Jiaodong Area Research Articles

Formation of the Liaoshang gold deposit, Jiaodong Peninsula, eastern China: Evidence from geochronology and geochemistry

The Liaoshang gold deposit in the Jiaodong area of the Shandong Province is best known for its super‐large size. Situated on the north‐eastern margin of the Jiaolai Basin, it forms a part of the Jiaobei terrane of the North China Block. Approximately 20 ore bodies within the Liaoshang gold deposit have been explored; of these, four are structurally controlled gold‐bearing pyrite–dolomite vein‐type deposits. These ore bodies lie in an NE‐trending altered fracture zone and are characterized by their thickness and high‐grade ores. The wall rocks of the ore bodies consist of Paleoproterozoic Jingshan Group metamorphic rocks and Mesozoic granites. Gold is hosted mainly in pyrite and dolomite. The ore is divided into two subtypes—the dominant pyrite–dolomite vein subtype and the subordinate altered rock subtype which contains pyrite and dolomite. Fluid inclusions within dolomite indicate that the main metallogenic period was dominated by a CO2–NaCl–H2O fluid system that had low‐moderate salinity, low density, high abundance of CO2, and a small amount of N2. The ore formed at 81‐ to 94‐MPa pressure and between 2.97‐ and 3.24‐km depth. Research on the S, Pb, C, O, and He–Ar isotopes in the gold‐bearing minerals suggests that the ore‐forming material was mainly crustal in origin, with some degree of crust–mantle mixing. The application of Rb–Sr isotope analysis to gold‐bearing pyrite yields a metallogenic age of 105.5 ± 9 Ma. The Sm–Nd isotope analysis of dolomite yields an age of 104.8 ± 5.1 Ma. We propose that gold mineralization in the Jiaodong area occurred in two phases: the early Early Cretaceous for gold deposits in the north‐west and the late Early Cretaceous for gold deposits in the east.

Influence of mine shallow roadway on airflow temperature

With the increase of the depth of mining, the working environment of deep well is worse; in order to improve the working environment of deep mine, on the basis of a lot of practice, the idea of adjusting the temperature of the air flow in the mine was put forward. Take Jiaodong area as an example, on the basis of the model of surface temperature variation, the influence of surface temperature on the temperature of the mine has been established, obtaining the influence of surface temperature on the shallow layer of the mine area. In assumption of the roadway, the heat exchange process of the surrounding rock and the air flow in the shallow layer of the different seasons was analyzed, a model of the relationship between the geometry size of the roadway and the air temperature change was established, in order to control the temperature of the mine into the air temperature by using the shallow tunnel temperature effect and then to improve the working environment of the mine working environment to lay a theoretical foundation.

Tectonic mechanism and evolution of eastern China during the Early Cretaceous: a view from magmatism in the middle to Southern Tan-Lu fault zone

ABSTRACT Mesozoic magmatic rocks are widely distributed in and around the Tan-Lu fault zone (TLF) and show great significance related to the destruction processes of the lithosphere and the evolution of magma sources. This study aims to decipher the petrogenesis of the Early Cretaceous magmatism along the TLF, in order to address the tectonic mechanism for the North China Craton (NCC) lithospheric destruction. This contribution combines investigations of geochemistry, SHRIMP zircon U-Pb ages and O-Hf isotopes of the intermediate to felsic rocks from middle-southern TLF with previous geochronological and geochemical characteristics of other rocks from the study area. Four different rocks are identified: high Mg# adakitic rocks (HMA), low Mg# adakitic rocks (LMA), normal intermediate-felsic rocks (NIF) and A-type granitoids. The emplacement time of the LMA rocks in the Dabie area (143 Ma) were earlier than in the Sulu area (130 Ma). The HMA rocks were formed at the same time (~135 Ma) in the above two areas but the magmatism lasted longer in Jiaodong area, which was near the subduction zone of the Paleo-pacific plate. The HMA rocks are concluded to be derived from the melting of a delaminated thickened lower crust and including reaction with overlying mantle. After 135 Ma, the magmatism in this area exhibited an eastward-younging trend, consistent with plate retreat in the Early Cretaceous. Plutons that were emplaced during 135–125 Ma have higher Ba/Th, Ba/La and Ce/Pb, suggesting magma source for these rocks was metasomatized by hydrous fluids from the subducted plate. At ~125 Ma, A-type granitoids began to be formed. The TLF acted as a favourable channel for transporting mantle material and fluids which made the lithosphere in this area more likely to be destroyed and thinned.

He–Ar Isotopic Tracing of Pyrite from Ore‐forming Fluids of the Sanshandao Au Deposit, Jiaodong Area

The Sanshandao Au deposit is located in the famous Sanshandao metallogenic belt, Jiaodong area. To date, accumulative Au resources of 1000 t have been identified from the belt. Sanshandao is a world‐class gold deposit with Au mineralization hosted in Early Cretaceous Guojialing‐type granites. Thus, studies on the genesis and ore‐forming element sources of the Sanshandao Au deposit are crucial. He and Ar isotopic analyses of fluid inclusions from pyrite (the carrier of Au) indicate that the fluid inclusions have 3He/4He=0.043–0.21 Ra with an average of 0.096 Ra and 40Ar/36Ar=488–664 with an average of 570.8. These values represent the initial He and Ar isotopic compositions of ore‐forming fluids for trapped fluid inclusions. The comparison of H–O isotopic characteristics combined with deposit geology and wall rock alteration reveals that the ore‐forming fluids of the Sanshandao Au deposit show mixed crust–mantle origin characteristics, and they mainly comprise crust‐derived fluid mixed with minor mantle‐derived fluid and meteoric water during the uprising process. The ore‐forming elements were generally sourced from pre‐Cambrian meta‐basement rocks formed by Mesozoic reactivation and mixed with minor shallow crustal and mantle components.

Study on water resources optimal regulation of inter-basin water transfer project

Water resources optimal regulation is an important means to mitigate the shortage of water resources and promote social and economic sustainable development in regions or watershed. With the rapid development of urban population and industrial and agricultural production in recent years, the shortage of water is becoming more and more serious in Jiaodong area. The four regions with serious water shortage including Weifang, Qingdao, Yantai and Weihai in Jiaodong area are the typical research areas. In combination with the water transfer project of Yellow river to Qingdao and the south-to-north water transfer project, the water diversion is carried out to alleviate the contradiction between water supply and demand of Jiaodong area. The year of 2014 deemed as the base year and the years of 2020 and 2025 are the planning years. Based on the supply and demand analysis of water resources, an optimal regulation model is built with the minimum total water shortage considering the constraints of water supply capacity of project, water distribution capacity and minimum water supply of bleeds and so on. The optimal regulation schemes are obtained by solution model using MATLAB programming. The results show that water shortage rate of the four cities decreases significantly in annual regulation. For different planning years, guarantee rate of 50%, 75% and 95%,the total water shortage rate will be reduced by 15.35%、15.75% and 16.85% respectively in 2020, and in 2025the total water shortage rate will be reduced by 13.27%、13.26% and 14.19% respectively. Therefore the water resources optimal regulation of inter-basin water transfer project can effectively mitigate water scarcity and the contradiction between water supply and demand in Jiaodong area.

The Alteration Age of Fracture Zone and Its Implication for the Formation of Gold Deposits in Jiaodong Area

The Alteration Age of Fracture Zone and Its Implication for the Formation of Gold Deposits in Jiaodong Area

Rb-Sr Isotopic Geochronology and Geological Implications of Dongfeng Gold Deposit in Jiaodong Area

<p>The superlarge Dongfeng gold deposit is located in the Potouqing faults-alteration belt of the eastern part of the ‘Zhao-Lai-gold ore belt’, which belongs to the northwestern part of the Jiaodong area. Tectonically, ore bodies are controlled by faults and gold mainly occurs in the pyrite and polymetallic sulfide-bearing quartz vein. In this paper, Rb–Sr isotopic analysis is carried out with the beresite, which formed by hydrothermal metasomatism, and the Rb–Sr isochron age is 125.5±6.7Ma, indicating this deposit set up in the early Cretaceous of the late Yanshanian. Based on the relationship between the Dongfeng gold deposit and the Mesozoic granite, it is suggested that the formation of the gold deposit is a complex geological process of gradual enrichment and precipitation of the ore-forming elements. The initial <sup>87</sup>Sr/<sup>86</sup>Sr ratio of the beresite is 0.711502±0.000069, which indicates the ore-forming materials mainly come from the crust. Combined with the complex mineralization process of the Dongfeng gold deposit and the reported H-O isotopic data, it is suggested that the ore-forming materials are mainly derived from the crust with some mantle materials, while the ore-forming fluids are originated primarily from magmatic hydrothermal and mantle with some precipitate water.</p>

Lateral variation in oxygen fugacity and halogen contents in early Cretaceous magmas in Jiaodong area, East China: Implication for triggers of the destruction of the North China Craton

Pacific subduction has been suggested as the trigger of the destruction of the North China Craton, but evidence for it remains ambiguous. To further investigate this issue, we studied Wulian pyroxene monzonite (123±1Ma) in the west and Rushan gabbro-diorite (115±1Ma) in the east of the Sulu orogen, East China. The rocks of both locations are characterized by low TiO2 but high SiO2 and K2O, fractionated REE patterns with notable negative Ta-Nb-Ti anomalies, and by high initial 87Sr/86Sr ratios and strongly negative εNd (t) and εHf (t) values. These geochemical and isotopic characteristics can be interpreted to be formed by partial melting of enriched lithosphere mantle refertilized by recycled crustal materials that were associated with the Sulu orogeny. Oxygen fugacities of the Rushan gabbro-diorites, estimated based on magnetite-ilmenite equilibration, are significantly higher than those of Wulian pyroxene monzonite. This lateral difference is mirrored by lower F and F/Cl but higher Cl in biotite in the Rushan gabbro-diorite compared to Wulian pyroxene monzonite. All these data suggest a spatially heterogeneous Cretaceous mantle source in terms of halogens and water contents beneath the Sulu orogen, which was most likely caused by the subduction processes of the Pacific plate. H2O-rich fluid in the mantle beneath the east of the Sulu orogen closer to the mantle wedge was prominently from early dehydration of subducted slab at shallow depth, while F-bearing fluid to further west was released by dehydrated deeper slab or stagnant oceanic slab within the mantle transition zone.

Cretaceous–Cenozoic tectonic history of the Jiaojia Fault and gold mineralization in the Jiaodong Peninsula, China: constraints from zircon U–Pb, illite K–Ar, and apatite fission track thermochronometry

The Jiaojia Fault (JJF) in the Jiaodong area of eastern China is an important NNE-trending structure that is subsidiary to the regional Tancheng–Lujiang (Tan-Lu) Fault Zone, and hosts >1200 t of gold reserves contained in disseminated and stockwork ore, dominantly in the footwall of the fault. We present new zircon U–Pb, apatite fission track, and illite K–Ar data along the JJF and have delineated its tectonic history focusing on its formation and reactivation. Zircon U–Pb dating shows that the Shangzhuang granite is a composite body with ages between 132 ± 1 and 127 ± 1 Ma. Illite K–Ar ages for the fault’s gouge range from 83 ± 2 to 68 ± 2 Ma, and the measured apatite fission track ages for ores are between 55 and 21 Ma. Previous zircon U–Pb geochronology and structural studies suggest that the JJF was originally activated in the Jurassic during 160–150 Ma as a sinistral fault. The JJF was a normal fault in the Early Cretaceous due to NW–SE orientated tension and NE–SW compression, which lasted from 135 to 120 Ma. This was followed by sinistral strike–slip faulting due to NW–SE compression and NE–SW tension during 120–110 Ma, and it changed to normal displacement at ca. 110 Ma. Our apatite fission track data analysis and thermal modeling of representative samples suggest that there was a subsequent dextral reactivation of the fault at ca. 55 Ma. Previous age data of ca. 130–110 Ma for gold mineralization along the JJF coincides with the Early Cretaceous magmatism and is coeval with the transition from normal faulting to sinistral strike–slip faulting of the JJF in Early Cretaceous, which is interpreted to be due to changing direction of the subducting Pacific Plate.

山东招远–平度断裂带二维地震剖面研究及其地质意义

自从地震勘探技术成为一种常规勘探方法以来，地震勘探技术始终处于不断改进之中。近几年在金属矿深部勘查中，地震勘探技术的应用逐步得到重视和推广，地震数据处理技术的提高使得地震勘探的精度得到很大的提升，其应用范围逐步扩展，与地震测量相结合的多元信息融合成为开展成矿预测、寻找深部隐伏矿的发展方向。本文在研究招平断裂带地质概况的基础上，以通过大尹格庄金矿的招平断裂带为重点，利用二维地震勘探，完成地震资料的采集、处理和解释工作，探索地震勘查对非层序地层区断裂构造带的解译效果。地震剖面较好的揭示了招平断裂带东西两侧及深部地质体结构特征及差异，清晰地的显示了控矿构造线性特征、多期岩浆活动形成的界面以及后期构造活动对控矿构造的影响，为分析区内断裂构造深部特征和活动期次、岩浆侵入界面和期次划分、构建岩浆–构造格架和建立已知金矿的地震物理勘查找矿模型提供了佐证。二维地震在招平断裂带研究效果显示良好，该数据的取得对胶东地区的深部找矿具有重要的指导意义。 The seismic exploration has become an ordinary exploration method since it was founded and seismic exploration techniques have always been continuously developed. The application of seismic exploration techniques for metallic ore exploration is a new and promising technique, and has gained more attentions. The interpretation precision and application degree of seismic explo-ration techniques can be improved by high precision seismic prospecting method and advanced data processing technique. The technique of coupling seismic exploration and seismic surveying is the developing direction of mineralization prediction and geophysics prospecting for concealed deposit. Based on the geological condition research of Zhaoping fault zone, this paper chose a typical part through Dayingezhuang mining area of Zhaoping fault zone as the object, and focused on the 2D seismic prospecting data acquisition, actual seismic data processing and seismic interpretation, and gained a better effect. The available seismic sections with high quality for structure interpretation have been obtained in the study area. Result of tomography reveals the deep-seated structural features, the linear feature of ore-controlling structure and the contact surfaces among different geologic bodies clearly. These researches will facilitate the depth study of the deep structure features, large-scale tectono-magmatic activities, the tectono-magmatic evolutionary history, and will be helpful for the setting of seismic exploration ore-prospecting model. The successful application of 2D seismic prospecting technology is very important for the deep mineral exploration in Jiaodong area.

Interaction between Structures' Formation and Plutons Intrusion: An Seismic Profile Evident Coming from the Depth of Zhaoping Faults, Jiaodong Area

Interaction between Structures' Formation and Plutons Intrusion: An Seismic Profile Evident Coming from the Depth of Zhaoping Faults, Jiaodong Area

Mesozoic Tectonomagmatic Evolution and Gold Metallogeny in Jiaodong Area, East China

There were twice major collision orogenic events in Jiaodong area in Mesozoic period. It showed as three times of magmatic activities and stretching in Jiaodong area. In this paper, based on collecting age datas, referring to the previous classification scheme, a chronological frame pattern of Yanshanian granites had been put forward: Linglong-Kunyushan granite emplacement was in in 160~150Ma; the formation of Guojialing granodiorite was in 130~126Ma; Weideshan granodiorite-granite emplacement was in 120~110Ma; Laoshan A-type miarolitic cavity parlkaline alkali feldspar granite emplacement was in 110~100Ma and represented the end of Yanshan movement. Gold mineralization in three periods in this area had coupled relation with Linglong-Kunyushan granite, Guojialing granodiorite and Weideshan granodiorite-granite. Jiaodong tectonic-magmatic events and gold mineralization were controlled by the interactions among Tethyan tectonic domain, Paleo-ocean tectonic domain and the Pacific tectonic domain.

Stable isotope geochemistry and Re–Os ages of the Yinan gold deposit, Shandong Province, northeastern China

The Yinan gold deposit in the Luxi area of Shandong Province in northeastern China is a skarn-type ore deposit. In this article, we present results from sulphur, lead, carbon–oxygen, and helium–argon isotope chemistry to characterize the ore genesis and source features. We also present rhenium–osmium ages from molybdenite to evaluate the timing of ore formation. The δ34S values of pyrite from the ore deposit range from 0.7‰ to 5.60‰ with a mean at 2.70‰, close to mantle and meteorite sulphur. Among Pb isotopes, 206Pb/204Pb values range from 18.375 to 18.436, 207Pb/204Pb values from 15.694 to 15.8, and 208Pb/204Pb values from 38.747 to 39.067. The δ13C values of calcite associated with the ores range from −0.2‰ to −0.5‰ and their δ18O values show variation from 9.4‰ to 12.6‰, suggesting a mixed fluid source. The 3He/4He and 40Ar/36Ar ratios of fluids trapped in pyrite are in the range of 0.27–1.11 Ra and 439.4–826, respectively, with calculated proportion of the mantle-derived He ranging from 3.25% to 14.03% and atmosphere argon ranging from 35.8% to 67.3%. The data suggest that the ore-forming fluids were derived from the crust and were mixed with a distinct contribution of mantle helium. The Re and Os values vary from 32 × 10−6 to 93.02 × 10−6 and from 0.01 × 10−9 to 0.34 × 10−9, respectively. The model ages of molybdenite range from 126.96 ± 1.82 Ma to 129.49 ± 2.04 Ma, with a weighted mean age of 128.08 ± 0.75 Ma and isochron age of 130.3 ± 3 Ma. These ages are close to the age of the associated quartz diorite porphyrite pluton, suggesting a close relationship between Cretaceous magmatism and metallogeny in NE China. A comparison of the Yinan gold deposit in the Luxi area with those of the Jiaodong area shows that the contrast in metallogenic features between the two are linked with the tectonic and geodynamic history.

Geodynamics of gold metallogeny in the Shandong Province, NE China: An integrated geological, geophysical and geochemical perspective

The Shandong Province along the southeastern margin of the North China Craton is the largest gold producing region in China. The nature and extent of gold metallogeny between the Western Shandong (Luxi) and Eastern Shandong (Jiaodong) sectors display marked contrast. In this paper, we synthesize the information on mineralization and magmatism, S–Pb–H–O–C–He–Ar isotopic data of the ores and Sr–Nd–Pb–Hf isotopic data of the Mesozoic plutons from the Shandong region. Combined with the salient regional geophysical data, we discuss the geodynamic setting of the gold mineralization in Shandong. The age data converge to indicate that the peak of gold metallogeny in this region occurred at ca. 120±10Ma. The mineralization in Luxi area shows links with sources in the Tongjing and Yinan complexes. The ore-forming materials in the Jiaodong area were derived from multiple sources and show clear evidence for crust–mantle mixing. The Moho depth on both sides of the Tan–Lu fault is broadly similar with only a minor variation across the Tan–Lu fault. The LAB (lithosphere–asthenosphere boundary) in the Jiaodong region is shallower than that in the Luxi area. The Tan–Lu fault is identified as a major corridor for asthenosphere upwelling. Geochemical features show that the mantle beneath the Luxi area is mainly of EM1 type, whereas the mantle in the eastern part, close to the Tan–Lu fault shows mixed EM1 and EM2 features. In contrast, the mantle beneath the Jiaodong area is mainly of EM2 type, suggesting the existence of more ancient lithospheric mantle beneath the Luxi area, in comparison to the extensively modified lithospheric mantle and asthenosphere beneath the Jiaodong area. The gold metallogeny in Shandong Province occurred in the geodynamic setting of lithospheric thinning. The differences in the character and intensity of gold mineralization between the Western and Eastern Shandong regions might be a reflection of the contrasting tectonic histories. The Western Shandong region preserves imprints of destruction through the Yangtze plate collision which probably marks the prelude for gold metallogeny in Jiaodong area. Subsequent magmatic input and cratonic destruction through Pacific plate subduction provided the settings for the later widespread mineralization in multiple phases.

The Mesozoic Tectonic Dynamics and Chronology in the Eastern North China Block

Mesozoic tectonic events in different areas of the eastern North China Block (NCB) show consistency in tectonic time and genesis. The Triassic collision between NCB and Yangtze results in the nearly S-N strong compression in the Dabie, Jiaodong, and west Shandong areas in Middle Triassic-Middle Jurassic. Compression in the Yanshan area in the north part of NCB was mainly affected by the collision between Mongolia Block and NCB, as well as Siberia Block and North China-Mongolia Block in Late Triassic-Late Jurassic. However, in the eastern NCB, compressive tectonic system in Early Mesozoic was inversed into extensional tectonic system in Late Mesozoic. The extension in Late Mesozoic at upper crust mainly exhibits as extensional detachment faults and metamorphic core complex (MCC). The deformation age of extensional detachment faults is peaking at 120–110 Ma in Yanshan area and at 130–110 Ma in the Dabie area. In the Jiaodong area eastern to the Tan-Lu faults, the compression thrust had been continuing to Late Mesozoic at least in upper crust related to the sinistral strike slipping of the Tan-Lu fault zone.The extensional detachments in the eastern NCB would be caused by strong crust-mantle action with upwelling mantle in Late Mesozoic.

Zircon U–Pb age, geochemistry and Sr–Nd–Pb isotopic compositions of adakitic volcanic rocks from Jiaodong, Shandong Province, Eastern China: Constraints on petrogenesis and implications

A zircon U–Pb age of adakitic rocks from Jiaodong, the Shandong Province, indicates that the volcanic rocks erupted at 123.6 ± 0.8 Ma. The volcanic rocks are composed only of trachyandesite with SiO 2 contents ranging from 59 to 62 wt.% and Al 2O 3 contents from 14 to 16 wt.%. Their K 2O contents range from 3.1 to 3.9 wt.% and those of Na 2O from 4.2 to 4.9 wt.%, indicating that these rocks belong to the alkaline K-rich series. These rocks are characterized by enrichment in light rare earth elements (LREE) and depletion in heavy rare earth elements (HREE). They show strongly positive Ba anomalies and negative Nb, Ta, and Ti anomalies. The trachyandesites have high concentration of Sr, ranging from 919 to 1376 ppm, and low Yb (0.92–1.16 ppm) and Y contents (13.3–15.0 ppm), resulting in high Sr/Y (65–98) and La/Yb ratios (38–51), all of which are characteristics of adakites defined by Defant and Drummond [Defant, M.J., and Drummond, M.S., 1990. Derivation of some modern arc magmas by melting of young subducted lithosphere. Nature 347, 662–665]. Isotopic compositions have high Sr and Pb ratios ( 87Sr/ 86Sr = 0.7097–0.7099; 208Pb/ 204Pb = 37.71–38.30; 207Pb/ 204Pb = 15.34–15.54; 206Pb/ 204Pb = 16.95–17.19), but low Nd ( 143Nd/ 144Nd = 0.51150–0.51153; ε Nd( t) = −18.5 to −19.1). These geochemical features suggest a mafic, lower crust magma source. High Sr/Y and La/Yb ratios and negative Nb and Ti anomalies of the adakitic rocks suggest that garnet and amphibole were stable as two residual phases during partial melting, implying that the crustal thickness exceeded 40 km in the Early Cretaceous. The present thickness of the crust in the Jiaodong area is only ∼32 km, and therefore the crust appears to have been thinned by at least 8–10 km since Early Cretaceous times. The high MgO (2.7–3.3 wt.%), Cr (93–274 ppm), and Ni (60–115 ppm) contents and high Mg # (46–52) values in the adakitic rocks favours interaction between the pristine melts and mantle peridotite prior to eruption.

Study of thrust and nappe tectonics in the eastern Jiaodong Peninsula, China

Thrust and nappe tectonics have affected the eastern Jiaodong Peninsula, the easternmost terminal of the Sulu Ultra-high Pressure Metamorphic Belt. Four nappes have been mapped, named respectively the Shidao, Rongcheng, Mishan and Mouping nappes. The methods used included multi-scale structural analysis and structural chronology analysis. These nappes define four deep level slip-thrust shear zones that were mainly active in the Mesozoic. The amount of ductile deformation decreases from the Shidao to Rongcheng to Mouping to Mishan shear zones, and shows an inverse relationship with temperature. 40Ar/39Ar chronological analysis and the chronological results of former workers reveal four movement steps defined by the development of thrusts and nappes in the late Triassic (210–180 Ma), extensional movement from the Jurassic to early Cretaceous (180–130 Ma), slip-thrust movement in the Early Cretaceous (130–120 Ma), and extensional movement since the Late Cretaceous (120 Ma). The order of boundary shear zone motion in the period of slip-thrust movement during the Early Cretaceous (130–120 Ma) was along the Shidao, Rongcheng, Mouping and finally the Mishan shear zone. This resulted in clockwise rotation of the nappes relative to block west to the Tan-Lu Faults. Because of the similar evolutionary history of the Tan-Lu Faults and the thrust and nappe structure in the eastern Jiaodong Peninsula, slip dislocation along the Tan-Lu Faults might have been absorbed by thrust and nappe tectonics in the Jiaodong area in the Mesozoic era, resulting in much less dislocation on the Tan-Lu faults in North Eastern China than that in south along the Jiaodong Peninsula.

Mesozoic tectonics in the Eastern Block of the North China Craton: implications for subduction of the Pacific plate beneath the Eurasian plate

Abstract The Jiao-Liao massif is located in the hanging wall of the north-dipping Dabie–Sulu suture zone and is an important part of the Eastern Block of the North China Craton. Several important tectonic models for the tectonic evolution of Eastern Asia rely on critical information from the Jiao-Liao massif. This paper combines new sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages of the Dandong Granite in the southern Liaoning Province, China, with extensive field data for the eastern North China Craton, including the Bohai Bay Basin. Combined with other recent SHRIMP dating, we use this information to summarize the Mesozoic tectonic reactivation and evolutionary processes of the Jiao-Liao massif of the Eastern Block of the North China Craton. In this study we identify a c . 160 Ma episode of partial melting of Palaeoproterozoic plutons in the Jiao-Liao massif. Cathode luminescence and backscatter electron imagery reveal c . 167–157 Ma magmatic euhedral single zircons and magmatic zircon rims surrounding c . 2100 Ma cores in the Dandong Granites near the Liaonan Neoarchaean terrane. This partial melting is probably related to in situ remelting of ancient lower continental material, mostly the North China Craton. The Dandong plutons are aligned in a NE–SW direction and are extensively deformed by subhorizontal ductile thrust-related shearing and subsequent NNE–SSW trending folds. Here, we show that for the Dandong area the first deformation occurred between 195 and 193 Ma, based on K–Ar and 40 Ar/ 39 Ar ages of muscovites from east–west-trending shear zones on the Liaodong Peninsula. Based on the field relationships between the plutons and structural fabrics, a range from 153 to 145 Ma is defined as the duration of the second deformation in the Dandong Granites. The third deformation is marked by the formation of NNE–SSW strike-slip faults between 135 and 95 Ma. This deduced age range is similar to an 40 Ar/ 39 Ar age range of 128–132 Ma of initial sinistral strike-slip faulting of the Tan-Lu fault in Anhui Province and to a biotite cooling age of 100±2.3 Ma of the Yilan–Yitong segment of the Tan-Lu fault in the Jilin Province. These faults are transtensive and controlled the formation of pull-apart basins. However, during the third deformation, some metamorphic core complexes in Eastern China formed in the overlapping area between the large-scale sinistral faults. Our SHRIMP data also indicate that the Liaodong basement and its Early Mesozoic magmatism are similar to the Jiaodong basement and its Mesozoic magmatism. Therefore, the Early Mesozoic evolution of the Liaodong area, similar to that of the Jiaodong area, was also closely related to the Sulu orogen in the Early Mesozoic and to the Pacific subduction throughout the Mesozoic.

Fractal Principle of Mineral Deposit Size Forecasting and Its Implication for Gold Resource Potential Evaluation in China

AbstractMineralization distributions are very heterogeneous in nature. As large or superlarge mineral deposits are quite rare whether in time or in space, it is difficult to detect all the largest mineral deposits in a region in a limited period of time owing to the restriction of technology and exploration degrees—this is called “not all discovered”. However, all discovered large, especially superlarge, mineral deposits generally have a complete census in the geological literatures. On the other hand, not all discovered small mineral deposits are recorded in the geological literatures because for economic reasons people have not much interest in them—this is called “not all recorded”. This practice often results in the observation truncations, that is, the data points near the two ends in an observable population, which is obtained by fitting a power law size‐frequency distribution to discovered mineral deposits in a given region, show concave‐down departure from the correlation line fitted. The authors suggest that the size and number of undiscovered deposits may be forecast by fitting a fractal size distribution to discovered mineral deposit sizes between the upper and lower truncation observations and then extrapolating the scale‐independent area to deposit sizes larger than the upper truncation limit. Based on the statistical results obtained by the fractal size‐frequency distributions of 394 discovered gold deposits with sizes greater than 2 t Au in China and 83 known gold deposits with sizes over 0.3 t Au in the Jiaodong area of China, the authors forecast according to the present commercial standards for gold ores that the total resources of undiscovered gold deposits ranging in tonnage from 50 to 2000 t Au are more than 4500 t in China, and that in the Jiaodong area of China the total resources of potential gold deposits with sizes in the range of 30 to 650 t Au are about 700 t.

Genesis and geological-geochemical characters of the Rushan gold deposit, Shandong, China

The Rushan gold deposit, explored in recent years in the Jiaodong area, Shandong Province, is a quartz vein-type gold deposit hosted in granite. The temperature of its major mineralization episode is between 220°C and 280°C. The salinity of the ore-forming fluid is 5 % to 9% NaCl equivalent, with H2O and CO2 as the dominant gas constituents. The fluid is rich in Na+, Ca2+ and Cl−, but relatively impoverished in K+ and F−, characterized by either Ca2+ > Na+ > K+ (in three samples) or Na+ > Ca2+ > K+ (in six samples). Hydrogen and oxygen isotopes in the ore-forming fluid are highly variable with δ18 $$O_{H_2 0} $$ ranging between − 7.70‰ and 5. 97‰ and $$\delta D_{H_2 0} $$ between − 128‰ and − 71‰. The possibility of lamprophyre serving as the source of gold can be excluded in view of its low gold content on the order of 2.5 × 10−9. Rb-Sr isochron ages of the deposit and the host Kunyushan granite are ( 104.8 ± 1.5) Ma and 134.6 Ma respectively with the respective initial Sr ratios of 0. 71307 and 0.7096. It is considered that the emplacement of the lamprophyre under a tensile environment had provided sufficient heat energy to facilitate deep circulation of meteoric water by which ore metals were extracted from the Kunyushan granite through long-term water-rock reaction.