Middle-Lower Yangtze Metallogenic Belt Research Articles

Geochemical characteristics of magnetite in Longqiao skarn iron deposit in the Middle-Lower Yangtze Metallogenic Belt, Eastern China

The Longqiao Fe deposit is the only large stratabound Fe skarn in Eastern China. This extensive ore body is suitable for investigating the spatial variations in trace elements in magnetite from the intrusion to the wall rocks and tracing the evolution of the mineralizing fluid in a skarn deposit. Magnetite samples were collected every 200 m from the ore-forming gabbro-diorite to the edge of the ore body, including the diopside-magnetite and epidote-chlorite-magnetite stages. Our results show that magnetite proximal to the gabbro-diorite displays lower Mg, Al, and Si and higher contents of Ti and V than those found further from the gabbro-diorite. The hydrothermal fluids in both diopside-magnetite and epidote-chlorite-magnetite stages were influenced by reaction with marine sedimentary rocks. Magnetites from different parts of the ore body display a wide range of trace element contents and fall into the porphyry and skarn fields on a (Mn + Al) vs. (Ti + V) discrimination diagram. Based on our results and published data, we propose that the early-stage magnetite from skarn and iron oxide-apatite (IOA) Fe deposits is compositionally similar, and fluid compositional variations are largely dependent on differences in the composition of the wall rock and the intensity of fluid-rock interactions. This results in a large variation in (Ti + V) in magnetite compositions from skarn deposits in the (Mn + Al) vs. (Ti + V) discrimination diagram, which is different from IOA deposits. This study shows that magnetite trace element evolution trends can provide a reliable indication to recognize skarn and IOA deposit types.

Geological characteristic and discrimination criteria of the ore-related granitoids from the Edong and Juirui districts in the Middle-Lower Yangtze Metallogenic Belt

Geological characteristic and discrimination criteria of the ore-related granitoids from the Edong and Juirui districts in the Middle-Lower Yangtze Metallogenic Belt

Genesis of Early Cretaceous porphyrite-type iron deposits and related sub-volcanic rocks in the Ningwu Volcanic Basin, Middle-Lower Yangtze Metallogenic Belt, Southeast China

ABSTRACTThe Ningwu Volcanic Basin (NVB), located in the Lower Yangtze Metallogenic Belt, is characterized by the widespread occurrence of porphyritic iron-ore deposits. These deposits are clustered in three areas within the basin: the northern, central, and southern districts. Our study shows that the differences are existed in geochemistry of the rocks and the mineralization of the deposits among these three districts. Though results of Sr–Nd isotopes indicate that the parental magma of the sub-volcanic rocks in NVB were derived from EMI and EMII, however, the sub-volcanic rocks from the northern and southern districts have higher εNd(t) values (t = 130 Ma) and lower initial 87Sr/86Sr ratios (t = 130 Ma) than those from middle district. The rocks from northern and southern districts are similar to EMI in geochemistry; in contrast, rocks from the middle district are close to EMII. Meanwhile, the deposits from different districts show some differences in mineralization. The magnetites from the northern ore deposits are rich in Cu, Mo, Zn, and Mg and poor in Ca, Al, and Ti, which probably indicates that the magnetites from the northern ore deposits closer to hydrothermal genesis than to magmatic genesis, but the magnetites from the centre are closer to both magmatic and hydrothermal geneses. Based on the fact that a part of the sub-volcanic rocks is closer to EMI and another part to EMII in geochemistry, we suggested that the incorporation of the lower and upper crustal materials into the source regions of the sub-volcanic rocks has taken place by different manner and processes. Integrated with analysis of the tectonic evolution of NVB, we come to the conclusion that the sub-volcanic rocks have recorded the geochemical imprints of the subduction of Yangtze block towards North China block during Indosinian Period and the delamination of the lower crust of Yangtze block during Yanshanian Period.

An Early Cretaceous carbonate replacement origin for the Xinqiao stratabound massive sulfide deposit, Middle-Lower Yangtze Metallogenic Belt, China

Stratabound massive sulfide deposits are widespread along the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and serve as an important copper producer in China. Two contrasting genetic models have been proposed, interpreting the stratabound massive sulfide deposits as a Carboniferous SEDEX protore overprinted by Cretaceous magmatic-hydrothermal system or an Early Cretaceous carbonate replacement deposit. These two contrasting models have been applied to the Xinqiao stratabound Cu-Au sulfide deposit, which is dominated by massive sulfide ores hosted in marine carbonates of the Carboniferous Chuanshan and Huanglong Formations, with minor Cu-Au skarn ores localized in the contact zone between the Cretaceous diorite Jitou stock and the Carboniferous carbonate rocks. New SIMS zircon U-Pb dating suggests that the Jitou stock formed at 138.5±1.1Ma (2σ, MSWD=0.6). Pyrite Re-Os dating yields an imprecise date of 142±47Ma (2σ, MSWD=7.8). The geochronological data thus constrain the mineralization of the Xinqiao deposit at Early Cretaceous.Fluid inclusions in prograde skarn diopside have homogenization temperatures of 450–600°C and calculated salinities of 13–58wt.% NaCl equiv. Quartz from the stratabound ores and pyrite-quartz vein networks beneath the stratabound ores have homogenization temperatures of 290–360 and 200–300°C, with calculated salinities of 5–12 and 2–10wt.% NaCl equiv., respectively. Quartz from the skarn ores and veins beneath the stratabound ores have δ18O values of 12.32±0.55 (2 SD, n=22) and 15.57±1.92‰ (2 SD, n=60), respectively, corresponding to calculated δ18O values of 6.22±1.59 (2σ) and 6.81±2.76‰ (2σ) for the equilibrated ore-forming fluids. The fluid inclusion and oxygen isotope data thus support a magmatic-hydrothermal origin rather than a SEDEX system for the stratabound ores, with the hydrothermal fluids most likely being derived from the Jitou stock or associated concealed intrusion. Results from this study have broad implications for the genesis and exploration of other stratabound massive sulfide deposits along the MLYMB.

A Broadband Seismic Network in the Middle-Lower Yangtze Metallogenic Belt, China

The middle–lower Yangtze Metallogenic belt (MLYMB) is surrounded by the North China Block in the northwest, the Dabie Orogen in the west, and the Yangtze Block in the south (Fig. 1a). The MLYMB experienced tectonic adjustment from south–north compression in the late Jurassic period to extension in the Cretaceous period (Ren et al. , 1997), as indicated by the extensive Cretaceous calc‐alkaline to alkaline volcanism, granitoid magmatism, and synchronously rift volcanic basins. Major geologic features observed today, including the extensional tectonic settings in eastern China and the MLYMB, were basically formed in this transitional period. Figure 1. (a) Schematic map of the tectonic background in the middle–lower Yangtze Metallogenic belt (MLYMB) (study region). The blue patches are the known metallogenic regions. NZ, Ningzhen; NW, Ningwu; LZ, Luzong; TL, Tongling; AQ, Anqing; GC, Guichi; JR, Jiurui; EDN, Edongnan; XGF, Xiangfan‐Guangji fault; YCF, Yangxin‐Changzhou fault; and TLF, Tancheng‐Lujiang fault. The triangles denote the permanent stations deployed by China Digital Seismological Network. (b) Installation of the sensor. A flat marble board is fixed horizontally at the bottom of an excavation (the depth of the excavation is about 100 cm) using fast concrete mix. The sensor is then placed on this marble inside this excavation, with its horizontal components oriented north–south. The excavation is protected by a large, 50 cm×50 cm box without a base panel, which allows the closing of the geophone space and is used to thermally isolate the sensor. Seven large ore‐concentration districts with more than 200 kinds of polymetallic (Cu, Au, Mo, and so on) deposits are clustered in the narrow mineralization zone of the MLYMB. It is still unclear how such rich mineral resources are concentrated in such a narrow zone and what deep geodynamic processes and magmatic activities are …

Petrogenesis and Mineralization of the Paodaoling Au Deposit in Guichi Ore‐cluster Region, Middle‐Lower Yangtze Metallogenic Belt

Acta Geologica Sinica - English EditionVolume 88, Issue s2 p. 507-508 Meeting Abstracts Petrogenesis and Mineralization of the Paodaoling Au Deposit in Guichi Ore-cluster Region, Middle-Lower Yangtze Metallogenic Belt Liu'an DUAN, Liu'an DUAN CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaSearch for more papers by this authorXiaoyong YANG, Corresponding Author Xiaoyong YANG CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaCorresponding author. E-mail: xyyang555@163.comSearch for more papers by this author Liu'an DUAN, Liu'an DUAN CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaSearch for more papers by this authorXiaoyong YANG, Corresponding Author Xiaoyong YANG CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaCorresponding author. E-mail: xyyang555@163.comSearch for more papers by this author First published: 29 December 2014 https://doi.org/10.1111/1755-6724.12374_7Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume88, Issues2Special Issue: Meeting Abstracts: The 14th Quadrennial International Association on the Genesis of Ore Deposits Symposium. August 19–22, 2014, Kunming, ChinaDecember 2014Pages 507-508 RelatedInformation

Geochemical Constraints on Genesis of the Xinqiao Cu‐Au‐S‐Fe Deposit in the Tongling Ore‐Cluster Field, Middle‐Lower Yangtze Metallogenic Belt

Acta Geologica Sinica - English EditionVolume 88, Issue s2 p. 1666-1669 Meeting Abstracts Geochemical Constraints on Genesis of the Xinqiao Cu-Au-S-Fe Deposit in the Tongling Ore-Cluster Field, Middle-Lower Yangtze Metallogenic Belt Huasheng QI, Huasheng QI CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaSearch for more papers by this authorYuliang XIAO, Yuliang XIAO CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaSearch for more papers by this authorXiaoyong YANG, Corresponding Author Xiaoyong YANG CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaCorresponding author. E-mail: xyyang555@163.comSearch for more papers by this author Huasheng QI, Huasheng QI CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaSearch for more papers by this authorYuliang XIAO, Yuliang XIAO CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaSearch for more papers by this authorXiaoyong YANG, Corresponding Author Xiaoyong YANG CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026 ChinaCorresponding author. E-mail: xyyang555@163.comSearch for more papers by this author First published: 29 December 2014 https://doi.org/10.1111/1755-6724.12385_33Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume88, Issues2Special Issue: Meeting Abstracts: The 14th Quadrennial International Association on the Genesis of Ore Deposits Symposium. August 19–22, 2014, Kunming, ChinaDecember 2014Pages 1666-1669 RelatedInformation

3D electrical structure of porphyry copper deposit: A case study of Shaxi copper deposit

Located in Lu-Zong ore concentration area, middle-lower Yangtze metallogenic belt, ShaXi porphyry copper deposit is a typical hydrothermal deposit. To investigate the distribution of deep ore bodies and spatial characteristics of host structures, an AMT survey was conducted in mining area. Eighteen pseudo-2D resistivity sections were constructed through careful processing and inversion. These sections clearly show resistivity difference between the Silurian sandstones formation and quartz diorite porphyry and this porphyry copper formation was controlled by the highly resistive anticlines. Using 3D block Kriging interpolation method and 3D visualization techniques, we constructed a detailed 3D resistivity model of quartz diorite porphyry which shows the shape and spatial distribution of deep ore bodies. This case study can serve as a good example for future ore prospecting in and around this mining area.

Review of the stable isotope geochemistry of Mesozoic igneous rocks and Cu–Au deposits along the middle–lower Yangtze Metallogenic Belt, China

Ore deposition took place in the Yangtze Valley episodically during the Jurassic and Cretaceous periods, generating approximately 200 polymetallic Cu–Fe–Au, Mo, Zn, Pb, and Ag deposits. We analysed the stable isotopes of sulphur, oxygen, and hydrogen from the Cu–Au deposits and correlated our new data with published stable isotope for associated Yanshanian (Mesozoic) igneous rocks. The latter bears a close relationship to Cu–Au mineralization in the area. Cu–Au deposits in the middle–lower Yangtze Valley can be divided into three types: skarn, porphyry, and volcanic. The S–O–H isotopic values allow constraints to be placed on the conditions of origin of these famous Cu–Au ores and their related igneous rocks. Sulphur from the sulphide ores mostly was derived from a magmatic source; however, a few deposits reflect a sedimentary source of sulphur. Oxygen isotope values in quartz from the Shaxi porphyry Cu–Au deposit and from the Tongling skarn Cu–Au deposits range from 2.6‰ to 12.5‰ and from −1.3‰ to 24.5‰, respectively; these values represent larger variations compared with those from other Cu–Au deposits in this metallogenic belt. Hydrogen versus oxygen isotope plots of the Cu–Au ore-forming fluids demonstrate that the fluids came from different sources: the most important involved the mixing of magmatic and meteoric water; the second most important was strictly magmatic water; and the third most important may have been a mixture of formation water or meteoric water that had reacted with carbonate wall rocks.

Tectonic-magmatic-metallogenic system, Tongling ore cluster region, Anhui Province, China

The Tongling ore district of the Middle-Lower Yangtze metallogenic belt is a famous Cu-Au-Fe-S polymetal region, and its tectonic deformation, magmatic evolution, and metallogenic processes have been studied for decades. In this article, we propose a comprehensive tectonic-magmatic-metallogenic model of the ore-forming mechanism constrained by magmatism and regional deformation. In the Tongling district, the tectonic regime underwent two transitions. (1) In the Middle Triassic, the tectonic regime transitioned from quiescence to intense compression. During contraction, the lithosphere thickened and a series of NE-trending folds developed in the cover sequence; because of the multi-layered structure of this caprock, bedding faults, typically cut by steeply dipping faults, developed widely. (2) From 134 to 150 Ma, the tectonic regime changed from compression to extension. During this transition, mantle–crust interaction was prominent; ore-bearing magma was generated by the mixing of crust-derived and mantle-derived melts triggered by delamination of the thickened lithosphere. Meanwhile, detachment faults developed along the interfaces, for example between the lower and upper crust, serving as emplacement sites for several magma chambers. Ore-bearing magma dikes containing large amounts of volatiles derived from a shallow chamber at about –10 km depth migrated into the cover sequence along the pre-existing steeply dipping faults. Melt injection reworked the structural framework, facilitating further development of steeply dipping faults, as well as the vertical transport of ore-bearing fluids. Hydrothermal fluids derived from the emplaced magmas not only formed a range of deposits, including skarns, porphyries, and cryptobreccias around the intrusions but also widely replaced carbonates along bedding-parallel faults and formed so-called stratabound skarn ore bodies, as well as superimposing synsedimentary orebodies developed in the quiescence stage to form several large polymetallic hydrothermal ore deposits. Various types of ore deposits at different depths are clustered in a single orefield, composing a multi-layered mineralization network. In the network, skarn deposits dominate and are characterized by fluid immiscibility processes and diverse element enrichments. The intense mineralization in the Tongling region was caused by the abundance of metals derived from the mantle, favourable ore-controlling structures, and widespread fluid boiling of magmatic hydrothermal fluids, which facilitated metal deposition during the Mesozoic, as well as the superposition of Mesozoic hydrothermal reworking of earlier Palaeozoic sedimentary ore bodies.

Petrogenetic–metallogenetic setting and temporal–spatial framework of the Yueshan district, Anhui Province, east-central China

The Yueshan district is located in the Anqing–Guichi ore deposit area of the Middle–Lower Yangtze Metallogenic Belt. Two groups of intrusive rocks and three main types of ore mineralization occur in this district: diorite plutons (e.g. Yueshan, Zongpu, Wuheng, and Yangshan) and granite plutons (Hongzhen and Dalongshan), Cu–Au–(Fe) skarn deposits (e.g. Anqing, Tiepuling), Cu–Mo–Au–(Pb–Zn) hydrothermal vein-type deposits (Tongniujing), and hydrothermal uranium mineralization (Dalongshan). Detailed geological and geochemical work suggests that the Cu–Au–(Fe) skarn deposits and the Cu–Mo–Au–(Pb–Zn) hydrothermal vein-type deposits have a close spatial and genetic relationship with the dioritic plutons, whereas the hydrothermal uranium mineralization is associated with A-type granite plutons. Based on the highly precise dating of metal deposits and related plutons in the Yueshan district, such as the molybdenite Re–Os, Os–Os dating, 39Ar–40Ar dating of potassium-bearing minerals and quartz, several Rb–Sr isochrons, SHRIMP zircon U–Pb dating + single-grain zircon U–Pb dating, and the SHRIMP zircon U–Pb dating of Hongzhen granite pluton, we suggest that the extensive magmatism and mineralization in the Yueshan district took place in two episodes: (1) the first episode involved the mineralization of both skarn and vein-type hydrothermal deposits, c.a. 136–139 Ma, related to diorite plutons emplaced at 138.7 ± 0.5 Ma; (2) the second episode attended the hydrothermal uranium mineralization at 106.4 ± 2.9 Ma, related to granite intrusive activity at 126.8 ± 1.0 Ma. These two times of Yueshan petrogenetic–metallogenetic development appear to be consistent with a tectonic environment transition from compression to extension.