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1.
Fe and Cu skarn deposits are very important skarn types worldwide, but it is currently unclear whether the nature of intrusions related to Fe and Cu skarn deposits exerts a key influence on variations in metal associations between Fe and Cu skarn deposits. The Qiman Tagh area of Qinghai Province (QTQP), located in the Eastern Kunlun Orogen (EKO), provides a good opportunity to address this issue. Here, integrating new zircon U–Pb ages, trace elements and Hf isotopes from this study with published data, we constrain the sources of magma associated with Fe and Cu skarn deposits within the QTQP and discuss their role in controlling differences between Fe and Cu skarn deposits.Combined with published data, two discrete suites of the intrusions associated Fe and Cu skarn deposits have been recognized in the QTQP: (1) 245.1 ± 1.5 Ma granodiorite (related to a 245.5 ± 1.6 Ma Cu skarn deposit) has zircon εHf(t) values of −11.9 to −2.1; (2) 235–224 Ma monzonites, quartz monzonites, granodiorite porphyries, monzogranites, and granites associated with 234–225 Ma Fe skarn deposits are characterized by relatively high zircon εHf(t) values (−5.1 to +5.9). The Sr–Nd–Hf isotopic data suggest that the intrusions of Suite 1 and 2 were dominantly derived by partial melting of a Mesoproterozoic juvenile mafic lower crust. Suite 2 intrusions associated with Fe skarn deposits have more mantle components in their magma sources than rocks of Suite 1 that are related to a Cu skarn deposit. Furthermore, zircon εHf(t) values of intrusions associated with Fe and Cu skarn deposits in the QTQP show a negative correlation between mantle components in the magma sources and the contents of Cu and Zn in these deposits. Zircon trace elements indicate that the intrusions associated with Fe skarn deposits are relatively less oxidized than the rock associated with Cu skarn deposit in the QTQP, reflecting a positive correlation between crustal components in the magma sources and oxygen fugacity of the magmas. This indicates that different proportions of mantle and crustal materials in the magma sources may affect oxygen fugacity and Fe contents of the magmas, which possibly leads to the variations in metal associations between Fe and Cu skarn deposits in the QTQP. Zircon U–Pb ages, trace elements and Hf isotopic compositions, combined with geological, geochronological, and geochemical evidence, indicates that having different proportions of mantle components in the magma sources of intrusions associated with Fe and Cu skarn deposits is one of the most critical factors controlling differences in metal association between Fe and Cu skarn deposits.  相似文献   

2.
The Hongniu-Hongshan porphyry and skarn copper deposit is located in the Triassic Zhongdian island arc, northwestern Yunnan province, China. Single-zircon laser ablation inductively coupled plasma mass spectrometry U–Pb dating suggests that the diorite porphyry and the quartz monzonite porphyry in the deposit area formed at 200 Ma and 77 Ma, respectively. A Re–Os isotopic date of molybdenite from the ore is 78.9 Ma, which indicates that in addition to the known Triassic Cu–(Au) porphyry systems, a Late Cretaceous porphyry Cu–Mo mineralization event also exists in the Zhongdian arc. The quartz monzonite porphyry shows characteristics of a magnetite series intrusion, with a high concentration of Al, K, Rb, Ba, and Pb, low amount of Ta, Ti, Y, and Yb, and a high ratio of Sr/Y (average 26.42). The Cretaceous porphyry also shows a strong fractionation between light and heavy rare earth elements (average (La/Yb)N 37.9), which is similar to those of the Triassic subduction-related diorite porphyry in the Hongniu-Hongshan deposit and the porphyry hosting the Pulang copper deposit. However, in contrast to the older intrusions, the quartz monzonite porphyry contains higher concentrations of large ion lithophile elements and Co, and lesser Sr and Zr. Therefore, whereas the Triassic porphyry Cu–(Au) mineralization is related to slab subduction slab in an arc setting, the quartz monzonite porphyry in the Hongniu-Hongshan deposit formed by the remelting of the residual oceanic slab combined with contributions from subduction-modified arc lithosphere and continental crust, which provided the metals for the Late Cretaceous mineralization.  相似文献   

3.
In this paper, we present U–Pb ages and trace element compositions of titanite from the Ruanjiawan W–Cu–Mo skarn deposit in the Daye district, eastern China to constrain the magmatic and hydrothermal history in this deposit and provide a better understanding of the U–Pb geochronology and trace element geochemistry of titanite that have been subjected to post-crystallization hydrothermal alteration. Titanite from the mineralized skarn, the ore-related quartz diorite stock, and a diabase dike intruding this stock were analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Titanite grains from the quartz diorite and diabase dike typically coexist with hydrothermal minerals such as epidote, sericite, chlorite, pyrite, and calcite, and display irregular or patchy zoning. These grains have low LREE/HREE and high Th/U and Lu/Hf ratios, coupled with negative Eu and positive Ce anomalies. The textural and compositional data indicate that titanite from the quartz diorite has been overprinted by hydrothermal fluids after being crystallized from magmas. Titanite grains from the mineralized skarn are texturally equilibrated with retrograde skarn minerals including actinolite, quartz, calcite, and epidote, demonstrating that these grains were formed directly from hydrothermal fluids responsible for the mineralization. Compared to the varieties from the quartz diorite stock and diabase dike, titanite grains from the mineralized skarn have much lower REE contents and LREE/HREE, Th/U, and Lu/Hf ratios. They have a weighted mean 206Pb/238U age of 142 ± 2 Ma (MSWD = 0.7, 2σ), in agreement with a zircon U–Pb age of 144 ± 1 Ma (MSWD = 0.3, 2σ) of the quartz diorite and thus interpreted as formation age of the Ruanjiawan W–Cu–Mo deposit. Titanite grains from the ore-related quartz diorite have a concordant U–Pb age of 132 ± 2 Ma (MSWD = 0.5, 2σ), which is 10–12 Ma younger than the zircon U–Pb age of the same sample and thus interpreted as the time of a hydrothermal overprint after their crystallization. This hydrothermal overprint was most likely related to the emplacement of the diabase dike that has a zircon U–Pb age of 133 ± 1 Ma and a titanite U–Pb age of 131 ± 2 Ma. The geochronological results thus reveal two hydrothermal events in the Ruanjiawan deposit: an early one forming the Wu–Cu–Mo ores related to the emplacement of the quartz diorite stock and a later one causing alteration of the quartz diorite and its titanite due to emplacement of diabase dike. It is suggested that titanite is much more susceptible to hydrothermal alteration than zircon. Results from this study also highlight the utilization of trace element compositions in discriminating titanite of magmatic and hydrothermal origins, facilitating a more reasonable interpretation of the titanite U–Pb ages.  相似文献   

4.
西藏革吉县尕尔穷铜金矿矽卡岩特征及成因意义   总被引：1，自引：0，他引：1  
通过对矽卡岩岩石学特征、矿物学特征研究,发现矽卡岩主要产于大理岩和石英闪长岩、花岗斑岩接触带上,垂向上多有大理岩-硅化角岩-矽卡岩化大理岩-硅灰石矽卡岩-透辉石矽卡岩-石榴子石矽卡岩-石英闪长岩的分带特征。矽卡岩岩石地球化学特征、稀土元素和微量元素特征显示矽卡岩主要为钙矽卡岩,具有弱Eu负异常和轻稀土富集等特征;同时具有富集Rb、Th、Cs、U等大离子亲石元素和亏损Hf、Ti、Y等高场强元素特征。矽卡岩地球化学特征受大理岩和石英闪长岩、花岗斑岩的控制和影响,显示其与大理岩、石英闪长岩和花岗斑岩成因上有密切关系。通过对班公湖-怒江成矿带成矿背景和时空关系的讨论,指示了尕尔穷矿床成因是与岩浆热液有关的接触交代型矿床。  相似文献   

5.
The Great Xing'an Range (GXR), Northeast (NE) China, is a major polymetallic metallogenic belt in the eastern segment of the Central Asian Orogenic Belt. The newly discovered Xiaokele porphyry Cu (–Mo) deposit lies in the northern GXR. Field geological and geochronological studies have revealed two mineralization events in this deposit: early porphyry‐type Cu (–Mo) mineralization, and later vein‐type Cu mineralization. Previous geochronological studies yielded an age of ca. 147 Ma for the early Cu (–Mo) mineralization. Our 40Ar/39Ar dating yielded 40Ar/39Ar plateau ages of 124.8 ± 0.4 to 124.3 ± 0.4 Ma on K‐feldspar in altered Cu‐mineralized diorite porphyrite dikes that represent the overprinting vein‐type Cu mineralization, consistent with zircon U–Pb ages of the diorite porphyrite (126.4 ± 0.5 to 125.0 ± 0.5 Ma). The Cr and Ni contents and Mg# of the Xiaokele diorite porphyrites are high. The diorite porphyrites at Xiaokele are enriched in light rare‐earth elements (REEs), and large‐ion lithophile elements (e.g., Rb, Ba, and K), are depleted in heavy REEs and high‐field‐strength elements (e.g., Nb, Ta, and Ti), and have weak negative εHf(t) values (+0.29 to +5.27) with two‐stage model ages (TDM2) of 1,164–845 Ma. Given the regional tectonic setting in Early Cretaceous, the ore‐bearing diorite porphyrites were likely formed in an extensional environment related to lithospheric delamination and asthenospheric upwelling induced by subduction of the Paleo‐Pacific Plate. These tectonic events caused large‐scale magmatic activity, ore mineralization, and lithospheric thinning in NE China.  相似文献   

6.
天宝山大型多金属矿集区位于兴蒙造山带东缘,西拉木伦-长春断裂带与敦(化)-密(山)断裂带交汇部位的北东侧,已发现矽卡岩型Pb-Zn-Ag矿化(如立山和选厂后山)、隐爆角砾岩中的Pb-Zn-Ag矿化(如新兴)、沉积变质-热液改造型CuPb-Zn矿化(如东风南山)和热液脉型Mo矿化(如东风北山)等多种矿化类型。为建立该区的成岩成矿年代学格架,采用LAICP-MS单颗粒锆石U-Pb法,对立山成矿闪长岩与东风北山含矿黑云母石英闪长岩开展了同位素测年研究;并对东风北山钼矿床开展了辉钼矿Re-Os法测年。结果表明,立山闪长岩体与东风北山黑云母石英闪长岩体中锆石的加权平均年龄分别为266.2±3.9Ma(MSWD=14)和278.4±1.8Ma(MSWD=2.9),两岩体均属海西晚期岩浆事件的结果;东风北山钼矿床中6件辉钼矿样品的Re-Os模式年龄介于190.3±3.1Ma~194.6±2.8Ma,等时线年龄为192±3.1Ma,表明钼的成矿作用发生于燕山早期。立山铅锌矿化属接触交代型,成矿岩体的年龄基本代表成矿时代,所以立山铅锌矿床形成于海西晚期;东风北山钼矿床为热液脉型,虽然含矿岩体的侵位时代为海西期,但钼矿化发生于燕山早期,成矿与矿区深部或外围的燕山早期侵入体有关。因此,天宝山矿集区至少发生过海西期和燕山期两期大规模岩浆成矿事件。不同期次构造-岩浆-成矿作用的叠加应是该矿床矿化类型复杂、矿种多和规模大的主因。  相似文献   

7.
The Dawan Mo–Zn–Fe deposit located in the Northern Taihang Mountains in the middle of the North China Craton (NCC) contains large Mo‐dominant deposits. The mineralization of the Dawan Mo–Zn–Fe deposit is associated with the Mesozoic Wanganzhen granitoid complex and is mainly hosted within Archean metamorphic rocks and Proterozoic–Paleozoic dolomites. Rhyolite porphyry and quartz monzonite both occur in the ore field and potassic alteration, strong silicic–phyllic alteration, and propylitic alteration occur from the center of the rhyolite porphyry outward. The Mo mineralization is spacially related to silicic and potassic alteration. The Fe orebody is mainly found in serpentinized skarn in the external contact zone between the quartz monzonite and dolomite. Six samples of molybdenite were collected for Re–Os dating. Results show that the Re–Os model ages range from 136.2 Ma to 138.1 Ma with an isochron age of 138 ± 2 Ma (MSWD = 1.2). U–Pb zircon ages determined by laser ablation inductively coupled plasma mass spectrometry yield crystallization ages of 141.2 ± 0.7 (MSWD = 0.38) and 130.7 ± 0.6 Ma (MSWD = 0.73) for the rhyolite porphyry and quartz monzonite, respectively. The ore‐bearing rhyolite porphyry shows higher K2O/Na2O ratios, ranging from 58.0 to 68.7 (wt%), than those of quartz monzonite. All of the rock samples are classified in the shoshonitic series and characterized by enrichment in large ion lithophile elements; depletion in Mg, Fe, Ta, Ni, P, and Y; enrichment in light rare earth elements with high (La/Yb)n ratios. Geochronology results indicate that skarn‐type Fe mineralization associated with quartz monzonite (130.7 ± 0.6 Ma) formed eight million years later than Mo and Zn mineralization (138 ± 2 Ma) in the Dawan deposit. From Re concentrations in molybdenite and previously presented Pb and S isotope data, we conclude that the ore‐forming material of the deposit was derived from a crust‐mantle mixed source. The porphyry‐skarn type Cu–Mo–Zn mineralization around the Wanganzhen complex is related to the primary magmatic activity, and the skarn‐type Fe mineralization is formed at the late period magmatism. The Dawan Mo–Zn–Fe porphyry‐skarn ores are related to the magmatism that was associated with lithospheric thinning in the NCC.  相似文献   

8.
The Dongguashan skarn-porphyry Cu-Au deposit, located in the Tongling district of the Middle-Lower Yangtze River Valley metallogenic belt (MLYB), consists of skarn ore bodies in the upper part and porphyry ore bodies in the lower part, both of which are hosted in quartz diorite and quartz monzodiorite. Zircon U-Pb age and geochemical studies show that the quartz diorite of the Dongguashan intrusion formed at 140.3 ± 2.0 Ma (MSWD = 0.19) and belongs to the high potassium calc-alkaline series. It is enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), depleted in high field-strength elements (HFSE) and heavy rare earth elements (HREE), and has a slightly negative Eu anomaly. 176Hf/177Hf values of the rims of zircons show a variable range (0.282087–0.282391), corresponding with calculated εHf(t) values of − 10.72 to − 21.46. Plagioclases in the quartz diorite have unbalanced structure characterized by bright andesine and labradorite (An = 37.0–65.5) cores with higher contents of Fe and Sr and are corroded by dark oligoclase (An = 13.8–27.6) rim. Major elements, trace elements, Hf isotope, and the composition of plagioclases indicate that the parental magma of the Dongguashan intrusion was produced by the mixing of underplating mafic magma and felsic magma formed by remelting of Paleoproterozoic and Neoarchean crustal rocks, Neoproterozoic crust may also provide some material to the felsic magma. Mafic magma played a key role and made the parental magma rich in water, sulfur, metals (Cu, Au) and gave it a high oxygen fugacity. During its magmatic evolution, the parental magma underwent fractional crystallization of hornblende, apatite, sphene and other mafic minerals. Some quartz diorite and quartz monzodiorite samples that show adakitic signatures, may result from injection of mafic magma. Some inherited zircons of the quartz diorite in the Dongguashan intrusion gave ages of 2.40–2.50 Ga, 1.95–2.05 Ga and 0.74–0.81 Ga, coming from ultramafic, mafic and andesitic igneous rocks, and this indicates that there may have been three periods (2.4, 2.0, and 0.8 Ga) of magmatic activity in the Tongling district.  相似文献   

9.
The Ga'erqiong‐Galale skarn–porphyry copper–gold ore‐concentrated area is located in the western part of the Bangong‐Nujiang suture zone north of the Lhasa Terrane. This paper conducted a systematic study on the magmatism and metallogenic effect in the ore‐concentrated area using techniques of isotopic geochronology, isotopic geochemistry and lithogeochemistry. According to the results, the crystallization age of quartz diorite (ore‐forming mother rock) in the Ga'erqiong deposit is 87.1 ± 0.4 Ma, which is later than the age of granodiorite (ore‐forming mother rock) in the Galale deposit (88.1 ± 1.0 Ma). The crystallization age of granite porphyry (GE granite porphyry) in the Ga'erqiong deposit is 83.2 ± 0.7 Ma, which is later than the age of granite porphyry (GL granite porphyry) in the Galale deposit (84.7 ± 0.8 Ma).The quartz diorite, granodiorite, GE granite porphyry and GL granite porphyry both main shows positive εHf(t) values, suggesting that the magmatic source of the main intrusions in the ore‐concentrated area has the characteristics of mantle source region. The Re–Os isochron age of molybdenite in the Ga'erqiong district is 86.9 ± 0.5 Ma, which is later than the mineralization age of the Galale district (88.6 ± 0.6 Ma). The main intrusive rocks in the ore‐concentrated area have similar lithogeochemical characteristics, for they both show the relative enrichment in large‐ion lithophile elements(LILE: Rb, Ba, K, etc.), more mobile highly incompatible lithophile elements(HILE: U, Th) and relatively depleted in high field strength elements (HFSE: Nb, Ta, Zr, Hf, etc.), and show the characteristics of magmatic arc. The studies on the metal sulfides' S and Pb isotopes and Re content of molybdenite indicate that the metallogenic materials of the deposits in the ore‐concentrated area mainly come from the mantle source with minor crustal source contamination. Based on the regional tectonic evolution process, this paper points out that the Ga'erqiong‐Galale copper–gold ore‐concentrated area is the typical product of the Late Cretaceous magmatism and metallogenic event in the collision stage of the Bangong‐Nujiang suture zone.  相似文献   

10.
朱乔乔  谢桂青  韩颖霄 《岩石学报》2017,33(11):3484-3494
湖北狮子立山锶(铅锌)矿床是我国重要的超大型锶矿床之一,产出于鄂东矿集区北部铁山岩体东缘的狮子立山岩体(主要为石英闪长玢岩)与三叠纪蒸发岩地层(嘉陵江组)的接触带或附近。本文对矿区内的石英闪长玢岩与成矿作用之间的关系和该岩体的年代学开展了详细的研究工作。结果表明,狮子立山岩体与锶矿成矿作用可能存在密切的联系,矿床中的部分Sr可能来自于石英闪长玢岩的强烈蚀变。锆石SHRIMP U-Pb的定年工作得到2个石英闪长玢岩样品的形成时代分别为138.6±0.8Ma和138.9±1.2Ma,二者在误差范围内基本一致,这些数据与前人获得的铁山岩体的成岩时代基本一致,暗示本次测得的石英闪长玢岩的样品年龄可靠性较高,且很可能与铁山岩体是同一地质背景下的产物,即形成于区域晚侏罗-早白垩世岩石圈由挤压到伸展的转换环境。狮子立山岩体的侵位地层及矿床中硫同位素组成的特征与程潮和金山店矽卡岩型铁矿具有明显的相似性,暗示在狮子立山矿床附近具有寻找矽卡岩型铁矿床的潜力。  相似文献   

11.
藏南努日矿床位于冈底斯成矿带南缘,前人获得的辉钼矿Re-Os同位素年龄为23 Ma,与明则和程巴矿床成矿时代一致,但矿区内至今未发现与矿化有关的成矿斑岩体。本文报道了努日矿区新发现的与矿化关系密切的石英闪长岩的地球化学特征,获得石英闪长岩的LA-ICP-MS锆石U-Pb年龄为93.42±0.76 Ma,与同一成矿带内桑布加拉和克鲁铜金矿成矿时代一致(90~93 Ma),表明矿区可能存在两期成矿事件。石英闪长玢岩的主量微量元素SiO_2含量为57.19%~58.23%,A1_2O_3含量为15.78%~16.03%,MgO含量为4.74%~5.32%,Mg~#指数为65.2~67.3;富集大离子亲石元素(Rb、Sr、Ba、U等)及轻稀土元素,亏损高场强元素,显示出埃达克岩特征。研究表明石英闪长玢岩形成于洋壳俯冲阶段的弧岩浆岩,洋壳熔融形成的母岩浆侵入近地表形成早期铜多金属矽卡岩矿化。晚白垩世成矿事件的发现进一步佐证了研究区存在两期矿化叠加事件,拓展了研究区找矿方向。  相似文献   

12.
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   

13.
The recently discovered Baizhangyan skarn‐porphyry type W–Mo deposit in southern Anhui Province in SE China occurs near the Middle–Lower Yangtze Valley polymetallic metallogenic belt. The deposit is closely temporally‐spatially associated with the Mesozoic Qingyang granitic complex composed of g ranodiorite, monzonitic g ranite, and alkaline g ranite. Orebodies of the deposit occur as horizons, veins, and lenses within the limestones of Sinian Lantian Formation contacting with buried fine‐grained granite, and diorite dykes. There are two types of W mineralization: major skarn W–Mo mineralization and minor granite‐hosted disseminated Mo mineralization. Among skarn mineralization, mineral assemblages and cross‐cutting relationships within both skarn ores and intrusions reveal two distinct periods of mineralization, i.e. the first W–Au period related to the intrusion of diorite dykes, and the subsequent W–Mo period related to the intrusion of the fine‐grained granite. In this paper, we report new zircon U–Pb and molybdenite Re–Os ages with the aim of constraining the relationships among the monzonitic granite, fine‐grained granite, diorite dykes, and W mineralization. Zircons of the monzonitic granite, the fine‐grained granite, and diorite dykes yield weighted mean U–Pb ages of 129.0 ± 1.2 Ma, 135.34 ± 0.92 Ma and 145.3 ± 1.7 Ma, respectively. Ten molybdenite Re–Os age determinations yield an isochron age of 136.9 ± 4.5 Ma and a weighted mean age of 135.0 ± 1.2 Ma. The molybdenites have δ34S values of 3.6‰–6.6‰ and their Re contents ranging from 7.23 ppm to 15.23 ppm. A second group of two molybdenite samples yield ages of 143.8 ± 2.1 and 146.3 ± 2.0 Ma, containing Re concentrations of 50.5–50.9 ppm, and with δ34S values of 1.6‰–4.8‰. The molybdenites from these two distinct groups of samples contain moderate concentrations of Re (7.23–50.48 ppm), suggesting that metals within the deposit have a mixed crust–mantle provenance. Field observation and new age and isotope data obtained in this study indicate that the first diorite dyke‐related skarn W–Au mineralization took place in the Early Cretaceous peaking at 143.0–146.3 Ma, and was associated with a mixed crust–mantle system. The second fine‐grained granite‐related skarn W–Mo mineralization took place a little later at 135.0–136.9 Ma, and was crust‐dominated. The fine‐grained granite was not formed by fractionation of the Qingyang monzonitic granite. This finding suggests that the first period of skarn W–Au mineralization in the Baizhangyan deposit resulted from interaction between basaltic magmas derived from the upper lithospheric mantle and crustal material at 143.0–146.3 and the subsequent period of W–Mo mineralization derived from the crust at 135.0–136.9 Ma.  相似文献   

14.
The Laoshankou Fe–Cu–Au deposit is located at the northern margin of Junggar Terrane, Xinjiang, China. This deposit is hosted in Middle Devonian andesitic volcanic breccias, basalts, and conglomerate-bearing basaltic volcanic breccias of the Beitashan Formation. Veined and lenticular Fe–Cu–Au orebodies are spatially and temporally related to diorite porphyries in the ore district. Wall–rock alteration is dominated by skarn (epidote, chlorite, garnet, diopside, actinolite, and tremolite), with K–feldspar, carbonate, albite, sericite, and minor quartz. On the basis of field evidence and petrographic observations, three stages of mineralization can be distinguished: (1) a prograde skarn stage; (2) a retrograde stage associated with the development of Fe mineralization; and (3) a quartz–sulfide–carbonate stage associated with Cu–Au mineralization. Electron microprobe analysis shows that garnets and pyroxenes are andradite and diopside-dominated, respectively. Fluid inclusions in garnet yield homogenization temperatures (Th) of 205–588 °C, and salinities of 8.95–17.96 wt.% NaCl equiv. In comparison, fluid inclusions in epidote and calcite yield Th of 212–498 and 150–380 °C, and salinities of 7.02–27.04 and 13.4–18.47 wt.% NaCl equiv., respectively. Garnets yield values of 6.4‰ to 8.9‰ δ18Ofluid, whereas calcites yield values of − 2.4‰ and 4.2‰ δ18Ofluid, and − 0.9‰ to 2.4‰ δ13CPDB, indicating that the ore-forming fluids were dominantly magmatic fluids in the early stage and meteoric water in the late stage. The δ34S values of sulfides range from − 2.6‰ to 5.4‰, indicating that the sulfur in the deposit was probably derived from deep-seated magmas. The diorite porphyry yields LA–MC–ICP–MS zircon U–Pb age of 379.7 ± 3.0 Ma, whereas molybdenites give Re–Os weighted mean age of 383.2 ± 4.5 Ma (MSWD = 0.06). These ages suggest that the mineralization-related diorite porphyry was emplaced during the Late Devonian, coincident with the timing of mineralization within the Laoshankou Fe–Cu–Au deposit. The geological and geochemical evidence presented here suggest that the Laoshankou Fe–Cu–Au deposit is a skarn deposit.  相似文献   

15.
The newly discovered Zhunuo porphyry Cu-Mo-Au deposit is located in the western part of the Gangdese porphyry copper belt in southern Tibet, SW China. The granitoid plutons in the Zhunuo region are composed of quartz diorite porphyry, diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry. The quartz diorite porphyry yielded zircon U-Pb ages of 51.9±0.7 Ma(Eocene) using LA-ICP-MS, whereas the diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry yielded ages ranging from 16.2±0.2 to 14.0±0.2 Ma(Miocene). CuMo-Au mineralization is mainly hosted in the Miocene granodiorite porphyry. Samples from all granitoid plutons have geochemical compositions consistent with high-K calc-alkaline series magmatism. The samples display highly fractionated light rare-earth element(REE) distributions and heavy REE distributions with weakly negative Eu anomalies on chondrite-normalized REE patterns. The trace element distributions exhibit positive anomalies for large-ion lithophile elements(Rb, K, U, Th and Pb) and negative anomalies for high-field-strength elements(Nb and Ti) relative to primitive mantlenormalized values. The Eocene quartz diorite porphyry yielded εNd(t) values ranging from-3.6 to-5.2,(~(87)Sr/~(86)Sr)i values in the range 0.7046–0.7063 and initial radiogenic Pb isotopic compositions with ranges of 18.599–18.657 ~(206)Pb/~(204)Pb, 15.642–15.673 ~(207)Pb/~(204)Pb and 38.956–39.199 ~(208)Pb/~(204)Pb. In contrast, the Miocene granitoid plutons yielded ε_(Nd)(t) values ranging from-6.1 to-7.3 and(87Sr/86Sr)i values in the range 0.7071–0.7078 with similar Pb isotopic compositions to the Eocene quart diorite. The Sr-Nd-Pb isotopic compositions of the rocks are consistent with formation from magma containing a component of remelted ancient crust. Zircon grains from the Eocene quartz diorite have ε_(Hf)(t) values ranging from-5.2 to +0.9 and two-stage Hf model ages ranging from 1.07 to 1.46 Ga, while zircon grains from the Miocene granitoid plutons have ε_(Hf)(t) values from-9.9 to +4.2 and two-stage Hf model ages ranging from 1.05–1.73 Ga, indicating that the ancient crustal component likely derives from Paleo- to Mesoproterozoic basement. This source is distinct from that of most porphyry Cu-Mo-Au deposits in the eastern part of the Gangdese porphyry copper belt, which likely originated from juvenile crust. We therefore consider melting of ancient crustal basement to have contributed significantly to the formation Miocene porphyry Cu-Mo-Au deposits in the western part of the Gangdese porphyry copper belt.  相似文献   

16.
The Saishitang skarn type copper deposit, located in the southeast part of the Dulan–Ela Mountain Triassic volcanic–magmatic arc and forearc accretionary wedge, belongs to the Tongyugou–Saishitang tin–copper polymetallic ore field in West Qinling, Qinghai province. Based on the contact/crosscutting relationships, mineral associations and mineralization characteristics, hydrothermal fluid evolution can be divided into three stages: skarn (I), quartz sulfide (II) and polymetallic sulfide-bearing quartz–calcite vein (III). The quartz sulfide stage (II) can be further divided into a massive sulfide stage (II-1) and a layered sulfide stage (II-2). This paper presents detailed analysis of fluid inclusions, H–O, S and Pb isotope compositions of rock samples from each of the above three stages as well as analysis of fluid inclusions from quartz diorite. The homogenization temperature, salinity, density and pressure of fluid inclusions in quartz diorite and typical transparent minerals showed a tendency of gradual decline in these evolutionary stages. The ore-forming fluid can be classified as a Na+–Ca2 +–SO42 − Cl− system with a minor proportion of a Na+–Ca2 +–NO3− SO42 − system, which likely resulted from mixing of magmatic and formation water. The H–O isotope composition indicates that the proportion of formation water increased during the ore-forming process, and meteoric water was mixed in the late quartz–calcite vein stage. The δ34S (CDT) values (− 6.45–5.57‰) and Pb isotope compositions show that the ore-forming materials were mainly derived from magmatic fluid. Ore-forming fluid was boiling during the main ore-forming stage (II-1) due to pressure decrease. Consequently, the physical and chemical conditions (i.e., pH, Eh, fO2, fS2) changed, and metallic elements (including Cu) in the fluid could no longer exist in the form of complexes and precipitated from the fluid. According to the integrated analysis of ore features, mineral associations, alteration characteristics, ore-forming environment and fluid evolutionary process, it is concluded that the Saishitang deposit is a typical skarn deposit.  相似文献   

17.
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   

18.
通过对新疆东天山雅满苏岛弧带双龙铜矿成岩地质特征、岩石地球化学特征及Hf同位素分析,认为赋矿岩体为一套形成于后碰撞环境下的准铝质高钾钙碱性岩石系列的石英闪长岩,LA-ICP-MS锆石U-Pb同位素年龄为(300.9±1.2)Ma。岩石地球化学显示,赋矿岩石具富集大离子亲石元素(LILE)K,Rb等及高场强元素(HFSE)Th,U,Zr和Hf,贫Nb,Ta,Ti,Sr,P特征,可能形成于后碰撞构造环境。石英闪长岩锆石176Hf/177Hf变化范围0.282949~0.283002,平均值0.282979,εHf(t)值为12.32~14.40,平均13.40,tDM2(Hf)为375~482Ma,平均429Ma,表明岩浆物源可能来自志留纪新生地壳的部分熔融。  相似文献   

19.
火神庙岩体位于华北陆块南缘栾川矿集区西部,为一杂岩体,该岩体与火神庙钼矿床密切相关.目前,人们对火神庙岩体的研究程度较低,严重制约了对火神庙钼矿床成因的认识.系统开展了年代学、地球化学和Hf同位素组成研究.结果表明,石英闪长岩、二长花岗岩和花岗斑岩的形成年龄分别为150.3±0.6Ma、146.0±0.6Ma和145.1±0.5Ma,为栾川矿集区晚侏罗世第2次大规模岩浆活动的产物.火神庙杂岩体属于I型花岗岩,是不同源区部分熔融形成的岩浆上升就位的结果.石英闪长岩是富集岩石圈地幔部分熔融的产物;二长花岗岩和花岗斑岩是富集岩石圈地幔部分熔融形成的镁铁质岩浆与太华群TTG岩系部分熔融形成的长英质岩浆混合后上升就位的结果.   相似文献   

20.
The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zircon U-Pb isotopic dating,in conjunction with cathodoluminescence images,reveals that the quartz diorite and granodiorite were emplaced from 220 Ma to 216 Ma,while the monzogranite was emplaced at～210 Ma.In-situ zircon Hf isotopic analyses show that theε_(Hf)(t) values of the quartz diorite a...  相似文献   

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