初论稀有金属矿床研究的一些重要进展

稀有金属矿是重要的战略性储备资源,其成矿机制和成矿作用研究也一直受到了国际上的广泛关注。本文从矿床类型特征、岩浆岩、碳酸岩体与稀有金属矿化的关系、矿床成矿流体与成矿机制和成矿年代学等4个方面,对近年来的研究进展进行了简要的论述。稀有金属矿床以花岗岩型和花岗伟晶岩型为主,与稀有金属矿化有关的岩体的地球化学组成可以有效指示稀有金属矿化趋势,锆石常具有特殊的化学组成特征(高Th/U比值(1~10)、Y/Ho20、Sm/Nd0.5、Nb/Y0.08和Hf2wt%)。流体不混溶作用在稀有金属矿床,尤其是伟晶岩型矿床的成矿流体中常见,成矿多经历了从岩浆-热液多个阶段,流体成分较复杂,除B、F等外,最近还发现了较少见的碳酸盐矿物,其成矿机制值得深入研究。     

中南部非洲镍矿成矿规律及资源潜力分析

中南部非洲镍矿资源丰富,大体可分为岩浆型和风化壳型2种预测类型。本文在对中南部非洲243处镍矿床/点资料系统收集整理的基础上,将产出的镍矿初步划分为新太古代、古元古代、中元古代和新元古代4个成矿期,南非卡普瓦尔北缘古元古代Cr-Ni-Cu（PGE）成矿带、津巴布韦大岩墙新太古代Ni-Cr（PGE）成矿带、博茨瓦纳弗朗西斯敦—赛莱比—皮奎新太古代Ni-Cu-Au成矿带、赞比亚赞比西津巴—卢萨卡新元古代Au-Ni-Cu成矿带、坦桑尼亚乌本迪—乌萨嘎仁古元古代Ni-Cu成矿带和坦桑尼亚—布隆迪基巴拉中元古代Ni-Cu-Co成矿带共6个成矿带,从整体上构成了北东向的中南部非洲巨型镍矿带;并分别对研究区内典型的与大陆边缘裂解有关的Ni-Cu（PGE）矿床、与造山带伸展背景有关的Ni-Cu矿床、与地幔柱有关的Ni-Cu（PGE）矿床和风化壳型镍矿床的矿床地质特征和成矿模式进行了研究。综合研究表明,布什维尔德矿集区、津巴布韦大岩墙矿集区、博茨瓦纳弗朗西斯敦—赛莱比—皮奎矿集区、坦桑尼亚—布隆迪穆松加迪—卡邦加矿集区镍矿资源潜力巨大,找矿前景优越。     

Indium in cassiterite and ores of tin deposits

The results obtained with LA-ICP-MS by less abundant lighter ¹¹³In isotope and EPMA show that in cassiterite of cassiterite–quartz veins the indium contents do not exceed 160 ppm, while cassiterite from Sn–sulfide veins is characterized by higher indium contents from 40 to 485 ppm; sulfides of Sn–sulfide veins unlike sulfides of cassiterite–quartz veins also have the highest indium contents: Fe-sphalerite (100–25,000 ppm), chalcopyrite (up to 1000 ppm), and stannite (up to 60,000 ppm). Indium contents in the Sn–sulfide ore of the Tigrinoe and Pravourmiiskoe deposits obtained using SR-XRF, ICP-MS and atomic absorption methods range from 10 to 433 ppm with average values of 56–65 ppm. Indium-rich Sn–sulfide mineralization in five large Sn–Ag ore districts of the Far East Russia (Khingansky, Badzhalsky, Komsomolsky, Arminsky, Kavalerovsky) provides the impetus for further exploration of deposits with Sn–sulfide mineralization as the most promising indium resources in Russia. Empirical observations from geology and geochronology of cassiterite–quartz and Sn–sulfide mineralization show that the combined contribution from granite and alkaline–subalkaline mafic sources and multistage ore-forming processes doubled indium resources of deposits being the main factors in the formation of high grade indium mineralization.     

U–Pb and Re–Os Geochronology of the Tongcun Molybdenum Deposit and Zhilingtou Gold‐Silver Deposit in Zhejiang Province,Southeast China,and Its Geological Implications

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.     

甘肃北山南金山金矿床矿床成因研究

南金山金矿床产于北山岛弧构造带内海相火山碎屑岩之中。矿床的岩矿石微量元素组合为Ba、La、Ce、Sr、Nd、Sm、Zr、Hf、Y等不相容元素,各类岩石样品的分布曲线非常相似,都具有明显的Pb正异常,表明有较多的地壳物质的加入,并有明显的La,Ce,Ti负异常。稀土总量∑REE(不包括叶蜡石)变化范围为(9.91~221.86)×10-6,其配分形式均为明显右倾曲线,轻、重稀土分馏,轻稀土相对富集而重稀土相对亏损。稀土总量较高,说明矿区内稀土元素在随岩浆迁移的过程中,上升到地壳时有一定的损失。矿物流体包裹体的均一温度、盐度、压力、气相成分等特征研究表明,南金山金矿床成矿流体以中低温,中低盐度,且有大量大气降水加入为特征,为典型的浅成中低温热液矿床。     

Geochronological and geochemical constraints on formation of the Tongling metal deposits,middle Yangtze metallogenic belt,east‐central China

The Tongling district is one of the most important non‐ferrous metal producers in China. The origin of Cu–Au deposits in the region is closely related to Late Mesozoic intermediate intrusions, which are mainly high‐K calc‐alkaline and shoshonitic series. Geochemical characteristics indicate that these granitic rocks are mixtures of more than two compositional end‐members, i.e. mantle‐derived melts and crust components incorporated through assimilation. Three important magmatic intrusions related to the Cu–Au deposits in the Tongling region – the Jiguanshi quartz monzodiorite, the Xishizishan quartz diorite and the Miaojia diorite porphyry – were selected for this study. Zircon U–Pb dating by LA ICP‐MS yielded two groups of ages (～130–132 and 138–140 Ma) for these intrusions. Pyrite Re–Os age for the Xinqiao Cu–Fe–S deposit in the Tongling region is 126±11 Ma. Trace elements of zircon grains show that the earlier Cu–Au mineralization event was associated with adakitic rocks characterized by high positive Ce anomalies, produced at an elevated oxygen fugacity range. In contrast, later iron‐sulphur mineralization was closely related to low positive Ce anomalies, reflecting low oxygen fugacities. Considering that Pacific lithospheric subduction was the dominant factor that controlled major tectonic evolution in eastern China during the Early Cretaceous, the geochemical characteristics of these coeval ore‐forming intermediate intrusive rocks in the Tongling district were likely the result of Pacific plate underflow.     

Genesis for Rare Earth Elements Enrichment in the Permian Manganese Deposits in Zunyi,Guizhou Province,SW China

The Zunyi manganese deposits, which formed during the Middle to Late Permian period and are located in northern Guizhou and adjacent areas, are the core area of a series of large-medium scale manganese enrichment minerogenesis in the southern margin and interior of the Yangtze platform, Southern China. This study reports the universal enrichment of rare earth elements(REEs) in Zunyi manganese deposits and examines the enrichment characteristics, metallogenic environment and genesis of REEs. The manganese ore bodies present stratiform or stratoid in shape, hosted in the silicon–mud–limestones of the Late Permian Maokou Formation. The manganese ores generally present lamellar, massive, banded and brecciated structures, and mainly consist of rhodochrosite, ropperite, tetalite, capillitite, as well as contains paragenetic gangue minerals including pyrite, chalcopyrite, rutile, barite, tuffaceous clay rock, etc. The manganese ores have higher ΣREE contents range from 158 to 1138.9 ppm(average 509.54 ppm). In addition, the ΣREE contents of tuffaceous clay rock in ore beds vary from 1032.2 to 1824.5 ppm(average 1396.42 ppm). The REEs from manganese deposits are characterized by La, Ce, Nd and Y enriched, and existing in the form of independent minerals(e.g., monazite and xenotime), indicating Zunyi manganese deposits enriched in light rare earth elements(LREE). The Ce_(anom) ratios(average-0.13) and lithofacies and paleogeography characteristics indicate that Zunyi manganese deposits were formed in a weak oxidation-reduction environment. The(La/Yb)_(ch), Y/Ho,(La/Nd)_N,(Dy/Yb)_N, Ce/Ce* and Eu/Eu* values of samples from the Zunyi manganese deposits are 5.53–56.92, 18–39, 1.42–3.15, 0.55–2.20, 0.21–1.76 and 0.48–0.86, respectively, indicating a hydrothermal origin for the manganese mineralization and REEs enrichment. The δ~(13) C_(V-PDB)(-0.54 to-18.1‰) and δ~(18) O_(SMOW)(21.6 to 26.0‰) characteristics of manganese ores reveal a mixed source of magmatic and organic matter. Moreover, the manganese ore, tuffaceous clay rock and Emeishan basalt have extremely similar REE fractionation characteristic, suggesting REEs enrichment and manganese mineralization have been mainly origin from hydrothermal fluids.     

Chronology of the Tungsten Deposits in Southern Jiangxi Province,and Episodes and Zonation of the Regional W‐Sn Mineralization – Evidence from High‐precision Zircon U‐Pb,Molybdenite Re‐Os and Muscovite Ar‐Ar Ages

Previous studies have obtained some petrogenetic and metallogenic chronological data with SHRIMP (sensitive high-resolution ion microprobe) zircon U-Pb, zircon LA-ICPMS (laser-ablation–inductively coupled plasma mass spectroscopy) U-Pb, molybdenite Re-Os isochron and muscovite Ar-Ar methods in southern Jiangxi Province and its adjacent areas. Based on these, the purpose of this paper is to study the petrogenetic and metallogenic ages and their time gap for different genetic types of W-Sn deposits, and thus to research their numerous episodes, zonal arrangement and their geodynamic background. The result shows that the large-scale W-Sn mineralization in southern Jiangxi Province occurred in the middle to late Jurassic (170–150 Ma), the skarn W-Sn-polymetallic deposits formed much earlier (170–161 Ma), and all of the wolframite – quartz vein type, greisen type, altered granite type and fractured zone type tungsten deposits formed in the late Jurassic (160–150 Ma). In one ore field or ore district, greisen type tungsten deposits formed earlier than quartz vein type ones hosted in the endo- or exo-contact zone; and quartz vein type hosted in the endocontact zone formed earlier than that of exocontact zone. There is no significant time difference between tungsten-tin mineralization and its intimately associated parent granite emplacement (1–6 Ma). They all formed in the same rock-forming and ore-forming system and under the same geodynamic setting. Regionally, rock-forming and ore-forming processes of the W-Sn deposits in the Nanling region (include southern Jiangxi Province, southern Hunan Province, northern Guangdong Province and eastern Guangxi Zhuang Autonomous Region) exhibit numerous episodes. The mineralization in the Nanling region mainly occurred at (240–210) Ma, (170–150) Ma and (130–90) Ma. The tungsten-tin deposits in this region are centered by the largest scale in southern Jiangxi Province and southern Hunan Province, and become small in the east, west, south and north directions. This displays a zonal arrangement and temporal and spatial distribution regularity. Integrated with the latest research results, it is concluded that the W-Sn mineralization in southern Jiangxi Province and its adjacent areas corresponds to the second large-scale mineralization in South China. The Indosinian W-Sn mineralization formed under the extensional tectonic regime between collisional compressional stages, while the Yanshanian large-scale petrogenetic and metallogenic processes occurred in the Jurassic intraplate extensional geodynamic setting of lithosphere extension.     

Rhenium in porphyry copper deposits of the urals

The overwhelming majority of porphyry Mo-Au-Cu deposits in the Urals are related to the low-K quartz diorite minor intrusions of the island-arc type, which were formed from Silurian Middle-Late Carboniferous. In the South Urals, the Cu/Mo ratio of ore decreases eastward along with enrichment in Re. At the same time, molybdenite is depleted in this metal in compliance with more sialic crust and potassium content in ore-bearing dioritic rocks. Quartz diorites at the highest-Re deposits contain 1–2 wt % K₂O. At most Early-Middle Devonian deposits and occurrences of the western Tagil-Magnitogorsk-West Mugodzhary femic megazone, molybdenite is sporadic. The Re content in rocks was mainly determined using the kinetic method and to a lesser extent with ICP-MS. A Cameca SX-100 microprobe was also used for study of molybdenite. The Cu/Mo ratio of ore exceeds 600; the Mo content is commonly 1–15 ppm (occasionally up to 30 ppm and higher); the Re content is up to 0.01–0.04 ppm, sporadically increasing to 0.08–0.17 ppm. At the same time, the Re content in molybdenite often reaches 0.2–0.4 wt %. The highest Re concentration was established in the ore of the largest Mikheevsky deposit formed in the Late Devonian-Early Carboniferous and localized in the easternmost part of the East Ural sialic-femic megazone. The Re content in the orebodies of this deposit often reaches 0.2–0.5 ppm (up to 1.4–2.7 ppm) and 0.21 wt % in molybdenite. The average Mo grade of ore is 80 ppm and Cu/Mo ratio is 66. These data and Sr isotopic composition of ore-bearing granitoid and metasomatic rocks [(⁸⁷Sr/⁸⁶Sr)_t = 0.7038–0.7051; (?_Nd)_t = 3–7] testify to the mantle source of matter with insignificant admixture of crustal material. The same is apparently valid for Re and Cu in contrast to Mo. This statement is corroborated by the inverse correlation between Cu/Mo and Mo/Re ratios in the ore. Fluid-crystal fractionation of ore-bearing dioritic rocks is accompanied by enrichment of ore in Mo and by decrease in Re content in molybdenite. In the Tarutino ore field, the pyrite-chalcopyrite mineralization gives way to the molybdenite mineralization in line with in-sequence intrusion of diorite with quartz-bearing groundmass and granodiorite porphyry. Because of increasing silica content in granitoids, the Re concentration in molybdenite commonly remains below 0.07 wt % as is noted at the rare deposits localized in the sialic megazones.     

Zircon U–Pb and Molybdenite Re–Os Ages of the Lakange Porphyry Cu–Mo Deposit,Gangdese Porphyry Copper Belt,Southern Tibet,China

The Lakange porphyry Cu–Mo deposit within the Gangdese metallogenic belt of Tibet is located in the southern–central part of the eastern Lhasa block, in the Tibetan Tethyan tectonic domain. This deposit is one of the largest identified by a joint Qinghai–Tibetan Plateau geological survey project undertaken in recent years. Here, we present the results of the systematic logging of drillholes and provide new petrological, zircon U–Pb age, and molybdenite Re–Os age data for the deposit. The ore‐bearing porphyritic granodiorite contains elevated concentrations of silica and alkali elements but low concentrations of MgO and CaO. It is metaluminous to weakly peraluminous and has A/CNK values of 0.90–1.01. The samples contain low total REE concentrations and show light REE/heavy REE (LREE/HREE) ratios of 17.51–19.77 and (La/Yb)_N values of 29.65–41.05. The intrusion is enriched in the large‐ion lithophile elements (LILE) and depleted in the HREE and high field‐strength elements (HFSE). The ore‐bearing porphyritic granodiorite yielded a Miocene zircon U–Pb crystallization age of 13.58 ± 0.42 Ma, whereas the mineralization within the Lakange deposit yielded Miocene molybdenite Re–Os ages of 13.20 ± 0.20 and 13.64 ± 0.21, with a weighted mean of 13.38 ± 0.15 Ma and an isochron age of 13.12 ± 0.44 Ma. This indicates that the crystallization and mineralization of the Lakange porphyry were contemporaneous. The ore‐bearing porphyritic granodiorite yielded zircon εHf(t) values between ?3.99 and 4.49 (mean, ?0.14) and two‐stage model ages between 1349 and 808 Myr (mean, 1103 Myr). The molybdenite within the deposit contains 343.6–835.7 ppm Re (mean, 557.8 ppm). These data indicate that the mineralized porphyritic granodiorite within the Lakange deposit is adakitic and formed from parental magmas derived mainly from juvenile crustal material that partly mixed with older continental crust during the evolution of the magmas. The Lakange porphyry Cu–Mo deposit and numerous associated porphyry–skarn deposits in the eastern Gangdese porphyry copper belt (17–13 Ma) formed in an extensional tectonic setting during the India–Asia continental collision.     

Timing of carbonatite-hosted U-polymetallic mineralization in the supergiant Huayangchuan deposit,Qinling Orogen:Constraints from titanite U-Pb and molybdenite Re-Os dating

The newly-discovered supergiant Huayangchuan uranium(U)-polymetallic(Sr,Se,REEs,Ba,Nb and Pb) deposit is located in the Qinling Orogen,central China.The deposit underwent multistage mineralization,with the main carbonatite ore stage being the most important for the U,Nb,REE,Sr and Ba endowments.According to the mineral assemblages,the main carbonatite ore stage can be divided into three substages,i.e.,sulfate(Ba-Sr),alkali-rich U and REE-U mineralization.Main-stage titanite from the Huayangchuan igneous carbonatite are rich in high field strength elements(HFSEs,e.g.,Zr,Nb and REEs),and show clear elemental substitutions(e.g.,Ti vs.Nb+Fe+Al and Ca+Ti vs.Fe+Al+REE).High-precision LA-ICP-MS titanite dating yielded a U-Pb age of 209.0 ± 2.9 Ma,which represents the mainstage mineralization age at Huayangchuan,and is coeval with the local carbonatite dyke intrusion.This mineralization age is further constrained by the Re-Os dating of molybdenite from the Huayangchuan carbonatite,which yielded a weighted mean age of 196.8 ± 2.4 Ma.Molybdenite Re contents(337.55-392.75 ppm) and C-OSr-Nd-Pb isotopic evidence of the Huayangchuan carbonatite both suggest a mantle origin for the carbonatite.Our study supports that the Late Triassic carbonatite magmatism was responsible for the world-class U-Mo-REE mineralization in the Qinling Orogen,and that the regional magmatism and ore formation was likely caused by the closure of the Mianlue ocean and the subsequent North China-South China continent-continent collision.     

Timing and formation of porphyry Cu–Mo mineralization in the Chuquicamata district, northern Chile: new constraints from the Toki cluster

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.     

Lithogeochemical,Re–Os and U–Pb Geochronological,Hf–Lu and S–Pb Isotope Data of the Ga'erqiong‐Galale Cu–Au Ore‐Concentrated Area: Evidence for the Late Cretaceous Magmatism and Metallogenic Event in the Bangong‐Nujiang Suture Zone,Northwestern Tibet,China

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 ε_Hf(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.     

甘肃铜矿资源特征与新一轮找矿思路

甘肃省铜矿资源丰富，矿床类型发育齐全，而目前探明的铜储量与已发现的铜矿产数量和矿化分布范围与强度极不相称，进一步找矿潜力巨大，笔者试图通过对甘肃铜矿矿特征的总结分析，在借鉴邻区和国内外铜矿勘查成功经验的基础上，按容矿岩石将甘肃的铜矿划分为6种类型，并提出了主要铜成矿区（带）新一轮找矿思路。     

Re–Os and U–Pb Geochronology of the Erlihe Pb–Zn Deposit, Qinling Orogenic Belt, Central China, and Constraints on Its Deposit Genesis

The Erlihe Pb–Zn deposit is an important mine of the Pb–Zn metallogenic zone in the South Qinling Orogen. It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold. Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials. The Re–Os isotopic data of four pyrite samples construct an isochron, yielding a weighted average age of 226±17 Ma (mean square weighted deviation=1.7), which is considered the main mineralization age. A dioritic porphyrite vein sample, showing weaker mineralization, was also dated using the SHRIMP zircon U–Pb isotopic method to constrain the youngest metallogenic age of the ore deposit, because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field, but also the main ore bodies. The dioritic porphyrite sample yields a weighted mean 206Pb/238U age of 221±3 Ma, which is slightly younger than the Re–Os isotopic isochron age of the pyrites, considered as the upper age limit of the mineralization, namely the ending age of the mineralization. The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma-related fluid, and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle. The Erlihe Pb–Zn deposit and associated dioritic porphyrite vein, important records of Qinling tectonic–magmatism–mineralization activities, were formed during the Triassic collisional orogeny processes.     

基于地质异常的内蒙古新达来草原覆盖区钼铜多金属矿产定量预测

内蒙古新达来草原覆盖区位于古亚洲成矿域的二连—东乌旗钼铜多金属成矿带西段,分布有乌兰德勒、准苏吉花等与中酸性侵入体有关的内生金属矿床,成矿地质条件优越。然而,因受牧草和第四系大面积覆盖的影响,该区各种成矿/示矿信息具有间接、叠加、隐蔽、微弱、不完整等特点,给找矿勘查带来更大的不确定性和风险。因此,必须加强矿产定量预测研究,为覆盖区找矿工作指明方向。本文以赵鹏大院士等提出的地质异常理论为指导,分析新达来草原覆盖区及邻区成矿多样性,总结矿化垂向分布规律,进而通过S-A多重分形滤波模型降低覆盖层对土壤地球化学测量数据和地面高精度地磁数据的干扰,识别和提取深部源引起的弱异常,并将提取的断层、侏罗纪中酸性岩体、岩脉、岩体与围岩接触带、PC1和PC2元素组合异常、高精度磁异常,以及成矿单元与非成矿单元的地理位置X-Y坐标作为随机森林模型的输入预测变量。本文采用SMOTE采样技术克服覆盖区矿床(点)数量少所造成的训练样本不足的缺陷,通过500次随机森林模拟来定量表征与成矿关系密切的综合地质异常,模拟结果的平均袋外误差为2.26%,AUC值达到0.972,且成矿有利度≥0.783的地质异常中分布有88.46%的已知矿床和矿点,说明该方法的有效性。为了进一步降低勘查风险,本文进行了风险与回报分析,发现除1个矿化点外,其余25个矿床和矿点均分布在回报值的正值区域,另有3个矿点和矿化点位于风险值的中高等级区域。在此基础上,利用处于低风险-高回报区的地质异常成矿有利度重新作图,最终圈定出找矿有利地段。     

Geochronology of the Limu W–Sn–Nb–Ta‐Bearing Granite Pluton in South China

Limu W–Sn–Nb–Ta mining district is located in the Nanling Range W–Sn poly‐metallic mineralization belt in south China. The district includes a number of Sn–Nb–Ta and W–Sn ore occurrences; all of them are spatially associated with granite stocks of a largely‐unexposed pluton, the Limu granitic pluton. A granite sample collected from the Sn–Nb–Ta‐bearing Jinzhuyuan granite stock yields a zircon SHRIMP U–Pb age of 218.3 ± 2.4 Ma, a muscovite ⁴⁰Ar/³⁹Ar plateau age of 212.4 ± 1.4 Ma, and a muscovite ⁴⁰Ar/³⁹Ar isochron age of 213.2 ± 2.2 Ma. Another granite sample collected from the W–Sn‐bearing Sangehuangniu granite stock yields a zircon SHRIMP U–Pb age of 214 ± 5 Ma. The geochronological data provide new constraints on the age of the Limu granite pluton and the timing of the associated W–Sn–Nb–Ta mineralization—at least it sets a reasonable upper age limit for the mineralization of the W–Sn–Nb–Ta ores. The reported ages suggest an active Late Triassic granitic magmatism in Limu area which is part of a regional magmatic event near the end of the Indosinian orogeny in south China.     

The Late Early Cretaceous Mo Mineralization in the South China Mo Province: Constraints from U–Pb and Re–Os Geochronology of the Lufeng Porphyry Mo Deposit

Compared to other Mo provinces, few studies focused on the South China Mo Province(SCMP), especially for Early Cretaceous Mo mineralization. The Lufeng porphyry Mo deposit in the SCMP is characterized by disseminated and veinlet-type mineralization in granite porphyry, gneiss, and rhyolite. In this study, six molybdenite samples yield a Re–Os isochron age of 108.0±1.8 Ma, which is consistent with the zircon U–Pb age of the granite porphyry(108.4±0.8 Ma). The coincidence of magmatic and hydrothermal activities indicates that Mo mineralization was associated with the intrusion of granite porphyry during the late Early Cretaceous. A compilation of U–Pb and Re–Os chronological data suggests that an extensive and intensive Mo mineralization event occurred in the SCMP during the late Early Cretaceous. The marked difference in molybdenite Re contents between Cu-bearing(85–536 ppm) and Cu-barren(1.3–59 ppm) Mo deposits of the late Early Cretaceous indicates that the ore-forming materials were derived from strong crust–mantle interactions. Together with regional petrological and geochemical data, this study suggests that late Early Cretaceous Mo mineralization in the SCMP occurred in an extensional setting associated with the roll-back of the Paleo-Pacific slab.     

中国铜矿成矿规律概要

中国铜矿资源丰富.本文在对全国814处铜矿床及其他5000余个矿(化)点资料系统梳理的基础上,完善了对中国铜矿产预测类型的划分方案,分为10个类型,认为斑岩型、矽卡岩型应该作为重点预测类型;其中又以斑岩型铜矿资源最主要,集中分布于冈底斯、昌都-三江、德兴、东天山等地区;成矿时代以新生代和中生代最为重要.系统搜集了全国范围内有关铜矿床的成矿年代学资料,划分为4个铜的主要成矿期;厘定出27个以铜为主的矿床成矿系列,提升了我国铜矿成矿规律研究的程度,为我国铜矿资源的潜力评价预测工作提供了理论依据.     

Geochronology of the Xihuashan Tungsten Deposit in Southeastern China: Constraints from Re–Os and U–Pb Dating

Xihuashan tungsten deposit is one of the earliest explored tungsten deposits in southeastern China. It is a vein type deposit genetically associated with the Xihuashan granite pluton. Here we report new dating and zircon geochemistry results. Re–Os isotopic dating for molybdenite intergrowth with wolframite in the oldest generation of the Xihuashan pluton yielded an isochron age of 157.0 ± 2.5 Ma (2σ). Zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) dating shows that the pluton crystallized at 155.7 ± 2.2 Ma (2σ). This age is similar to the molybdenite Re–Os age for the ore deposit within error. This, together with published data, suggests that the major W(Mo)‐Sn mineralization occurred between 160–150 Ma in southeastern China. These deposits constitute a major part of the magmatic‐metallogenic belt of eastern Nanlin. The lower Re content in molybdenite of the Xihuashan tungsten deposit shows crustal origin for the ore‐forming material. The limited direct contributions from the subducting slab for the tungsten mineralization in the Nanling region suggest a change of the style of the paleo‐Pacific plate beneath southeastern China.