major types characteristics and geodynamic mechanism of upper paleozoic copper deposits in northern xinjiang northwestern china abstract syn and post orogenic cu mineralization in the northern xinjiang paleozoic accretionary and collisional orogenic belt in northwestern china is of great economic interest about 40 cu bearing deposits have been discovered in the area making it one of the most important metallogenic belts in china according to their host rocks these deposits can be classified into four principal types 1 volcanic hosted massive sulfide cu pb zn deposits 2 porphyry cu mo au deposits 3 magmatic cu ni sulfide deposits and 4 cu mo au ag skarn deposits tectonically the development of these upper paleozoic deposits was closely associated with subduction and collision of the ancient asian ocean between the siberian block and the tarim craton an important metallogenic epoch involving formation of cu pb zn polymetallic deposits formed during southwestern rollback and associated slab detachment during devonian time 400 370 ma in southern altay southwestern direct rollback and associated slab detachment occurred during the devonian 400 370 ma in response to later collision at the accreted continetal margin xiao w j windley b f badarch g sun s li j l qin k z wang z h 2004 palaeozoic accretionary and convergent tectonics of the southern altaids implications for the lateral growth of central asia journal of the geological society of london 161 339 342 during which the ashele cu pb zn and keketale pb zn deposits formed subduction led to the accretion of the junggar ocean arc system in the middle devonian in the lower to middle carboniferous north dipping subduction beneath the dananhu arc triggered the emplacement of granitic porphyries in the tousuquan and dananhu island arc belt in the east tianshan leading to the formation of the tuwu and yandong porphyry cu mo au ag deposits in the upper carboniferous to lower permian large mafic ultramafic complexes were emplaced during closure of the ancient tianshan ocean resulting in the formation of several magmatic cu ni sulfide deposits including the kalatongke cu ni deposits in north junggar and cu ni sulfide deposits in the huangshan jing erquan area of east tianshan mountains also associated with this extensional event were emplacement of voluminous anatectic granitoids and eruption of volcanic rocks which led to formation of skarn cu mo suoerkuduk cu mo deposit and cu ag deposits weiquan cu ag deposit the tectonic settings geological features and temporal and spatial distribution of these different types of cu deposits reflect to a great extent the accretionary and collisional tectonics that occurred between the siberian block and tarim block

multi temporal uav data for automatic measurement of rill and interrill erosion on loess soil the fragile landscape of the north european loess belt is prone to soil erosion due to soil properties and intense land use of the fertile region exact measurement of surface changes with high temporal and spatial resolution over large areas is necessary to quantify and understand rill and interrill erosion processes high resolution aerial imagery acquired by an unmanned aerial vehicle uav is used to automatically generate precise digital surface models dsms of high spatial resolution by applying structure from motion image processing tools during an investigation period of ten months a 600 m2 field plot is observed during four field campaigns a stable reference system is established for multi temporal comparison the overall accuracy of the dsms generated from uav images is less than 1 cm verified by comparison with terrestrial laser scanner tls data furthermore a method for automatic rill extraction and rill parameter calculation is developed which enables objective rill description with cm accuracy and resolution soil surface roughness and rill development as well as volumetric quantifications are analysed for multi temporal change detection surface changes during winter season are controlled by soil consolidation crusting and sheet erosion during rainy spring season sheet erosion and rill incision occur two thunderstorms in summer season cause dominant rill erosion erosion rills are more dominantly deepening than widening from to 2 to 4 cm depth and from 17 to 23 cm width resulting in average per rill erosion values of 0 03 and 0 07 m3 respectively an orientation dependent lateral rill shift is revealed implying rill widening in eastern direction due to dominant winds from the west volumetric quantifications indicate high erosion volumes reaching up to 121 tha 1 during the summer events highest erosion volumes are due to rill erosion rather than interrill erosion copyright 2014 john wiley sons ltd

u pb ages and hf o isotopes of zircons from late paleozoic mafic ultramafic units in the southern central asian orogenic belt tectonic implications and evidence for an early permian mantle plume abstract u pb age and hf o isotope data of zircons from the mafic ultramafic complexes and their related rhyolites and granites in the eastern tianshan and beishan regions were obtained by sims and la icpms the hf o isotopic composition and hf model age of the zircons are closely related to their tectonic setting and formation age the zircons from the mafic ultramafic complexes in the bogeda haerlike and jueluotage belts have higher ehf t 8 17 and lower 18o 4 6 whereas most of the zircons in the gabbros granites and rhyolite from the middle tianshan massif and beishan rift display lower ehf t 0 8 and higher 18o 5 8 the positive ehf t and relatively lower 18o values suggest that these mafic ultramafic complexes were derived from depleted mantle which was subjected to subduction related modification processes the hf isotopic composition of zircons in the granites has revealed that the growth of juvenile crust was also very significant in the southern margin of the central asian orogenic belt during the paleozoic the hf model ages of the analyzed zircons together with the regional geology suggest that the beishan area had a northward subduction possibly from ca 900 ma to ca 400 ma whereas the eastern tianshan had a south directed subduction most likely from ca 600 ma to ca 310 ma additionally zircons with ca 280 ma u pb ages display wider and more scattered ehf t and 18o variations than the relatively older and younger ones which further support the early permian mantle plume model

a review of the cu ni sulphide deposits in the chinese tianshan and altay orogens xinjiang autonomous region nw china principal characteristics and ore forming processes abstract several cu ni sulphide deposits and occurrences have recently been discovered along parallel deep faults in the chinese tianshan and altay orogenic belts xinjiang province nw china the kalatongke and several other cu ni mineralized intrusions are located along the irtysh fault which separates the altay orogenic belt from the junggar basin the huangshan huangshandong xiangshan tudun erhongwa tula ergen and hongling deposits occur along the kanggurtag suture which separates the jueluotage orogenic belt from the turpan hami tuha basin the baishiquan tianyu and tianxiang deposits are located along the arqikekuduke fault which separates the jueluotage orogenic belt from the central tianshan precambrian terrane the poyi poshi and luodong deposits are located along the baidiwa fault which separates the central tianshan precambrian terrane from the beishan paleozoic rift re os dating of cu ni sulphide ores reveals that these cu ni ore belts formed in a narrow age range of 298 282 ma this age range is about the same as those of associated intrusions and dykes dated by the shrimp zircon u pb method tectonic and geochronological constraints suggest that the amalgamation of continental blocks mainly occurred during the late carboniferous in the central asian orogenic belt large scale hydrothermal and magmatic metallogenesis in the region occurred during post collisional stages of latest carboniferous to early permian age the cu ni sulphide deposits are part of this metallogenic event the cu ni orthomagmatic sulphide deposits in northern xinjiang are represented by 1 net textured type deposits by segregation of a cu ni metal sulphide melt and 2 magma conduit type some mafic ultramafic suites exhibit lithological zoning caused by strong differentiation stratiform orebodies are hosted by ultramafic rocks at the base of the magma chamber good examples are the kalatongke huangshandong and poshi deposits others such as the xiangshan baishiquan tianyu and tula ergen deposits are hosted by magma conduits consisting of peridotite troctolite and pyroxenite these ultramafic rocks either occur within faults or are surrounded by gabbroic and dioritic intrusions these two types of orthomagmatic cu ni sulphide deposits are also distributed along the same ore belts for instance the differentiated sill related huangshandong deposit co exists with the magma conduit type tula ergen deposit in the jueluotage orogenic belt orthomagmatic cu ni sulphide deposits in northern xinjiang formed during post collisional extension and are possibly related to a late carboniferous early permian mantle plume event the mafic ultramafic suites and associated cu ni deposits are commonly accompanied by dyke swarms and are characterized by elongated outcrops occurring along parallel e w trending regional faults these mafic ultramafic suites and accompanying dyke swarms are generally fractionated implying that they were feeders of presently eroded flood basalts

quantifying submerged fluvial topography using hyperspatial resolution uas imagery and structure from motion photogrammetry quantifying the topography of rivers and their associated bedforms has been a fundamental concern of fluvial geomorphology for decades such data acquired at high temporal and spatial resolutions are increasingly in demand for process oriented investigations of flow hydraulics sediment dynamics and in stream habitat in these riverine environments the most challenging region for topographic measurement is the wetted submerged channel generally dry bed topography and submerged bathymetry are measured using different methods and technology this adds to the costs logistical challenges and data processing requirements of comprehensive river surveys however some technologies are capable of measuring the submerged topography through water photogrammetry and bathymetric lidar are capable of reasonably accurate measurements of channel beds in clear water whilst the cost of bathymetric lidar remains high and its resolution relatively coarse the recent developments in photogrammetry using structure from motion sfm algorithms promise a fundamental shift in the accessibility of topographic data for a wide range of settings here we present results demonstrating the potential of so called sfm photogrammetry for quantifying both exposed and submerged fluvial topography at the mesohabitat scale we show that imagery acquired from a rotary winged unmanned aerial system uas can be processed in order to produce digital elevation models dems with hyperspatial resolutions c 0 02 m for two different river systems over channel lengths of 50 100 m errors in submerged areas range from 0 016 m to 0 089 m which can be reduced to between 0 008 m and 0 053 m with the application of a simple refraction correction this work therefore demonstrates the potential of uas platforms and sfm photogrammetry as a single technique for surveying fluvial topography at the mesoscale defined as lengths of channel from c 10 m to a few hundred metres this article is protected by copyright all rights reserved

geochemistry and isotope composition sr pb δ 66 zn of vulcano fumaroles aeolian islands italy abstract we present and discuss temperatures major and trace element gas geochemistry radiogenic isotopes pb sr and the first zn isotope data of fumarole condensates and altered rocks from the vulcano fumarolic field the fumaroles of the la fossa cone sampled on 5th may 2015 have temperatures ranging between 233 and 427 c they plot compositionally on the mixing trend between the magmatic and hydrothermal end members defined by previous studies but are strongly displaced towards the hydrothermal component correlations of radiogenic sr pb and stable isotopes of zn with 13 c co2 and several trace elements of the fumarolic acid condensates support mixing between the above mentioned distinct magmatic and hydrothermal fluids the magmatic end member has a less radiogenic sr 87 sr 86 sr 0 7045 and heavier zn isotope composition 66 zn 0 3 the hydrothermal fluid end member has a more radiogenic 87 sr 86 sr signature 0 7055 which could be due to leaching of radiogenic sr from the crystalline basement rocks or reflect seawater sr it is also characterized by lighter zn isotope composition 66 zn pb isotope compositions of the fumaroles sampled in this study show a shift towards less radiogenic values compared to pre 2001 fumaroles this could indicate either a change in the hydrothermal circulation pattern leading to leaching of rocks with different isotopic compositions or the involvement of a new isotopically distinct magmatic fluid the alteration zones around the fumarole vents are also characterized by systematic correlations of pb and zn isotopes with major and trace elements we interpret these as the result of the addition onto the substratum volcanic rock of pb and zn from the fumaroles zn isotope signatures of the alteration zones are significantly heavier than those of the corresponding fumaroles 66 zn 0 3 1 6 probably due to equilibrium fractionation occurring during sphalerite precipitation at the vent discharge

fore arc basalts and subduction initiation in the izu bonin mariana system recent diving with the jamstec shinkai 6500 manned submersible in the mariana fore arc southeast of guam has discovered that morb like tholeiitic basalts crop out over large areas these fore arc basalts fab underlie boninites and overlie diabasic and gabbroic rocks potential origins include eruption at a spreading center before subduction began or eruption during near trench spreading after subduction began fab trace element patterns are similar to those of morb and most izu bonin mariana ibm back arc lavas however ti v and yb v ratios are lower in fab reflecting a stronger prior depletion of their mantle source compared to the source of basalts from mid ocean ridges and back arc basins some fab also have higher concentrations of fluid soluble elements than do spreading center lavas thus the most likely origin of fab is that they were the first lavas to erupt when the pacific plate began sinking beneath the philippine plate at about 51 ma the magmas were generated by mantle decompression during near trench spreading with little or no mass transfer from the subducting plate boninites were generated later when the residual highly depleted mantle melted at shallow levels after fluxing by a water rich fluid derived from the sinking pacific plate this magmatic stratigraphy of fab overlain by transitional lavas and boninites is similar to that found in many ophiolites suggesting that ophiolitic assemblages might commonly originate from near trench volcanism caused by subduction initiation indeed the widely dispersed jurassic and cretaceous tethyan ophiolites could represent two such significant subduction initiation events

characteristics and dynamic origin of the large scale jiaoluotage ductile compressional zone in the eastern tianshan mountains china abstract the jiaoluotage ductile compressional zone jdcz in the eastern tianshan mountains china developed in volcanic and sedimentary rocks that were deposited in a carboniferous back arc basin situated between the jungar plate and middle tianshan terrane the ductile compressional zone 500 km long and 20 50 km wide consists of a number of east trending vertical foliation zones that display an augen geometry in plan view and a fan like geometry in transverse profiles ductile compressional deformation has produced pervasive foliation radial stretching lineations contemporaneous folds and various macroscopic to microscopic symmetric structures within the jdcz rotations of most clasts and porphyroclasts are bidirectional the preferred orientation patterns of the optical axes of calcite and quartz display axial or orthorhombic symmetry three kinds of strain patterns have been determined in the jdcz apparent flattening plane strain and apparent constriction the overall strain character of the jdcz is cream cake style the volcanic and sedimentary rocks within the jdcz were metamorphosed into greenschist facies with temperature of 400 600 c and pressure of 300 400 mpa development of the jdcz is interpreted as due to n s coaxial compression caused by the collision between the tarim plate and the middle tianshan arc jiaoluotage basin jungar plate system during the permian between 270 and 290 ma

generation of sodium rich magmas from newly underplated basaltic crust sodium rich rocks of trondhjemite tonalite dacite ttd or granodiorite ttg suites form much of precambrian continental crust1 they are thought to have formed by partial melting of subducted oceanic crust2 3 a process that would have been much more widespread early in earth history than at present owing to the higher thermal gradients prevailing at that time4 phanerozoic ttd suites do exist however and seem also to relate to subduction zones5 defant and drummond6 proposed that these suites form where young 25 myr hot oceanic lithosphere is subducted and melts thus locally simulating the conditions that led to widespread crustal growth in the archaean here we describe plutonic and volcanic rocks from the cordillera blanca complex in peru which have characteristics of the high al ttd suite but which were produced above a subduction zone containing a 60 myr old slab we present evidence that the complex formed by partial melting of newly underplated basaltic crust and argue that this mechanism should be considered more generally as an additional way of generating sodium rich arc magmas

optimisation of uavs sfm data collection in aeolian landform morphodynamics a case study from the gonghe basin china uavs sfm unmanned aerial vehicles structure from motion systems can generate high resolution 3d topographic models of aeolian landforms to explore the optimisation of uavs sfm for use in aeolian landform morphodynamics this study tested flight parameters for two contrasting aeolian landform areas free dune and blowout to assess the 3d reconstruction accuracy of the uavs survey compared with field point measurements using differential rtk gps real time kinematic global positioning system the results reveal the optimum uavs sfm flight set up at the free dune site was flying height 74 m camera tilt angle 90 photo overlap ratio 85 70 heading sideways the horizontal vertical location error was around 0 028 0 055 m and 0 053 0 069 m respectively and a point cloud density of 463 m3 was found to generate a clear texture using these flying parameters for the 20m deep blowout the optimum set up with highest accuracy and the lowest cliff texture distortion was flying height 74 m combined camera tilt angle 90 and 60 photo overlap ratio 85 70 heading sideways and an evenly distributed gcps ground control points density of 42 km2 using these flying parameters when the depth of the blowouts exceeded 40 m the optimum flight survey parameters changed slightly to account for more challenging cliff texture generation flying height 80 m with 90 and 60 combined camera tilt angle gcps density 63 km2 to generate horizontal and vertical location error of 0 024 m and 0 050 m respectively and point cloud density of 2597 11 m3 the main external factors that affect the successful 3d reconstruction of aeolian landforms using uavs sfm are the weather conditions manipulation errors and instrument system errors the uavs sfm topographic monitoring results demonstrate that uavs provide a viable and robust means for aeolian landform morphodynamics monitoring importantly the rapid and high precision 3d reconstruction processes were significantly advanced using the optimal flight parameters reported here

ice cored moraine degradation mapped and quantified using an unmanned aerial vehicle a case study from a polythermal glacier in svalbard ice cored lateral frontal moraines are common at the margins of receding high arctic valley glaciers but the preservation potential of these features within the landform record is unclear recent climatic amelioration provides an opportunity to study the morphological evolution of these landforms as they de ice this is important because high arctic glacial landsystems have been used as analogues for formerly glaciated areas in the mid latitudes this study uses sfm structure from motion photogrammetry and a combination of archive aerial and uav unmanned aerial vehicle derived imagery to investigate the degradation of an ice cored lateral frontal moraine at austre lovenbreen svalbard across the study area as a whole over an 11 year period the average depth of surface lowering was 1 75 0 89 m the frontal sections of the moraine showed low or undetectable rates of change spatially variable rates of surface lowering are associated with differences in the quantity of buried ice within the structure of the moraine morphological change was dominated by surface lowering with limited field evidence of degradation via back wastage this permits the moraine a greater degree of stability than previously observed at other sites in svalbard it is unclear whether the end point will be a fully stabilised ice cored moraine in equilibrium with its environment or an ice free lateral frontal moraine complex controls on geomorphological change e g topography and climate and the preservation potential of the lateral frontal moraine are discussed the methods used by this research also demonstrate the potential value of sfm photogrammetry and unmanned aerial vehicles for monitoring environmental change and are likely to have wider applications in other geoscientific sub disciplines

tectonic evolution of the south tianshan orogen and adjacent regions nw china geochemical and age constraints of granitoid rocks geochemical and geochronological evidence was obtained from granitoids of the south tianshan orogen and adjacent regions which consist of three individual tectonic domains the kazakhstan yili plate the central tianshan terrane and the tarim plate from north to south the central tianshan terrane is structurally bounded by the early paleozoic nikolaev line north nalati fault and late paleozoic atbashy inyl chek south nalati qawabulak fault zones against the kazakhstan yili and tarim plates respectively the meta aluminous to weakly peraluminous granitic rocks which are exposed along the kekesu river and the bikai river across the central tianshan terrane have a tholeiitic calc alkaline or high potassium calc alkaline composition i type geochemical trace element characteristics and the y versus rb nb or y versus nb discrimination diagrams favor a continental arc setting for these granitoid rocks shrimp u pb and la icp ms u pb zircon age data indicate that the magmatism started at about 480 ma continued from 460 to 330 ma and ended at about 275 ma the earlier magmatism 470 ma is considered to be the result of a simultaneous southward and northward subduction of the terskey ocean beneath the northern margin of the tarim plate and the kazakhstan yili plate respectively the later magmatism 460 330 ma is related to the northward subduction of the south tianshan ocean beneath the southern margin of the kazakhstan yili central tianshan plate the dataset presented here in conjunction with previously published data support a late paleozoic tectonic evolution of the south tianshan orogen not a triassic one as recently suggested by shrimp u pb zircon dating for eclogites

how fast does tufa grow very high resolution measurement of the tufa growth rate on artificial substrates by the development of a contactless image based modelling device

genesis of the paleozoic aqishan yamansu arc basin system and fe cu mineralization in the eastern tianshan nw china abstract the formation of the eastern tianshan orogen northern xinjiang nw china with a number of ew trending mineralization belts was closely linked to the evolution of the junggar and south tianshan oceans probably part of the paleo asian ocean among these eastern tianshan mineralization belts the carboniferous aqishan yamansu fe cu belt hosts a total reserve of 207 mt fe and economic cu endowments for many deposits these fe cu deposits are hosted in submarine volcanic rocks lower carboniferous yamansu formation and upper carboniferous tugutublak formation and are featured by the presence of extensive skarn alteration without apparently causative intrusive rocks which leads to debates over their genesis in this paper we have summarized the ore deposit geology geochemistry and stable isotopes of the aqishan yamansu fe cu deposits and discuss their genesis under the regional tectonic framework we suggest that the carboniferous aqishan yamansu belt may have been a forearc basin formed by the south dipping subduction of the kangguer ocean beneath the central tianshan massif the yamansu formation volcanic rocks and some syngenetic fe deposits may have formed during the opening of the forearc basin the tugutublak formation volcanic rocks and most fe cu deposits may have formed during the subsequent late carboniferous basin inversion in these aqishan yamansu fe cu deposits the fe mineralization occurred earlier and was likely formed directly from the magmatic hydrothermal fluids whereas the subsequent cu mineralization was likely caused by the gradual increase of seawater or basinal brine influx into the fluid system external sulfur the probable external sulfur input the absence of clear plutonic link and the temporal coincidence of peak mineralization and basin inversion for the carboniferous aqishan yamansu fe cu mineralization are comparable to the mesozoic iocg mineralization in the central andes

closing history of the southern tianshan oceanic basin western china an oblique collisional orogeny abstract the tianshan tien shan range is an important paleozoic collisional orogenic belt and the key to understand the central asia tectonic evolution this paper integrates our research results with the existing chinese and international literature on sedimentology geochemistry isotopic geochronology paleontonology and paleomagnetism of the tianshan and tarim regions to propose that the oblique collision may have played an important role in the late paleozoic closing of the southern tianshan oceanic basin as a result of the sinian latest proterozoic younger than 800 ma continental extension and rifting process the tarim and yili blocks separated from their parent continent in the late cambrian ordovician the southern tianshan oceanic crusts between the two blocks subducted northward beneath the southern margin of the yili block in the silurian during the devonian early carboniferous the tarim block rapidly drifted to the north and rotated about 46 clockwise this process induced the collision of the yili micro continent with the eastern segment present geographical position of the tarim continent in the late devonian and the southern tianshan oceanic crust evolved to be a west facing remnant oceanic basin during the late carboniferous early permian the tarim block located within an almost constant latitude range rotated about 26 clockwise with respect to the yili micro continent which ultimately closed the remnant oceanic basin in a scissors like manner from east to west and completed the tarim yili collision subsequent a type subduction of the tarim continental crust and lithosphere scale sinistral shearing generated a magmatic arc on the southern margin of the tarim yili suture zone the late permian early triassic clastics deposited in a peripheral foreland basin developed above the arc

high resolution mapping of supra glacial drainage pathways reveals link between micro channel drainage density surface roughness and surface reflectance this paper reports on the use of a small unmanned aerial vehicle suav carrying a standard compact camera to construct a high resolution orthomosaic om and digital elevation model dem over the lower reaches of the glacier midtre lovenbreen svalbard structure from motion sfm techniques were used to build the om and dem and together these reveal insights into the nature of supra glacial drainage major meandering supra glacial drainage pathways show clear dynamism via meander cutoffs and abandoned channels in addition the imagery reveals a very extensive network of smaller channels that may well carry substantial amounts of water this network of channels is in part controlled by the structure of the glacier but in turn these channels have a significant impact on the ice surface roughness of the ice surface is higher where channels are most extensive in addition we find a relationship between channel density and surface reflectance such that greater channel density is associated with lower reflectance values given the role of surface reflectance and roughness in the energy balance of glaciers it is therefore apparent that extensive networks of small supra glacial channels across such glaciers have the potential to have an important impact on energy exchanges between the atmosphere and the ice surface copyright 2015 john wiley sons ltd

high resolution monitoring of himalayan glacier dynamics using unmanned aerial vehicles himalayan glacier tongues are commonly debris covered and they are an important source of melt water however they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles observations of debris covered glaciers are therefore scarce and airborne remote sensing may bridge the gap between scarce field observations and coarse resolution space borne remote sensing in this study we deploy an unmanned aerial vehicle uav before and after the melt and monsoon season may and october 2013 over the debris covered tongue of the lirung glacier in nepal based on stereo imaging and the structure for motion algorithm we derive highly detailed ortho mosaics and digital elevation models dems which we geometrically correct using differential gps observations collected in the field based on dem differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial accuracy on average mass loss is limited and the surface velocity is very small however the spatial variability of melt rates is very high and ice cliffs and supra glacial ponds show mass losses that can be an order of magnitude higher than the average we suggest that future research should focus on the interaction between supra glacial ponds ice cliffs and englacial hydrology to further understand the dynamics of debris covered glaciers finally we conclude that uav deployment has large potential in glaciology and it may revolutionize methods currently applied in studying glacier surface features

characteristics and genesis of kanggur gold deposit in the eastern tianshan mountains nw china evidence from geology isotope distribution and chronology abstract the kanggur gold deposit lies in east tianshan mountains eastern section of central asia orogenic belt the gold mineralization occurs on the northern margin of the aqishan yamansu island arc in the tarim plate it is mainly hosted in lower carboniferous volcanic rocks and controlled by syn tectonic intrusions and the ductile shear zone the host rock is a calc alkaline volcanic rock series consisting of andesite dacite tuff and subvolcanic rocks the gold ore bodies were distributed in transition zone from strong ductile deformation to weak deformation ore controlling structure is ew trending normal brittle ductile shear zone the gold ore bodies are composed of au bearing altered rocks and a few au bearing sulfide quartz veins the mineralization shows vertical zonation in which au was enriched in the upper orebodies au pb zn were enriched in the middle and au cu were enriched in the lower orebodies according to mineral assemblages and alteration intensity hydrothermal alteration could be divided into three zones silicification chloritization pyritization and magnetization zone major ore body pyrite phyllic rock and or sericite alteration zone and sericite chlorite alteration zone five mineralization stages are identified on the basis of mineral assemblage and crosscutting relationship of veins the 34 s values of sulfide in the ores range from 0 9 to 3 3 similar to those of the volcanic and subvolcanic rocks 3 21 1 3 indicating that the sulfur isotope composition is characterized by unfractionated mantle sulfur the lead isotope compositions of ores are between those of the volcanic rocks and subvolcanic rocks the initial 87 sr 86 sr ratios of the ores vary between 0 7077 and 0 7106 similar to those of the host rocks 0 7079 0 7125 according to the sr s and pb isotopic data it is indicated that the ore forming materials were derived from the surrounding volcanic rocks and feature deep source the 18 o values of the ore fluids vary from 3 83 to 1 77 and the d values from 46 to 66 the 18 o vs d and 18 o vs 87 sr 86 sr diagrams indicate that ore fluids were derived from dynamic metamorphic water magmatic water and meteoric water the ore forming ages of kanggur gold deposit are determined by rb sr and sm nd isochron methods the results show that the main ore forming stages of kanggur gold deposit are 290 282 ma secondary mineralization stages are 275 254 ma studies on regional geology ore geology isotope geochemistry and ore forming ages have proved that the kanggur gold deposit was formed in the compression extension transition stage during the latest paleozoic continental collision and is characterized by orogenic gold deposits

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

assessing the performance of structure from motion photogrammetry and terrestrial lidar for reconstructing soil surface microtopography of naturally vegetated plots soil microtopography is a property of critical importance in many earth surface processes but is often difficult to quantify advances in computer vision technologies have made image based three dimensional 3d reconstruction or structure from motion sfm available to many scientists as a low cost alternative to laser based systems such as terrestrial laser scanning tls while the performance of sfm at acquiring soil surface microtopography has been extensively compared to that of tls on bare surfaces little is known about the impact of vegetation on reconstruction performance this article evaluates the performance of sfm and tls technologies at reconstructing soil microtopography on 6 m 2 m erosion plots with vegetation cover ranging from 0 to 77 results show that soil surface occlusion by vegetation was more pronounced with tls compared to sfm a consequence of the single viewpoint laser scanning strategy adopted in this study on the bare soil surface elevation values estimated with sfm were within 5 mm of those from tls although long distance deformations were observed with the former technology as vegetation cover increased agreement between sfm and tls slightly degraded but was significantly affected beyond 53 of ground cover detailed semivariogram analysis on meter square scale surface patches showed that tls and sfm surfaces were very similar even on highly vegetated plots but with fine scale details and the dynamic elevation range smoothed out with sfm errors in the tls data were mainly caused by the distance measurement function of the instrument especially at the fringe of occlusion regions where the laser beam intersected foreground and background features simultaneously from this study we conclude that a realistic approach to digitizing soil surface microtopography in field conditions can be implemented by combining strengths of the image based method simplicity and effectiveness at reconstructing soil surface under sparse vegetation with the high accuracy of tls like technologies copyright 2015 john wiley sons ltd

from experimental plots to experimental landscapes topography erosion and deposition in sub humid badlands from structure from motion photogrammetry in the last decade advances in surveying technology have opened up the possibility of representing topography and monitoring surface changes over experimental plots 10 m2 in high resolution 103 points m 1 yet the representativeness of these small plots is limited with structure from motion sfm and multi view stereo mvs techniques now becoming part of the geomorphologist s toolkit there is potential to expand further the scale at which we characterise topography and monitor geomorphic change morphometrically moving beyond previous plot scale work using terrestrial laser scanning tls surveys this paper validates robustly a number of sfm mvs surveys against total station and extensive tls data at three nested scales plots 30 m2 within a small catchment 4710 m2 within an eroding marl badland landscape 1 km2 sfm surveys from a number of platforms are evaluated based on i topography ii sub grid roughness and iii change detection capabilities at an annual scale oblique ground based images can provide a high quality surface equivalent to tls at the plot scale but become unreliable over larger areas of complex terrain degradation of surface quality with range is observed clearly for sfm models derived from aerial imagery recently modelled doming effects from the use of vertical imagery are proven empirically as a piloted gyrocopter survey at 50m altitude with convergent off nadir imagery provided higher quality data than an unmanned aerial vehicle uav flying at the same height and collecting vertical imagery for soil erosion monitoring sfm can provide data comparable with tls only from small survey ranges 5 m and is best limited to survey ranges 10 20 m synthesis of these results with existing validation studies shows a clear degradation of root mean squared error rmse with survey range with a median ratio between rmse and survey range of 1 639 and highlights the effect of the validation method e g point cloud or raster based on the estimated quality

bathymetric structure from motion extracting shallow stream bathymetry from multi view stereo photogrammetry stream bathymetry is a critical variable in a number of river science applications in larger rivers bathymetry can be measured with instruments such as sonar single or multi beam bathymetric airborne lidar light detection and ranging or acoustic doppler current profilers however in smaller streams with depths less than 2 m bathymetry is one of the more difficult variables to map at high resolution optical remote sensing techniques offer several potential solutions for collecting high resolution bathymetry in this research i focus on direct photogrammetric measurements of bathymetry using multi view stereo photogrammetry specifically structure from motion sfm the main barrier to accurate bathymetric mapping with any photogrammetric technique is correcting for the refraction of light as it passes between the two different media air and water which causes water depths to appear shallower than they are i propose and test an iterative approach that calculates a series of refraction correction equations for every point camera combination in a sfm point cloud this new method is meant to address shortcomings of other correction techniques and works within the current preferred method for sfm data collection oblique and highly convergent photographs the multi camera refraction correction presented here produces bathymetric datasets with accuracies of 0 02 of the flying height and precisions of 0 1 of the flying height this methodology like many fluvial remote sensing methods will only work under ideal conditions e g clear water but it provides an additional tool for collecting high resolution bathymetric datasets for a variety of river coastal and estuary systems copyright 2016 john wiley sons ltd

guidelines on the use of structure from motion photogrammetry in geomorphic research as a topographic modelling technique structure from motion sfm photogrammetry combines the utility of digital photogrammetry with a flexibility and ease of use derived from multi view computer vision methods in conjunction with the rapidly increasing availability of imagery particularly from unmanned aerial vehicles sfm photogrammetry represents a powerful tool for geomorphological research however to fully realize this potential its application must be carefully underpinned by photogrammetric considerations surveys should be reported in sufficient detail to be repeatable if practical and results appropriately assessed to understand fully the potential errors involved to deliver these goals robust survey and reporting must be supported through i using appropriate survey design ii applying suitable statistics to identify systematic error bias and to estimate precision within results and iii propagating uncertainty estimates into the final data products

late paleozoic mafic ultramafic intrusions in southern central asian orogenic belt nw china insight into magmatic ni cu sulfide mineralization in orogenic setting abstract the mafic ultramafic intrusions hosting magmatic ni cu sulfide ore deposits usually present within the precambrian cratons and on their margin have been extensively studied whereas those occurring within the phanerozoic orogenic belts have received little attention the southern margin of the central asian orogenic belt is a region of late paleozoic mafic ultramafic intrusions emplaced during post orogenic stage in order to recognize the mineralization features this study compares barren or weakly mineralized mafic ultramafic intrusions in the beishan with those hosting ni cu sulfide ore deposit in the altay and eastern tianshan in petrology mineralogy and geochemistry aspects several mineralization features can be recognized with respects to petrology mineralogy and geochemistry from comprehensive comparisons among the mineralization indicators we highlight strong alteration accompanying sulfide emplacement post erosion exposure of magma conduit abundant primary hydrous minerals and potential transportation mechanism of ore forming elements other indicators are the presence of orthopyroxene and pyroxenite for potential sulfide formation through crystal fractionation restricted fo and ni ranges in olivines for sulfide segregation and some other special geochemical characteristics related to crustal contamination the variation in mineralization could be ascribed to different degrees of partial melting crustal assimilation and subduction related modification of a mantle source we suggest that the ni cu sulfide mineralization of mafic ultramafic intrusions within orogenic belts is remarkably different from that of cratonic and continental marginal settings in respects of petrogenesis and mineralizing mechanism magmatic conduit type ni cu sulfide ore deposit is a target for future prospecting and exploration for mafic ultramafic intrusions in the orogenic belts

field application of close range digital photogrammetry crdp for grain scale fluvial morphology studies in situ measurement of grain scale fluvial morphology is important for studies on grain roughness sediment transport and the interactions between animals and the geomorphology topics relevant to many river practitioners close range digital photogrammetry crdp and terrestrial laser scanning tls are the two most common techniques to obtain high resolution digital elevation models dems from fluvial surfaces however field application of topography remote sensing at the grain scale is presently hindered mainly by the tedious workflow challenges that one needs to overcome to obtain high accuracy elevation data a recommended approach for crdp to collect high resolution and high accuracy dems has been developed for gravel bed flume studies the present paper investigates the deployment of the laboratory technique on three exposed gravel bars in a natural river environment in contrast to other approaches having the calibration carried out in the laboratory removes the need for independently surveyed ground control targets and makes for an efficient and effective data collection in the field optimization of the gravel bed imagery helps dem collection without being impacted by variable lighting conditions the benefit of a light weight three dimensional printed gravel bed model for dem quality assessment is shown and confirms the reliability of grain roughness data measured with crdp imagery and dem analysis evidences sedimentological contrasts between gravel bars within the reach the analysis of the surface elevations shows the effect variable grain size and sediment sorting have on the surface roughness by plotting the two dimensional structure functions and surface slopes and aspects we identify different grain arrangements and surface structures the calculation of the inclination index allows determining the surface forming flow direction s we show that progress in topography remote sensing is important to extend our knowledge on fluvial morphology processes at the grain scale and how a technique customized for use by fluvial geomorphologists in the field benefits this progress copyright 2016 john wiley sons ltd

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

the association of mafic ultramafic intrusions and a type magmatism in the tian shan and altay orogens nw china implications for geodynamic evolution and potential for the discovery of new ore deposits abstract the nw china region is characterised by tectonic and lithostratigraphic domains such as the tian shan and altay orogens the tarim junggar and turpan basins the tian shan and altay orogens are part of the central asian orogenic belt the nw china region was affected by a series of thermal events that occurred between the silurian and the triassic which resulted in the emplacement of numerous granitic plutons and mafic ultramafic intrusions a number of these granitic plutons are of a type affiliation which on the basis of the positive end values are likely to have been derived from mantle sources in addition at least two large igneous provinces lips can be recognised in nw china namely the 345 325 ma tian shan lip and the ca 270 280 ma tarim lip age and field data suggest a spatial and temporal relationship between the mafic ultramafic intrusions and a type granites within the lips in this paper we discuss mafic ultramafic intrusions that host magmatic ni cu sulphide deposits kalatongke in the altay huangshan and poyi poshi in the eastern tian shan these intrusions are typically zoned characterised by an envelope of early gabbroic rocks that enclose later ultramafic units these zoned mafic ultramafic intrusions have some features that are comparable with alaskan type complexes taking into consideration the spatial temporal relationship of the mafic mafic ultramafic rocks and a type granites we suggest that these magmatic events occurred during an extensional regime possibly related to a mantle superplume event that affected much of central asia during the permian of which the siberian traps and the emeishan continental flood basalts of sw china are part if the a type felsic magmatism took place during a superplume event we also suggest that these rocks may be conducive to host iron oxide copper gold iocg style mineralisation we conclude with a model that attempts to explain the relationship between the zoned mafic ultramafic intrusions and mantle plume activity in nw china during the permian

paleozoic magmatism and metamorphism in the central tianshan block revealed by u pb and lu hf isotope studies of detrital zircons from the south tianshan belt nw china as a major precambrian microcontinent in the southernmost central asian orogenic belt caob the central tianshan block cts in the chinese tianshan is essential for understanding the final assembly of the southern caob it experienced multistage paleozoic magmatism and metamorphism but the detailed processes are still controversial and far from being completely understood this paper reports coupled u pb and lu hf isotopic data of detrital zircons from late paleozoic meta sedimentary strata in the south tianshan belt which can provide new insight into deciphering the paleozoic evolution of the eastern segment of the cts block characterized by typical oscillatory zoning and high th u ratios 0 2 detrital zircons in the permian sedimentary samples yield dominant age populations at ca 505 490 ma 475 440 ma 430 400 ma and 340 250 ma pinpointing the development of four episodes of magmatism in the eastern cts block particularly ordovician silurian 475 440 ma zircons possessing low negative ehf t values predominate in sedimentary strata in and surrounding the cts block indicating that the 475 440 ma magmatic rocks probably constitute the main body of the cts block the origin of this early paleozoic episode of magmatism was most likely related to the southward subduction of the junggar ocean beneath the cts block carboniferous triassic 340 250 ma zircons have dominantly positive ehf t values probably derived from the post collisional juvenile rocks in the cts block combined with previous studies our data suggest that the single source terrane for the sampled strata was the cts block which had been a topographic high providing substantial detritus to the surrounding areas at least since the early permian in the metasedimentary sample detrital zircons mostly show partially fully recrystallized internal textures and low th u ratios 0 2 probably sourced from the amphibolite to granulite facies metamorphosed rocks in the eastern cts block the youngest zircons suggest that the sampled metasedimentary strata were carboniferous 341 305 ma in age rather than neoproterozoic or early sinian in chinese literatures as previously interpreted based on u pb hf isotopes and ti in zircon thermometer of metamorphic zircons in this study as well as previous investigations we suggest that the eastern cts block has experienced a a 400 370 ma collisional event related to the closure of the eastern segment of the south tianshan ocean and b a 360 340 ma extensional event as a result of post collisional mantle upwelling therefore the final assembly of the eastern tianshan took place during late carboniferous time

external sulphur in iocg mineralization implications on definition and classification of the iocg clan abstract although the sources of the ore metals remain problematic in most iron oxide cu and au iocg deposits external sulphur either from surficial basinal brines and seawater e g central andean and carajas deposits or from formation water and metamorphic fluids e g the cloncurry deposits or introduced by magmatic assimilation of metasedimentary units e g phalaborwa has been documented in many major cu rich iocg centres however only the evaporite sourced fluids yield diagnostically high 34s values i e 10 while sedimentary formation water or metamorphic fluids commonly have lower values and are less clearly distinguishable from magmatic fluids as in the cloncurry deposits in which the involvement of external fluids is revealed by other evidence such as noble gas isotopes on the basis of these arguments iocg deposits could be redefined as a clan of cu au ag u deposits containing abundant hypogene iron oxide magnetite and or hematite in which externally derived sulphur probably plays an important role for the cu au ag u mineralization in this definition all kiruna type magnetite deposits hydrothermal iron deposits e g skarn fe deposits and magnetite rich porphyry cu au and skarn cu au deposits are excluded two subtypes of iocg deposits are recognized on the basis of the predominant iron oxide directly associated with the cu au mineralization whether magnetite or hematite neither magnetite nor hematite rich iocg deposits show any preference for specific host rocks and both range in age from neoarchean to pleistocene within a broad tectonic environment

straightforward reconstruction of 3d surfaces and topography with a camera accuracy and geoscience application topographic measurements for detailed studies of processes such as erosion or mass movement are usually acquired by expensive laser scanners or rigorous photogrammetry here we test and use an alternative technique based on freely available computer vision software which allows general geoscientists to easily create accurate 3d models from field photographs taken with a consumer grade camera the approach integrates structure from motion sfm and multi view stereo mvs algorithms and in contrast to traditional photogrammetry techniques it requires little expertise and few control measurements and processing is automated to assess the precision of the results we compare sfm mvs models spanning spatial scales of centimeters a hand sample to kilometers the summit craters of piton de la fournaise volcano with data acquired from laser scanning and formal close range photogrammetry the relative precision ratio achieved by sfm mvs measurement precision observation distance is limited by the straightforward camera calibration model used in the software but generally exceeds 1 1000 i e centimeter level precision over measurement distances of 10s of meters we apply sfm mvs at an intermediate scale to determine erosion rates along a 50 m long coastal cliff seven surveys carried out over a year indicate an average retreat rate of 0 70 0 05 m a 1 sequential erosion maps at 0 05 m grid resolution highlight the spatio temporal variability in the retreat with semivariogram analysis indicating a correlation between volume loss and length scale compared with a laser scanner survey of the same site sfm mvs produced comparable data and reduced data collection time by 80

melting behavior of fluid inclusions in laboratory grown halite crystals in the systems naclh2o naclkclh2o naclmgcl2h2o and naclcacl2h2o abstract the chemical composition of aqueous fluid inclusions in crystals of halite can be accurately determined from observed melting behaviors of ice hydrohalite and sylvite some fluid inclusion melting behaviors observed in laboratory grown halite crystals systems nacl h 2 o nacl kcl h 2 o nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o differ from predicted stable equilibrium relations in the nacl h 2 o and nacl kcl h 2 o systems observed first melt temperatures are up to 15 c below the equilibrium eutectic temperatures of 21 2 and 22 9 c respectively the final melting temperature of ice in the presence of hydrohalite and the final melting temperature of hydrohalite are reproducible and match predicted melting temperatures the limit of detection of sylvite daughter crystals in the nacl kcl h 2 o system is approximately 5 wt 1 molal kcl final melting temperatures of sylvite match published equilibrium data to within 0 3 c in the nacl kcl h 2 o system at halite saturation m kcl can be determined from the final sylvite dissolution temperature or from the final melting temperature of hydrohalite fluid inclusions in the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems that form stable salt hydrates mgcl 2 12h 2 o and cacl 2 6h 2 o during freezing first melt within 3 c of predicted eutectic temperatures 37 and 52 c however fluid inclusions with mgcl 2 or cacl 2 may also start melting at temperatures as low as 80 c such low first melt temperatures indicate the presence of metastable salt hydrates presumably mgcl 2 8h 2 o mgcl 2 6h 2 o or cacl 2 4h 2 o the formation of metastable phases during freezing of fluid inclusions can lead to misinterpretation of the chemical composition of fluid inclusions in natural samples this is especially true for fluid inclusions with first melt temperatures below 37 c which may be erroneously interpreted as being rich in cacl 2 the final melting of ice in the presence of hydrohalite may vary by more than 15 c in fluid inclusions of different size but identical bulk composition and occurs at lower temperatures than predicted in fluid inclusions from the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems however the final melting temperature of ice in inclusions which fail to nucleate hydrohalite and the final melting temperature of hydrohalite are reproducible to within 0 1 c and can be used to determine mgcl 2 and cacl 2 molalities

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spatial and temporal zoning of hydrothermal alteration and mineralization in the sossego iron oxide copper gold deposit carajas mineral province brazil paragenesis and stable isotope constraints the sossego iron oxide copper gold deposit 245 mt 1 1 cu 0 28 g t au in the carajas mineral province of brazil consists of two major groups of orebodies pista sequeirinho baiano and sossego curral with distinct alteration assemblages that are separated from each other by a major high angle fault the deposit is located along a regional wnw ese striking shear zone that defines the contact between metavolcano sedimentary units of the 2 76 ga itacaiunas supergroup and tonalitic to trondhjemitic gneisses and migmatites of the 2 8 ga xingu complex the deposit is hosted by granite granophyric granite gabbro and felsic metavolcanic rocks the pista sequeirinho baiano orebodies have undergone regional sodic albite hematite alteration and later sodic calcic actinolite rich alteration associated with the formation of massive magnetite apatite bodies both these alteration assemblages display ductile to ductile brittle fabrics they are cut by spatially restricted zones of potassic biotite and potassium feldspar alteration that grades outward to chlorite rich assemblages the sossego curral orebodies contain weakly developed early albitic alteration and very poorly developed subsequent calcic sodic alteration these orebodies contain well developed potassic alteration assemblages that were formed during brittle deformation that resulted in the formation of breccia bodies breccia matrix commonly displays coarse mineral infill suggestive of growth into open space sulfides in both groups of deposits were precipitated first with potassic alteration and more importantly with a later assemblage of calcite quartz epidote chlorite in the sequeirinho orebodies sulfides range from undeformed to deformed sulfides in the sossego curral orebodies are undeformed very late weakly mineralized hydrolytic alteration is present in the sossego currral orebodies the sulfide assemblage is dominated by chalcopyrite with subsidiary siegenite and millerite pyrrhotite and pyrite are minor constituents of ore in the sequerinho orebodies while pyrite is relatively abundant in the sossego curral bodies oxygen isotope partitioning between mineral pairs constrains temperatures in the deposit spatially and through time in the sequeirinho orebody the early sodic calcic alteration stage was characterized by temperatures exceeding 500 c and delta text 18 text o text h text 2 text o values for the alteration fluid of 6 9 0 9 temperature declines outward and upward from the zone of most intense alteration paragenetically later copper gold mineralization displays markedly lower temperatures 300 c and was characterized by the introduction of 18o depleted hydrothermal fluids 1 8 3 4 the calculated dh2o and delta text 18 text o text h text 2 text o values suggest that the fluids that formed the early calcic sodic alteration assemblage were of formational metamorphic or magmatic origin the decrease of delta text 18 text o text h text 2 text o values through time may reflect influx of surficially derived waters during later alteration and mineralization events influx of such fluids could be related to episodic fluid overpressure resulting in dilution and cooling of the metalliferous fluid causing deposition of metals transported as metal chloride complexes