paragenesis and geochemistry of ore minerals in the epizonal gold deposits of the yangshan gold belt west qinling china six epizonal gold deposits in the 30 km long yangshan gold belt gansu province are estimated to contain more than 300 t of gold at an average grade of 4 76 g t and thus define one of china s largest gold resources detailed paragenetic studies have recognized five stages of sulfide mineral precipitation in the deposits of the belt syngenetic diagenetic pyrite py0 has a framboidal or colloform texture and is disseminated in the metasedimentary host rocks early hydrothermal pyrite py1 in quartz veins is disseminated in metasedimentary rocks and dikes and also occurs as semi massive pyrite aggregates or bedding parallel pyrite bands in phyllite the main ore stage pyrite py2 commonly overgrows py1 and is typically associated with main ore stage arsenopyrite apy2 late ore stage pyrite py3 arsenopyrite apy3 and stibnite occur in quartz calcite veins or are disseminated in country rocks post ore stage pyrite py4 occurs in quartz calcite veins that cut all earlier formed mineralization electron probe microanalyses and laser ablation inductively coupled plasma mass spectrometry analyses reveal that different generations of sulfides have characteristic of major and trace element patterns which can be used as a proxy for the distinct hydrothermal events syngenetic diagenetic pyrite has high concentrations of as au bi co cu mn ni pb sb and zn the py0 also retains a sedimentary co ni ratio which is distinct from hydrothermal ore related pyrite early hydrothermal py1 has high contents of ag as au bi cu fe sb and v and it reflects elevated levels of these elements in the earliest mineralizing metamorphic fluids the main ore stage py2 has a very high content of as median value of 2 96 wt and au median value of 47 5 ppm and slightly elevated cu but relatively low values for other trace elements arsenic in the main ore stage py2 occurs in solid solution late ore stage py3 formed coevally with stibnite contains relatively high as median value of 1 44 wt au fe mn mo sb and zn and low bi co ni and pb the main ore stage apy2 compared to late ore stage arsenopyrite is relatively enriched in as whereas the later apy3 has high concentrations of s fe and sb which is consistent with element patterns in associated main and late ore stage pyrite generations compared with pyrite from other stages the post ore stage py4 has relatively low concentrations of fe and s whereas as remains elevated 2 05 3 20 wt which could be interpreted by the substitution of as for s in the pyrite structure these results suggest that syngenetic diagenetic pyrite is the main metal source for the yangshan gold deposits where such pyrite was metamorphosed at depth below presently exposed levels the ore forming elements were concentrated into the hydrothermal fluids during metamorphic devolatilization and subsequently during extensive fluid rock interaction at shallower levels these elements were precipitated via widespread sulfidation during the main ore stage

fe cu deposits in the kangdian region sw china a proterozoic iocg iron oxide copper gold metallogenic province numerous fe cu deposits are hosted in the late paleoproterozoic dongchuan and dahongshan groups in the kangdian region sw china the dongchuan group is composed of siltstone slate and dolostone with minor volcanic rocks whereas the dahongshan group has undergone lower amphibolite facies metamorphism and consists of quartz mica schist albitite quartzite marble and amphibolite with local migmatite deposits in the dongchuan group are commonly localized in the cores of anticlines in fault bends and intersections and at lithological contacts orebodies are closely associated with breccias which are locally derived from the host rocks fe oxides magnetite and or hematite and cu sulfides chalcopyrite bornite form disseminated vein like and massive ores and typically fill open spaces in the host rocks the deposits have extensive albite alteration and local k feldspar alteration overprinted by quartz carbonate sericite and chlorite deposits in the dahongshan group have orebodies sub parellel to stratification and show crude stratal partitioning of metals fe oxide ores occur as massive and or banded replacements within the breccia pipes whereas cu sulfide ores occur predominantly as disseminations and veinlets within mica schists and massive magnetite ores ore textures suggest that cu sulfides formed somewhat later than fe oxides but are possibly within the same mineralization event both ore minerals predated regional neoproterozoic metamorphism both orebodies and host rocks have undergone extensive alteration of albite scapolite amphibole biotite sericite and chlorite silica and carbonate alterations are also widespread ore hosting strata have a la icp ms zircon u pb age of 1681 13 ma and a dolerite dyke cutting the fe oxide orebodies has an age of 1659 16 ma thus the mineralization age of the dahongshan deposit is constrained at between the two all ores from the two groups have high fe and low ti with variable cu contents locally they are rich in mo co v and ree but all are poor in pb and zn sulfides from the fe cu deposits have 34s values mostly in the range of 2 to 6 per mil suggesting a mix of several sources due to large scale leaching of the strata with the involvement of evaporites isotopic dating and field relationships suggest that these deposits formed in the late paleoproterozoic ore textures mineralogy and alteration characteristics are typical of iocg type deposits and thus define a major iocg metallogenic province with significant implications for future exploration

geochemistry and textures of gold bearing arsenian pyrite twin creeks nevada implications for deposition of gold in carlin type deposits this study relates morphology size texture and chemistry of arsenian pyrite in the twin creeks carlin type gold deposits to the chemical position and amount of gold that it contains arsenian pyrite is confirmed as the most important gold hosting mineral and four types of gold bearing arsenian pyrite are recognized among these four types the lowest amount of gold and arsenic 1 wt as 17 60 ppm au is contained in arsenian pyrite with relatively large grain sizes 10 30 mu m it formed at relatively high temperatures 250 degrees c and k super h super ratios adularia stable probably relatively slowly the largest amount of gold and arsenic 1 05 2 43 wt as 595 1 465 ppm au is contained in arsenian pyrite with small grain sizes up to 2 mu m that formed at low temperatures 120 degrees 200 degrees c and moderate k super h super ratios illite stable probably by relatively rapid deposition xanes exafs and sims analyses show that gold in arsenian pyrite is both structurally bound au i and in submicroscopic inclusions of free gold au highest amounts of structurally bound gold were observed in the relatively coarse grained arsenian pyrite noted above whereas most inclusions of free gold were observed in fine grained arsenian pyrite in general there is a good correlation between gold and arsenic in arsenian pyrite although au as ratios vary from one pyrite to another it is suggested that gold in arsenian pyrite was deposited by direct deposition of native gold and by adsorption of au i from hydrothermal solutions adsorption of gold by arsenian pyrite can take place from solutions that are not saturated with respect to native gold relative volumes of gold bearing pyrite from different paragenetic stages at twin creeks suggest that as much as 50 percent of the total gold in the deposit could have formed from solutions that were not saturated with respect to native gold because both au and au i are found together in arsenian pyrite it is likely that they were deposited by the same process consideration of possible depositional reactions suggests that a decrease in the activity of reduced sulfur is most likely to cause gold deposition

signatures in flowing fluid electric conductivity logs flowing fluid electric conductivity logging provides a means to determine hydrologic properties of fractures fracture zones or other permeable layers intersecting a borehole in saturated rock the method involves analyzing the time evolution of fluid electric conductivity fec logs obtained while the well is being pumped and yields information on the location hydraulic transmissivity and salinity of permeable layers the original analysis method was restricted to the case in which flows from the permeable layers or fractures were directed into the borehole inflow recently the method was adapted to permit treatment of both inflow and outflow including analysis of natural regional flow in the permeable layer a numerical model simulates flow and transport in the wellbore during flowing fec logging and fracture properties are determined by optimizing the match between simulation results and observed fec logs this can be a laborious trial and error procedure especially when both inflow and outflow points are present improved analyses methods are needed one possible tactic would be to develop an automated inverse method but this paper takes a more elementary approach and focuses on identifying the signatures that various inflow and outflow features create in flowing fec logs the physical insight obtained provides a basis for more efficient analysis of these logs both for the present trial and error approach and for a potential future automated inverse approach inflow points produce distinctive signatures in the fec logs themselves enabling the determination of location inflow rate and ion concentration identifying outflow locations and flow rates typically requires a more complicated integral method which is also presented in this paper

trace element and sulfur isotopic evidence for redox changes during formation of the wallaby gold deposit western australia abstract wallaby is a major gold deposit of the st ives gold field of western australia with an estimated resource of 8 million ounces of gold it has a well established paragenesis across five vein sets that displays macroscopic evidence of changing redox through time from hematite to magnetite micro analysis of pyrite from each vein generation shows a progressive and gradual change in redox conditions the sulfur isotope composition has a 34 s range of 7 7 to 9 8 using 3 m spots on the sensitive high resolution iron micro probe stable isotope shrimp si negative values indicative of an oxidized sulfur signature are found in the earliest generation of pyrite which coexists with hematite that also contains high concentrations of as ni zn ag sb cu and pb conversely positive values representative of reduced sulfur are found in later generations of pyrite with lower concentrations of as ni sb cu zn and pb these later pyrite crystals display higher as ni as sb and as bi and lower cu te these geochemical trends are the result of redox controlled transport and partitioning into pyrite of minor and trace elements now within the pyrite structure previous studies suggested a single orogenic event formed the wallaby deposit this is not supported by the present study trace element ratios such as as ni clearly delineate the high au generations and could be used as an exploration tool it is suggested that pyrite from the wallaby gold deposit formed via desulfidation and a gradual change in redox conditions within an evolving fluid and did not result from mixing of two separate fluids as previously advocated utilizing pyrite to link the entire fluid history of wallaby demonstrates the general use of pyrite as a valuable mineral tracer in gold bearing fluid systems

comparison of surface aquifer and pore waters from a mesozoic basin and its underlying palaeozoic basement southeast france chemical evolution of waters and relationships between aquifers abstract as part of the deep geology of france gpf ardeche project water samples were collected along the ardeche margin of the massif central crystalline shield water is contained within various rocks including early jurassic carbonate triassic sandstone and evaporite permian continental deposits and the crystalline basement three sample types were studied surface water from streams and springs formation water sampled from fractured zones aquifers at various depths and pore water from rocks cored in the morte merie scientific borehole drilled to a depth of 980 m in 1993 as part of the ardeche project three main water chemistry signatures are associated with the three major geological groups 1 hco 3 ca mg water occurs in early jurassic carbonate and late triassic sandstone with dolomitic cement 2 ca so 4 water occurs in triassic sulphated shale and sandstone 3 na cl water occurs in permian sandstone and crystalline basement the samples enable a comparison between waters that flow on the surface those that have been in the underlying geological formations for a short time and those that have resided in closed pores of the host rock for a long time saturation indices computed for surface and formation waters show that dissolution reactions progressively increase the concentration of elements until saturation is reached surface waters were saturated for quartz and carbonate and formation waters for quartz carbonate gypsum muscovite and k feldspar saline water 12 g l tds from the permian rocks is controlled by a mineralogical assemblage of quartz calcite anhydrite muscovite k feldspar and albite at temperatures 80 90 c although equilibrium was reached for the formation waters concentrations in the pore waters reflect a general enrichment as compared to free formation waters from the fractured zones of the corresponding formation which suggests introduction of mobile elements in the solution only in permian rocks was a stable equilibrium observed since pore waters show no enrichment as compared to formation waters no water mixing was observed except along faults that form pathways for the fluid between formations each geological group generally behaves as a closed system except the permian rocks that seem to be or were exposed to circulation from the crystalline basement

a stand alone co mineral deposit in northeastern hunan province south china its timing origin of ore fluids and metal co and geodynamic setting abstract the hengdong cobalt co deposit located in northeastern hunan province of south china is hosted by the low grade metamorphic volcaniclastic sedimentary rocks of the early neoproterozoic lengjiaxi group the co orebodies strictly controlled by the ne to ene trending changsha pingjiang deep fault zone cpdfz and its secondary structures occurring in altered breccias and cataclasites with similar mineral assemblages co mineralization is characterized by zoned alteration with predominant silicification and chloritization proximal to the orebodies and sericitization and carbonatization distal from the mineralization the integrated field and microscope observations reveal three hydrothermal stages marked by quartz pyrite muscovite chalcopyrite of the early stage mineralization e stage quartz polymetallic sulfides chlorite of the middle stage mineralization m stage and quartz chlorite carbonate of the late stage mineralization l stage muscovite from both the e stage co bearing altered breccia and the cpdfz mylonite yield 40ar 39ar plateau ages of 124 7 0 6 ma 1 and 130 3 1 4 ma 1 respectively indicating an early cretaceous mineralization likely associated with the last movement of cpdfz strike slip shearing the 34s values of pyrite and chalcopyrite ranging from 1 5 to 15 9 with a majority between 7 5 and 15 9 and the lead isotope compositions of the pyrite 206pb 204pb 18 156 18 761 207pb 204pb 15 645 15 662 and 208pb 204pb 38 469 39 172 overlapping with those of upper crust indicate a main crust derived source the chemical compositions of pyrite further indicate the ore fluids and metal co of the hengdong deposit are most likely linked to the meta mafic and volcanic rocks of the neoarchean to paleoproterozoic lianyunshan group but with a contamination by the wall rocks of lengjiaxi group and lianyunshan granitoids fluid inclusion investigations from hengdong deposit reveal the decreasing homogenization temperatures from 250 to 320 c peak of 280 300 c at the e stage through 220 320 c peak of 270 300 c at the m stage and to 150 230 c at the l stage without obviously salinity 7 0 15 wt nacl equiv changed in the m stage the presence of coexisting lv inclusions and v rich inclusions with the similar homogenization temperature consistent with the chlorite geothermometry data is interpreted to be the result of fluid immiscibility which was caused by cyclic pressure release during fault zone movement combined with the late mesozoic tectonism of south china the present data support the hengdong deposit formed under an extension associated tectonic regime most likely induced by slab roll back of the subducted paleo pacific plate during the early cretaceous this extensional event not only caused the reactivation of the pre existing structures as manifested by the cpdfz characteristic of stress transformation from compression to extension but also likely resulted in the release of large amounts of co bearing ore fluids from the proterozoic or older volcanogenic rocks when the ore fluids migrated along the cpdfz and its secondary faults the decompression adiabatic cooling of the hydrothermal fluids shifted the ore fluid to the immiscibility field significantly reduced the degree of cobalt undersaturation and caused cobalt to precipitate which finally formed the hengdong co mineral deposit

geochemical and isotopic composition of auriferous pyrite from the yongxin gold deposit central asian orogenic belt implication for ore genesis abstract the yongxin gold deposit is a large fracture controlled ore deposit in the duobaoshan gold copper metallogenic belt within the eastern domain of the central asian orogenic belt caob silicification sericitization and potassic alteration are the main hydrothermal alteration types which display successive zoning surrounding the ore bodies pyrite galena sphalerite and chalcopyrite are the major metallic minerals in the deposit and gold is mainly distributed in pyrite here we investigate the trace element composition and isotope pb and s characteristics of pyrite from this deposit the auriferous pyrite is mainly allotriomorphic and homogeneous in chemistry with a homogenous distribution of as ni mo and fe from the core to rim of grains these features are consistent with the 207pb 206pb 206pb 204pb and 208pb 204pb 206pb 204pb of the grains that suggest a single source with no evidence for involvement of late fluids the 34s values range from 3 5 to 5 4 with an average of 4 48 suggesting a mantle derived magmatic provenance for the sulfur the high co content and co ni ratios low ni and mo ni ratios suggest a mafic ultramafic source for the yongxin gold deposit the co ni as relation indicates a magmatic hydrothermal affinity with a classification as epithermal gold deposit high arsenic and gold contents on the rims of pyrite grains indicate that au and as were simultaneously precipitated in anoxic low temperature and near surface conditions

distribution mineralogy and geochemistry of selenium in felsic volcanic hosted massive sulfide deposits of the finlayson lake district yukon territory canada three significant base metal deposits were recently discovered in the finlayson lake district yukon territory canada however widely varying selenium contents e g 1 100 ppm avg se at wolverine 200 ppm avg se at kudz ze kayah and 7 ppm avg se at gp4f have hindered their rapid exploitation observations and data from the deposits in the finlayson lake district show a strong positive correlation between high temperature 300 c copper rich sulfide assemblages at the base of volcanic hosted massive sulfide vhms and the selenium content of all sulfide minerals thermodynamic calculations for selenide and sulfide minerals indicate significantly higher temperatures of formation and lower solubilities of selenide versus sulfide minerals which is consistent with petrographic observations and can explain the distribution of selenium in zone refined vhms and volcanic sediment hosted massive sulfide deposits volumetric mass balance calculations indicate that some selenium could be sourced from contemporaneous volatile degassing of seo 4 its rapid reduction to h 2 se and subsequent entrainment into hydrothermal ore fluid however estimates for the kudz ze kayah and wolverine deposits suggest an additional large se reservoir volumetric mass balance estimates indicate that contemporaneous volcanic rocks and black shales are likely selenium reservoirs for the kudz ze kayah and wolverine deposits respectively

morphotectonic evolution of the adriatic piedmont of the apennines an advancement in the knowledge of the marche abruzzo border area abstract this study focuses on the morphotectonic evolution of the apennines central adriatic piedmont and in particular on the region along the marche abruzzo border stratigraphically the rocks of this area are typical of a marine environment which characterised the central periadriatic basin up to the early pleistocene a differential regional uplift produced a north eastward tilting of the area this led to the development of a parallel drainage network across the emerged coastal plain during the middle pleistocene these tectonic events along with a series of climatic changes during the quaternary caused alternating phases of fluvial incision and deposition which eventually produced four levels of fluvial terraces as outcropping lithologies seldom display a full record of significant tectonic deformation we carried out morphometric analysis along with a geomorphological survey in order to enhance our morphotectonic understanding of the area and to better define the role of neotectonics in the morphological evolution of the area we also analysed the morphological evidence of tectonics including field surveys focusing on fluvial and alluvial fan terraces as they are valuable indicators of neotectonic evolution finally we employed geostatistical analysis to facilitate the detection of fluvial terraces even when affected by neotectonics our results indicate an active control on drainage evolution by nw se to wnw ese tectonic lineaments intersected by sw ne and wsw ene ones these tectonic lines continued to be active up to the formation of the third level of terraces late pleistocene river captures and diversions followed during the late pleistocene and the holocene in some cases favoured by passive tectonic control

morphological and geological aspects related to large slope failures on oceanic islands the huge la orotava landslides on tenerife canary islands huge volcanic landslides are one of the most hazardous geomorphological processes that can occur during the evolution of volcanic ocean islands the causes of these phenomena however are very complex and combine non volcanic and volcanic factors in the canary islands more than 20 events have been detected during the last decades a detailed analysis was carried out for la orotava amphitheatre on tenerife in order to understand the relationship between geomorphological and geological aspects and huge volcanic landslides the results indicated four major features that play a significant role in such mass movements deep erosive canyons high coastal cliffs widespread residual soils and structural axes high coastal cliffs and deep erosive canyons locally reduce the stability conditions and control both the seaward and the lateral boundary of the landslide weak residual soils formed above phonolitic pyroclastic deposits occur repeatedly in the stratigraphic column of la orotava and are characterised by their large extent thus one of these soils may have evolved into the slip surface of the failure part of the head scarp of the amphitheatre is defined by a volcanic rift zone as indicated by the measurement of dike orientation and a density map of eruptive vents the four features are not able to trigger a failure but to destabilise the volcano flank and determine the boundary of the slide therefore information on depth and orientation of canyons location and height of coastal cliffs stratigraphic repetition extension and thickness of residual soils and orientation and density of dikes and eruptive vents along structural axes should be incorporated into a hazard assessment on large landslides on volcanic islands

geometric and temporal evolution of an extensional detachment fault hohhot metamorphic core complex inner mongolia china the early cretaceous hohhot metamorphic core complex and its master hohhot detachment fault are 400 km west of beijing in the daqing shan mountains of inner mongolia the complex developed across the east trending yinshan fold and thrust belt within 4 m y following cessation of thrusting ca 125 ma see note added in proof in main text postcontractional extension was initiated within a mid crustal zone of mylonitic and ductile shear that was in part controlled by carboniferous strata sandwiched between its proterozoic and archean crystalline basement and an overlying thrust sheet of similar crystalline rocks the hohhot detachment fault appears to have rooted into deep kinematically active levels of the mid crustal shear zone higher inactive levels of the mylonitic section were transected by the fault and carried upward in its footwall geometries of the footwall mylonitic rocks indicate localized ramp flat geometries of the fault within and across them the crosscut top of the mylonitic sequence defines a mylonitic front that departs from the gently south dipping detachment fault and dips northward into its footwall early cretaceous extension was widespread elsewhere in northern china and was particularly pronounced in the yunmeng shan core complex north of beijing the gravitational collapse of orogenically thickened crust acting in concert with localized centers of deep seated plutonism appear to have led to the development of isolated metamorphic core complexes within a broad region of more distributed extensional deformation

gold deposits of the northern margin of the north china craton multiple late paleozoic mesozoic mineralizing events the northern margin of the north china craton is well endowed with lode gold deposits hosting a resource of approximately 900 tonnes t of gold the 1 500 km long region is characterized by east trending blocks of metamorphosed archean and proterozoic strata that were episodically uplifted during variscan indosinian and yanshanian deformational and magmatic events at least 12 gold deposits from the daqinshan yan liao includes the zhangjiakou yanshan and chifeng gold districts and changbaishan gold provinces contain resources of 20 100 t au each most deposits are hosted in uplifted blocks of precambrian metamorphic rocks although felsic paleozoic and mesozoic plutons are typically proximal and host 30 of the deposits the lodes are characterized by sulfide poor quartz veins in brittle structures with low base metal values and high au ag ratios although phyllic alteration is most common intensive alkali feldspar metasomatism characterizes the wulashan dongping and zhongshangou deposits but is apparently coeval with variscan alkalic magmatism only at wulashan stepwise 40ar 39ar geochronology on 16 samples from gangue and alteration phases combined with unpublished shrimp u pb dates on associated granitoids suggest that gold mineralizing events occurred during variscan indosinian and yanshanian orogenies at circa 350 250 200 180 150 and 129 ma however widespread permo triassic 250 ma and early jurassic 180 ma thermal events caused variable resetting of most of the white mica and k feldspar argon spectra as well as previously reported k ar determinations compiled and new stable isotope and fluid inclusion data show that most 18o values for ore stage veins range from 8 to 14 indicating a fluid in equilibrium with the precambrian metamorphic basement rocks d values from fluid inclusions range widely from 64 to 154 which is indicative of a local meteoric component in some veins and highly variable 34s data 7 to 17 even within individual deposits indicate various local country rock sources for sulfur fluid inclusions from all districts show variable homogenization temperatures between 240 and 400 c and are consistently characterized by low salinity h2o co2 ch4 n2 solutions although the data are largely consistent with that from orogenic gold veins intrusion related veins and epithermal veins are also recognized the multiple episodes of mineralization are coincident with episodic tectonic reactivations and associated magmatism along the northern margin of the north china craton electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 001 0239 2

pattern and kinematic polarity of late mesozoic extension in continental ne asia perspectives from metamorphic core complexes 1 late mesozoic extension in ne asia resulted in the development of a large extensional province metamorphic core complexes mccs are the major features in this province and have 40ar 39ar ages of 130 110 ma for the mylonites and u pb zircon ages of 150 110 ma for the integral granitic intrusions based on this and previous studies this paper summarizes major characteristics of these mccs and recognizes a regional kinematic shear sense most mccs in the transbaikalia region sino mongolia border tract and the northwest central portion of the north china craton ncc show a top to the southeast se shear whereas those in the eastern and southern ncc locally underwent top to the northwest nw shear the three largest basins songliao huabei and ordos in north china are located in the transitional zone between domains of opposing shear sense we interpret the extension in the transbaikalia sino mongolia tract and northwestern part of the ncc to reflect late orogenic collapse of thickened crust following middle late jurassic collision along the okhotsk suture the southeastward extension is probably controlled by crustal scale top to the se tangential shear the transition from contraction to extension is marked by detachment faults that nucleated as extensional crenulation cleavage ecc i e c in sub horizontal ductile shear zones late in orogenic crustal thickening the combined effect of gravitational loading and thermal uplifting is considered to be the origin of the late or post orogenic collapse the top to the nw extension in the ne of the ncc might reflect antithetic sub extensional zones or mesozoic back arc extension as a far field effect of cretaceous pacific plate subduction

timing and processes of late mesozoic mid lower crustal extension in continental ne asia and implications for the tectonic setting of the destruction of the north china craton mainly constrained by zircon u pb ages from metamorphic core complexes abstract late mesozoic large scale crustal extension occurred across the northeastern section of continental asia and metamorphic core complexes mccs are the major features in this region this paper presents new zircon u pb and ar ar ages of biotite and hornblende for pre or syn mylonitized and post kinematic unmylonitized intrusions from these mccs and attempts to determine the timing of initiation duration and termination of the mid lower crustal ductile extension by integrating with geochronological data from previous studies these mccs have similar 40 ar 39 ar biotite and hornblende ages 130 to 110 ma mainly from 130 to 120 ma which are interpreted as the cooling ages and represent the timing of the late stage formation of the mccs zircon u pb ages for syn to post kinematic intrusions from some mccs suggest that the mid lower crustal extension probably initiated at ca 150 145 ma with a peak occurring 145 130 ma and continued to 130 120 ma which is older than that suggested by 40 ar 39 ar ages by 10 20 ma the early ductile extension most likely initiated in mongolia and northern china during the late jurassic 150 145 ma at a deeper level then propagated southwards 140 130 ma and finally developed throughout the entire continental ne asia 130 120 ma based on the timing and processes of the extension a geodynamic model and tectonic setting of the destruction of the north china craton ncc are proposed

evolution of interstitial waters along the passive margin of the southeast basin of france welcom well chemical on line monitoring applied to balazuc 1 well ardeche abstract as part of the geologie profonde de la france gpf deep geology of france programme investigating the passive margin of the southeast basin of france studies are being made on the possibility of modelling mass transfer in the summer of 1990 when the first hole in the area balazuc 1 was being drilled along a basement rooted fault chemical monitoring of the drilling fluids welcom enabled the composition of the interstitial fluids contained within the intersected rocks to be reconstructed the computations were compared to on core leaching carried out during the drilling following which the welcom results were calibrated the interstitial fluids from the drilled formations show very contrasted compositions from the top to the bottom of the hole it has been possible to distinguish diagenetically evolved seawater within the hettangian limestone modified continental fluids within the upper part of the triassic sandstone reservoirs and evaporated seawater within the middle triassic evaporites several zones of intensive fluid circulation are also indicated by dolomitization of the basal hettangian limestone circulation of fluids expelled from the evaporites within the upper part of triassic sandstone reservoirs and continental derived hydrothermal fluid flow within the lower triassic sandstone reservoir and carboniferous silty shale the results show that chemical logging of drilling fluids can provide valuable data concerning interstitial fluids where other techniques are not available

earthquake triggering of landslides in highly jointed rock masses reconstruction of the 1783 scilla rock avalanche italy abstract the scilla rock avalanche occurred on 6 february 1783 along the coast of the calabria region southern italy close to the messina strait it was triggered by a mainshock of the terremoto delle calabrie seismic sequence and it induced a tsunami wave responsible for more than 1500 casualties along the neighbouring marina grande beach based on subaerial and submarine surveys a 5 106 m3 subaerial landslide was identified together with a 3 106 m3 submarine scar area whereas block deposits are present in both the subaerial and submerged regions a detailed geological reconstruction of the slope was obtained and a geomechanical characterisation of the metamorphic rocks involved in the landslide was performed based on this reconstruction intense jointing conditions of the rock mass can be related to main fault zones parallel and normally oriented to the actual coastline an engineering geology model of the landslide was devised according to an equivalent continuum approach to evaluate both stiffness and strength of the rock mass within the slope a finite difference stress strain numerical modelling of the scilla landslide was performed under dynamic conditions to back analyse the landslide trigger as well as local seismic amplifications this modelling gave new insights into the physical interactions between seismic inputs and slopes as it demonstrated the fundamental role played by i the interaction between the seismic input and geological setting of unsheared rock slopes i e without preexisting landslide masses ii cumulated strain effects due to seismic sequences and iii jointing conditions of the involved rock masses responsible for the seismic amplification of the landslide prone volume driving it toward failure conditions

metamorphic core complex dynamics and structural development field evidences from the liaodong peninsula china east asia metamorphic core complexes mcc constitute remarkable features within wide rifts based on analogue and numerical modelling mcc dynamics and structural development are mainly controlled by first geothermal gradient second the compositional layering and after the strain rate and partial melting in the late mesozoic continental extension occurred in east asia leading to the development of mcc magmatism and extensional sedimentary basins based on an integrated study i e structural and finite strain analysis petrofabrics anisotropy of magnetic susceptibility ams and u pb on zircon dating this paper aims at constraining the tectonic evolution and deformation mechanisms in the south liaodong peninsula ne china the gudaoling massif is identified as a migmatitic mcc developed from upper jurassic ca 157 154 ma to early cretaceous ca 128 113 ma intrusion of the yinmawanshan synkinematic pluton early cretaceous to the south of the dome marks out the final stages of shearing along the gudaoling detachment zone and of exhumation of the mcc into the upper crust the gudaoling mcc and the yinmawanshan pluton stay in line with the coeval south liaodong mcc to the south all making a 140x30km wide extensional band formed during a regional e w to nw se crustal stretching the area shows a bi phased development with a slow and a fast stage which correspond to 1 crustal necking and 2 dome amplification exhumation stages according to published thermo mechanical modelling results finally the gudaoling mcc lower unit almost exclusively displays migmatites and anatectic granitoids of late jurassic and early cretaceous respectively occurrence of partial melting during earlier stages of extension seems controlling the initiation of mcc as a soft anomaly within lower crust in east asia a regional scale thermal event during jurassic cretaceous times may have significantly reduced the bulk lithosphere strength and locally induced partial melting emphasizing pervasive deformations and development of a wide rift system

new data on holocene relative sea level along the abruzzo coast central adriatic italy abstract a continuously cored borehole was used to analyse holocene relative sea level changes in the pescara coastal plain located along the central adriatic coast abruzzo central italy the core was retrieved from the uppermost 19 m deposits 600 m from the present day shoreline sedimentological and palaeontological analyses identified a transition from fluvial strata to brackish water lagoon and foreshore deposits five biological sea level markers were sampled and their ages constrained by ams 14 c dating span between 2 39 and 7 68 ka cal bp heights m above mean sea level of the collected samples have been corrected taking into consideration uncertainties of the vertical positioning with respect to palaeo sea level vertical tectonic displacements have been evaluated through the comparison of relative sea level data with the site specific predicted holocene sea level curve correlations with available morphotectonic and stratigraphic data also were used the results suggest negligible rates of vertical tectonic displacement during the holocene at least along a coastal strip of 40 km located between pescara and sangro river mouths abruzzo

the history and economics of gold mining in china abstract as the largest producer of gold in the world china s gold reserves are spread across a number of orogenic belts that were constructed around ancient craton margins during various subduction collision cycles as well as within the cratonic interior along reactivated paleo sutures among the major gold deposits in china is the unique class of world s richest gold mines in the jiaodong peninsula in the eastern part of the north china craton with an overall endowment of 3000 tons following the dawn of metal in the third millennium bc in western china placer gold mining was soon in practice particularly during the xia shang and zhou dynasties during 1096 ad mining techniques were developed to dig underground tunnels and the earliest mineral processing technology was in place to pan gold from crushed rock ores however ancient china did not witness any major breakthrough in gold exploitation and production and the growth in the gold ownership was partly due to the silk road that enabled the sale of silk products and exquisite artifacts to the west in exchange of gold products in the modern times the proven reserves of gold resources in china have steadily increased from 4614 7 tons in 2005 up to 6864 79 tons in 2010 with a growth rate of 48 76 in the past ten years the rate of production increased by 70 launching china as the top producer of gold in the world in 2008 when the production reached 300 tons per year the gross industrial output of gold industry in china increased sharply from 20 82 billion yuan up to 229 29 billion yuan between 2000 and 2010 registering 9 times growth and breaking the world record a simultaneous hike in the proportion of gross value in gdp from 0 21 in 2003 up to 0 58 in 2010 is also recorded

new contributions to the understanding of kiruna type iron oxide apatite deposits revealed by magnetite ore and gangue mineral geochemistry at the el romeral deposit chile abstract iron oxide apatite ioa or kiruna type deposits are an important source of iron and other elements including ree u ag and co the genesis of these deposits remains controversial with models that range from a purely magmatic origin to others that involve variable degrees of hydrothermal fluid involvement to elucidate the formation processes of this deposit type we focused on the chilean iron belt of cretaceous age and performed geochemical analyses on samples from el romeral one of the largest ioa deposits in northern chile we present a comprehensive field emission electron microprobe analysis fe empa dataset of magnetite apatite actinolite pyroxene biotite pyrite and chalcopyrite obtained from representative drill core samples two different types of magnetite grains constitute the massive magnetite bodies an early inclusion rich magnetite type i and a pristine inclusion poor magnetite type ii that usually appears as an overgrowth around type i magnetite high v 2500 2800 ppm and ti concentrations 80 3000 ppm and the presence of high temperature silicate mineral inclusions e g pargasite 800 1020 c determined by micro raman analysis indicate a magmatic origin for type i magnetite on the other hand high v 2300 2700 ppm and lower ti 50 400 ppm concentrations of pristine inclusion poor type ii magnetite indicate a shift from magmatic to hydrothermal conditions for this mineralization event furthermore the composition of primary actinolite ca and mg rich cores within type ii magnetite and the presence at depth of fluorapatite and high co ni ratios 1 10 of pyrite mineralization are consistent with a high temperature up to 840 c genesis for the deposit at shallow depths of the deposit the presence of pyrite with low co ni ratios

comparison of hydrogeochemical logging of drilling fluid during coring with the results from geophysical logging and hydraulic testing example of the morte merie scientific borehole ardeche france deep geology of france programme abstract a 980 m deep well was cored on the ardeche border of the southeastern basin of france as part of the deep geology of france gpf programme hydrogeochemical logging was carried out during drilling which involved the monitoring of physico chemical parameters ph eh temperature and conductivity and chemical parameters concentrations of he rn co 2 ch 4 o 2 ca cl and sio 2 of the drilling fluid permanently circulating in the well this logging programme was complemented by geophysical logging and two hydraulic tests the combination of these measurements enabled identification of a transmissive interval due to fractures in the jurassic carbonates and of fluid inflow both at the base of the porous and slightly permeable triassic sandstones and from an open fracture in the permian conglomerates these intervals are marked by changes in the drilling fluid chemistry such as an increase in chemical species content or a drop in ph the degree of modification depends on the natural permeability of the fractures and the salinity of the fluids the porous and permeable intervals are also marked by he anomalies which act as a tracer for these zones comparison between the geophysical and hydrogeochemical logs reveals that the latter provide information on the liquid phase whether the fractures are productive or not whereas the geophysical logs are more directly related to the solid phase

types characteristics and metallogenesis of gold deposits in the jiaodong peninsula eastern north china craton abstract the jiaojia type gold deposits in the jiaodong peninsula of the north china craton represent an emerging major gold reserve and constitute one of the two important types of gold deposits in china the other being the linglong type the gold mineralization in these deposits can be subdivided into seven categories namely altered rock type in the fracture zone gold bearing quartz vein type braided quartz vein type along fracture zones quartz sulfide vein type interlayer type along the detachment belt altered conglomerate type and breccia type along the basin margin faults the peak gold mineralization occurred during early cretaceous with the metallogeny controlled by extensive crust mantle interaction the deposits are hosted in the early precambrian basement and mesozoic intrusions which experienced phyllic sulfidic silicic and potassic alterations the structures of the ore bodies include pinchout repetition splay branches composite lateral tilting echelon and imbrications the upwelling of hot magma fluid activity and extensional detachment resulted in the formation of extensive gold deposits in the jiaodong peninsula the extensional detachment derived from magma upwelling provided favorable ore hosting structure for the gold deposition the ladder type ore hosting structures show variation from sharp to gentle dips with marked enrichment of the gold ores at the gentle angle of the fault segments and at the transition from steep to gentle dip angles displaying a step fault controlled ore deposition the formation of the gold deposits in the jiaodong peninsula coincided with the large scale early cretaceous thinning of the lithosphere in the north china craton mainly controlled by extensional tectonics

the ereendavaa range north eastern mongolia an additional argument for mesozoic extension throughout eastern asia mesozoic rift basins locally bounding metamorphic core complexes have been recognized in transbaikalia and northern china numerous basement outcrops located between these two regions in eastern mongolia are considered as pre palaeozoic in age one of these the ereendavaa range appears as a gneissic core marked by amphibolite facies metamorphic conditions the range is overlain to the nw by the unmetamorphosed mesozoic onon basin below the basin the upper part of the range consists of a gently nw dipping shear zone associated with top to the nw motion the structural pattern is consistent with syn extensional exhumation of the range preliminary geochronological data indicate that the shear zone is late jurassic to early cretaceous in age coeval with the onon basin these new data from eastern mongolia constitute a link between transbaikalia and northern china indicating that nw se extensional mesozoic tectonics occurred throughout the entire region

tectonics and distribution of gold deposits in china an overview gold exploration in china has expanded rapidly during the last two decades since a modern approach to economic development has become a national priority china currently produces 180 tonnes t of gold annually which is still significantly less than south africa usa and australia however china is now recognized as possessing significant gold resources in a wide range of mineral deposit types present estimates of gold resources in china exceed 4 500 t which comprise 60 in gold only deposits more than 25 in base metal rich skarn porphyry and vein deposits and more than 10 in placer accumulations the major gold provinces in china formed during the main episodes of phanerozoic tectonism such tectonism involved interaction of china s three major precambrian cratons north china tarim and yangtze or south china when combined with cathaysia block with the angara or siberian kazakhstan kyrgyzstan and indian cratons resulting collisions included deformation of accreted oceanic sequences between the cratonic blocks the most important ore forming orogenies were 1 the late paleozoic variscan 405 270 ma which led to amalgamation of the angara north china and yangtze cratons 2 the indosinian 270 208 ma which led to the collision of north china and south china cratons 3 the yanshanian 208 90 ma which was largely influenced by the subduction of the izanagi pacific plates beneath eastern china and 4 the himalayan 90 ma indentation of the indian continent into eurasia no important precambrian gold systems are recognized in china mainly because of reworking of exposed precambrian rocks by these younger orogenies but there are a few caledonian 600 405 ma gold bearing systems in northern xinjiang most of china s orogenic epithermal and carlin like gold deposits are in the reworked margins of major cratonic blocks and in metasedimentary rock dominated fold belts adjacent to these margins accordingly the major gold provinces are present along the northern southeastern and southern margins of the north china craton along the southwestern and northwestern margins of the yangtze craton in the tianshan and altayshan orogenic belts in northern xinjiang and throughout the southeastern china fold belt gold placer deposits derived from these primary deposits are concentrated in the northernmost part of northeastern china and along the northwestern margin of the yangtze craton the major provinces with significant gold in porphyry related copper systems and base metal skarns are present in the yangtze river area along the northeastern and southeastern margin of the yangtze craton in the fold belt in southwestern china and scattered through northern china three quarters of the chinese gold only deposits occur within the north china craton margins half are located in the uplifted precambrian metamorphic rocks and most of the remainder are hosted in the phanerozoic granitoids that intruded the reworked precambrian terranes the abundance of granite hosted gold contrasts the north china craton with other precambrian cratons such as those in western australia central canada and zimbabwe where gold is mainly hosted in the archean greenstone belts this difference may be explained by the multiple episodes of phanerozoic tectonism along the north china craton margins resulting from the collision of the angara north china and south china cratons and from subduction of the izanagi pacific oceanic plates underneath the eastern china continent

gold telluride nanoparticles revealed in arsenic free pyrite pyrite the most abundant sulfide on earth and a common component of gold deposits can be a significant host for refractory gold this is the first documentation of pore attached composite au telluride nanoparticles in arsenic free pyrite trace elements mapping in pyrite from an intrusion hosted au deposit with orogenic overprint dongping china shows trails of tellurides overlapping co ni zonation intragranular microfracturing anomalous anisotropy and high porosity are all features consistent with devolatilization attributable to the orogenic event the pyrite hosted nanoparticles are likely the frozen solid expression of te rich au ag pb bearing vapors discharged at this stage nanoparticle formation as presented here provides the smallest scale tool to fingerprint au trapping during crustal metamorphism

the ischia debris avalanche first clear submarine evidence in the mediterranean of a volcanic island prehistorical collapse sector or flank collapse with related debris avalanches is increasingly recognized as a relatively common volcanic behaviour in particular for large hot spot related oceanic islands here we report the case of a catastrophic collapse that occurred at ischia volcanic island in prehistorical times and was driven by the volcano tectonic uplift of mt epomeo the major relief of the island the collapse left a subaerial to submarine horseshoe scar on the southern flank of the island and generated a debris avalanche incorporating thousands of giant blocks dispersed as far as 50 km from the island during the emplacement part of the debris avalanche evolved into a debris flow covering an area of 250 300 km2 this constitutes the first clear evidence of a submarine debris avalanche in the mediterranean sea the major collapse was followed and probably also preceded by recurrent less catastrophic terrestrial and underwater failures two other undersea hummocky deposits are found north and west of the island and might tentatively be correlated to the major southern collapse such volcanic behaviour previously unknown for ischia volcano has likely triggered tsunami waves over the entire bay of naples raising the question of their impact on prehistorical historical communities

quaternary sea level change and slope instability in coastal areas insights from the vasto landslide adriatic coast central italy abstract this paper focuses on the possible role of sea level change in triggering and controlling large coastal slope instabilities and focuses on the representative case study of the vasto landslide the town of vasto is 143 m a s l and sits atop an uplifted quaternary regressive sequence widely outcropping along the adriatic coast of central italy the coastal slope is affected by large slope instabilities e g vasto landslide including evidence of present activity well documented historical disruptive events affected the town and the coastal slope in 1816 1942 and 1956 field evidence suggests that sea cliff retreat must have removed considerable volumes of rock before the activation of the large slope failures thus a geological evolutionary model of the landslide is proposed here that considers the landforms geological evidence and borehole stratigraphy as well as the combined effect of quaternary uplift and eustatic oscillations on the coastal slope significant evolutionary steps were identified and a slope stability analysis was performed using a stress strain numerical modeling solved by a finite difference method fdm to analyze the following 1 the landslide mechanism 2 the type of activity and 3 the cumulative deformations that occurred during the morpho evolutionary steps numerical modeling was calibrated by considering the present landforms as well as the effects recorded during historical events the results confirm that the vasto landslide was activated in the middle pleistocene 215 ka bp as a consequence of wave cut erosion and progressive uplift of the coastal slope moreover the landslide evolved as a retrogressive single styled landslide comprising two major blocks using this framework the historical events are interpreted as local re activations due to meteorological factors of the ancient rupture surfaces affecting the entire slope

bonanza grade accumulations of gold tellurides in the early cretaceous sandaowanzi deposit northeast china the sandaowanzi epithermal gold deposit 0 5 moz or ca 14 tons located at the northern edge of the great xing an range ne china is unique in that nearly all the gold 95 is contained in gold tellurides mostly in bonanza grade ore shoots the highest grade being up to 20 000 g t the bonanza ores are hosted in the central parts of large scale 3 m wide 200 m long quartz veins which crosscut early cretaceous andesitic trachyte and trachytic andesite and are in turn crosscut by diabase dykes of similar age there are two ore types low grade disseminated ores and high grade vein ores in the former very fine grains of ag rich tellurides mainly hessite and petzite coexist with sulfides pyrite sphalerite galena and chalcopyrite occurring as disseminated grains or sometimes as grain aggregates in the high grade vein ores coarse grained au ag tellurides calaverite sylvanite krennerite and petzite form a major part of quartz telluride veins chalcopyrite forms separate monomineralic veins emplaced within the quartz telluride veins spectacular textures among coarse grained up to 3 cm in diameter tellurides and micron scale bamboo shoot like grains are observed two and three phase telluride symplectites are common in the vein ores fluid inclusion studies suggest that the mineralizing fluids are a mixture of magmatic and meteoric fluids that homogenized in the temperature range of 260 280 c sulfur isotope compositions of pyrite and chalcopyrite 34s 1 64 to 1 91 support the origin of fluids from a deep source it is suggested that faulting temperature changes and variation in fs2 and fte2 were major factors contributing to the two main types of mineralization and the differences between them early rapid cooling and subsequent slow cooling of the later fluids along fault and fracture zones were instrumental in formation of the two superposed ore types open space filling and crack sealing along fractures predominates over replacement during telluride mineralization the sandaowanzi deposit is a unique bonanza grade accumulation of gold tellurides genetically related to subalkaline magmatism which was genetically associated with early cretaceous regional extension

pyrite as a record of hydrothermal fluid evolution in a porphyry copper system a sims empa trace element study porphyry copper deposits are currently the world s largest source of copper and molybdenum and are also among the largest reservoirs of gold in the upper crust despite the fact that pyrite is a ubiquitous mineral phase in these deposits and secondary cu enrichment processes are commonly controlled by the abundance of this sulfide the major and trace element chemistry of pyrite from porphyry systems remains unconstrained in this study we report the first comprehensive trace element database of pyrite from the dexing deposit china s largest porphyry cu deposit by combining high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capabilities of secondary ion mass spectrometry sims in a suite of samples from the dexing deposit we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and heavy metals e g cu co ni zn hg in pyrite from porphyry systems are more significant than previously thought among the elements analyzed cu as au and ni are the most abundant with concentrations that vary from sub ppm levels to a few wt i e 6 wt cu 3 wt as 0 25 wt au and 0 2 wt ni detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrite from the dexing deposit is characterized by complex chemical zoning where the studied elements occur in different mineralogical forms while as occurs as a structurally bound element in pyrite cu and au can occur as both solid solution and micro to nano sized particles of chalcopyrite and native au or au tellurides respectively indicating that pyrite can control metal speciation and partitioning during porphyry cu mineralization the well developed oscillatory zoning detected in pyrite where cu rich as depleted growth zones alternate with cu depleted as rich layers indicates that cu is geochemically decoupled from as suggesting that this selective partitioning of metals into pyrite is most likely the result of changes in hydrothermal fluid composition

trace element and fluid inclusion geochemistry constraint for genesis of gold polymetallic mineralization in the songhung deposit dpr korea abstract the songhung deposit is located in the southwestern part of the yangdok metamorphic core complex ymcc in the northern portion of the pyongnam basin the eastern part of the sino korean craton in this paper we present a detailed study on the magma sources of the granitoids yangdok and hoechang graintic intrusions genesis of pyrite and fluid inclusion characteristics for sufficient and additional understanding of tectonic events petrogenesis of the granitoids and mineralization in the study deposit the yangdok granite has lower al2o3 tio2 ratios mean value of 60 58 than the hoechang granite mean value of 994 46 indicating the higher temperature magma source of the former on the rb ba vs rb sr and cao tfeo mgo tio2 vs cao tfeo mgo tio2 discriminant diagrams the magma source of the yangdok granite belongs in the plagioclase rich and clay poor source rocks while those of the hoechang granite plots either in the plagioclase rich and clay poor source rocks for granite and fine grained granite or in the plagioclase poor and clay rich source rocks for granite porphyry and felsite on the nb vs y ta vs yb rb vs y nb and rb vs yb ta tectonomagmatic discrimination diagrams these two granites are connected with the volcanic arc related setting and plot in post collision setting moreover some data of the hoechang granite fall in wpg field suggesting that the volcanic arc setting may be changed to an intraplate setting from middle cretaceous the pyrite trace element geochemistry showing the high co ni ratio than one with an average of 8 2 and high co content and low ni content suggests that its formation was closely linked with i type granitic magma derived hydrothermal fluid mixed with meteoric water it could also be assumed by the co and as contents in pyrite indicating a certain degree of meteoric water in the ore forming fluid it is consonant to the pb s c and o isotope geochemistry in the previous study suggesting that ore forming fluids and metals could be derived from both the yangdok granite and the proterozoic and paleozoic meta sedimentary rocks exposed in the study area all of the pyrite grains have not compositional zoning and the similar distribution patterns of co and ni are appeared in single pyrite grain from core to rim suggesting the stable crystallization environment of pyrites and same ore forming fluid source in pyrite grains the positive correlation between gold and arsenic is appeared the au exists either as a micro and nano size inclusion in pyrite and other minerals or as a solid solution in pyrite lattice based on the petrological and microthermometric characteristics of the fluid inclusions in ore bearing quartz we suggest that the ore forming fluid is represented as nacl h2o or nacl kcl h2o systems with low salinity the absence of co2 enriched phase and vapor only or liquid only primary inclusions in quartz indicates the homogenous magma derived ore forming fluids and a lack of boiling during ore forming process the formation temperature and pressure of this deposit approximately vary from 317 to 326 c and from 105 46 to 111 69 105 pa respectively exhibiting the hydrothermal deposit origin in conclusion the songhung deposit is originated from i type granitic magma source derived hydrothermal fluid which was mixed with meteoric water

the liaonan metamorphic core complex southeastern liaoning province north china a likely contributor to cretaceous rotation of eastern liaoning korea and contiguous areas abstract the mesozoic liaonan metamorphic core complex mcc of the southeastern liaoning province north china is an asymmetric cordilleran style complex with a west rooting master detachment fault the jinzhou fault a thick sequence of lower plate fault related mylonitic and gneissic rocks derived from archean and early cretaceous crystalline protoliths has been transported ese ward from mid crustal depths u pb ages of lower plate syntectonic plutons ca 130 120 ma 40 ar 39 ar cooling ages in the mylonitic and gneissic sequence ca 120 110 ma and a cretaceous supradetachment basin attest to the early cretaceous age of this extensional complex the recent discovery of the coeval and similarly west rooting waziyu mcc in western liaoning darby b j davis g a zhang x wu f wilde s yang j 2004 the newly discovered waziyu metamorphic core complex yiwulushan western liaoning province north china earth science frontiers 11 145 155 indicates that the gulf of liaoning which lies between the two complexes was the center of a region of major crustal extension clockwise crustal rotation of a large region including eastern liaoning province and the korean peninsula with respect to a non rotated north china block has been conclusively documented by paleomagnetic studies over the past decade the timing of this rotation and the reasons for it are controversial lin et al lin w chen y faure m wang q 2003 tectonic implication of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china journal of geophysical research 108 b 6 epm 5 1 to 5 17 proposed that a clockwise rotation of 22 5 10 2 was largely post early cretaceous in age and was the consequence of extension within a crustal domain that tapers southwards towards the bohai sea of which the gulf of liaoning is the northernmost part paleomagnetic studies of early cretaceous strata ca 134 120 ma in the yixian fuxin supradetachment basin of the waziyu mcc indicate the non rotation of north china and the basin zhu r x shao j a pan y x shi r p shi g h li d m 2002 paleomagnetic data from early cretaceous volcanic rocks of west liaoning evidence for intracontinental rotation chinese science bulletin 47 1832 1837 such upper plate non rotation supports our conclusion that the lower plates of the waziyu and liaonan metamorphic core complexes were displaced ese ward in an absolute sense away from the stable north china block thus contributing to the rotation of korea and contiguous areas rotation is inferred to have affected only the upper crust above mid crustal levels into which we believe the jinzhou and waziyu detachment fault zones flattened if this is the case the regional tan lu fault that lies between the two core complexes was truncated at mid crustal depth since in areas to the south it forms the boundary between the north and south china lithospheric blocks it is noteworthy that the two extensional complexes lie not far north of the bohai bay the area proposed by lin et al lin w chen y faure m wang q 2003 tectonic implication of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china journal of geophysical research 108 b 6 epm 5 1 to 5 17 as the site of the pole of rotation for korea s clockwise displacement lin et al lin w chen y faure m wang q 2003 tectonic implication of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china journal of geophysical research 108 b 6 epm 5 1 to 5 17 were unaware of the liaonan and waziyu mcc s and argued that most of the regional block rotation was post early cretaceous and in part early cenozoic however the ca 130 120 ma ages of the two liaoning mcc s and a songliao basin mcc xujiaweizi the latter discovered only by recent drilling through its younger stratigraphic cover support our and some korean coworkers conclusions that most of the clockwise rotation was early cretaceous

catastrophic collapse of the volcanic island of hierro 15 ka ago and the history of landslides in the canary islands landslides play an important role in the evolution of many volcanic islands producing huge fields of blocky volcanic debris on their submarine slopes sidescan sonar images presented in this paper provide evidence for a large debris avalanche el golfo on the northern flank of hierro island in the canary islands angular blocks as much as 1 2 km across and 200 m high cover the debris avalanche surface el golfo avalanche is related to both the canary debris flow and a volcaniclastic turbidite found in the madeira abyssal plain 600 km west of the canaries dating of the turbidite and the failure scarp onshore indicates that the failure probably occurred between 13 and 17 ka there appears to be a general correlation between volcaniclastic turbidites in the abyssal plain sequence and landslides in the canaries during the past 750 ka tentatively this correlation suggests that seven major landslides have affected the canaries in that time

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

genesis of the songhung gold polymetallic deposit in the hoechang district the democratic people s republic of korea constraints from geology petrochemistry and pb s c o isotope geochemistry abstract the songhung deposit is located in the southwestern part of the yangdok uplift zone yuz in the northern part of the pyongnam basin in the sino korean craton most of large and small scale gold deposits and occurrences were discovered and exploited in the western part of the yuz several tectonic events in this area are the key to understanding the gold and polymetallic mineralization in the sonhung deposit the yuz comprises the neoarchean rangnim metamorphic belt proterozoic and early paleozoic rocks in the central domain and granitoid intrusions of crustal and mantle derivation yangdok granitoid intrusions two extensive nne trending fault zones with mylonitized rocks are interpreted to represent detachment fault and two ne sw trending regional rift structures represent zones of subsidence e g the tokchon maengsan to the west the kowon to the east and the junghwa samdung subsidence to the south it is suggested that the yuz is a metamorphic core complex mcc similar to those in the north china craton ncc polymetallic mineralization in the songhung deposit is divided into early and late stages the early mineralization was formed during compressional deformation in the triassic accompanied by low grade metamorphism of the sedimentary host rocks variations in pb s c and o isotope ratios indicate that the ore forming fluids and metals were derived from the country rocks the au grade is insignificant in this style of mineralization the main gold polymetallic mineralization in the songhung deposit is related to tectonic extension of the region the pb s c and o isotope data indicate that these elements as well as ore forming fluids could be derived from both the granitic intrusion yangdok granitoid and the proterozoic and paleozoic country rocks

la icp ms trace element analysis of pyrite from the xiaoqinling gold district china implications for ore genesis abstract the xiaoqinling district the second largest gold producing district in china is located on the southern margin of the north china craton it consists of three ore belts namely the northern ore belt the middle ore belt and the southern ore belt pyrite from the dahu gold deposit in the northern ore belt and wenyu and yinxin gold deposits in the southern ore belt were investigated using a combination of ore microscopy and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms a range of trace elements was analyzed including au te ag pb bi cu co ni zn mo hg as and si the results show that there are no systematic differences between the trace element compositions of pyrite in the three deposits from different ore belts in general au concentrations in pyrite are low from 2 rich ore fluids spatial association with large scale compressional structures of the qinling orogen 18 o and d data suggestive of mixing between metamorphic and meteoric waters 34 s and pb isotopic data that point to a mixed crustal mantle source all point to typical orogenic type gold deposits high ni concentrations up to 8425 ppm of pyrite possibly linked to deep seated mafic ultramafic metamorphic rocks provide further evidence on the orogenic gold deposit affinity but against the model of a granitic derivation of the mineralizing fluid as previously suggested by some workers generally low au concentration in pyrite is also consistent with those from worldwide orogenic gold deposits therefore the gold mineralization in the xiaoqinling district is described as orogenic type and is probably related to indosinian collision between the north china craton and the yangtze craton

minor and trace elements in bornite and associated cu fe sulfides a la icp ms studybornite mineral chemistry abstract in situ laser ablation inductively coupled mass spectroscopy la icp ms has been used to provide a baseline dataset on the minor element contents in hypogene bornite and accompanying cu sulfides from 12 deposits with emphasis on syn metamorphic cu vein systems in norway and skarn porphyry and epithermal systems in se europe bornite contains significant concentrations of both ag and bi especially in the vein and skarn deposits studied and has the potential to be a major ag carrier in such ores concentrations of up to 1 wt of both elements are documented measured concentrations appear to be independent of whether discrete ag and or bi minerals are present within the analyzed sulfide where bornite and chalcocite or mixtures of cu sulfides coexist ag is preferentially partitioned into chalcocite over co existing bornite and bi is partitioned into the bornite bornite is a relatively poor host for au which mimics ag by being typically richer in coexisting chalcocite most anomalous au concentrations in bornite can be readily tracked to micron and submicron scale inclusions but bornite and chalcocite containing up to 3 and 28 ppm au in solid solution can be documented selenium and te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample selenium distributions show some promise as a vector in exploration offering the possibility to track a fluid source bornite and chalcocite are poor hosts for a range of other elements such as co ni ga and ge etc which have been reported to be commonly substituted within sulfides hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary supergene bornite

geochemistry of the la erma and qiongmo au se deposits in the western qinling mountains china abstract the microdisseminated gold deposits at la erma and qiongmo are typically hosted in cambrian chert formation in western qinling mountains china both in the host rocks and the gold ores selenium is present in high abundance as selenide minerals or isomorphous admixtures in sulfides with independent selenium orebodies can be delineated in some localities intergrowth of selenides and native gold is commonly observed selenium is also noticed in considerably high content in fluid inclusions in quartz and barite which are closely related to gold mineralization studies show that gold and selenium may have been transported together in ore solutions as au s se complex in view of the wide difference in electrode potential between selenium and sulfur the two elements would be separated under oxidizing conditions selenium would mostly occur as isomorphic mixtures in sulfides during the early stage of mineralization when the environment is more reducing but would precipitate as selenides during the late oxidizing stage simultaneous enrichment of gold and selenium would be favored by boiling of the ore solution or mixing of ore solution with oxygen rich water at shallow depths

a reinterpretation of the role of granitoids in the genesis of neoproterozoic gold mineralization in the telfer dome western australia the telfer gold mine in the paterson province of western australia is one of australia s largest gold deposits with more than 4 million oz m oz or 125 t of gold produced since mining commenced in 1977 hosted by low grade dominantly marine metasedimentary sequences of the upper yeneena group approximately 1 000 750 ma the neoproterozoic mineralization 700 600 ma is localized within the northwest trending telfer dome which consists of two en echelon asymmetric doubly plunging anticlines called the main dome and the west dome within these two domes gold and minor copper occur as a series of vertically stacked strata bound to stratiform gold copper sulfide quartz reefs up to several meters in thickness linked by zones of intense stockwork and sheeted veins carbon oxygen boron lead and sulfur isotope data including shrimp microanalysis from ore sulfides and alteration minerals carbonates and tourmalines in conjunction with tourmaline and pyrite compositional data indicate that the ore fluid solutes were derived chiefly from sedimentary host rocks and not neoproterozoic granitoids a model for telfer mineralization is proposed such that granitoids act primarily as sources of heat that drive thermal convection cells in which heated saline formational contact metamorphic fluids scavenge gold copper and sulfur from the surrounding sedimentary wall rocks at depth this style of ore fluid generation shares some similarities with a convective porphyry copper gold model although the lack of hornfelses proximal granitoids and types of alteration characteristic of porphyry copper deposits implies that the telfer dome deposits did not form in the near porphyry environment these data do suggest however highly channelized fluid flow to the domal sites of mineralization after an initial period of extensive deep fluid circulation and leaching of sulfur and metals from the sedimentary wall rocks adjacent to the pluton s a regional scale deep structure capable of focusing these deeper fluids to higher stratigraphic levels is the north northwest trending telfer lineament upon which the telfer dome is situated periodic reactivation of this structure during the the paterson orogeny would allow for episodes of widespread fluid advection at depth under essentially lithostatic fluid pressures followed by rapid ingress of fluids into the structure triggered by a decrease in fluid pressure during reactivation

genesis of the maikhura tungsten tin skarn deposit tajik tien shan insights from petrology mineralogy and fluid inclusion study abstract the maikhura w sn skarn deposit is situated in the gissar segment of the southern tien shan it associates with a late carboniferous early permian composite granitoid pluton which includes earlier ilmenite series transitional metaluminous to peraluminous i type granodiorite and later magnetite series biotite to biotite tourmaline granite leucogranite the oxidized granitic intrusions exhibit a type granite affinity and define a geochemically and genetically distinct group of w sn deposits the deposit incorporates both pyroxene and garnet dominant prograde and retrograde skarns with scheelite and locally magnetite overprinted by highly reduced pyrrhotite stable post skarn mineral assemblages of hydrosilicate and phyllic alteration stages containing scheelite cassiterite and sulfides the fluid inclusions data indicate the involvement of carbonic free aqueous moderately saline 9 9 16 wt nacl eq high pressure 2 1 0 5 kbar hot fluid which was sourced from crystallizing magma and formed prograde calcic skarn this fluid evolved into a sodic chloride slightly less saline 8 6 11 wt nacl eq lower pressure 1 7 0 5 kbar cooler fluids toward the retrograde skarn stage this stage was characterized by deposition of scheelite in association with magnetite the hydrosilicate propylitic alteration was formed from a low salinity ca enriched homogenous aqueous carbonic methane rich fluid at lower temperatures 350 400 c with precipitation of scheelite and cassiterite particularly in phlogopite chlorite oligoclase quartz assemblage corresponding ph decrease explains the trend toward overlapping fields of insoluble cassiterite and scheelite the phyllic alteration assemblages were formed from a boiling aqueous carbonic co2 dominated low salinity fluid at temperatures of 310 250 c and pressure of 1 85 0 1 kbar the alteration evolving from chlorite through muscovite to albite dominant paragenesis indicates a trend toward higher ph less acidic conditions and was accompanied by precipitation of scheelite and cassiterite with further deposition of sulfides a homogeneity of 34s values suggests sulfur isotope homogenization in a magmatic chamber whereas their proximity to the meteorite standard supports a magmatic source of sulfur the depletion in heavy sulfur isotope of sulfides from hydrosilicate propylitic alteration 34s 1 8 to 0 7 to sulfides from phyllic alteration 34s 0 1 to 0 8 is consistent with the evolution from ilmenite series to magnetite series magmatic source

gold mineralization in the guilaizhuang deposit southwestern shandong province china insights from phase relations among sulfides tellurides selenides and oxides abstract the guilaizhuang gold deposit is composed of limestone and breccia type ores in the limestone ores gold is hosted by pyrite as bearing pyrite and arsenopyrite whereas in the breccia ores tellurides are the main gold carriers selenium often isomorphously substitutes for sulfur in sulfides in the limestone ores but occurs as selenides in the breccia ores hematite is the only oxide in the breccia ores associated with barite and other tellurides in this paper the thermodynamic parameters especially the gibbs free energies of formation and reaction of related sulfides tellurides selenides and oxides are computed to explain the distinct mineral styles in the limestone and breccia type ores we construct the phase relations among minerals delineated by phase diagrams at 250 c the temperature for gold precipitation in the guilaizhuang deposit according to the phase relations between sulfides and selenides we propose that gold has been transported as au hs hse 2 and released during rapid formation of pyrite as pyrite and arsenopyrite at log f s 2 g between 12 8 and 11 4 250 c in the breccia ores log f te 2 g and log f se 2 g are constrained within 12 9 to 9 4 and 12 4 to 6 9 250 c respectively based on the mineral assemblages observed in the ores the phase relations between tellurides and selenides indicate that calaverite the only stable gold telluride mineral in nature was not stable in the breccia ores at 250 c during the gold precipitation based on empa analysis the so called calaverite revealed from microscopic observations is in fact au ag telluride probably derived from the decomposition of sylvanite auagte 4 and petzite auag 3 te 2 the only two stable au ag tellurides in nature at high temperature however we do not exclude the possibility that calaverite occurs in this deposit which may have precipitated in early relatively high tellurium concentration stage preceding gold mineralization selenium was not detected in gold bearing tellurides implying that selenide is unrelated with gold precipitation directly in the breccia ores but can buffer the tellurium fugacity and thus influence the gold precipitation indirectly furthermore in log f o 2 g range of 35 4 at 250 c the majority of the tellurides and selenides can be stable in the breccia ores but residual sulfides are proposed to be oxidized into sulfate minerals which could also free some gold into ores although less important relative to that formed from telluride decomposition

in situ trace element and sulfur isotope of pyrite constrain ore genesis in the shapoling molybdenum deposit east qinling orogen china abstract the early cretaceous ca 128 ma shapoling vein type molybdenum mo mineralization associated with the huashan intrusion is a newly discovered deposit in the xiong ershan district east qinling china where pyrite is a ubiquitous mineral phase here we present results from an integrated study on the texture in situ trace element chemistry from laser ablation inductively coupled plasma mass spectrometry la icp ms and sulfur isotopic composition using secondary ion mass spectrometry sims with a view to understand the geochemical variation genesis of mo mineralization and ore forming process the distinct textural patterns as revealed by petrographic observations suggest three types of pyrites py1 is composed of coarse grained euhedral pyrite in the wall rock and early barren quartz vein at stage i py2 is represented by subhedral anhedral grains coexisting with molybdenite in quartz veins at stage ii and py3 forms irregular interstitial grains in the quartz k feldspar molybdenite dominated veins at stage iii the mo enrichment mainly occurred in py3 with co ni ratios 1 and 34s values mainly