Qingshan Group Research Articles

Petrogenesis of Late Mesozoic trachydacites in the Jiaolai Basin, Eastern China: Implications for the destruction of the North China Craton

The North China Craton has witnessed a large-scale lithospheric thinning event in the Mesozoic. The volcanic rocks of the Qingshan Group formed during the destruction of the North China Craton, therefore retaining important information to the deep processes in this region. Zircon U-Pb dating and geochemical analyses have been carried out on volcanic rocks of the Qingshan Group collected from southeastern margin of the Jiaolai Basin. In combination with previously published data on the volcanic rocks of the Qingshan Group, the newly acquired data show that: (1) the volcanic rocks of Qingshan Group in Mashan have SiO2 content of 62.82 ∼ 66.3 wt% and total alkali content (K2O + Na2O) of 7.64 ∼ 9.34 wt%. According to TAS diagram, they belong to trachydacite which experienced strong fractionation between LREEs and HREEs with depletion of HFSEs and enrichment of LILEs. (2) The crystallization age of trachydacite in Mashan is 116.4 ± 2.3 Ma (MSWD = 1.9, n = 9). The magma originated from the partial melting of the ancient lower crust and the enriched lithospheric mantle metasomatized by the fluids/melts released from the subducted slab of the Yangtze Craton. (3) The formation age of magmatic rocks in western Shandong is generally earlier than that in eastern Shandong, while the lower crust delamination in western Shandong preceded that in eastern Shandong. The occurrence of magmatism in eastern Shandong is probably attributed to the delamination process in western Shandong as well as the ongoing tectonic activities along the Tan-Lu fault zone. The lithospheric thinning of the North China Craton was mainly controlled by the change of the subduction angle of the Paleo-Pacific plate, and is probably influenced by the continuous activity of the Tan-Lu fault zone in eastern Shandong.

Revisiting the stratigraphical, sedimentological and provenance evolution of Lingshan Island, offshore of east China: Implications for the destruction of the north China craton

The Cretaceous strata of Lingshan Island, offshore of East China, are a key sedimentary archive for understanding the destruction of the North China Craton (NCC). However, there has been limited progress in characterizing its stratigraphical, sedimentological and provenance evolution in the context of the progressive lithospheric thinning and magmatism associated with the destruction of the NCC. We report field logging data, sandstone framework petrography, and detrital and volcanic zircon U–Pb geochronology data from the Cretaceous strata of Lingshan Island, and correlate these data with coeval sediments in the Jiaolai Basin and volcanic units in the East China. Our results indicate rapid deposition of the Laiyang and Qingshan groups from c. 124–123 Ma with an upward thickening and coarsening succession from the lacustrine turbidites of the Laiyang Group to the deltaic rocks of the Qingshan Group, accompanied by an increase in volcanic activity up-section. Sandstone petrology and detrital zircon U–Pb ages indicates that the source areas for the Laiyang and Qingshan Groups were syn-depositional volcanic rocks and plutonic rocks, with some contributions from the Yangtze Craton and Sulu terrane. Our compilation of detrital zircon U–Pb ages (n = 8513) from the Cretaceous strata of Lingshan island and the Jiaolai Basin in the hinterland implies provenance contributions from four different sources. The zircon Th/U ratios from this large dataset suggests that Cretaceous magmatic zircons formed in an extensional setting (Th/U ratios >1 but with significant variation). The Eu anomalies in magmatic zircons (n = 550) from the Jiaodong Peninsula indicate continuous lithospheric thinning in Eastern China since c. 130 Ma, leading to the destruction of the NCC. Based on all available data, Lingshan Island most likely was a rift basin during the Cretaceous.

Revised onset age of magnetochron M0r: Chronostratigraphic and geologic implications

Abstract The timing of the onset of magnetochron M0r and its duration are disputed, reflecting both a limited set of radioisotopic dates and uncertain magnetostratigraphic correlations. We present a chronostratigraphic framework for a reversed polarity interval based on two chronometers (40Ar/39Ar, U-Pb) and newly published paleomagnetic data from the Qingshan Group, Jiaolai Basin, China. Bayesian modeling of U-Pb zircon and 40Ar/39Ar sanidine dates suggests a minimum duration of 540 ± 37 k.y. (95% credible interval) for the reversed polarity interval. These findings are compatible with an astrochronologic age model for M-sequence seafloor magnetic anomalies, indicating that the reversely magnetized sediments correspond to magnetochron M0r rather than the shorter chron “M-1r.” Integration of U-Pb and 40Ar/39Ar ages constrains the onset of M0r to 120.29 ± 0.09 Ma, which is ~1 m.y. younger than that inferred in the current geologic time scale (GTS 2020). This finding also implies that the Cretaceous normal superchron (CNS) began at 119.70 ± 0.12 Ma and that the average seafloor spreading rate during the CNS was ~3.5% higher than that inferred from GTS 2020. It also suggests that oceanic anoxic event 1a began at 119.40 ± 0.12 Ma, thereby providing an updated chronologic basis for exploring the primary trigger of this carbon cycle perturbation.

Sinistral displacement along the Tan–Lu Fault during the Cretaceous induced by Paleo-Pacific subduction: Constraints from new paleomagnetic and U–Pb geochronological data

The Jiaodong Peninsula in eastern China is separated from the main mass of the North China Craton by the Tancheng–Lujiang (Tan–Lu) Fault, the largest fault system in eastern Asia. Although accumulating lines of evidence have suggested that the Tan–Lu Fault underwent strike-slip movement in the Mesozoic, there is still debate about the timing and magnitude of the displacement. To decipher this problem, we conducted paleomagnetic and U–Pb geochronological studies of the Lower Cretaceous volcanic rocks of the Qingshan Group on the Jiaodong Peninsula, to the east of the Tan–Lu Fault on the southeastern edge of the North China Craton. LA–ICP–MS U–Pb dating of zircons from five samples yielded consistent ages of ca. 120 Ma. Stepwise thermal demagnetization conducted on 308 samples (40 sites) from two sections revealed stable characteristic remanent magnetization directions. After paleomagnetic tests and rejecting inappropriate data, the mean direction from 288 samples (31 independent units) is 200.3°/–51.4° (α95 = 4.1°), with a corresponding pole at 215.1°/73.0° (A95 = 4.8°). The paleolatitude calculated for the Jiaodong Peninsula is lower than that of the main block of the North China Craton, which indicates that latitudinal offset occurred between these two parts, and this offset can be ascribed to strike-slip movement along the Tan–Lu Fault. Our data provide new constraints on regional tectonic movement and Paleo-Pacific subduction processes during the late Mesozoic.

Geochemical Characteristics and Ecological Risk Assessment of Heavy Metals in Surface Soil of Gaomi City.

Gaomi City, the hinterland of Jiaolai Plain in Shandong Peninsula, was selected as the research object. A total of 8197 surface soil samples were collected to determine the contents of eight soil heavy metals (HMs)including Copper (Cu), Lead (Pb), Zinc (Zn), Nickel (Ni), Chromium (Cr), Cadmium (Cd), Arsenic (As), and Mercury (Hg). Statistical methods were used to find out the geochemical background (GCB) in the area, systematic clustering and factor analysis were used to study the homology between HMs, and single-factor evaluation method was used to evaluate the ecological risks in the study area. The results of the study show that the ecological risk of the surface soil in the study area is relatively low, dominated by a planar distribution, with only a few high-risk points. The uneven distribution of Hg in the surface soil is affected by human activities to a certain extent. The ratio of the GCB of the geological unit area to the GCB of the whole area shows that the Hg content of the Qingshan Group and Dasheng Group geological units is higher, and the Pb content in the subvolcanic rock area is slightly higher. The ecological pollution risk in the study area is generally low, and only exists individual high-risk areas, distributed radially in densely populated areas.

Study on geothermal genesis in Juxian area, Shandong Province

In order to explore and develop geothermal resources in Juxian area, Shandong Province has studied the causes of geothermal in Juxian area. On the basis of field investigation, drilling and logging, and water quality inspection in Juxian area, the metallogenic conditions were analyzed from the aspects of geothermal source, geothermal storage, caprock, and geothermal channel formed by geothermal water, and finally the geothermal causes in Juxian area. The surface water and atmospheric precipitation in the study area infiltrated through the fault near the Yishu fault, and after 3,150 m deep circulation, the heat was obtained by the normal geothermal heating method, while dissolving the mineral components in the surrounding rock, and finally gathered in the Qingshan Group andesite, It forms high-quality hot mineral water rich in minerals such as fluorine, strontium, lithium, metaboric acid and metasilicic acid. The andesite caprocks of the Qingshan Group effectively hindered the loss of the geothermal water and heat energy of the geothermal water gathered here. The geothermal water enters the geothermal well through faults and strata dissolution holes, and surges up to the surface.

Zircon U-Pb ages of the cetaceous sedimentary rocks in the Laiyang Basin, eastern China and their tectonic implications

The Laiyang Basin is located in the northern margin of the Sulu high-pressure and ultrahigh-pressure (HP-UHP) metamorphic belt. The sediment source and depositional time of the Laiyang Basin can provide important insights into the exhumation mechanism of the Sulu Orogen and the formation of the Tancheng-Lujiang (Tan-Lu) Fault, but have not been well constrained. In this study, seven samples were collected from typical sections of the Laiyang and Qingshan groups in the southern margin of the Laiyang Basin in the Sulu Orogen. LA-ICPMS U-Pb dating of detrital zircon from these samples yielded ages from 3145 Ma to 115 Ma and can be divided into four groups: (1) 3145–1728 Ma, which indicate a provenance from the Precambrian basement rocks of the North China Craton; (2) 908–522 Ma, which are consistent with the ages of the protolith of the Sulu HP-UHP rocks; (3) 240–220 Ma, which are identical to the ages of the HP-UHP metamorphism. This suggests that the HP-UHP rocks of the Sulu Orogen had been exposed to the surface and contributed to the deposition of the Laiyang Group by the Early Cretaceous; (4) 148–115 Ma (weighted mean age: 125 ± 0.5 Ma; MSWD = 1.2), which, as the main group, suggests that the major source of the sediments in the Laiyang Group was from Early Cretaceous igneous rocks. These young ages, combined with the ages of 119 ± 1 (MSWD = 0.7) Ma determined from the overlain Qingshan Group, confine the depositional age of the Laiyang Group to 119–125 Ma. Further comparison of detrital zircon U-Pb age spectrum between the Laiyang Basin and the Hefei Basin indicates that these two basins were developed independently, rather than developed from single basin and then truncated by the Tan-Lu Fault as suggested by previous studies. Based on the formation age of the Laiyang Basin and other age constraints, we further suggest that the Tan-Lu Fault was formed during the Late Triassic to Early Jurassic. The Mesozoic geological settings in the Sulu Orogen, including the sediments of the Laiyang Basin, Early Cretaceous magmatic intrusive and detachment activities of the Wulian Fault, imply that the Cretaceous exhumation of the Sulu HP-UHP belt was consistent with a metamorphic core complex model.

The Cretaceous of Shandong Province

A well preserved terrestrial Cretaceous succession outcrops in Shandong Province. Although previous studies have conducted much work on the geochronology, subdivision of stratigraphic units, regional correlation and paleontology, high controversies remain about geochronology, subdivision of stratigraphic units and sedimentology. Here, we report a synthesized study of the Cretaceous successions and stratigraphy in Shandong based on the new results. Accordingly, reconstruction of framework of the Cretaceous stratigraphy in Shandong is summarized as, in descending order, the Mengyin Group of the Jurassic/Cretaceous transition, the Lower Cretaceous Laiyang Group, Qingshan Group, Dasheng Group and the Upper Cretaceous Wangshi Group.

Detrital zircon U–Pb geochronology of early Cretaceous sedimentary rocks in Dingzi Bay and Taolin area from the Sulu Orogen: Provenances and tectonic implications

Early Cretaceous sedimentary rocks in the Sulu Orogen (SO) have been a popular topic in recent years. The provenances of sedimentary rocks can help elucidate the tectonic history of the SO, China. The Dingzi Bay and Taolin areas in the SO have always been poorly known. Thus, we date detrital zircons from four sedimentary rock samples including sandstone, siltstone, and greywacke collected in both areas. Age distributions from Dingzi Bay exhibit three major age populations including Palaeoproterozoic (1900–1800 Ma), Neoproterozoic (800–700 Ma), and Early Cretaceous (136–106 Ma) ages and small age populations including early Mesozoic, Palaeozoic, and Palaeoproterozoic–Archean ages, while age distributions in the Taolin area show the largest age population of Early Cretaceous (132–102 Ma) with minor early Mesozoic, Palaeozoic, and Neoproterozoic populations. The youngest detrital zircon populations yield weighted mean ages of ca. 116 Ma in Dingzi Bay and ca. 120 Ma in the Taolin area as the maximum depositional ages, which correspond to the Early Cretaceous Lower Qingshan Group. Age distributions in both areas indicate that the local SO served as the primary source area, whereas the Yangtze Block might have been a lesser source of detrital zircons. The comparison of geochronological, geochemical, and sedimentary data among Dingzi Bay, Taolin, Laoshan, and Lingshan Island suggests an Early Cretaceous marine basin formed over the SO. Further, considering previous regional tectonic history, we propose a two‐stage (Laiyang and Qingshan stages) evolutionary model for this marine basin. We suggest that transpression between the Laiyang and Qingshan stages due to subduction of the Pacific Plate might have caused rapid uplift of the south‐eastern SO and closing of the marine basin. Correspondingly, this process influenced the input of the source material from the Yangtze Block to the marine basin during the Qingshan stage.

Zircon U-Pb geochronology of crystal tuff on Lingshan Island and its geological implications for magmatism, stratigraphic age and geological events

Due to the unique location in the Ludong region, geochronological study of this area is essential for the understanding of the Cretaceous tectonic evolution of Eastern China. Sedimentary sequences interbedded with tuff layers unconformably overlay metamorphic rocks in the Sulu Orogen. This research presents a more reliable geochronological dataset of a tuff layer on Lingshan Island in Qingdao. A total of 103 valid age values from 216 zircon grains were obtained in three fresh tuff samples. Approximately 87% of these zircon ages are dated as the Early Cretaceous, and their peak ages shift from the Aptian stage to the Albian stage. The spatial-temporal relationship between the tuff and the Mesozoic igneous rocks of Eastern China indicate the impact of the Pacific Plate subduction beneath the Asian continent. Six Albian single detrital zircons have a weighted average age of 103.8 ± 1.4 Ma, with the youngest age (103.4 ± 1.4 Ma) constraining the maximum depositional age of the tuff layer. The age sequence of four sections on Lingshan Island is defined in this study: sections A and B belong to the Laiyang Group, and sections C and D are considered the Qingshan Group and were deposited in the Late Cretaceous. Two pre-Cretaceous zircon age peaks were also observed. These age peaks coincide with the magmatic and metamorphic ages preserved in the Sulu Orogen; thus, the Sulu Orogen is the provenance of the sedimentary rocks on Lingshan Island.

Soft-sediment deformation structures related to volcanic earthquakes of the Lower Cretaceous Qingshan Group in Lingshan Island, Shandong Province, East China

The study on soft-sediment deformation structures (SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years, and SSDS developed in turbidite system in the Laiyang Group are widely known by domestic researchers. However, few studies were conducted on the SSDS in fan delta system in the Qingshan Group, Lingshan Island.This study analyzes the classification and characteristics of SSDS especially their lithofacies association and lithologic characteristics through field outcrops investigation and thin section analysis as well. A conclusion was acquired that the paleoenvironment was a fan delta system with occurrence of several volcanic eruptions, where the water became gradually shallower.The SSDS types in the Qingshan Group includes load and flame structure, ball and pillow structure, water-escape structure, hydroplastic deformation structure, plastic sandstone breccia structure, volcanic drop stone and V-shaped ground fissure mainly caused by volcanic earthquakes of three types: (1) seismic waves, (2) gravity and inertia effect of pyroclastic flows, (3) instant differential air pressure; which is different from slumping and tectonic earthquakes occurred in the Laiyang Group. In addition, with the lithofacies association analysis between pyroclastic flow and SSDS beds, a distribution model of SSDS related to volcanic earthquakes can be established: SSDS types changed gradually with their distance further away from the volcanic activity core. Brittle deformation which was common in the proximal zone disappeared gradually; liquefied and plastic SSDS continued to dominate in the medial zone; and slightly liquefied SSDS were developed in the distal zone. Meanwhile, the scale and size of SSDS is negatively correlated with the distance of SSDS depositional locations from the volcanic vent.

Early Cretaceous exhumation of the Sulu orogenic belt as a consequence of the eastern Eurasian tectonic extension: insights from the newly discovered Wulian metamorphic core complex, eastern China

The mechanisms of thinning of the lithosphere and destruction of the North China Craton have been debated in recent decades. Their causal link with regional tectonic extension is well exemplified by the exhumation of the Wulian metamorphic core complex (mcc), along the Sulu orogenic belt to the SE of the North China Craton. The Wulian mcc is a Cordilleran type mcc with a northwestward dipping low-angle master detachment fault zone (the Wulian detachment fault zone), an Early Cretaceous supradetachment basin (the Zhucheng Basin) and a lower plate of ultrahigh-pressure metamorphic rocks in the Sulu orogenic belt. Synthetic structural, fabric and thermochronological data suggest that tectonic extension is responsible for the exhumation of the lower plate and triggered syn- and post-tectonic magmatisms. A new cooling path for the lower plate rocks indicates that the lower plate was exhumed at a high rate of 2.0 km Ma −1 from before c . 128 Ma to 123 Ma and at a moderate rate of 0.35 km Ma −1 from 81 to 61 Ma. The rapid exhumation is consistent temporally with the sedimentation of terrestrial deposits of the Laiyang Group in the Zhucheng supradetachment basin. The post-kinematic granitic intrusions are dated as c. 122 Ma, which marks the cessation of rapid exhumation of the lower plate. Vast amount of andesitic volcanic rocks from 120 to 105 Ma in the Qingshan Group in the Zhucheng Basin may be related to the peak of lithospheric thinning in the Wulian area. These data highlight the importance of regional tectonic extension in the formation of the detachment fault zone and the exhumation of the Wulian mcc, and in triggering syn- and post-kinematic magmatisms. The scenario is consistent with the parallel extension tectonics model in which tectonic extension of the lithosphere led to detachment faulting in both the crust and mantle, resulted in the loss of some of the subcontinental roots, gave rise to the exhumation of the mccs, and triggered plutonic emplacement and volcanic eruptions of hybrid magmas.

Detrital zircon dating and tracing the provenance of dinosaur bone beds from the Late Cretaceous Wangshi Group in Zhucheng, Shandong, East China

The mass burial of dinosaur bone fossils in the Late Cretaceous Wangshi Group in Zhucheng, Shandong Province has been a research focus in recent years. However, the provenance of the dinosaur bone fossils and the accurate depositional age of the bone beds remain ambiguous. Through U–Pb dating of detrital zircons collected from six conglomerate samples from the dinosaur bone beds, we found that the youngest single grain age (YSG) of sample 090414-24-D was 77.3 Ma, representing the maximum depositional age of the dinosaur fossil beds and sediments. This also indicates that the Hongtuya Formation was deposited during the Campanian. Dating results revealed an age peak of 120–110 Ma, which corresponds with the peak age of volcanic rocks of the Lower Cretaceous Qingshan Group. The volcanic rocks of the Qingshan Group are mainly exposed in Laiyang, to the north of Zhucheng, although a few also appear to the south and northwest. Through analysis of conglomerate composition and palaeocurrents in the sediments containing the bone beds, we found that the three different data sets of gravel compositions of the conglomerates were mainly composed of volcanic or pyroclastic rocks. Three different data sets of palaeocurrents suggested that the main sediment source of the Wangshi Group dinosaur bone beds was from the north−northwest of the Basin. Only one data set had a provenance south of the basin. This study revealed that the areas of Laiyang and the Yishu Fault Zone were the main provenance areas of both the dinosaur bone fossils and the sediments of the Wangshi Group in Zhucheng. The southern margin of the Zhucheng Basin may be a secondary source area. This research provides an important basis for judging the deposition time and the sediment source of fossil layers in the Wangshi Group, as well as reconstructing the palaeogeography of the Wangshi Group in the Jiaolai Basin.

Cretaceous deepwater lacustrine dedimentary sequences from the northernmost South China block, Qingdao, China

A sequence of terrigenous siliciclastic rocks crop out at Baxiandun, Qingdao, near the Mesozoic collisional boundary between North China block (NCB) and South China block (SCB). These low-grade metamorphosed siliciclastic rocks are dominated by greywacke with shale, manganiferous fine-grained sandstone, arkose and conglomerate layers. There are two basic interpretations about the formation of these rocks. One considered that this sequence was formed within NCB, and is part of the Cretaceous Laiyang Group and Qingshan Group fluvial facies and volcanic debris facies, as shown on the Shandong Regional Geological Map. Another opinion suggested that these rocks represent turbidity depositional systems in the slope and the basin facies was mainly deposited in Ordovician. Based on field observation, petrological analysis, and most importantly, geochemical results in this study, the sedimentary strata at Baxiandun Section mainly consist of siltstone, sandstone and mudstone lithologies. They are dominated by deepwater debris and turbidity deposits in the slope and base of a lake. The U-Pb detrital zircon dating of the rocks at the Baxiandun Section indicates that the source rocks are very complex and their ages are varied from Archean to Early Cretaceous. The youngest age of the terrigenous detritus could represent the age of the sedimentary strata. Therefore, we infer that the sedimentary rocks belong to Early Cretaceous deepwater lacustrine sedimentary sequences and have multiple sources origined from the erosion of the Sulu UHP orogen and South China block margin.

山东鲁东地区中生代构造–岩浆事件与金矿成矿作用

山东鲁东地区处于特提斯、古亚洲洋和太平洋三大构造域的结合部位，它们的相互作用过程决定并影响着鲁东的成矿环境，在中生代区内有印支和燕山二次造山事件。燕山造山事件在鲁东地区表现为三个造山幕，每一幕表现为挤压与伸展的旋回性，这种旋回性是鲁东金矿和多金属矿成矿的地质背景。中生代构造演化对山东的构造–岩浆事件、沉积环境和成矿作用起着制约与控制作用，岩浆–沉积–构造–成矿事件与区域构造事件具有相互耦合性，金矿、多金属矿的形成与定位同燕山期三个构造幕紧密相联，3期成矿事件160~140 Ma、130~110 Ma和105~80 Ma则与玲珑、郭家岭和伟德山岩体的构造–岩浆热事件相耦合。文章在统计区内已报道的金矿成矿年龄样品318件的基础上，划分了81~105 Ma、110~130 Ma和141~160 Ma三个年龄集中区间，按照成矿作用、矿床类型和成矿时序，认为区内成矿作用与三个构造幕同步，为第一幕Mo-W-Au、第二幕Au-Ag和第三幕Cu-Pb-Zn-Mo-Au成矿作用。Mo-W-Au成矿系列典型矿床是邢家山钼钨矿、铜矿和留村金矿；Au-Ag成矿系列是鲁东地区主成矿期的表现形式，可进一步分为与早白垩世壳幔岩浆作用有关的Au、Ag矿床成矿亚系列、与早白垩世壳幔岩浆作用有关的Au、Ag、Cu、多金属矿床成矿亚系列和与早白垩世壳幔岩浆期后热液活动有关的Cu、Au、Fe、Ag、硫铁矿矿床亚系列，其典型矿床为焦家金矿、三山岛金矿和玲珑金矿等。Cu-Pb- Zn-Mo-Au成矿系列与伟德山造山晚期闪长岩–花岗闪长岩–花岗岩组合、浅成–超浅成石英闪长玢岩–花岗闪长斑岩–石英二长玢岩组合和青山群石前庄组中酸性火山喷发建造关系密切，是区内金矿的叠加成矿期及多金属矿的主成矿期，成矿年龄81~105 Ma。 Eastern Shandong Province is situated at the intersection of three tectonic domains as Tetisi, Paleo-Asian Ocean and Pacific Ocean. Interaction process of these three global tectonic domains control and affect the metallogenic environment of eastern ShandongProvince. This area has experienced lndosinian orogenic event and Yanshanian oro- genic event during Mesozoic period. Yanshanian orogenic event represents three tectonic episodes. Each episode repre- sents cyclicity of extrusion and extension. This cyclicity is the geological background of mineralization in Ludong gold deposit and other polymetallic deposits. Mineralization geological environment of three world-class gold fields with the reserve over one thousand tons, such as Sanshaodao gold field, Jiaojia gold field and Linglong gold field have the char- acteristics of uniqueness and induplication. Mesozoic tectonic evolution controls tectonic-magmatic event, sedimentary environment and gold mineralization. There is a strong coupling relationship between magma-sedimentary-tectonism -mineralization event and regional tectonic evolution. The formation and location of gold deposits and polymetallic deposits also have close connections with three tectonic episodes of Yanshanian orogenic event. Three mineralization events (160 - 140 Ma, 130 - 110 Ma and 105 - 80 Ma) have coupling relationship with three regional tectonic-magmatic hydrothermal events of Linglong rock mass, Guojialing rock mass and Weideshan rock mass respectively. On the basis of gold mineralization ages gained from 318 samples which have been reported in this area, three age concentration periods have been divided as 81 - 105 Ma, 110 - 130 Ma and 141 - 160 Ma. According to mineralization, deposit types and ore-forming sequences, it is regarded that mineralization in this area is synchronous with three tectonic episodes. That is the first Mo-W-Au tectonic episode, the second Au-Ag tectonic episode and the third Cu-Pb-Zn-Mo-Au tectonic episode mineralization. Typical deposits of Mo-W-Au metallogenic series are Xiangjiashan molybdenum and tungsten deposit, copper deposit and Liucun gold deposit. Au-Ag metallogenic series are major representative type of main min- eralization stages in eastern Shandong Province. It can be further divided into Au-Ag metallogenic sub-series which has close relation with mantle-crust magma interaction in early Cretaceous period; Au-Ag-Cu metallogenic sub-series which has close relation with mantle-crust magma in early Cretaceous period; and Cu-Au-Fe-Ag metallogenic sub-se- ries which has close relation with post-magmatic hydrothermal in early Cretaceous period. Typical deposits are Jiaojia gold deposit, Sanshandao gold deposit and Linglong gold deposit. Cu-Pb-Zn-Mo-Au metallogenic series is the main stage of superimposition mineralization and polymetallic mineralization with a mineralization age at 81 - 105 Ma. This series is closely related to the diorite-granodiorite-granite and quartz diorite porphyry-granodiorite porphyry-monzonite porphyry of the late Weideshan orogenic stage, and acid-intermediate volcanic-sedimentary formation of Shiqianzhuang formation in Qingshan Group.

A possible azhdarchid pterosaur from the Lower Cretaceous Qingshan Group of Laiyang, Shandong, China

ABSTRACT A new pterodactyloid pterosaur is identified from the Early Cretaceous Doushan Formaiton of Laiyang, Shandong Province, China, based on a fragmentary humerus. The humerus exhibits several diagnostic characters: deltopectoral crest is elongate and un-warped, its base is slightly displaced relative to the humeral shaft axis, and the crest is swollen terminally and ventrally displaced; humeral shaft is straight and thin-walled with a ‘D’-shaped cross-section. Based on these features, the specimen is referable to the superfamily Azhdarchoidea as Azhdarchidae indet. As the oldest known azhdarchid fossil, the specimen represents a significant stratigraphic range extension for the family. Other non-azhdarchid azhdarchoids such as tapejarids and chaoyangopterids are common in the Jiufotang Formation of western Liaoning, which possibly is equivalent to the Doushan Formation of Laiyang with an age of about 120 Ma. Consequently, the possible coexistence of these azhdarchoids lineages documents that the azhdarchids split from the main azhdarchoid clade occurred no later than the Early Cretaceous.

Zircon U-Pb dating on the Mesozoic volcanic suite from the Qingshan Group stratotype section in eastern Shandong Province and its tectonic significance

A geochronological study of zircon U-Pb on the volcanic rocks from the stratotype section of the Qingshan Group within the Jiaozhou Basin, eastern Shandong Province, is presented. The zircons were analyzed using the method of in situ ablation of a 193 nm excimer laser system coupled with an up to date ICP-MS system. Among the three formations of the Qingshan Group, zircons recovered from the lowest part of the Houkuang Fm. were dated at 106±2 Ma (95% confidence, the same below), whereas those from the lower and upper parts of the Shiqianzhuang Fm. were given ages of 105±4 Ma and 98±1 Ma, respectively. A spatially decreasing trend for the Mesozoic magmatic timing from west to east in the province is observed through comparing the data of this study with those by previous works on the Qingshan volcanic lavas occurring at western Shandong and within the Yishu fault zone. The Qingshan volcanic rocks are constituent of the ‘Shoshonite Province’ in East China. Exposed at most provinces of central East China along the Tan-Lu fault and the Yangtze fault zones, these volcanic suites are characterized by shoshonite and high-K calcalkalic rocks in lithology and thought to be correlated with the partial melting of continental mantle in genesis. It is also shown that the Qingshan potassic volcanic suite from eastern Shandong basins is distinctly younger than those from other areas of the shoshonite province. By contrary, ages of the Mesozoic to Cenozoic alkaline basalts, sourced by asthenospheric mantle, from both northern Huaiyan basin and northern Dabie belt along the Tan-Lu fault zone and from the Ningwu, Lishui and Luzong basins along the Yangtze fault zone are observably older than those occurring within eastern Shandong. The revealed temporal and spatial patterns in magmatism for the two types of volcanic suites make an important geochronological constraint on the Mesozoic to Cenozoic dynamic evolution model of the subcontinental lithosphere in East China.

A new lizard from the Lower Cretaceous of Shandong, China

ABSTRACT A new squamate taxon is described from the Lower Cretaceous Doushan Formation, Qingshan Group, Laiyang, Shandong Province, China. Two incomplete mandibles represent a morphologically peculiar lizard taxon, which has heavily built jaws and highly specialized crushing teeth in a greatly shortened tooth row. Results of phylogenetic analysis show that the new taxon is a member of the Scincomorpha, and can be grouped with the Lacertiformes on the basis of character states related to jaw structures.

99/01779 Selective leaching characteristics of samples of the Pittsburgh and Illinois #6 coal beds: Mroczkowski, S. J. et al. Prepr. Ext. Abstr. ACS Natl. Meet., Am. Chem. Soc., Div. Environ. Chem., 1998, 38, (2), 200–203

The mass burial of dinosaur bone fossils in the Late Cretaceous Wangshi Group in Zhucheng, Shandong Province has been a research focus in recent years. However, the provenance of the dinosaur bone fossils and the accurate depositional age of the bone beds remain ambiguous. Through U–Pb dating of detrital zircons collected from six conglomerate samples from the dinosaur bone beds, we found that the youngest single grain age (YSG) of sample 090414-24-D was 77.3 Ma, representing the maximum depositional age of the dinosaur fossil beds and sediments. This also indicates that the Hongtuya Formation was deposited during the Campanian. Dating results revealed an age peak of 120–110 Ma, which corresponds with the peak age of volcanic rocks of the Lower Cretaceous Qingshan Group. The volcanic rocks of the Qingshan Group are mainly exposed in Laiyang, to the north of Zhucheng, although a few also appear to the south and northwest. Through analysis of conglomerate composition and palaeocurrents in the sediments containing the bone beds, we found that the three different data sets of gravel compositions of the conglomerates were mainly composed of volcanic or pyroclastic rocks. Three different data sets of palaeocurrents suggested that the main sediment source of the Wangshi Group dinosaur bone beds was from the north−northwest of the Basin. Only one data set had a provenance south of the basin. This study revealed that the areas of Laiyang and the Yishu Fault Zone were the main provenance areas of both the dinosaur bone fossils and the sediments of the Wangshi Group in Zhucheng. The southern margin of the Zhucheng Basin may be a secondary source area. This research provides an important basis for judging the deposition time and the sediment source of fossil layers in the Wangshi Group, as well as reconstructing the palaeogeography of the Wangshi Group in the Jiaolai Basin.

99/01781 Thermal decomposition characteristic of vacuum residue in Athabasca tar sand bitumen: Satou, M. et al. Prepr. Symp. Am. Chem. Soc., Div. Fuel Chem., 1998, 43, (3), 426–430

The mass burial of dinosaur bone fossils in the Late Cretaceous Wangshi Group in Zhucheng, Shandong Province has been a research focus in recent years. However, the provenance of the dinosaur bone fossils and the accurate depositional age of the bone beds remain ambiguous. Through U–Pb dating of detrital zircons collected from six conglomerate samples from the dinosaur bone beds, we found that the youngest single grain age (YSG) of sample 090414-24-D was 77.3 Ma, representing the maximum depositional age of the dinosaur fossil beds and sediments. This also indicates that the Hongtuya Formation was deposited during the Campanian. Dating results revealed an age peak of 120–110 Ma, which corresponds with the peak age of volcanic rocks of the Lower Cretaceous Qingshan Group. The volcanic rocks of the Qingshan Group are mainly exposed in Laiyang, to the north of Zhucheng, although a few also appear to the south and northwest. Through analysis of conglomerate composition and palaeocurrents in the sediments containing the bone beds, we found that the three different data sets of gravel compositions of the conglomerates were mainly composed of volcanic or pyroclastic rocks. Three different data sets of palaeocurrents suggested that the main sediment source of the Wangshi Group dinosaur bone beds was from the north−northwest of the Basin. Only one data set had a provenance south of the basin. This study revealed that the areas of Laiyang and the Yishu Fault Zone were the main provenance areas of both the dinosaur bone fossils and the sediments of the Wangshi Group in Zhucheng. The southern margin of the Zhucheng Basin may be a secondary source area. This research provides an important basis for judging the deposition time and the sediment source of fossil layers in the Wangshi Group, as well as reconstructing the palaeogeography of the Wangshi Group in the Jiaolai Basin.