First Reliable Re–Os Ages of Pyrite and Stable Isotope Compositions of Fe(‐Cu) Deposits in the Hami Region,Eastern Tianshan Orogenic Belt,NW China

The Eastern Tianshan Orogenic Belt (ETOB) in NW China is composed of the Dananhu–Tousuquan arc belt, the Kanggurtag belt, the Aqishan–Yamansu belt and the Central Tianshan belt from north to south. These tectonic belts have formed through arc–continent or arc–arc collisions during the Paleozoic. A number of Fe(‐Cu) deposits in the Aqishan–Yamansu belt, including the Heifengshan, Shuangfengshan and Shaquanzi Fe(‐Cu) deposits, are associated with Carboniferous–Early Permian volcanic rocks and are composed of vein‐type magnetite ores. Metallic minerals are dominated by magnetite and pyrite, with minor chalcopyrite. Calcite, chlorite, and epidote are the dominant gangue minerals. Pyrite separates of ores from those three deposits have relatively high and variable Re contents ranging from 3.7 to 184 ppb. All pyrite separates have very low common Os, allowing us calculation of single mineral model ages for each sample. Pyrite separates from the Heifengshan Fe deposit have an ¹⁸⁷Re–¹⁸⁷Os isochron age of 310 ± 23 Ma (MSWD = 0.04) and a weighted mean model age of 302 ± 5 Ma (MSWD = 0.17). Those from the Shuangfengshan Fe deposit have an isochron age of 295 ± 7 Ma (MSWD = 0.28) and a weighted mean model age of 292 ± 5 Ma (MSWD = 0.33). The Shaquanzi Fe‐Cu deposit has pyrite with an isochron age of 295 ± 7 Ma (MSWD = 0.26) and a weighted mean model age of 295 ± 6 Ma (MSWD = 0.23). Pyrite separates from these Fe(‐Cu) deposits have δ³⁴S_CDT ranging from ?0.41‰ to 4.7‰ except for two outliers. Calcite from the Heifengshan Fe deposit and Shaquanzi Fe‐Cu deposit have similar C and O isotope compositions with δ¹³C_PDB and δ¹⁸O_SMOW ranging from ?5.5‰ to ?1.0‰ and from 10‰ to 12.7‰, respectively. These stable isotopic data suggest that S, C, and O are magmatic‐hydrothermal in origin. The association of low‐Ti magnetite and Fe/Cu‐sulfides resembles those of Iron–Oxide–Copper–Gold (IOCG) deposits elsewhere. Our reliable Re–Os ages of pyrite suggest that the Fe(‐Cu) deposits in the Aqishan–Yamansu belt formed at ～296 Ma, probably in a back‐arc extensional environment.     

Re–Os pseudo-isochron of disseminated ore from the Kalatongke Cu–Ni sulfide deposit,Xinjiang, Northwest China: Implications for Re–Os dating of magmatic Cu–Ni sulfide deposits

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.     

Effects of Subduction of Pacific Plate on the Great Xing’an Range: Constriants from Geochronology and Geochemistry of the Shaxilate Granite Porphyry

As a widely‐developed mineral in various types of rocks, pyrite features important geological information such as temperature and pressure during its formation and evolution (An et al., 2014; An et al., 2018). It is an important geological formation for studying the origins of rocks, mineralization, and deposits (Xue et al., 2014; An et al., 2016). The study of the genesis of gold deposits is a research hotspot in current geology and mineral deposits not only because of high economic value, but also because of important practical significance (An et al., 2017; Yang et al., 2014). Shandong Zhaoyuan, as the third largest gold production area in the world, has important research significance of the origin and generation of gold‐bearing minerals (Xue et al., 2014; Wen et al., 2014). In this study, pyrite from augen granite (figure 1a), syenite (figure 1b), basite (figure 1c) and gold ore (figure 1d) at Zhaoyuan gold deposit Shandong Province, was selected as the research object. The morphological and structural micro‐fabrics were analysed by polarized light microscopy (PLM) and Raman spectroscopy to reveal the source and process of gold further.     

Ni-Cu-Co-rich hydrothermal manganese mineralization in the Wallis and Futuna back-arc environment (SW Pacific)

The Wallis and Futuna back-arc system is a complex area composed of at least two active oceanic spreading centers (the Futuna and Alofi spreading centers) and young volcanic zones characterized by diffuse magmatism locally affected by the Samoan hotspot. This geological setting is favorable to the establishment of hydrothermal systems, in the form of either high-temperature (HT) hydrothermal venting or low-temperature (LT) diffuse flow. During the 2010 Futuna cruise aboard the R/V L'Atalante, three remarkable inactive LT Fe-Si-Mn deposits were discovered (Utu Uli, Anakele and Utu Sega). Some of the Mn-rich precipitates discovered exhibit the highest base metals concentrations so far recorded in ferromanganese rocks, including in the well-documented hydrogenetic crusts and polymetallic nodules. The deposits lie on top of volcanoes and formed in close association with the volcanic facies. The manganese mineralization occurs in the form of massive layered crusts and Mn-rich cements within strongly altered basaltic pyroclastic rocks, brecciated lavas and, more rarely, in sediments. Field observations and mineralogical and chemical studies support a hydrothermal origin for the mineralization and show that nickel, cobalt and copper enrichments are controlled by the precipitation of 7 Å and 10 Å manganates. The conventional geochemical classifications (e.g. Bonatti et al., 1972) used to decipher the origin of Mn mineralization cannot be used for this new type of deposit and new robust discrimination diagrams need to be established. We suggest that the unusual enrichment of metals recorded in our samples is due to (i) a lack of precipitation of high-temperature massive sulfides at depths that would have retained metals (e.g. Cu, Ni, Co); (ii) isolation of the hydrothermal system, thereby avoiding Ni, Co and Cu losses in the water column; and (iii) the ability of birnessite and buserite/todorokite to scavenge Co, Ni, and Cu from aqueous fluids. The Utu Uli and Anakele deposits share certain characteristics with the active hydrothermal system at Loihi seamount (e.g. the depth of mineralization, relationships with pyroclastic volcanoes, and the influence of a mantle plume source) and thus might represent late-stage products of this specific type of hydrothermal activity. Elsewhere, the Co-rich mineralization of the Calatrava volcanic field (CVF) in Spain may be a potential analog of the Utu Sega deposit. The Mn-(Co) deposits of the CVF formed in close proximity to Pliocene volcanic rocks. Metals were transported by epithermal hydrothermal solutions with high fO₂ and cobalt was scavenged by Mn oxides. Together with the well-documented stratabound Mn deposits (González et al., 2016; Hein et al., 2008; Hein et al., 1996), the Mn deposits discovered in the Wallis and Futuna back-arc provide crucial insights into LT hydrothermal activity in the deep ocean. The metal-rich character of this LT hydrothermal activity may be of major importance for future research on the net flux of hydrothermally derived metals (e.g. Ni, Co, Cu) to the open ocean.     

The “El Pilote” fluorite skarn: A crucial deposit in the understanding and interpretation of the origin and mobilization of F from northern Mexico deposits

Fluorite deposits are widespread in northern Mexico and those deposits have traditionally been categorized as exclusively hydrothermal–magmatic in origin. Recently, two different fluorite-bearing type models have been proposed for the Northern Mexican deposits: (1) MVT-like deposits formed from basinal brines mobilized during the Laramide Orogeny (La Encantada deposit, Gonzalez-Partida et al., [Gonzalez-Partida, E., Carrillo-Chavez, A., Grimmer, J.O.W., Pironon, J., 2002. Petroleum-rich fluid inclusions in fluorite, Purisima mine, Coahuila, Mexico. International Geological Review 44 (8), 751–763.]; Tritlla et al., [Tritlla, J., Gonzalez-Partida, E., Levresse, G., Banks, D., Pironon, J., 2004. Fluorite deposits at Encantada-Buenavista, Mexico: products of Mississippi Valley type processes — a reply. Ore Geology Reviews 25, 329–332.]); and (2) fluorite-bearing skarns in close contact with rhyolite intrusives (Levinson, [Levinson, A.A., 1962. Beryllium–fluorine mineralization at Aguachile Mountain, Coahuila, Mexico. American Mineralogist 47, 67–75.]). The El Pilote fluorite deposit falls into the second category, and is the only known example of a magmatic-related fluorite deposit in the area. The fluorite trace-element patterns from both the El Pilote skarn and La Encantada MVT deposits display comparable and very low relative abundances as well as comparable chondrite-normalized REE patterns; this would suggest that the skarn F-source comes from the remobilization of a MVT fluorite manto.     

与海相火山作用有关的铁-铜-铅-锌矿床成矿系列类型及成因初探

文章初步厘定了与海相火作用有关的铁、铜、铅、锌矿床成矿系列类型的概念，并对其进行了分类，讨论了其成因，认为内生外成（沉）是其主要特征，即成矿物质主要由火山作用从深部提供，而矿石又是通过沉积作用在海底形成的。在一定程度上，可从成矿类型的角度将块状硫化物矿床与BIF型或磁铁石英岩型矿床联系起来考虑。该类矿床成矿系列类型的演化特点在一定程度上可以反映地球演化的历史轨迹。     

Raman Spectroscopic Core Scanning for Iron Ore Characterisation

Automated core scanning technologies for mineralogical characterisation of diamond core, drill chips pulps is now an established technique, particularly in the Australian iron ore industry, for mineral analysis in exploration and mining. Application of reflectance spectroscopy over the 400–2500 nm, visible to near-infrared wavelength range, has been used to characterise the iron ore oxide mineralogy of bedded iron deposit (BID) derived iron ores in India (Thangavelu et al., 2011) and Brazil (da Costa et al., 2009), and used to define the ore and gangue (e.g., clay) mineralogy in ironstone or channel iron deposits (CID) in the Pilbara region of Western Australia (e.g., Haest et al., 2012).     

Gold Distribution in Tellurium-Rich Pyrite and Tellurides from the Xiaoqinling Gold District,Southern Margin of the North China Craton

Gold is commonly associated with arsenic in Asrich pyrite or arsenopyrite in a variety types of gold deposit, such as sediment-hosted gold deposits, epithermal Au-Ag deposits, Au-rich VMS deposits, and mesothermal lode gold deposits (Ciobanu and Cook,2002; Pals et al. , 2003; Zacharias et al. , 2004;Wagner et al. , 2007; Large et al. , 2009).     

新疆雅满苏铁矿床矽卡岩和磁铁矿矿物学特征及其地质意义

雅满苏铁矿床位于东天山中段,矿体赋存于下石炭统雅满苏组安山质火山碎屑岩中,受近EW向断裂及环形断裂构造控制。矿体主要呈层状、似层状、透镜状,近矿围岩蚀变强烈,形成石榴石矽卡岩及复杂矽卡岩。电子探针分析结果表明,石榴石为钙铁榴石-钙铝榴石系列,其化学组成可表示为And45.68~100Gro0.67~57.95(A1m+Sps)11~29.03,与典型的矽卡岩型铁矿中石榴石端员组分相似。在磁铁矿Ca+Al+Mn-Ti+V图解中,大部分样品落入矽卡岩型铁矿区;TiO2-Al2O3-MgO图解中,大多数的样品落入沉积变质接触交代磁铁矿趋势区,部分早期磁铁矿落在岩浆趋势区内。结合矿床地质特征和矿物学研究,认为大多数样品经过了一个热液交代作用过程,表明雅满苏铁矿的形成与岩浆热液交代作用有关。     

新疆东天山成矿带成矿系统研究现状及存在问题

天山造山带东段的东天山成矿带是中国重要成矿带之一。笔者分析了东天山成矿带的大地构造演化、成矿作用及矿床类型和成矿时代,重点分析了卡拉塔格、阿奇山等VMS型Cu-Zn、土屋—延东斑岩型Cu-Mo(Au)、玉海斑岩型Cu-Mo(Au)、白鑫滩Cu-Ni硫化物等矿床类型和成矿时代。结合石英滩金矿、康古尔金矿、康南金矿(点)、三岔口斑岩型铜钼矿、黄山东Cu-Ni矿等矿床类型和成矿时代,以及这些矿床与康古尔构造带时空演化间的耦合关系,认为应重新审视土屋—延东等斑岩型矿床的矿床类型和成矿时代。维权银及多金属矿床、红云滩铁铜、雅满苏铁(铜、铅锌)矿的早期蚀变特征,与新近发现的阿奇山VMS型Pb-Zn矿床的蚀变特征一致性,反映在这些地区具有与阿奇山型Pb-Zn矿床成矿潜力。航磁资料结果表明,土屋—延东斑岩型Cu-Mo矿床以西地区具有与东部黄山一带基性-超基性岩体引起的航磁异常一致性特征,说明西部地区有基性-超基性岩体的存在。建议在东天山地区加强典型矿床研究,对康古尔剪切带周围的二叠纪花岗质岩石、基性-超基性岩体以及雅满苏成矿带深部进行评价工作。     

古魔翼龙和披羽蛇翼龙的水上起飞能力

Many of the large pterodactyloid pterosaurs come from marine sediments or inland freshwater deposits (Lawson, 1975; Bennett, 1994; Wang et al., 2005; Unwin, 2006).     

Failles normales Paléocène à Lutétien en zone sud-pyrénéenne (Aragon,Espagne) et flexuration de la plaque ibérique

Close to the South Pyrenean thrust front, synsedimentary normal faults develop in the ‘Garumnian’ continental deposits (Maastrichtian to Palaeocene) and in the carbonate platform during the Lutetian. During the Lutetian, this deformation is accompanied by a change in the sedimentation characterized by the deposit of two series of laminated limestones associated to monogenetic breccias. These normal faults would have formed at the bending of the Iberian plate subducting under Europe. They may also be considered as the starting point for the megaturbidites that deposited further north in the Eocene turbiditic basin. To cite this article: Y. Hervouët et al., C. R. Geoscience 337 (2005).     

Geochemistry and geochronology of quartz diorite host rocks of the Liudaowaizi skarn copper deposit in Jilin Province,NE China

The Liudaowaizi Cu deposit is located in the east of Jilin Province and represents one of the few known Early Jurassic skarn Cu deposits in NE China. Here, we present new whole-rock major and trace element, zircon U–Pb and Hf isotopic data of quartz diorite exposed in the Liudaowaizi skarn Cu deposit. The quartz diorite belongs to the calc-alkaline series, is enriched in some of the large-ion lithophile elements (LILE; e.g., Rb, Ba, Th, and K) and is depleted in high-field-strength elements (HFSE; e.g., Ta, Nb, and Ti). LA-ICP-MS dating of zircons from the quartz diorite in the deposit yielded ages of 196 ± 1 Ma that are interpreted to be the emplacement age of this intrusion. Positive εHf values (6.6–11.6) and young T_DM2 (490–813 Ma) of the quartz diorite indicate that the parent magma was derived from the partial melting of a juvenile lower crust, and magmatism and Cu mineralization were possibly related to the subduction of the Paleo-Pacific Plate.     

Re–Os and U–Pb Geochronology of Porphyry and Skarn Types Copper Deposits in Jilin Province,NE China

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.     

Metallogenic Province and Large Scale Mineralization of Volcanogenic Massive Sulfide Deposits in China

Volcanogenic massive sulfide (VMS) deposits are one of the most important base–metal deposit types in China, are major sources of Zn, Cu, Pb, Ag, and Au, and significant sources for Co, Sn, Se, Mn, Cd, In, Bi, Te, Ga, and Ge. They typically occur at or near the seafloor in submarine volcanic environments, and are classified according to base metal content, gold content, or host-rock lithology. The spatial distribution of the deposits is determined by the different geological settings, with VMS deposits concentrated in the Sanjiang, Qilian and Altai metallogenic provinces. VMS deposits in China range in age from Archaean to Mesozoic, and have three epochs of large scale mineralization of Proterozoic, Palaeozoic and Mesozoic. Only Hongtoushan Cu–Zn deposit has been recognized so far in an Archaean greenstone belt, at the north margin of the North China Platform. The Proterozoic era was one of the important metallogenic periods for the formation of VMS mineralization, mainly in the Early and Late Proterozoic periods. VMS-type Cu–Fe and Cu–Zn deposits related to submarine volcanic-sedimentary rocks, were formed in the Aulacogens and rifts in the interior and along both sides of the North China Platform, and the southern margin of the Yangtze Platform. More than half of the VMS deposits formed in the Palaeozoic, and three important VMS–metallogenic provinces have been recognized, they are Altai–Junggar (i.e. Ashele Cu–Pb–Zn deposit), Sanjiang (i.e. Laochang Zn–Pb–Cu deposit) and Qilian (i.e. Baiyinchang Cu–Zn deposit). The Triassic is a significant tectonic and metallogenic period for China. In the Sanjiang Palaeo–Tethys, the Late Triassic Yidun arc is the latest arc–basin system, in which the Gacun-style VMS Pb–Zn–Cu–Ag deposits developed in the intra-arc rift basins, with bimodal volcanic suites at the northern segment of the arc.     

Paragenesis of cobalt and nickel in the Black Butte shale-hosted copper deposit,Belt Basin,Montana, USA

The Black Butte copper deposits (formerly known as Sheep Creek) are a group of sediment hosted, laterally extensive Cu–(Co–Ag) deposits hosted in dolomitic shale of the mid-Proterozoic Newland Formation. Copper–cobalt mineralization occurs in zones of massive, laminated pyrite that were locally reworked and infiltrated by Cu-rich fluids during early diagenesis. Cobalt, along with substantial nickel and arsenic, mainly occurs as impurities within early, porous pyrite, or as minute grains of sulpharsenides (i.e., cobaltite, glaucodot, and/or alloclasite). Later thermal events remobilized the Co, Ni, and As to form intergrowths of siegenite (Co,Ni)₃S₄ and tennantite. The temperature of this later event is constrained by the mineralogical assemblage to have been relatively low, between 125 and 225 °C. Although many of the characteristics of SEDEX-type deposits are present at Black Butte (e.g., laterally extensive massive pyrite horizons, interbedded black shales, abundant barite and local phosphate horizons, and rifted continental margin setting), the lack of economic Pb and Zn mineralization in the main deposits, and the abundance of Cu with high Co, is more typical of sediment-hosted stratiform copper deposits. The Neihart Formation, a hematitic quartz sandstone resting below the base of the Belt Supergroup, may have been an important source bed for Cu–Co–Ni–Ag fluids. It is speculated that these fluids, ideal for forming Cu deposits, were expelled along growth faults near the margin of the Belt Basin and deposited metals on or just below the sea floor in a setting that is typical of SEDEX deposits. This unique mineral deposit model may have applications to other districts where Cu–Co-rich sulfides are deposited in an exhalative setting.     

Molybdenite Re–Os and albite 40Ar/39Ar dating of Cu–Au–Mo and magnetite porphyry systems in the Yangtze River valley and metallogenic implications

The area of the Middle–Lower Yangtze River valley, Eastern China, extending from Wuhan (Hubei province) to western Zhenjiang (Jiangsu province), hosts an important belt of Cu–Au–Mo and Fe deposits. There are two styles of mineralization, i.e., skarn/porphyry/stratabound Cu–Au–Mo–(Fe) deposits and magnetite porphyry deposits in several NNE-trending Cretaceous fault-bound volcanic basins. The origin of both deposit systems is much debated. We dated 11 molybdenite samples from five skarn/porphyry Cu–Au–Mo deposits and 5 molybdenite samples from the Datuanshan stratabound Cu–Au–Mo deposit by ICP-MS Re–Os isotope analysis. Nine samples from the same set were additionally analyzed by NTIMS on Re–Os. Results from the two methods are almost identical. The Re–Os model ages of 16 molybdenite samples range from 134.7 ± 2.3 to 143.7 ± 1.6 Ma (2σ). The model ages of the five samples from the Datuanshan stratabound deposit vary from 138.0 ± 3.2 to 140.8 ± 2.0 Ma, with a mean of 139.3 ± 2.6 Ma; their isochron age is 139.1 ± 2.7 Ma with an initial Os ratio of 0.7 ± 8.1 (MSWD = 0.29). These data indicate that the porphyry/skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system. Albite ⁴⁰Ar/³⁹Ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 Ma, i.e., 10–20 Ma later. Both mineralization styles characterize transitional geodynamic regimes, i.e., the period around 140 Ma when the main NS-trending compressional regime changed to an EW-trending lithospheric extensional regime, and the period of 125–115 Ma of dramatic EW-trending lithospheric extension.     

Sub-millennial scale variations in East Asian monsoon systems recorded by dust deposits from the north-western Chinese Loess Plateau

Previous work has demonstrated that magnetic properties and sediment particle size of Chinese loess deposits provide information on past behaviour of Chinese summer and winter monsoons, respectively (Heller and Evans, 1995; Derbyshire et al, 1997). It has been suggested that the East Asian winter monsoon system in particular is teleconnected on earth orbital and sub-orbital timescales to climatic states and events in high northern latitudes, especially northern hemisphere ice volume and Heinrich events, (Porter and An, 1995; Chen et al., 1997). However, the majority of this research has been performed around the central part of the Chinese Loess Plateau where the rate of dust accumulation is relatively low, thus limiting the potential resolution of palaeoclimatic records. Here we present a high resolution (5mm / ~20 yr interval) magnetic susceptibility record from an thick loess deposit located at Caoxian in the north-western part of the Loess Plateau. The record spans the “Lateglacial” (last glacial / interglacial transition) and when placed on a palaeomagnetic chronology shows a relationship with the GISP2 proxy air temperature record from Greenland (Grootes et al., 1993; Meese et al., 1994; Stuiver et al 1995). The results demonstrate that several Lateglacial climatic fluctuations previously reported in the North Atlantic region and in Europe are also recorded in China. In addition, the apparent absence of a signal corresponding to the Bølling Interstadial in China during the early deglaciation suggests that, at certain times, the apparent North Atlantic — Asian monsoon teleconnection may have collapsed. The demonstrated ability of the loess deposits to resolve sub-millennial scale climate variations points to their potential as a previously unexplored archive for very high-resolution studies of terrestrial climate.     

A study of igneous rocks related to Zn–Pb mineralization in the Shinyemi and Gagok deposits of the Taebaeksan Basin,South Korea

The Shinyemi and Gagok deposits, located in the Taebaeksan Basin, South Korea, display Zn–Pb mineralization along a contact between Cretaceous granitoids and Cambrian–Ordovician carbonates of the Joseon Supergroup. The Shinyemi mine is one of the largest polymetallic skarn‐type magnetite deposits in South Korea and comprises Fe and Fe–Mo–Zn skarns, and Zn–Cu–Pb replacement deposits. Both deposits yield similar Cretaceous mineralization ages, and granitoids associated with the two deposits displaying similar mineral textures and compositions, are highly evolved, and were emplaced at a shallow depth. They are classified as calc‐alkaline, I‐type granites (magnetite series) and were formed in a volcanic arc. Compositional variation is less in the Shinyemi granites and aplites (e.g., SiO₂ = 74.4–76.6 wt% and 74.4–75.1 wt%, respectively) than in the Gagok granites and aplites (e.g., SiO₂ = 65.6–68.0 wt% and 74.9–76.5 wt%, respectively). Furthermore, SiO₂ vs K/Rb and SiO₂ vs Rb/Sr diagrams indicate that the Shinyemi granitoids are more evolved than the Gagok granitoids. Shinyemi granitoids had been already differentiated highly in deep depth and then intruded into shallow depth, so both granite and aplite show the highly evolved similar chemical compositions. Whereas, less differentiated Gagok granitoids were separated into two phases in the last stage at shallow depth, so granite and aplite show different compositions. The amounts of granites and aplite are similar in the Shinyemi deposit, whereas the aplite appears in an amount less than the granite in the Gagok deposit. For this reason, the Shinyemi granitoids caused not only Fe enrichment during formation of the dolomite‐hosted magnesian skarn but also was associated with Mo mineralization in the Shinyemi deposit. Zn mineralization of the Gagok deposit was mainly caused by granite rather than aplite. Our data suggest that the variation in mineralization displayed by the two deposits resulted from differences in the compositions of their associated igneous intrusions.     

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.