Geology and mineralization of the Sanshandao supergiant gold deposit(1200 t)in the Jiaodong Peninsula,China:A review

The Jiaodong Peninsula in Shandong Province,China is the world’s third-largest gold metallogenic area,with cumulative proven gold resources exceeding 5000 t.Over the past few years,breakthroughs have been made in deep prospecting at a depth of 500‒2000 m,particularly in the Sanshandao area where a huge deep gold orebody was identified.Based on previous studies and the latest prospecting progress achieved by the project team of this study,the following results are summarized.(1)3D geological modeling results based on deep drilling core data reveal that the Sanshandao gold orefield,which was previously considered to consist of several independent deposits,is a supergiant deposit with gold resources of more than 1200 t(including 470 t under the sea area).The length of the major orebody is nearly 8 km,with a greatest depth of 2312 m below sea level and a maximum length of more than 3 km along their dip direction.(2)Thick gold orebodies in the Sanshandao gold deposit mainly occur in the specific sections of the ore-controlling fault where the fault plane changes from steeply to gently inclined,forming a stepped metallogenic model from shallow to deep level.The reason for this strong structural control on mineralization forms is that when ore-forming fluids migrated along faults,the pressure of fluids greatly fluctuated in fault sections where the fault dip angle changed.Since the solubility of gold in the ore-forming fluid is sensitive to fluid pressure,these sections along the fault plane serve as the target areas for deep prospecting.(3)Thermal uplifting-extensional structures provide thermodynamic conditions,migration pathways,and deposition spaces for gold mineralization.Meanwhile,the changes in mantle properties induced the transformation of the geochemical properties of the lower crust and magmatic rocks.This further led to the reactivation of ore-forming elements,which provided rich materials for gold mineralization.(4)It can be concluded from previous research results that the gold mineralization in the Jiaodong gold deposits occurred at about 120 Ma,which was superimposed by nonferrous metals mineralization at 118‒111 Ma.The fluids were dominated by primary mantle water or magmatic water.Metamorphic water occurred in the early stage of the gold mineralization,while the fluid composition was dominated by meteoric water in the late stage.The S,Pb,and Sr isotopic compositions of the ores are similar to those of ore-hosting rocks,indicating that the ore-forming materials mainly derive from crustal materials,with the minor addition of mantle-derived materials.The gold deposits in the Jiaodong Peninsula were formed in an extensional tectonic environment during the transformation of the physical and chemical properties of the lithospheric mantle,which is different from typical orogenic gold deposits.Thus,it is proposed that they are named“Jiaodong-type”gold deposits.

Geology and mineralization of the Dayin’gezhuang supergiant gold deposit(180 t)in the Jiaodong Peninsula,China:A review

The Dayin’gezhuang gold deposit is located in the central part of the Zhaoping Fault metallogenic belt in the Jiaodong gold province-the world’s third-largest gold metallogenic area.It is a typical successful case of prospecting at a depth of 500-2000 m in recent years,with cumulative proven gold resources exceeding 180 t.The main orebodies(No.1 and No.2 orebody)generally have a pitch direction of NNE and a plunge direction of NEE.As the ore-controlling fault,the Zhaoping Fault is a shovel-shaped stepped fault,with its dip angle presenting stepped high-to-low transitions at the elevation of -2000-0 m.The gold mineralization enrichment area is mainly distributed in the step parts where the fault plane changes from steeply to gently,forming a stepped metallogenic pattern from shallow to deep.It can be concluded from previous studies that the gold mineralization of the Dayin’gezhuang gold deposit occurred at about 120 Ma.The ore-forming fluids were H_(2)O-CO_(2)-NaCl-type hydrothermal solutions with a medium-low temperature and medium-low salinity.The H-O isotopic characteristics indicate that the fluids in the early ore-forming stage were possibly magmatic water or mantle water and that meteoric water gradually entered the ore-forming fluids in the late ore-forming stage.The S and Pb isotopes indicate that the ore-forming materials mainly originate from the lower crust and contain a small quantity of mantle-derived components.The comprehensive analysis shows that the Dayin’gezhuang gold deposit was formed by thermal uplifting-extensional tectonism.The strong crust-mantle interactions,large-scale magmatism,and the material exchange arising from the transformation from adakitic granites to arc granites and from the ancient lower crust to the juvenile lower crust during the Early Cretaceous provided abundant fluids and material sources for mineralization.Moreover,the detachment faults formed by the rapid magmatic uplift and the extensional tectonism created favorable temperature and pressure conditions and space for fluid accumulation and gold precipitation and mineralization.

Geology,Geochemistry and Zircon U-Pb Geochronology of Porphyries in the Dabate Mo-Cu Deposit,Western Tianshan,China:Petrogenesis and Tectonic Implications

The Dabate Mo-Cu deposit is a medium-sized porphyry-type deposit in the Sailimu Lake region, western Tianshan, China. We present the geology, geochemistry and zircon U-Pb geochronology of granite porphyries from the Dabate district with the intent to constrain their tectonic setting and petrogenesis. Porphyries in the Dabate district include granite porphyry I（gray white color with large phenocrysts）, granite porphyry II（pink color with small phenocrysts） and quartz porphyry. Granite porphyry II is the Cu and Mo ore-bearing granitoid in the Dabate deposit. LA-ICPMS zircon U-Pb analyses indicate that granite porphyry II was emplaced at 284.2±1.8 Ma. Granite porphyry I and II have similar geochemical features and are both highly fractionated granites：（1） They have high SiO2 content（70.93–80.18 wt% and 72.14–72.64 wt%, respectively）, total alkali（7.58–8.95 wt% and 9.35–9.68 wt%, respectively）, mafic index（0.95–0.98 and 0.93–0.94, respectively） and felsic index（0.79–0.94 and 0.89–0.91, respectively）;（2） They are characterized by pronounced negative Eu anomaly, ＂seagullstyle＂ chondrite-normalized REE patterns and ＂tetrad effect＂ of REE;（3） They are rich in Rb, K, Th, Ta, Zr, Hf, Y and REE, but depleted in Sr, P, Ti and Nb. The magma of granite porphyries in Dabate can be interpreted to have been generated by partial melting of the upper crust due to mantle-derived magma underplating in a post-collisional extensional setting.

Petrogenesis and tectonic implications of the Silurian adakitic granitoids in the eastern segment of the Qilian Orogenic Belt,Northwest China

Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.

Experimental and numerical interpretation on composite foundation consisting of soil-cement column within warm and ice-rich frozen soil

Affected by climate warming and anthropogenic disturbances, the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet engineering corridor(QTEC) is continuously decreased, which may delay the construction of major projects in the future. In this study, based on chemical stabilization of warm and icerich frozen ground, the soil-cement column(SCC) for ground improvement was recommended to reinforce the foundations in warm and ice-rich permafrost regions. To explore the validity of countermeasures mentioned above, both the original foundation and the composite foundation consisting of SCC with soil temperature of -1.0℃ were prepared in the laboratory, and then the plate loading tests were carried out. The laboratory investigations indicated that the bearing capacity of composite foundation consisting of SCC was higher than that of original foundation, and the total deformation of original foundation was greater than that of composite foundation, meaning that overall stability of foundation with warm and ice-rich frozen soil can be improved by SCC installation. Meanwhile, a numerical model considering the interface interaction between frozen soil and SCC was established for interpretating the bearing mechanism of composite foundation. The numerical investigations revealed that the SCC within composite foundation was responsible for the more applied load, and the applied load can be delivered to deeper zone in depth due to the SCC installation, which was favorable for improving the bearing characteristic of composite foundation. The investigations provide the valuable guideline for the choice of engineering supporting techniques to major projects within the QTEC.

The Discovery of Deep Potassium and Lithium Resources in the Huangjinkou Anticline, Northeast of Sichuan

Objectives Important clues have been found for potassium prospecting in the Huangjinkou anticline of the northeast Sichuan Basin in the 1970s(Zheng et al.,2015;Lin et al.,2004).In 2008,China Geological Survey launched a prospective investigation of potash resources in the western region of China,and the local governments and private-owned enterprises also responded positively.Then,

Identified the hydrochemical and the sulfur cycle process in subsidence area of Pingyu mining area using multi-isotopes combined with hydrochemistry methods

Groundwater serves as an important water source for residents in and around mining areas.To achieve scientific planning and efficient utilization of water resources in mining areas,it is essential to figure out the chemical formation process and the ground water sulfur cycle that transpire after the coal mining activities.Based on studies of hydrochemistry and D,^(18)O-H_(2)O,^(34)S-SO_(4)isotopes,this study applied principal component analysis,ion ratio and other methods in its attempts to reveal the hydrogeochemical action and sulfur cycle in the subsidence area of Pingyu mining area.The study discovered that,in the studied area,precipitation provides the major supply of groundwater and the main water chemistry effects are dominated by oxidation dissolution of sulfide minerals as well as the dissolution of carbonate and silicate rocks.The sulfate in groundwater primarily originates from oxidation and dissolution of sulfide minerals in coal-bearing strata and human activities.The mixed sulfate formed by the oxidation of sulfide minerals and by human activities continuously recharges the groundwater,promoting the dissolution of carbonate rock and silicate rock in the process.

Ore-bearing Formations and Mineral Resource Prospects of the Peripheral Areas of the Tarim Block

The tectonic development of the Tarim block has experienced four stages, i. e. Earth's core accretion and block formation in the Precambrian, margin splitting, opening-closing and piecing up in the Early Palaeozoic, rift formation and plate unification in the Late Palaeozoic, and basin-mountain coupling and landform shaping in the Meso-Cenozoic, forming six ore-bearing formations and ore deposits of various genetic types in the Tianshan Mountains, Kunlun Mountains and Altun Mountains. In the peripheral areas of Tarim there are four giant intercontinental metallogenic belts passing through, the Central Tianshan and southwestern Tianshan belts in the former USSR and the Qinling-Qilian-Kunlun and Palaeo-Tethys belts in China. According to the macro-analysis on the nearly one thousand known deposits (occurrences) and geophysical-geochemical anomalies, and the information from reconnaissance in some areas, the region has very good prospects for mineral resources. Some of the metallogenic belts may well become the reserve bases for exploration of mineral resources in China.

Characteristics and Development Significance of Baishuiyan Tourism Geological Resources in Lianhua County, Jiangxi Province

A systematic survey of tourism geological resources in Baishuiyan tufa platform in Lianhua County,Jiangxi Province was conducted,and the characteristics of its tourism geological resources are summarized.Through the analysis and comparison of the same type of landscape resources at home and abroad,the development significance of tourism geological resources here is explored,and four points of thinking are proposed.

SHRIMP Zircon U-Pb Dating of Gabbro and Granite from the Huashan Ophiolite,Qinling Orogenic Belt,China: Neoproterozoic Suture on the Northern Margin of the Yangtze Craton

The recently identified Huashan ophiolitic mélange was considered as the eastern part of the Mianlüe suture in the Qinling orogenic belt. SHRIMP zircon U-Pb geochronology on gabbro from the Huashan ophiolite and granite intruding basic volcanic rocks indicates crystallization ages of 947±14 Ma and 876±17 Ma respectively. These ages do not support a recently proposed Hercynian Huashan Ocean, but rather favor that a Neoproterozoic suture assemblage （ophiolite） is incorporated into the younger （Phanerozoic） Qinling orogenic belt.

Geological Characteristics and Zircon U-Pb Dating of Volcanic Rocks from the Beizhan Iron Deposit in Western Tianshan Mountains, Xinjiang, NW China

The Beizhan large iron deposit located in the east part of the Awulale metallogenic belt in the western Tianshan Mountains is hosted in the Unit 2 of the Dahalajunshan Formation as lens, veinlets and stratoid, and both of the hanging wall and footwall are quartz-monzonite; the dip is to the north with thick and high-grade ore bodies downwards. Ore minerals are mainly magnetite with minor sulfides, such as pyrite, pyrrhotite, chalcopyrite and sphalerite. Skarnization is widespread around the ore bodies, and garnet, diopside, wollastonite, actinolite, epidote, uralite, tourmaline sericite and calcite are ubiquitous as gangues. Radiating outwards from the center of the ore body the deposit can be classified into skarn, calcite, serpentinite and marble zones. LA-ICP-MS zircon U-Pb dating of the rhyolite and dacite from the Dahalajunshan Formation indicates that they were formed at 301.3±0.8 Ma and 303.7±0.9 Ma, respectively, which might have been related to the continental arc magmatism during the late stage of subduction in the western Tianshan Mountains. Iron formation is genetically related with volcanic eruption during this interval. The Dahalajunshan Formation and the quartz-monzonite intrusion jointly control the distribution of ore bodies. Both ore textures and wall rock alteration indicate that the Beizhan iron deposit is probably skarn type.

Petrogenesis of Mesozoic High-Mg Diorites in Western Shandong: Evidence from Chronology and Petro-geochemistry

The high-Mg diorites, widely occurring in western Shandong, have important implications in the study of the relationship between the Mesozoic magmatism and the nature of the lithosphere and its thinning period in the eastern North China craton （NCC）. The Tietonggou and Jinling intrusions are typically representatives. LA-ICP-MS zircon U-Pb dating, major and trace element and Sr-Nd isotopic compositions of the Mesozoic intrusive rocks from western Shandong, eastern China, were analyzed. The weighted mean 106^pb/ 238^U ages from LA-ICP-MS zircon U-Pb dating results for early norite-diorite, late pyroxene-diorite from the Tietonggou intrusion and biotite-diorite from the Jinling intrusion are （131.4±4.9） Ma（n=15）, （134. 5±2.3） Ma（n=13）, and （132.8±4. 2） Ma（n=12）, respectively, implying that they were formed in the Early Cretaceous. The weighted mean 207^pb/ 204^Pb ages for round zircons from late pyroxene-diorite in the Tietonggou intrusion is （ 2 513 ± 54） Ma（ n= 8）, suggesting that the basement of the North China craton should exist in the research area. The high-Mg diorites are characterized by enrichment in MgO, Na20, and light rare earth elements （LREE）, and they are poor in heavy rare earth elements （HREE） and high field strength elements （HFSE）, being similar to adakite. The existence of the mantle peridotite xenoliths with a high-Mg feature for these intrusive rocks implies that their primary magma should be derived from the upper mantle. However, Sr-Nd isotopic composi- tions （Is： 0.704 75--0.707 15;ENd （130 Ma） values： --3.95 to -- 13.30）, depletion in HFSE, and the occurrence of Archean inherited zircons suggest that crustal materials could be involved in the derivation of the primary magma. The compositional difference between the diorites from the Tietonggou and Jinling intrusions could be attributed to those of magma sources and degrees of partial melting. The Early Cretaceous high-Mg diorites are considered to have been formed by the mixed melting of the delaminated lithosphere （lithospheric mantle ＋ crust） and asthenosphere, based on their geochemistry, the mantlederived xenoliths, and the Early Mesozoic lithospheric evolutionary history of the eastern North China craton.

Thrusting and Exhumation Processes of a Bounding Mountain Belt: Constraints from Sediment Provenance Analysis of the Hefei Basin

Lithic (or gravel) composition analyses of the Jurassic Sanjianpu Formation and Fenghuangtai Formation in the Hefei basin show that the sediment provenance consists mainly of four kinds of rock units: the basement metamorphic complex, granitic rocks, medium- and low-grade metamorphic rocks, and sandy and muddy sedimentary rocks, which are distributed along the bounding thrust belt. The whole stratigraphic section can be divided into 2 lithic sequences and 7 subsequences. The regular distribution and changes of lithic fragments and gravels in lithic (or gravel) sequences reflect that the bounding thrust belt of basin has undergone 2 thrusting cycles and 7 thrusting events. Lithic (or gravel) composition analyses of the basin fully reveal that the northern Dabie basement metamorphic complex was exhumed on the earth's surface in the Middle and Late Jurassic, and extensive intermediate and acid intrusive rocks were developed in the southern North Huaiyang or northern Dabie Mountains during the basin's syndepositional stage.

Chemical and stable isotopic geochemical characteristics of ore-forming fluid of the Shizishan copper and gold ore-field,Tongling,China

Shizishan ore-field is a nonferrous and noble metal ore-field which is most rich in copper and gold.There are many types of fluid inclusions in minerals of the deposits.The homogeneous temperatures and the salinities of the fluid inclusions in main mineralization stages have wide ranges,while the different types of the fluid inclusions existed together and their homogeneous temperatures are almost identical in the same mineralization stage,which indicates that the ore-forming process has great relation with the fluid boiling.The gas and liquid chemical compositions and the carbon,hydrogen and oxygen isotopic compositions of the fluid inclusions show that the ore-forming fluids of copper-gold deposits have the same characteristics and evolution tendency,which reflects that the ore-forming material mainly came from the magmatism.The stratigraphic component and the meteoric water may mix in ore- forming fluids in the later mineralization stages.Furthermore,with the fall of the ore-forming temperature the ratios of water and rock decreased.The characteristics of chemical composition and carbon isotopic composition of fluid inclusions indicate that CH4 may play an important role for separating copper and gold in the ore-forming process.

Deformation Stages and Ar-Ar Age Data of the Wan-Zhe-Gan Tectonic Zone,Southeast China,and Their Tectonic Significance

The major tectonic zone that passes through the border regions of the Anhui, Zhejiang, and Jiangxi Provinces in southeast China has been commonly referred to as the Wan-Zhe-Gan fault zone. Geologically, this zone consists of several regional fault belts of various ages and orientations. We have categorized the faults into four age groups based on field investigations. The Neoproterozoic faults are northeast striking. They start from the northeast Jiangxi Province and extend northeastward to Fuchuan in Anhui Province, the same location of the northeast Jiangxi-Fuchuan ophiolite belt. The faults probably acted during the Neoproterozoic as a boundary fault zone of a plate or a block suture with melange along the faults. The nearly east-west- or east-northeast-striking faults are of Silurian ages （40Ar/39Ar age 429 Ma）. This group includes the Qimen-Shexian fault and the Jiangwang-Jiekou ductile shear belt. They represent a major tectonic boundary in the basement because the two sides of the fault have clear dissimilarities. The third group of faults is north-northeast striking, having formed since the early-middle Triassic with 40Ar/39Ar ages of 230-254 Ma. They form a fault belt starting from Yiyang in northern Jiangxi and connect with the Wucheng as well as the Ningguo-Jixi faults. This fault belt is a key fault-magmatic belt controlling the formation of Jurassic-Cretaceous red basins, ore distribution, magmatic activity, and mineralization. When it reactivated during the late Cretaceous, the belt behaved as a series of reverse faults from southeast to northwest and composed the fourth fault group. Therefore, classifying the Wan-Zhe-Gan fault zone into four fault groups will help in the analysis of the tectonic evolution of the eastern segment of the Jiangnan orogen since the Neoproterozoic era.

Temporal-spatial distribution and ore-forming material source of gold,copper and silver polymetallic ore deposits in the Fuping mantle structure zone

This study was conducted following research on metallogenesis in the Zhangjiajie-Xuanhua and East Hebei mantle branch structure zones. The Fuping mantle branch structure zone is one where Au, Cu and Ag poly-metallic ore resources are concentrated in North Hebei. However, there has existed a long-standing controversy on the temporal-spatial distribution of ore resources and their ore-forming material sources. In terms of age dating and the comprehensive analysis of S, Pb, O, C and Si isotopes, it is considered that the temporal-spatial distribution of ore resources in this mantle branch structure zone is obviously controlled by the Fuping mantle branch structure. In space there is developed such a metallogenic pattern as to be Ag, Pb and Zn polymetallic ore deposits with gold appearing inside and copper appearing outside. Metallogenesis is dated mainly at Yanshanian, the ore-forming materials were derived predominantly from the deep interior of the Earth, and ore-forming fluids were derived largely from Yanshanian magmatism.

Properties of Continental Margin and its Hydrocarbon Exploration Significance in Cambrian in the Southern Ordos Kratogen of North China

It is important to determine the properties of the tectonics in Cambrian period for the sake of prospecting deep hydrocarbon in the near future in the southern Ordos Kratogen of North China. Authors chose the marginal areas of the southern Ordos basin as the object of research, avoided the effects of both the Qinling Orogenic Belts （QOB） and Weihe River Graben （WRG） whose geological structures are too complicated. By surveying typical Cambrian outcrops and profdes in the basin edges and based on the cores of 57 wells which penetrated the Cambrian in the basin, combined with the seismic profiles, the field gammaray measuement results and the carbon isotope analysis, Authors conclude that the southern margin of the Ordos Kratogen during Cambrian was a passive continental margin which resulted from sea-floor spreading of the Ancient Qinling Ocean. Epicontinental sea carbonate sediments formed in the south Ordos continental margin during Cambrian, and were predominant as tidal flat and o61itic shoal. Both transgression-regression process and the change in palaeostructure have the obvious cyclicity. Using the junction between the late Nangao age of Qiandong epoch and the early Duyun age of Qiandong epoch as a boundary, each had a full transgression cycle at the upper and lower stages. The early cycle is characterized by high energy clastic littoral facies while the late cycle is characterized by carbonate ramp on which clear water and muddy water developed alternately changing to carbonate platform last. During the early stages, An aulacogen was formed in the middle section of the southern margin. The southern Ordos margin was uplifted and denudated by the Huaiyuan Movement which occurred from the late Furongian age to the middle Flolan age and the history of the passive continental margin ended and entering into a new tectonic cycle. The unconformity surface caused by the Huaiyuan Movement, along with its neighborhood areas where dissolved pores and cavities are developed, may be another important district for good hydrocarbon reservoirs （excluding the unconformity surface on the top of the Ordovician in the Ordos basin）.

Sedimentary Evolution of the Qinghai-Tibet Plateau in Cenozoic and its Response to the Uplift of the Plateau

We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene- Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and iithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. （1） The Paleocene to Eocene is characterized by uplift and erosion in the Songpan-Garze and Gangdise belts, depression （lakes and pluvial plains） in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai-Tibet Plateau. （2） The Oligocene is characterized by uplift in the Gangdise--Himalaya and Karakorum regions （marked by the absence of sedimentation）, fluvial transport （originating eastward and flowing westward） in the Brahmaputra region （marked by the deposition of Dazhuka conglomerate）, uplift and erosion in western Kunlun and Songpan-Garze, and depression （lakes） in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. （3） For the Miocene, a widespread regional unconformity （ca. 23 Ma） in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions （lakes） in the Tarim, Qaidam, Xining-Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18-13 Ma, and north-south fault basins formed in southern Tibet ca. 13-10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. （4） Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil-Qiangtang, Tarim, and Qaidam. The continuous uplift and intensive taphrogeny in the plateau divided the original large basin into small basins, deposition of lacustrine facies decreased considerably, and boulderstone accumulated, indicating a response to the overall uplift of the plateau. Here, we discuss the evolution of tectonic lithofacies paleogeography in Cenozoic and its response to the tectonic uplift of the Qinghai-Tibet Plateau in relation to the above characteristics. We have recognized five major uplift events, which occurred during 58-53 Ma, 45-30 Ma, 25-20 Ma, 13-7 Ma, and since 5 Ma. The results presented here indicate that the paleogeomorphic configurations of the Qinghai-Tibet Plateau turned over during the late Miocene, with high elevations in the east during the pre-Miocene switching to high contours in the west at the end of Miocene.

Study on the geochemical characteristics of ocean-ridge and oceanic-island volcanic rocks in the Nan-Uttaradit zone, northern Thailand

Field investigations and laboratory integrated research as indicated that ophiolite mélange in the Nan-Uttaradit zone, northern Thailand, consists of fragments of tectonites such as metamorphic peridotite (extremely silicified serpentinite), cumulates (pyroxenolite, gabbro, and gabbro-diorite), ocean-ridge basalt, oceanic-island ba-salt and radiolarian silicalite, and it was formed during D3-P. The rock series, rock types and petrogeochemical characteristics of metamorphic tholeiites in the Nan area of the Nan-Uttaradit zone are similar to those of ocean-ridge basalts (C1) in China's Ailaoshan zone. As for the Hawaiites in the Nan area of the Nan-Uttaradit zone, their major elements, REEs and trace elements are similar to those of oceanic-island basalts in China's Jinshanjiang zone (P11). In the Uttaradit area of this zone the metamorphic alkaline basalts show transitional petrogeochemical characteristics between ocean-ridge basalts and oceanic-island basalts, which were still formed in oceanic-island environments. The above-described basalts are all oceanic volcanic rocks and they are the most important part of the Paleo-Tethys oceanic crust in the Nan-Uttaradit zone.

Rare Earth Element Geochemistry on Magmatic Rocks and Gold Deposits in Shizishan Ore-Field of Tongling, China

REE geochemical characteristics of the magmatic rocks and gold deposits in Shizishan ore-field of Tongling were studied. Three types of the magmatic rocks have almost the same chondrite-normalized REE patterns, Eu and Ce anomalous values, and ∑REE, ∑LREE/∑HREE regular changes, which indicates that their magmas come from the same source and their digenetic mechanism is fractional crystallization. In three gold deposits, the mineral ores and related altered rocks have similar chondrite-normalized REE patterns and sharp Eu positive anomalous values. The REE contents reduced from the magmatic rocks to skamization or alteration magmatic rocks, skam type ores, sulphide type ores, wall-rocks limestone or marble. The REE geochemical characteristics of the ores and related rocks show that primary fluids originated from magmatic differentiation in lower pressure of shallow crust, ore-forming hydrothermal solutions gained REE and mineralization elements further from leaching the magmatic rocks, then superimposed and reformed the limestones or marbles and deposited ore-forming material.