values between ?8.1 and ?3.1 ‰. The δ34S values of sulfates coexisting with sulfide are between 11.2 and 14.2 ‰; whereas, those from the weathering zone range from 3.7 to 4.3 ‰, indicating supergene sulfates derived from oxidation of hypogene sulfides. The δ13C (Vienna Peedee Belemnite (VPDB)) values of carbonate range from ?4.9 to 1.1 ‰ and are higher than magmatic values. The δ18O (V-SMOW) values of magmatic quartz phenocrysts and magmatic least-altered rocks vary between 6.2 and 10.1 ‰ and between 5.0 and 10.1 ‰, respectively, whereas altered magmatic rocks and hydrothermal minerals (quartz and magnetite) are relatively 18O-depleted (4.2 to 7.9 ‰ and ?6.3 to 1.5 ‰, respectively). Hydrogen isotope compositions of both least-altered and altered igneous rock samples are D-depleted (from ?133 to ?161 ‰ Vienna-Standard Mean Ocean Water (V-SMOW)), consistent with differential magma degassing and/or post-crystallization exchange between the rocks and meteoric ground water. Zircon from a chlorite-altered dike has a U–Pb crystallization age of 108.7?±?0.4 Ma; whereas, the same sample yielded a whole-rock Ar–Ar plateau age of 76.25?±?0.53 Ma. Likewise, molybdenite Re–Os model ages range from 75.8 to 78.2 Ma, indicating the mineralizing events are genetically related to Late Cretaceous volcano-plutonic intrusions in the area. The molybdenite Re–Os ages difference between the nearby Nucleus (75.9?±?0.3 to 76.2?±?0.3 Ma) and Revenue (77.9?±?0.3 to 78.2?±?0.3 Ma) mineral occurrences suggests an episodic mineralized system with two pulses of hydrothermal fluids separated by at least 2 Ma. This, in combination with geological features suggest the Nucleus deposit represents the apical and younger portion of the Revenue–Nucleus magmatic-hydrothermal system and may suggest an evolution from the porphyry to the epithermal environments.  相似文献   

9.
ABSTRACT

The Zhongtiao Mountain region is endowed with some of the largest Cu deposits in northern China, among which the Tongkuangyu Cu deposit contains 70% of the total reserves of copper. The orebodies in this deposit are confined to metamorphosed volcanic tuff and monzogranitic porphyry which are enclosed within metasediments. Metamorphism and deformation resulted in intense modification of the deposit, leading to debates surrounding its genesis. In this study, we investigate the lithology, hydrothermal alteration, and mineralization in the deposit. Secondary ion mass spectrometer and laser ablation ICPMS zircon U–Pb dating show that the meta-monzogranitic porphyry was emplaced contemporaneous with the surrounding lithologies at 2180–2190 Ma as a sill, and that the basic volcanic rocks erupted slightly earlier at ~2220 Ma. The Re–Os geochronological data on molybdenite from the deposit constrain the timing of copper mineralization to 2122 ± 12 Ma. Together with published information from previous studies on this region, we infer that during ~2100–2200 Ma the Zhongtiao Mountain region experienced continental or back-arc rifting. We exclude a porphyry copper model for the deposit and favour sediment-hosted stratiform explanation for this deposit.  相似文献   

10.
《International Geology Review》2012,54(11):1357-1376
The Jiazishan porphyry-type molybdenum deposit is located in the eastern Inner Mongolia Autonomous Region in China. Mineralization occurs mainly as veins, lenses, and layers within the host porphyry. To better understand the link between mineralization and host igneous rocks, we studied samples from underground workings and report new SHRIMP II zircon U–Pb and Re–Os molybdenite ages, and geochemical data from both the molybdenites and the porphyry granites. Seven molybdenite samples yield a Re–Os isochron weighted mean age of 135.4 ± 2.1 Ma, whereas the porphyry granite samples yield crystallization ages of 139 ± 1.5 Ma (Jiazishan deposit) and 133 ± 1 Ma (Taolaituo deposit). The U–Pb and Re–Os ages are similar, suggesting that the mineralization is genetically related to Early Cretaceous porphyry emplacement. Re contents of the molybdenite range from 21.74 ppm to 52.08 ppm, with an average of 35.92 ppm, whereas δ34 S values of the sulphide vary from 1.3‰ to 4.2‰. The ores have 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.178–18.385, 15.503–15.613, and 37.979–38.382, respectively. We also obtained a weighted mean U–Pb zircon age of 294.2 ± 2.1 Ma for the oldest granite in Jiazishan area. All granites are A-type granites. These observations indicate that the molybdenites and the porphyry granites were derived from a mixed source involving young accretionary materials and enriched subcontinental lithospheric mantle. A synthesis of geochronological and geological data reveals that porphyry emplacement and Mo mineralization in the Jiazishan deposit occurred contemporaneously with Early Cretaceous tectonothermal events associated with lithospheric thinning, which was caused by delamination and subsequent upwelling of the asthenosphere associated with intra-continental extension in Northeast China.  相似文献   

11.
The Qianhe gold deposit in the Xiong’ershan area is located along the southern margin of the Archean-Paleoproterozoic North China Craton. The deposit consists of six orebodies that are hosted in Paleoproterozoic andesites to basaltic andesites and structurally controlled by roughly EW-trending faults. Individual orebodies comprise auriferous quartz veins and disseminated Au-bearing pyrite within hydrothermally altered rocks on both sides of, or close to, the veins. Ore-related hydrothermal alteration has produced various mixtures of K-feldspar, quartz, sericite, chlorite, epidote, carbonate, and sulfides. Pyrite is the most important ore mineral, associated with minor amounts of galena, sphalerite, and chalcopyrite. Other trace minerals include molybdenite, arsenopyrite, scheelite, rutile, xenotime, and parisite. Gold occurs mostly as native gold and electrum enclosed in pyrite or along microfractures of sulfides and quartz. Microthermometric measurements of primary inclusions in auriferous quartz suggest that gold and associated minerals were precipitated in the range of 160–305 °C from aqueous or carbonic-aqueous fluids with salinities of 6–22 wt% NaCl equiv. Samples of molybdenite coexisting with Au-bearing pyrite have Re–Os model ages of 134–135 Ma, whereas ore-related hydrothermal sericite separates yield 40Ar/39Ar plateau ages between 127 and 124 Ma. The Re–Os and 40Ar/39Ar ages are remarkably consistent with zircon U–Pb ages (134.5?±?1.5 and 127.2?±?1.4 Ma; 1σ) of the biotite monzogranite from the Heyu-intrusive complex and granitic dikes in and close to the Qianhe gold mine, indicating a close temporal and thus possibly genetic relationship between gold mineralization and granitic magmatism in the area. Fluid inclusion waters extracted from auriferous quartz have δD values of ?80 to ?72 ‰, whereas the calculated δ 18OH2O values range from 3.1 to 3.8 ‰. The hydrogen and oxygen isotopes from this study and previous work indicate that ore fluids were likely derived from degassing of magmas, with addition of minor amounts of meteoric water. Gold mineralization at Qianhe is temporarily coincident with pervasive bimodal magmatism, widespread fault-basin formation, and well development of metamorphic core complexes in the whole eastern North China Craton that have been interpreted as reflecting reactivation of the craton in the late Mesozoic after prolonged stabilization since its formation in the late Paleoproterozoic. It is therefore concluded that the Qianhe gold deposit formed as a result of this craton reactivation event.  相似文献   

12.
The Miocene porphyry Cu–(Mo) deposits in the Gangdese orogenic belt in southern Tibet were formed in a post-subduction collisional setting. They are closely related to the Miocene adakite-like porphyries which were probably derived from a thickened basaltic lower crust. Furthermore, mantle components have been considered to have played a crucial role in formation of these porphyry deposits (Hou et al. Ore Geol Rev 36: 25–51, 2009; Miner Deposita doi:10.1007/s00126-012-0415-6, 2012). In this study, we present zircon Hf isotopes and molybdenite Re–Os ages on the newly discovered Gangjiang porphyry Cu–Mo deposit in southern Tibet to constrain the magma source of the intrusions and the timing of mineralization. The Gangjiang porphyry Cu–Mo deposit is located in the Nimu ore field in the central Gangdese porphyry deposits belt, southern Tibet. The copper and molybdenum mineralization occur mainly as disseminations and veins in the overlapped part of the potassic and phyllic alteration zones, and are predominantly hosted in the quartz monzonite stock and in contact with the rhyodacite porphyry stock. SIMS zircon U–Pb dating of the pre-mineral quartz monzonite stock and late intra-mineral rhyodacite porphyry yielded ages of 14.73?±?0.13 Ma (2σ) and 12.01?±?0.29 Ma (2σ), respectively. These results indicate that the magmatism could have lasted as long as about 2.7 Ma for the Gangjiang deposit. The newly obtained Re–Os model ages vary from 12.51?±?0.19 Ma (2σ) to 12.85?±?0.18 Ma (2σ) for four molybdenite samples. These Re–Os ages are roughly coincident with the rhyodacite porphyry U–Pb zircon age, and indicate a relatively short-lived episode of ore deposition (ca. 0.3 Ma). In situ Hf isotopic analyses on zircons by using LA-MC-ICP-MS indicate that the ε Hf(t) values of zircons from a quartz monzonite sample vary from +2.25 to +4.57 with an average of +3.33, while zircons from a rhyodacite porphyry sample vary from +5.53 to +7.81 with an average of +6.64. The Hf data indicate that mantle components could be partly involved in the deposit formation, and that mantle contributions might have increased over time from ca. 14.7 to 12.0 Ma. Combined with previous works, it is proposed that the Gangjiang deposit could have resulted from the convective thinning of the lithospheric root, and the input of upper mantle components into the magma could have played a key role in the formation of the porphyry deposits in the Miocene Gangdese porphyry copper belt in the Tibetan Orogen.  相似文献   

13.
The Eastern Tianshan Orogenic Belt of the Central Asian Orogenic Belt and the Beishan terrane of the Tarim Block, NW China, host numerous Fe deposits. The Cihai Fe deposit (>90 Mt at 45.6 % Fe) in the Beishan terrane is diabase-hosted and consists of the Cihai, Cinan, and Cixi ore clusters. Ore minerals are dominantly magnetite, pyrite, and pyrrhotite, with minor chalcopyrite, galena, and sphalerite. Gangue minerals include pyroxene, garnet, hornblende and minor plagioclase, biotite, chlorite, epidotite, quartz, and calcite. Pyrite from the Cihai and Cixi ore clusters has similar Re–Os isotope compositions, with ～14 to 62 ppb Re and ≤10?ppt common Os. Pyrrhotite has ～5 to 39 ppb Re and ～0.6 ppb common Os. Pyrite has a mean Re–Os model age of 262.3?±?5.6 Ma (n?=?13), in agreement with the isochron regression of 187Os vs. 187Re. The Re–Os age (～262 Ma) for the Cihai Fe deposit is within uncertainty in agreement with a previously reported Rb–Sr age (268?±?25 Ma) of the hosting diabase, indicating a genetic relationship between magmatism and mineralization. Magnetite from the Cihai deposit has Mg, Al, Ti, V, Cr, Co, Ni, Mn, Zn, Ga, and Sn more elevated than that of typical skarn deposits, but both V and Ti contents lower than that of magmatic Fe–Ti–V deposits. Magnetite from these two ore clusters at Cihai has slightly different trace element concentrations. Magnetite from the Cihai ore cluster has relatively constant trace element compositions. Some magnetite grains from the Cixi ore cluster have higher V, Ti, and Cr than those from the Cihai ore cluster. The compositional variations of magnetite between the ore clusters are possibly due to different formation temperatures. Combined with regional tectonic evolution of the Beishan terrane, the Re–Os age of pyrite and the composition of magnetite indicate that the Cihai Fe deposit may have derived from magmatic–hydrothermal fluids related to mafic magmatism, probably in an extensional rift environment.  相似文献   

14.
Re–Os dating of disseminated ore from the Kalatongke Cu–Ni sulfide mineral deposit, Xinjiang, Northwest (NW) China, yields an apparent isochron age of 433 ± 31 Ma with an apparent initial 187Os/188Os (433 Ma) ratio of 0.197 ± 0.027. This apparent age is older than not only the zircon U–Pb age of the host intrusion (287 ± 5 Ma, Han et al., 2004) but also the stratigraphic age of the intruded country rock. Thus, the regression line is a pseudo-isochron. However, previous Re–Os dating of massive ores of the same deposit yielded an age that is consistent, within analytical uncertainty, with the zircon U–Pb age (Zhang et al., 2008). This relationship is similar to that observed in the Jinchuan deposit, NW China. Therefore, we suggested that the same mechanism, post-segregation diffusion of Os (Yang et al., 2008), is applicable to the Kalatongke deposit.Re–Os isotopic studies of Kalatongke, Jinchuan and representative magmatic Cu–Ni sulfide deposits suggest that the massive ores of mafic–ultramafic-rock-associated Cu–Ni sulfide deposits would yield geologically meaningful Re–Os age, whereas a pseudo-isochron would be obtained for the disseminated ores. Therefore, to obtain a geologically meaningful Re–Os age, the type of the deposit, the type of the ore and the ore-forming process should be taken into account.  相似文献   

15.
Mesozoic ore deposits in Zhejiang Province, Southeast China, are divided into the northwestern and southeastern Zhejiang metallogenic belts along the Jiangshan–Shaoxing Fault. The metal ore deposits found in these belts are epithermal Au–Ag deposits, hydrothermal‐vein Ag–Pb–Zn deposits, porphyry–skarn Mo (Fe) deposits, and vein‐type Mo deposits. There is a close spatial–temporal relationship between the Mesozoic ore deposits and Mesozoic volcanic–intrusive complexes. Zircon U–Pb dating of the ore‐related intrusive rocks and molybdenite Re–Os dating from two typical deposits (Tongcun Mo deposit and Zhilingtou Au–Ag deposit) in the two metallogenic belts show the early and late Yanshanian ages for mineralization. SIMS U–Pb data of zircons from the Tongcun Mo deposit and Zhilingtou Au–Ag deposit indicate that the host granitoids crystallized at 169.7 ± 9.7 Ma (2σ) and 113.6 ± 1 Ma (2σ), respectively. Re–Os analysis of six molybdenite samples from the Tongcun Mo deposit yields an isochron age of 163.9 ± 1.9 Ma (2σ). Re–Os analyses of five molybdenite samples from the porphyry Mo orebodies of the Zhilingtou Au‐Ag deposit yield an isochron age of 110.1 ± 1.8 Ma (2σ). Our results suggest that the metal mineralization in the Zhejiang Province, southeast China formed during at least two stages, i.e., Middle Jurassic and Early Cretaceous, coeval with the granitic magmatism.  相似文献   

16.
《International Geology Review》2012,54(18):2276-2290
ABSTRACT

North Korea is host to world-class metallic mineral deposits, such as the Komdok Cu–Pb–Zn polymetallic mineral belt, but little is known about the resource. To better understand the genesis of the Cu mineralization around the China–North Korea border, we determined the U–Pb, Re-Os, and Rb–Sr ages of three deposits in the area. Sulfide samples from the Hyesan Cu deposit produced Rb–Sr isochron ages of 127.4 ± 4.5 Ma. The Wanbaoyuan Cu deposit yielded a molybdenite Re–Os isochron age of 127.5 ± 3.2 Ma, and a granodiorite sample from the Linjiang Cu deposit gave a zircon U–Pb age of 129.5 ± 0.8 Ma. Combined with geochronological data from previous studies, these new ages suggest that the Cu mineralization occurred mainly during the Cretaceous, and the rollback of the Paleo-Pacific Plate was responsible for the Cu mineralization in NE China–North Korea border.  相似文献   

17.
《International Geology Review》2012,54(14):1825-1842
The Longmala and Mengya’a deposits are two representative skarn Pb–Zn deposits of the Nyainqêntanglha Pb–Zn–(Cu–Mo–Ag) polymetallic belt in the Gangdese region, Tibet, China. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating of the mineralization-related biotite monzogranite from the Longmala deposit yielded a weighted mean age of 55.7 Ma, which can be interpreted as the emplacement age of the pluton. Re–Os dating of three molybdenite samples from the Longmala deposit yielded model ages of 51.8–54.3 Ma, with a weighted mean age of 53.3 Ma, which is interpreted as the mineralization age of the deposit and overlaps the age of the causative intrusion. The Re–Os dating of four molybdenite samples from the Mengya’a deposit yielded model ages of 60.4–65.8 Ma, with a weighted mean age of 63.6 Ma, which represents the mineralization age of this deposit. Our new precise age data for these two deposits are consistent with the existing ages of ca. 65–51 Ma for other skarn polymetallic deposits in the Nyainqêntanglha metallogenic belt. In addition, these new age data, combined with existing information on the geological evolution history of the Lhasa terrane, indicate that the belt of skarn deposits is closely related to initial collision between India and the Asian continents.  相似文献   

18.
The Xinlu Sn‐polymetallic ore field is located in the western Nanling Polymetallic Belt in northeastern Guangxi, South China, where a number of typical skarn‐, hydrothermal vein‐type tin deposits have developed. There are two types of Sn deposits: skarn‐type and sulfide‐quartz vein‐type. The tin mineralizations mainly occur on the south side of the Guposhan granitic complex pluton and within its outer contact zone. To constrain the Sn mineralization age and further understand its genetic links to the Guposhan granitic complex, a series of geochronological works has been conducted at the Liuheao deposit of the ore field using high‐precision zircon SHRIMP U‐Pb, molybdenite Re‐Os, and muscovite Ar‐Ar dating methods. The results show that the biotite‐monzogranite, which is part of the Xinlu intrusive unit of the Guposhan complex pluton, has a SHRIMP U‐Pb zircon age of 161.0 ± 1.5 Ma. The skarn‐type ore has a 40Ar‐39Ar muscovite plateau age of 160 ± 2 Ma (same as its isochron age), and the sulfide‐quartz vein‐type ore yields an Re‐Os molybdenite isochron age of 154.4 ± 3.5 Ma. The magmatic‐hydrothermal geochronological sequence demonstrated that the hydrothermal mineralization took place immediately following the emplacement of the monzogranite, with the skarn metasomatic mineralization stage predating the sulfide mineralization stage. Geochronologically, we have compared this ore field with 26 typical Sn deposits distributed along the Nanling Polymetallic Belt, leading to the suggestion of the magmatic‐metallogenic processes in the Xinlu ore field (ca. 161–154 Ma) as a component of the Early Yanshanian large‐scale Sn‐polymetallic mineralization event (peaked at 160–150 Ma) in the Nanling Range of South China. Petrogenesis of Sn‐producing granite and Sn‐polymetallic mineralization were probably caused by crust–mantle interaction as a result of significant lithospheric extension and thinning in South China in the Late Jurassic.  相似文献   

19.
The Huaheitan molybdenum deposit in the Beishan area of northwest China consists of quartz‐sulfide veins. Orebodies occur in the contact zone of the Huaniushan granite. LA‐ICPMS U–Pb zircon dating constrains the crystallization of the granite at 225.6 ± 2.2 Ma (2σ, MSWD = 4.5). Re–Os dating of five molybdenite samples yield model ages ranging from 223.2 ± 3.5 Ma to 228.6 ± 3.4 Ma, with an average of 225.2 ± 2.4 Ma. The U–Pb and Re–Os ages are identical within the error, suggesting that the granite and related Huaheitan molybdenum deposit formed in the Late Triassic. Our new data, combined with published geochronological results from the other molybdenum deposits in this region, imply that intensive magmatism and Mo mineralization occurred during 240 Ma to 220 Ma throughout the Beishan area.  相似文献   

20.
The Changfagou Cu deposit is a newly discovered porphyry deposit located in the southern Jilin Province of Northeastern China, on the northeastern margin of the North China Craton. To better understand the formation of the Cu deposit, we report the zircon U–Pb and molybdenite Re–Os dating, and Sr-, Nd-, and Hf- isotopic data of the granite porphyry. LA-ICP-MS dating of zircon grains from two mineral zones in the granite porphyry yield ages of 115.7 ± 0.8 and 115.3 ± 0.6 Ma, which is interpreted as the emplacement age of the granite porphyry. The molybdenite Re–Os model ages of 112.5 to 113.8 Ma, an isochron age of 113.3 ± 1.3 Ma, and a weighted mean model age of 113.0 ± 0.7 Ma, which represents the age of the Cu mineralization quite well. The Changfagou granite porphyry samples lack amphibole and muscovite, and are compositionally characterized by high SiO2, high Na2O+K2O, and low P2O5, enriched in some Rb, Th, U, and Pb, and depleted in Nb, Ta, Ti, P, and Eu. Mineralogical and geochemical features suggest that the Changfagou granite porphyry samples are slightly peraluminous and are of highly fractionated I-type granitoids. The granitic rocks also have relatively high (87Sr/86Sr)i (0.71199 to 0. 71422), and both low εNd(t) (?14.56 to ?13.19) and εHf(t) values (?14.916 to ?8.644), which suggest that Changfagou granite porphyry are derived from mixed sources of crustal and mantle, and diagenesis and mineralization were possibly related to the switch in subduction direction of the Palaeo-Pacific Plate in the late phase of Early Cretaceous.  相似文献   

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