multiple sulfur isotopes monitor fluid evolution of an archean orogenic gold deposit abstract the evolution of a gold bearing hydrothermal fluid from its source to the locus of gold deposition is complex as it experiences rapid changes in thermochemical conditions during ascent through the crust although it is well established that orogenic gold deposits are generated during time periods of abundant crustal growth and or reworking the source of fluid and the thermochemical processes that control gold precipitation remain poorly understood in situ analyses of multiple sulfur isotopes offer a new window into the relationship between source reservoirs of au bearing fluids and the thermochemical processes that occur along their pathway to the final site of mineralisation whereas 34s is able to track changes in the evolution of the thermodynamic conditions of ore forming fluids 33s is virtually indelible and can uniquely fingerprint an archean sedimentary reservoir that has undergone mass independent fractionation of sulfur mif s we combine these two tracers 34s and 33s to characterise a gold bearing laminated quartz breccia ore zone and its sulfide bearing alteration halo in the 6 moz au structurally controlled archean waroonga deposit located in the eastern goldfields superterrane of the yilgarn craton western australia over 250 analyses of gold associated sulfides yield a 34s shift from what is interpreted as an early pre mineralisation phase with chalcopyrite pyrrhotite 34s 0 7 to 2 9 and arsenopyrite cores 34s 0 5 to a syn mineralisation stage reflected in au bearing arsenopyrite rims 34s 7 6 to 1 5 this shift coincides with an unchanging 33s value 33s 0 3 both temporally throughout the au hosting hydrothermal sulfide paragenesis and spatially across the au ore zone these results indicate that sulfur is at least partially recycled from mif s bearing archean sediments further the invariant nature of the observed mif s signature demonstrates that sulfur is derived from a homogeneous mif s bearing fluid reservoir at depth rather than being locally sourced at the site of au precipitation finally by constraining the mif s bearing sulfur source to a fixed reservoir we are able to display the thermochemical evolution of the ore fluid in 34s space and capture the abrupt change in oxidation state that causes au precipitation our results highlight the importance of constraining multiple sulfur isotopes in space and time in order to elucidate the source and evolution of any given au bearing fluid

genetic implications of pyrite chemistry from the palaeoproterozoic olary domain and overlying neoproterozoic adelaidean sequences northeastern south australia abstract sulphide mineralisation associated with rocks from the palaeoproterozoic olary domain od and overlying neoproterozoic adelaidean sequences has undergone a complex history of metamorphism and remobilisation in this study new trace element and sulphur isotopic analyses of pyrites from a large number of deposits and paragenetic generations are combined with an existing data set to build up a sequence of mineralising events linked to the tectonometamorphic evolution of the region the typically high co ni ratios 10 indicate that early strata bound pyrite precipitated from a volcanic related fluid which had fluctuating activities of the two metals during the early stages of the evolution of the willyama basin this period of mineralisation was followed by a diagenetic concentration of sulphide mineralisation at the horizon known as the bimba formation which occurred as a result of the differing redox conditions between the upper and lower sequences in the willyama supergroup during the mesoproterozoic 1600 to 1500 ma olarian orogeny metamorphic remobilisation of strata bound pyrite resulted in an epigenetic signature the trace element concentrations of this generation were controlled primarily by the proximity of mineralisation to the mafic intrusive bodies found throughout the terrane further reworking of existing sulphides during the delamerian orogeny and associated granitoid intrusive rocks led to the formation of a new generation of epigenetic pyrite that occurs in quartz veins in the adelaidean sequences and veins that crosscut olarian fabrics in the olary domain 34s results range from 16 to 11 but most data fall between 2 and 4 this association is suggestive of an initial uniform deep seated crustal reservoir of sulphur which has been repeatedly tapped throughout the metallogenic history of the region the isotopic outliers can be explained by the input of biogenic sulphur or sulphur derived from oxidised possibly evaporitic sediments respectively previous workers have invoked the kupferschiefer and the zambian copperbelt as analogues to mineralisation processes in the olary domain this study shows that 34s and trace element data are suggestive of some affinities with the aforementioned analogues but a more likely link can be made between epigenetic remobilisation in the olary region and the iron oxide copper gold iocg style of mineralisation found at the nearby olympic dam deposit

lithological anomalies in a relict coastal dune geophysical and paleoenvironmental markers 1 ground exposures of migration surfaces slipfaces of a relict holocene coastal dune along the southeastern baltic sea coast provide an ideal opportunity for establishing the causes of prominent reflections on geophysical profiles high amplitude reflections on high resolution ground penetrating radar gpr images correlate well with two major lithological anomalies 1 paleosols developed on dune slipfaces and 2 slipfaces consisting of heavy mineral concentrations hmcs paleosols serve as indicators of dune stability represent datable chronostratigraphic surfaces and help reconstruct dune paleo morphology hmcs have substantially higher magnetic susceptibility values than background quartz rich sands and where they are well developed can be also used for spatial correlation based on their occurrence at the study site these enriched horizons likely represent periods of increased wind activity storminess multiple hmcs upwind of paleosol p1 800 670 cal years bp likely reflect periods of intensified wind activity along the southeast baltic region during the medieval warm period

factors controlling geochemical and mineralogical compositions of coals preserved within marine carbonate successions a case study from the heshan coalfield southern china abstract the late permian coals in the heshan coalfield of southern china are preserved within marine carbonate successions and characterized by super high organic sulfur 5 13 10 82 minerals identified in the coals include quartz kaolinite illite mixed layer illite smectite albite pyrite marcasite calcite and dolomite along with trace amounts of smectite fluorite strontianite rey bearing carbonate minerals jarosite and water bearing fe oxysulfate the coals are very rich in trace elements including f up to 3362 g g v up to 270 g g se up to 24 4 g g mo up to 142 g g u up to 111 g g and to a lesser extent sr y zr nb cd cs heavy rare earth elements hf ta w hg and th previous studies attributed the high organic sulfur and elevated trace elements to the seawater influence or the formation of soil horizons before the accumulation of peat in the basin however mineralogical and geochemical data presented in this study have shown that the sediment source region and multi stage hydrothermal fluids are the dominant influences on the mineralogical composition and elevated trace elements in the coal although seawater influence also contributed to the composition of the mineral matter for example a large proportion of the quartz and clay minerals as well as almost all the albite in both the coal benches and the parting mudstones were derived from detrital materials of terrigenous origin in the yunkai upland high concentrations of lithophile trace elements were also derived from the sediment source region minerals including fluorite calcite dolomite strontianite and rey bearing carbonate minerals were derived from multi stage hydrothermal activities high concentrations of v mo and u that occur through the coal seam sections were probably derived from hydrothermal solutions during peat accumulation or at the early diagenetic stages the hydrothermal fluids also corroded the syngenetically formed minerals quartz albite and pyrite and caused re distribution of lithophile elements from partings to the underlying coal benches resulting in higher key element ratios yb la nb ta and zr hf and more abundant heavy rare earth elements in the coal benches than in the immediately overlying partings

oxidized and reduced mineral assemblages in greenstone belt rocks of the st ives gold camp western australia vectors to high grade ore bodies in archaean gold deposits hydrothermal sulfide oxide gold mineral assemblages in gold deposits in the archaean st ives gold camp in western australia indicate extremely variable redox conditions during hydrothermal alteration and gold mineralization in space and time reduced alteration assemblages pyrrhotite pyrite occur in deposits in the southwest of the camp e g argo junction deposits and moderately to strongly oxidized assemblages magnetite pyrite hematite pyrite occur in deposits in the central corridor in the northeast e g north orchin revenge deposits reduced mineral assemblages flank the central corridor of oxidized deposits and locally cut across it along e w trending faults oxidized mineral assemblages in the central corridor are focused on gravity lows which are interpreted to reflect abundant felsic porphyritic intrusions at about 1 000 m below present surface hydrothermal magnetite predates and is synchronous with early phases of gold associated albite carbonate pyrite biotite chlorite hydrothermal alteration later stage gold associated pyrite is in equilibrium with hematite the spatial distribution and temporal sequence of iron sulfides and oxides with gold indicate the presence of at least two spatially restricted but broadly synchronous hydrothermal fluids with contrasting redox states sulfur isotope constraints support the argument that the different mineral assemblages reflect differences in redox conditions the 34s values for pyrite for the st ives gold camp range between 8 4 and 5 1 with the negative values occurring in oxidized magnetite rich domains and slightly negative or positive values occurring in reduced pyrrhotitic domains preliminary spatial and paragenetic analysis of the distribution of iron sulfides and oxides in the st ives camp suggests that gold grades are highest where the redox state of the hydrothermal alteration assemblages switches from relatively reduced pyrrhotite pyrite to relatively oxidized magnetite pyrite and hematite pyrite both in space and time gold deposition is inferred to have occurred where fluids of contrasting redox state mixed

characteristics and origin of the zhulazhaga gold deposit in inner mongolia china abstract the zhulazhaga gold deposit in the northern margin of the north china craton ncc is a large tonnage hydrothermal deposit with a reserve of about 50 t at about 4 g t au the deposit is characterized by an epigenetic style of mineralization in metasedimentary rocks dominated by slates low grade metamorphic clastic rocks and minor volcanic rocks gold mineralization is dominantly controlled by structures manifested by stratabound orebodies located immediately to the east and west of a major n s trending fault and associated extensional fractures and ne trending fault zones the mineralization is also preferentially located in the fourth sub member of first member of the agulugou formation there are many auriferous quartz veins parallel to the bedding of the host rocks which contain the orebodies and high grade ore preferentially occurs near to these quartz veins the structures provided pathways for transportation of gold bearing fluids within the formation that appears to form a particularly favorable host rock and depositional setting hydrogen and oxygen isotope data indicate that ore forming fluids were dominated by magmatic water mixed with minor meteoric water sulfur and lead isotope data indicate that some sulfur and lead came from the magmatic fluid the metallogenic age 280 ma of this deposit and the crystallization age 280 290 ma of the granite porphyry in the district indicate a link between the hercynian magmatism and gold mineralization the hercynian tectono magmatism and associated hydrothermal activity remobilized gold and drove ore forming fluids to the favorable depositional environment the northern margin of the ncc is prospective for gold mineralization hosted in metasedimentary rocks which may be one of the most important deposit types for future gold exploration in northern china

geology geochronology geochemistry and ore genesis of the wangu gold deposit in northeastern hunan province jiangnan orogen south china abstract the wangu gold deposit in northeastern hunan south china is one of many structurally controlled gold deposits in the jiangnan orogen the host rocks slates of the lengjiaxi group are of neoproterozoic age but the area is characterized by a number of late jurassic cretaceous granites and ne trending faults the timing of mineralization tectonic setting and ore genesis of this deposit and many similar deposits in the jiangnan orogen are not well understood the orebodies in the wangu deposit include quartz veins and altered slates and breccias and are controlled by wnw trending faults the principal ore minerals are arsenopyrite and pyrite and the major gangue minerals are quartz and calcite alteration is developed around the auriferous veins including silicification pyritic arsenopyritic and carbonate alterations field work and thin section observations indicate that the hydrothermal processes related to the wangu gold mineralization can be divided into five stages 1 quartz 2 scheelite quartz 3 arsenopyrite pyrite quartz 4 poly sulfides quartz and 5 quartz calcite the lianyunshan s type granite which is in an emplacement contact with the ne trending changsha pingjiang fracture zone has a zircon la icpms u pb age of 142 2 ma the dayan gold occurrence in the changsha pingjiang fracture zone which shares similar mineral assemblages with the wangu deposit is crosscut by a silicified rock that contains muscovite with a ca 130 ma 40ar 39ar age the gold mineralization age of the wangu deposit is thus confined between 142 ma and 130 ma this age of mineralization suggests that the deposit was formed simultaneously with or subsequently to the development of ne trending extensional faults the emplacement of late jurassic cretaceous granites and the formation of cretaceous basins filled with red bed clastic rocks in northeastern hunan which forms part of the basin and range like province in south china empa analysis shows that the average as content in arsenopyrite is 28 7 atom and the mineralization temperature of the arsenopyrite pyrite quartz stage is estimated to be 245 20 c from arsenopyrite thermometry the high but variable au as molar ratios 0 02 of pyrite suggest that there are nanoparticles of native au in the sulfides an integration of s pb h o he ar isotope systematics suggests that the ore fluids are mainly metamorphic fluids originated from host rocks possibly driven by hydraulic potential gradient created by reactivation of the wnw trending faults initially formed in paleozoic with possible involvement of magmatic and mantle components channeled through regional fault networks the wangu gold deposit shares many geological and geochemical similarities as well as differences with typical orogenic epithermal and carlin type gold deposits and may be better classified as an intracontinental reactivation type as proposed for many other gold deposits in the jiangnan orogen

petrology mineralogy and geochemistry of the lower cretaceous oil prone coal and host rocks from the laoheishan basin northeast china abstract the coal and host rocks mainly oil shale partings in the laoheishan basin ne china are oil prone this study uses petrological mineralogical and geochemical analyses to determine the reasons of high oil yield in the coal and the origin and modes of occurrence of the minerals and elements in the coal and oil shale partings the obtained data show that this sub bituminous b coal has higher oil yield av 10 than oil shale partings av 5 7 consistent with a higher hydrogen content in the coal this oil prone coal has potential for comprehensive utilization due to the relatively high gross calorific value av 17 23 mj kg in the semi coke the maceral composition suggests that the relatively high hydrogen content in the coal is mainly caused by higher resinite content palynological analysis of coal and oil shale partings mainly proved the presence of gymnosperms and ferns revealing that the paleovegetation is dominated by lygodiacean osmundacean ground ferns and cupressaceaen taxodiaceaen canopy trees these canopy trees would have provided abundant hydrogen rich components e g resin to the paleomire all the identified sporopollen suggests a warm humid subtropical paleoclimate minerals in the coal include kaolinite quartz illite and or illite smectite chlorite feldspar calcite and traces of pyrite rutile and zircon similar to the oil shale partings most of the minerals quartz feldspar clay minerals rutile and zircon occur in layers within detrovitrinite and probably are of detrital origin pyrite and calcite are of epigenetic origin and probably derived from hydrothermal fluids compared with average chinese coal the laoheishan coal is enriched in zr nb in and sb zirconium and nb mainly occur in zircon indium is both organically and inorganically associated whereas antimony largely occurs in pyrite rey rare earth elements and yttrium distribution patterns of coals and oil shale partings are dominated by heavy rey enrichment whereas roof and floor samples are medium rey enriched the m hrey enrichment is probably caused by low temperature hydrothermal fluids the sedimentary input is the major controlling factor of geochemical patterns in coal and host rocks the source rocks are probably felsic intermediate igneous rocks from the surrounding basement as indicated by relatively high al2o3 tio2 ratios 7 38 cross plot between zr ti and nb y negative eu anomalies 0 28 0 96 the presence of k feldspar and plagioclase and lithic fragment types such as granite and andesite in the samples in addition source rocks of sediments have caused high zr and nb concentrations in the coal

orogenic gold common or evolving fluid and metal sources through time abstract orogenic gold deposits of all ages from paleoarchean to tertiary show consistency in chemical composition they are the products of aqueous carbonic fluids with typically 5 20 mol co 2 although unmixing during extreme pressure fluctuation can lead to entrapment of much more co 2 rich fluid inclusions in some cases ore fluids are typically characterized by significant concentrations of ch 4 and or n 2 common estimates of 0 01 0 36 mol h 2 s a near neutral ph of 5 5 and salinities of 3 7 wt nacl equiv with na k ca mg this fluid composition consistency favors an ore fluid produced from a single source area and rules out mixing of fluids from multiple sources as significant in orogenic gold formation nevertheless there are broad ranges in more robust fluid inclusion trapping temperatures and pressures between deposits that support a model where this specific fluid may deposit ore over a broad window of upper to middle crustal depths much of the reported isotopic and noble gas data is inconsistent between deposits leading to the common equivocal interpretations from studies that have attempted to define fluid and metal source areas for various orogenic gold provinces fluid stable isotope values are commonly characterized by the following ranges 1 18 o for precambrian ores of 6 to 11 and for phanerozoic ores of 7 to 13 2 d and 34 s values that are extremely variable 3 13 c values that range from 11 to 2 and 4 15 n of 10 to 24 for the neoarchean 6 5 to 12 for the paleoproterozoic and 1 5 to 10 for the phanerozoic secular variations in large scale earth processes appear to best explain some of the broad ranges in the o s and n data fluid rock interaction particularly in ore trap areas may cause important local shifts in the o s and c ratios the extreme variations in d mainly reflect measurements of hydrogen isotopes by bulk extraction of waters from numerous fluid inclusion generations many which are not related to ore formation radiogenic isotopes such as those of pb sr nd sm and os measured on hydrothermal minerals are even more difficult to interpret for defining metal source particularly as the low salinity ore fluids transport limited amounts of these elements and significant amounts of these may be locally added to the minerals during alteration reactions at the sites of gold deposition noble gas and halogen data are equally equivocal fluid exsolution from granitoids emplaced into the upper and middle crust metamorphism of the crust or fluids entering trans crustal fault zones from below the crust all remain as permissive scenarios associated with orogenic gold formation as the abundant geochemical data are equivocal however geological and geochronological data weigh heavily against a magmatic hydrothermal model in the upper to middle crust there is no universal temporal association between orogenic gold and magmatism and where there is an overlap in age there is no specific type of magmatism consistently associated with gold formation nor element zonation around any specific pluton a crustal metamorphic model for fluid and metal sources is very consistent with geological geochronological and geochemical data although metamorphism on a regional scale that releases these components into major fault zones can be associated with many processes along active continental margins these can include crustal thickening and radiogenic heating slab rollback and heating during crustal extension or subduction of a spreading ridge heating the base of an accretionary prism in rare examples where phanerozoic orogenic gold deposits are hosted in precambrian high grade metamorphic terranes fluids and metals must however enter a transcrustal fault system from a sub crustal source this could either be a devolatilized subducted relatively flat perhaps stalled slab and its overlying sediment or the corner of the fertilized mantle wedge that releases a fluid during a thermal event

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

textures and in situ chemical and isotopic analyses of pyrite huijiabao trend youjiang basin china implications for paragenesis and source of sulfur many carlin like au deposits occur within the late paleozoic and triassic youjiang basin of southwest china the huijiabao trend in guizhou province contains over 300 metric tons t 10 6 moz of au at an average grade of 7 to 18 g t in a narrow corridor that is about 20 km long and 5 km wide petrographic and sem studies of pyrite in barren host rocks and high grade orebodies led to the recognition of four stages of pyrite py1 consists of fine grained framboidal crystals in black mudstone py2 is comprised of coarser grained euhedralsubhedral clusters that are spatially related to organic matter py3 is coarse grained euhedral and occurs as overgrowths on py1 and py2 py3 s porous texture inclusion of randomly oriented detrital minerals and association with quartz recrystallization suggest it was deformed during late triassic orogenesis with py1 and py2 py4 generally occurs as rims on py1 to py3 and is intergrown with arsenopyrite sensitive high resolution ion microprobe shrimp 34s analyses of each pyrite type and arsenopyrite show that py1 is related to py2 and that py3 is related to py4 and arsenopyrite the s isotope compositions of py1 7 5 to 5 9 and py2 5 3 to 7 9 are bimodal which suggests that h2s was generated by biogenic sulfate reduction in open marine and sulfate limited systems during sedimentation and or diagenesis the compositions of py3 2 6 to 1 5 py4 1 2 to 1 5 and arsenopyrite 0 8 to 0 9 are homogeneous and have an intermediate range of values near 0 that suggest that h2s was derived either from average pyrite 0 2 in sedimentary rocks or from a concealed magmatic source laser ablation inductively coupled plasma mass spectrometer la icp ms trace element analyses as ni co cu ag se v support different origins and show that py3 and py4 are ore related the lower w co w ni and w s w se ratios of py1 and py2 are consistent with formation during sedimentation or diagenesis whereas the higher ratios of py3 py4 and arsenopyrite are consistent with a hydrothermal origin the lower concentrations of au in py1 0 23 2 5 ppm and py2 0 06 12 ppm show that little au was added during sedimentation or diagenesis the higher concentrations of au in hydrothermal py3 1 1 110 ppm and py4 0 34 810 ppm indicate that most of the au was introduced during subsequent hydrothermal fluid flow the low au contents of arsenopyrite 0 09 0 52 ppm suggests they formed from au depleted fluids the au as ratios of py1 and py2 are typical of diagenetic pyrite whereas py3 and py4 have ratios that approach those of ore stage pyrite in nevada carlin type deposits the fracturing of py3 and its cementation by py4 suggests that ore fluid movement was associated with deformation published isochron ages on arsenopyrite re os 200 ma and late calcite realgar veinlets sm nd 135 ma in the huijiabao trend are older than mafic dikes 84 ma exposed 20 km to the east if the 200 and 135 ma ages are valid h2s and au may be derived from a sedimentary source because igneous intrusions of this age have not been found if these ages are not valid and the gold deposits are actually late cretaceous in age then h2s and au may be derived from a magmatic source additional geochronology and isotopic tracer studies are needed to resolve this uncertainty

the occurrence of buddingtonite in super high organic sulphur coals from the yishan coalfield guangxi southern china abstract this paper discusses the identification abundance modes of occurrence and origin of buddingtonite and associated minerals in three lopingian coals from the yishan coalfield guangxi province southern china the coals of this coalfield are preserved within carbonate successions and are characterized by super high organic sulphur contents mostly 6 9 three different types of feldspars have been identified in these coals buddingtonite albite and minor k feldspar both the albite and k feldspar in the coal were largely derived from detrital materials of terrigenous origin although some were authigenically deposited they were subsequently subjected to corrosion dissolution by percolating fluids buddingtonite was derived largely from k feldspar via diffusion mechanisms through the substitution of k by nh4 the latter coming from decomposition of organic matter in the coal or from changes in the organic matter with rank advance a small proportion of the buddingtonite was also derived from albite through the replacement of na by nh4

metallogeny in response to lithospheric thinning and craton destruction geochemistry and u pb zircon chronology of the yixingzhai gold deposit central north china craton article magmatism and associated metallogeny provide important constraints on geodynamic processes the hengshan terrain of northern taihang mountains located within the central north china craton is well known for several mesozoic gold deposits here we investigate the yixingzhai quartz vein hosted gold deposit associated with the sunzhuang quartz monzodiorite intrusive complex we present u pb data on zircon grains from the monzodiorite which constrain the timing of emplacement of the pluton as ca 134 ma coeval with the formation of yixingzhai quartz vein gold deposit at ca 131 ma the magmatism and metallogenesis during early creta ceous in the hengshan terrain are part of a major regional magmatic and metallogenic event in the taihang mountains and elsewhere in the north china craton at ca 130 ma ago we characterize the zircon grains from the sunzhuang quartz monzodiorite through morphology internal structures and chemistry and also present data from analyses of the chemistry co and ni and s pb d o isotopes of the minerals from the yixingzhai gold deposit and sunzhuang quartz monzodiorite our results reveal a lower crustal signature with mantle input for the source magma of the sunzhuang pluton the magma was enriched in water and alkalis and shows a wide range of crystallization temperature 850 550 c and mainly 650 to 700 c under high oxygen fugacity the ore minerals and the mineralizing fluids in the yixingzhai gold deposit were derived from magma generated in the lower crust with additional input of mantle components our study links the gold metallogenesis with magmatism in the hengshan terrain based on the new results reported in this study and in conjunction with our interpretation of the ultra broadband high precision magnetotelluric sounding profile from the region we suggest that the lithosphere beneath the hengshan terrain was strongly thinned and decoupled between the crust and mantle in the early cretaceous and that the partly destructed lithosphere was largely preserved through the cenozoic to present the metallogenesis in the hengshan terrain was closely related to the lithosphere thinning and crust mantle decoupling in the north china craton

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

geological and isotopic constraints on ore genesis huangjindong gold deposit jiangnan orogen southern china abstract the huangjindong gold deposit with gold resources of 80 t is hosted in neoproterozoic slates along the chang ping fault in the jiangnan orogen southern china the orebodies are dominated by auriferous arsenopyrite pyrite quartz scheelite veins quartz rich breccias that are cemented by late arsenopyrite pyrite muscovite and quartz auriferous stibnite quartz veins and disseminated gold in arsenopyrite pyrite sericite quartz altered rocks neither significant alteration zoning nor ore element zoning are recognized within the orebodies although the orebodies at shallower crustal levels are slightly more stibnite rich at the regional scale the first order control on the distribution of gold deposits is the nne to ne trending crustal scale sinistral strike slip chang ping fault as in other gold provinces globally this controlling fault is not gold mineralized the gold occurrs in wnw to e w trending zones of thrusts and fracture arrays associated with tight locked up asymmetrical folds the broadly e w trending orebodies formed independently within approximately ne trending fault bounded corridors defined by the first order chang ping and second order ni wan and keng shang chang long faults hydrothermal activity was initiated at the ductile brittle transition but evolved to brittle dominated deformation all within a transpressional environment oxygen and hydrogen isotope compositions of fluids d 44 4 to 34 2 18o 8 6 to 9 5 calculated from gold related hydrothermal quartz and hydrothermal sericite respectively are consistent with a metamorphic source sulfur isotope compositions of the gold bearing arsenopyrite and pyrite median values between 8 0 and 6 0 are generally distinct from 34s of the regional neoproterozoic slates in the jiangnan orogen but overlap the compositions of pyrites in global sediment hosted orogenic gold deposits lead isotope compositions of the gold bearing arsenopyrite and pyrite 206pb 204pb 17 049 to 18 417 207pb 204pb 15 263 to 15 712 208pb 204pb 37 597 to 39 220 suggest that the lead was sourced from metamorphic rocks involved in the orogenic events therefore both the stable and radiogenic isotopic data indicate that ore forming fluids and metals were derived from a metamorphic source although the precise nature of that source is unclear on the basis of these geological and isotopic data huangjindong is interpreted as an orogenic gold deposit the gold ore bodies show classic structural controls being adjacent at the province scale to the crustal scale chang ping fault but located in thrusts and associated tight anticlinal fold hinges that lie in corridors between markedly oblique relatively brittle fault arrays that parallel the chang ping fault

mineralogical and isotopic studies of base metal sulfides from the jiawula ag pb zn deposit inner mongolia ne china abstract the jiawula ag pb zn deposit is located in the northern part of the da hinggan mountains metallogenic belt in the eastern section of the central asian orogenic belt sphalerite galena pyrite chalcopyrite and arsenopyrite are the major sulfide minerals occurring in this deposit here we report results from electron probe micro analysis epma thermoelectricity and sulfur isotope studies of the constituent silver minerals and sulfide phases of the jiawula deposit petrographic observations and epma study reveal abundant silver mineralization in the ore especially within sphalerite and galena discrete grains of silver minerals including argentite pyrargyrite and canfieldite and isomorphism in silver bearing sulfides are identified silver and tellurium contents in galena are relatively high and show interrelationship significant substitution of s by te in the galena lattice facilitates silver entering the galena structure which might have been promoted by relatively low lg fs2 the thermoelectric coefficient of pyrite shows a marked gradient from n type to p type from pre to post metallogenic stages pyrites in jiawula are enriched in co and as and in the absence of ni displaying features typical of epithermal deposits the isotopic data present a close relationship between the sulfur source and magmatism

fluid chemical evolution as a factor in controlling the distribution of gold at the archean golden crown lode gold deposit murchison province western australia the golden crown lode gold deposit is one of a number of northwest southeast to north south trending quartz veins hosted by a steeply dipping 500 m thick differentiated dolerite sill the great fingall sill and adjacent graphitic shale in the day dawn district of the murchison province in the archean yilgarn craton western australia quartz veins of the golden crown deposit are shear zone hosted crosscut the dominant host rock stratigraphy at a high angle and are laminated partly boudinaged and generally bifurcate at their extremities veins are dominated by dark gray or milky white quartz with subordinate calcite and ankerite and in order of abundance arsenopyrite pyrrhotite pyrite galena chalcopyrite and minor sphalerite the vein sulfides coexist with native gold and are most abundant at vein margins textural evidence indicates that precipitation of the majority of these minerals overlapped and that most phases can be considered to have been in equilibrium during vein genesis mineral chemistry fluid inclusions alteration and ore assemblages show that there are significant systematic gradients in intensive variables within the golden crown deposit these are recorded over the approximately 450 m of vertical exposure of the vein system and over up to 30 m into the wall rocks based on proximal alteration assemblages and zoning patterns zoned wall rock alteration haloes are divisible into four sequences three of which are closely related to gold mineralization specific alteration sequences occur within different parts of the vein system biotite alteration predominates in the deeper portions whereas muscovite alteration characterizes the upper and southern portions of the system higher grade gold zones within the golden crown deposit are limited to the northern end of the system in the deeper portion of the veins and expand along strike to the south in the upper portions fluid inclusions interpreted to be trapped during gold mineralization are low salinity 10 wt nacl equiv h2o co2 ch4 inclusions with variable carbonic to aqueous contents that are interpreted to be due to fluid immiscibility inferred methane concentrations in the carbonic phase vary significantly from 19 7 mole percent in the vicinity of the shale contact to 5 2 mole percent in the shallower southern end of the deposit carbon and oxygen isotope compositions of carbonates 13ccalcite 10 5 to 1 9 13cankerite 5 3 to 4 1 18ocalcite 7 0 18 3 and 18oankerite 7 7 9 2 and oxygen isotope compositions of vein quartz 18oquartz 10 2 12 5 are well within the range of known archean orogenic lode gold deposits combining the results of all geothermometers and geobarometers a temperature of 300 to 400 c and pressure of 2 5 0 5 kbars are determined with temperature variations over the exposed quartz vein of less than 40 c the as content at of arsenopyrite and au ag ratios of native gold show significant compositional variation which appears to be controlled by parameters such as a h2s aq and f o2 not temperature gradients on the basis of the variations in fluid composition determined in the reefs the two major processes responsible for high grade gold mineralization are interpreted to have been phase separation in the deeper portions of the ore forming system approximately below 400 m level and above these levels mixing between two modified ore fluids one reduced fluid that had reacted with graphitic shale and a relatively oxidized fluid that had partly equilibrated with dolerite

visible gold in arsenian pyrite at the shuiyindong carlin type gold deposit guizhou china implications for the environment and processes of ore formation abstract carlin type gold deposits are best known for the scarcity of visible gold in their ores it has long been recognized that the majority of gold is invisible such that it cannot be resolved by conventional microscopy and resides in arsenian pyrite shuiyindong differs in that sub m to m sized native gold is present in arsenian pyrite veinlets and disseminations it is also the largest 55 tonnes and highest grade 7 to 18 ppm stratabound carlin type gold deposit in guizhou china and has produced 5 tonnes of gold from sulfide refractory ores extracted by underground mining methods in this study an electron microprobe analyzer empa was used to map the spatial distribution of invisible gold and sub m to m size visible gold particles in arsenian pyrite in high grade ore samples from the shuiyindong the samples studied are hosted in permian bioclastic ferroan limestone of the longtan formation and exhibit evidence of decarbonation silicification and sulfidation arsenian pyrite with detectable au 400 to 3800 ppm is disseminated in altered limestone and was deposited in two stages separated by an episode of corrosion in a veinlet the results show that there are two populations of native gold in arsenian pyrite one is comprised of sub m size gold particles 0 1 to 0 2 m that are occasionally present in the gold bearing arsenian pyrite disseminated in the host rocks this arsenian pyrite is interpreted to have been formed by sulfidation of ferroan calcite and dolomite another is comprised of coarser 1 to 6 m native gold grains present in the arsenian pyrite veinlet either on the first stage where it has been corroded or on the second stage the lack of fluid inclusion or other evidence of boiling and the low iron content of fluid inclusions in quartz suggest the veinlet formed by sulfidation of another fluid containing fe the fe bearing fluid may be a depleted ore fluid that gained fe by dissolution of ferroan limestone after h 2 s had been consumed the association of the largest visible gold grains with an episode of corrosion suggests that fluids episodically became undersaturated with arsenian pyrite while remaining saturated with gold e g ph decrease or an increase in the oxidation state this may have resulted from incursion of relatively acidic or oxidized fluids that were able to dissolve arsenian pyrite and remain saturated with gold in this case sulfidation of iron from the host rock was the most important depositional mechanism for au bearing arsenian pyrite with or without grains of native gold

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

late quaternary environments vegetation and agriculture in northern new zealand a sedimentological and plant microfossil history of the late quaternary is preserved in two sediment cores from early polynesian ditch systems on southern aupouri peninsula the study places human activities into a geomorphological and ecological context and allows comparison of natural and anthropogenic effects on two different geological settings a floodplain and a relatively closed peat swamp the data fill part of the current gap in the environmental record from northern new zealand namely mis 3 57k 26k yr bp there is evidence for an increase in fire frequency in the region after 40k 14c yr bp suggesting a shift to drier and cooler conditions pollen records show that conifer hardwood forest dominated by podocarps especially dacrydium prevailed prior to polynesian arrival and deforestation within the last millennium with fuscopsora insignificant throughout both cores show sections with gaps in deposition or preservation possible flood stripping of peat during the pre holocene and mechanical disturbance by early polynesians the identification of prehistoric starch grains and other microremains of introduced colocasia esculenta taro in both cores supports indirect evidence that the ditch systems of far northern new zealand were used for the extensive cultivation of this crop copyright 2006 john wiley sons ltd

palaeoenvironment of seam i in the marathousa lignite mine megalopolis basin southern greece the present study aims to elucidate the depositional environment of seam i in the megalopolis basin southern greece using existing geological data supported by maceral and mineralogical analyses as well as by natural radioactivity determinations very high pyrite and uranium contents and a very low tissue preservation index usually suggest a marine influence during deposition in seam i however these features are most probably the result of a karstic aquifer supplying the palaeomire with sulphate rich neutral to weakly alkaline water the pyrite formation and the u precipitation are attributed to the anaerobic conditions which prevailed during peat accumulation the petrographic mineralogical and geochemical data of the studied profile point to several changes in the surface runoff and the supply of clastic material during deposition

some genetic implications of silica and aluminosilicates in peat and coal abstract the inorganic content of okefenokee peat in the absence of a significant detrital contribution is a function of sponge spicule phytolith and diatom abundance in addition to the degree of organic matter decomposition and the frequency of fires the detrital component quartz dominates ash composition where it is present no clear correlation has been observed between the inorganic content of coals examined in this study and their maceral composition vitrinite rich coals have a wide range of ash yield these observations suggest that the minerals have been introduced detritally rather than accumulated as a result of peat degradation quartz in the coals appears to be detrital and the presence of 2m 1 mica indicates that there is also a detrital contribution to the clay minerals present

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

sulfur isotopes in sediment hosted orogenic gold deposits evidence for an early timing and a seawater sulfur source we report sulfur isotopic compositions of sulfides of various paragenetic stages in the giant sukhoi log sediment hosted orogenic au deposit in russia the overall mean value and the significant variability in early pyrite indicate that the sulfur was from the reduction of seawater sulfate the later generations of sulfide have 34s values in successively smaller ranges coincident with the mode that is around the median value of the whole data set together with textural evidence sulfide trace element data and gold occurrence the data demonstrate that metamorphism has gradually homogenized the early sulfur accompanied by the segregation of quartz and the release of au from the lattice of early pyrite and its reprecipitation as inclusions in later pyrite the s isotopic compositions of sulfides in sukhoi log and many other major orogenic au deposits hosted in sedimentary rocks of various ages show a pattern generally parallel to the seawater sulfate curve through geologic time indicating that the sulfur in most sediment hosted orogenic au deposits was probably also originally from the reduction of seawater sulfate we conclude that sulfidation and gold mineralization in many sediment hosted orogenic gold deposits was early during basin evolution when seawater was the principal active fluid rather than later during or after basin inversion as proposed in current models

isotope geochemistry and genesis of the liyuan gold deposit shanxi north china abstract the liyuan lode gold deposit is located in the shanxi province central north china craton gold orebodies are mainly hosted in archean metamorphic rocks and structurally controlled by the nne trending faults gold occurs in disseminated and auriferous quartz sulfide veins and veinlets within hydrothermally altered rocks mineralization can be divided into three intervals 1 quartz pyrite stage 2 quartz polymetallic sulfides stage and 3 quartz carbonate stage gold formed mainly in the middle stage sericite sample associated with the middle stage pyrite from phyllic alteration zones yields an well defined 40ar 39ar plateau age of 133 3 1 2 ma which is remarkably consistent with zircon u pb age 133 4 1 1 ma of the quartz porphyry dikes in the liyuan mine indicating a close relationship between gold mineralization and granitic magmatism in the area the sulfur isotopic compositions of pyrite py1 2 from the early stage have a narrow range from 0 3 to 4 1 indicating a deep seated magmatic source however the sulfides py3 5 sphalerite galena from the middle stage have lower 34sv cdt values of 7 2 to 3 0 which is thought to be a result of fluid oxidation during gold mineralization the pb isotopic compositions of sulfides from liyuan ores have 206pb 204pb 207pb 204pb and 208pb 204pb ratios of 16 671 16 860 15 236 15 255 and 41 452 44 159 respectively indicting a high thorium lower continental crust source of ore forming materials the 13cvpdb and 18ovsmow values of late stage calcite ranging from 7 1 to 5 8 and 12 2 to 13 7 respectively illustrating a deep seated magmatic source of carbon bearing portion given the absence of granite bodies at the present mining levels we speculate that the ore forming fluids may have been exsolved from a concealed granite pluton at greater depth based on the regional tectono magmatic events ore geology geochronologic and isotopic data obtained in this study together with the previous published fluid inclusion data we suggest that the liyuan deposit is an orogenic gold deposit that is probably related to the early cretaceous granite magmatism in the interior of the north china craton

the mongol okhotsk belt in mongolia an appraisal of the geodynamic development by the study of sandstone provenance and detrital zircons abstract the mongol okhotsk belt formed in a late stage of jurassic orogeny in the composite central asian orogenic belt the present paper investigates the late palaeozoic mesozoic sandstones associated with the belt in mongolia aimed at reconstructing the time and mode of ocean formation subduction and collision we apply provenance analysis including 1 heavy mineral and sandstone framework grain analysis 2 u pb laser ablation icp ms dating of detrital zircons for identifying contemporaneous volcanic arc activity and the recycling of older crustal material and 3 on dated zircon grains we analyze trace element contents and hf isotopic ratios in order to characterize the rock types in which they crystallized and the magma sources respectively the investigated samples are derived from 1 the adaatsag and doschgol terranes which represent the suture zone 2 the hangai hentei belt to the northwest and 3 the ereendavaa terrane and the middle gobi volcanic belt to the southeast of the suture the latter two are concurrent with the northern and southern margins of the mongol okhotsk ocean tectono stratigraphic arguments suggest that the mongol okhotsk ocean opened during the silurian within the early palaeozoic collage in the suture zone permian syn sedimentary zircon trace element contents confirm mafic rock sources and the mantle involvement in the magmatism epsilon hf t from 13 up to 20 n and s directed bi vergent subduction developed as revealed by contemporaneous zircons 1 along the northern margin hangai hentei from silurian early carboniferous subduction and accretion prevailed epsilon hf t from 3 up to 12 in associated zircons which was re initiated during the permian and 2 the contemporaneous silurian devonian southern margin ereendavaa middle gobi still represented an extensional continental margin showing reworking of neoproterozoic early palaeozoic zircons from the basement it turned into an active continental margin with starting arc magmatism in the carboniferous zircon mean epsilon hf t 5 75

authigenic quartz in the upper freeport coal bed west central pennsylvania cathodoluminescence petrography was used to examine quartz grains contained in facies of the upper freeport coal bed middle pennsylvanian of west central pennsylvania samples included ash concentrates polished blocks of different lithotypes and standard petrographic pellets of specific gravity separates of facies channel samples more than 80 of the quartz in mineral and vitrain rich bands in the polished blocks of the upper freeport coal bed do not exhibit cathodoluminescence in specific gravity separates of the coal 100 of the quartz examined in the lightest gravity separates did not luminesce in the heaviest gravity separates which included shale parting material 60 of the quartz did not luminesce in contrast in a sample of shale directly overlying the coal bed more than 90 of the quartz luminesced on the basis of these cathodoluminescence data and other published data quartz in the upper freeport coal bed is interpreted to be authigenic in origin the authigenic quartz grains are postulated to have been derived from phytoclasts

the granite hosted gold deposit of moulin de cheni saint yrieix district massif central france petrographic structural fluid inclusion and oxygen isotope constraints the moulin de cheni orogenic gold deposit is the only granite hosted deposit of the saint yrieix district french massif central it occurs in 338 1 5 ma old peraluminous leucogranites and is characterized by intense microfracturing and bleaching of the granite in relation to pervasive sulfide crystallization formation of quartz veins and gold deposition occurred in two successive stages an early mesozonal stage of quartz sulfide fe as s deposition usually devoid of gold and a late epizonal stage of base metal and gold deposition both stages postdate peak metamorphism and granite intrusion the genesis of the deposit is the result of four successive fluid events 1 percolation of aqueous carbonic metamorphic fluids under an assumed lithostatic regime of 400 450 c at a maximum depth of 13 km 2 formation of the main quartz lodes with coeval k alteration and introduction of as and s from aqueous carbonic fluids percolating along regional faults arsenopyrite and pyrite deposition was linked to the alteration of fe silicates into k feldspar and phengite at near constant iron content in the bulk granite temperature was similar to that of the preceding stage but pressure decreased to 100 50 mpa suggesting rapid uplift of the basement up to 7 5 km depth 3 the resulting extensional tectonic leads to the deposition of gold boulangerite galena and sphalerite in brecciated arsenopyrite and pyrite from aqueous fluids during a mixing process temperature and salinity decrease from 280 to 140 c and 8 1 wt eq nacl to 1 6 wt eq nacl respectively 4 sealing of the late fault system by barren comb quartz which precipitated from dilute meteoric aqueous fluids 1 6 wt eq nacl to 0 9 wt eq nacl under hydrostatic conditions at 200 150 c

investigating sulfur pathways through the lithosphere by tracing mass independent fractionation of sulfur to the lady bountiful orogenic gold deposit yilgarn craton abstract as sulfur is the primary complexing ligand for gold transport in aqueous fluids recent work has demonstrated that the archean systems can preserve mass independent fractionation of sulfur mif s to yield near zero values 33s1 0 0 5 in such cases interpretation of the geological significance of such isotopic signatures may be compromised as it is known that mass dependent fractionation of sulfur mdf s can yield small 33s values herein as 33sb often owing to geobiological reactions involving sulfur in this study we reassess the range of possible values of 33sb from the traditionally accepted value of 0 0 2 to demonstrate that this range is not constant but rather directly linked to the degree of 34s fractionation we present a multiple sulfur isotope dataset from the neoarchean lady bountiful orogenic gold deposit from the yilgarn craton western australia this deposit contains pyrite with an isotopic composition of 34s 2 1 0 8 and 33s 0 14 0 06 2sd on the mean the analysis of these results as well as of a data compilation from other 2 65 ga orogenic gold deposits of the yilgarn craton indicates that 33s1 values are too large to be the result of purely mdf s processes in addition when compared to a compilation of 3400 33s0 measurements of archean sedimentary rocks which shows highly variable positive and negative signals the remarkably constant positive mif s1 signature of gold deposits from the yilgarn craton with 33s1 values between 0 and 0 6 is evidence that the source of the auriferous fluids equilibrated at depth by mixing with a non mif s0 bearing sulfur reservoir by enhancing the application of mif s1 33s1 as a powerful and indelible tracer to understand the source and emplacement pathways of gold bearing fluids through the lithosphere the outcomes from this study demonstrate the recorded 33s1 signature in the auriferous fluids reflects the presence of sulfur that was at least partially sourced from an archean sediment reservoir

trace element characteristics of different pyrite types in mesoarchaean to palaeoproterozoic placer deposits a comparative in situ la icp ms trace element study on pyrite from three different variably auriferous archaean to palaeoproterozoic palaeoplacer deposits in the ouro fino syncline quadrilatero ferrifero brazil the elliot lake area north of lake huron se canada and several deposits within the witwatersrand basin south africa revealed systematic differences between morphologically different pyrite types and between the various palaeoplacer deposits especially the ni and au concentrations as well as co ni and mo ni ratios were found to be systematically different in detrital compact detrital porous and post sedimentary hydrothermal pyrite grains from different source areas high co ni ratios and low au concentrations are typical of post sedimentary pyrite which is hydrothermal in origin in contrast relatively low co ni ratios and high au contents characterise detrital porous banded and concentric pyrite grains au 1 ppm which are syn sedimentary in origin in the elliot lake area and the witwatersrand basin detrital compact rounded pyrite is characterised by high co ni ratios which is in agreement with derivation from a hydrothermal source low au concentrations in this pyrite type support the contention of the gold and the pyrite in these deposits coming from different source rocks in contrast derivation from an originally diagenetic pyrite is suggested for the detrital compact pyrite in the ouro fino syncline because of low to intermediate co ni ratios high au contents may indicate a genetic relationship between pyrite and gold there systematic differences exist between the three areas with respect to au ni co mo and cu distributions in detrital pyrite which reflects differences in the provenance a predominantly mafic ultramafic source is indicated for the ouro fino a felsic source for the elliot lake and a mixed felsic mafic provenance for the witwatersrand pyrite populations independently of pyrite type the higher au endowment of the studied witwatersrand and ouro fino conglomerates are also reflected by an overall higher au concentration in the respective pyrite grains compared to the relatively au poor samples from elliot lake in general a strong positive correlation between au and pb levels in the various pyrite grains is noted analogous to pb which is well known for not being easily accommodated in the pyrite crystal lattice but occurring as discrete pbs phases au is considered to be present mainly in the form of discrete au phases in minute pores and interstices of the pyrite grains rather than within the pyrite lattice

influence of structural setting on sulphur isotopes in archean orogenic gold deposits eastern goldfields province yilgarn western australia the published mean 34s values of ore related pyrites from orogenic gold deposits of the eastern goldfields province yilgarn craton lie between 4 and 4 as for orogenic gold deposits worldwide most deposits have positive means and a restricted range of 34s values but some have negative means and wider ranges of 34s values wall rock carbonation and back mixing of similar source fluids with different fluid pathways can explain some of the more negative 34s signatures however structural setting appears to be the most important factor controlling ore fluid oxidation state and hence the distribution of 34s values in gold related pyrites shear hosted deposits appear to have experienced fluid dominated processes such as phase separation whereas stockwork vein hosted or disseminated deposits formed under conditions of greater rock buffering at victory defiance in particular negative 34s values are more common in gently dipping dilational structures compared to more compressional steeply dipping structures it appears most likely that fluid pressure fluctuations during fault valve cycles establish different fluid flow regimes in structures with different orientations rapid fluid pressure fluctuations in dilational structures during seismic activity can cause partitioning of reduced gas phases from the ore fluid during extreme phase separation and hence are an effective method of ore fluid oxidation leading to large local fluctuations in oxidation state it is thus not necessary to invoke mixing with oxidised magmatic fluids to explain 34s signatures indicative of oxidation in any case available robust geochronology in the eastern goldfields province does not support the direct involvement of oxidised magmatic fluids from adjacent granitic intrusions in orogenic gold genesis thus negative mean 34s values and large variations in 34s values of ore related pyrites in world class orogenic gold deposits are interpreted to result from multiple mechanisms of gold precipitation from a single ubiquitous ore fluid in varying structural settings rather than from the involvement of oxidised ore fluids from a different source such signatures are indicative but not diagnostic of anomalously large orogenic gold systems

coal facies studies in the eastern united states coals in the eastern united states east of the mississippi river have been the subject of a number of coal facies studies going back to the 19th century such studies would not necessarily fall within a strict modern classification of coal facies studies but if a study encompassed some aspects of paleobotany palynology petrology geochemistry or sedimentology we assumed that some data and interpretations may be of use in evaluations of the facies references are presented as a guide for further research with annotation in the tables

application of arsenopyrite geothermometry and sphalerite geobarometry to the taebaek pb zn ag deposit at yeonhwa i mine republic of korea the taebaek pb zn ag deposit of the yeonhwa i mine republic of korea occurs in a broadly folded and reverse faulted terrain of paleozoic sedimentary rocks the taebaeksan basin the orebodies consist of several thin tabular orebodies of hydrothermal replacement type where they are hosted by carbonate rocks the pb zn ag mineralization can be divided into four distinct stages based upon the mode of occurrence of ore minerals ore textural relationships and their composition based on temperatures inferred from arsenopyrite compositions by means of electron microprobe and fluid inclusions the estimated temperatures for the stages i ii iii and iv reach 330 to 350 c 270 to 340 c 230 to 250 c and 220 c respectively the sulphur activity atm of ore formation at the taebaek deposit was estimated for each stage as 10 11 to 10 11 5 10 9 5 to 10 13 10 13 5 to 10 15 and 10 15 respectively even though application of sphalerite geobarometry is problematic because of the absence of good mineral assemblages sphalerite coexisting with pyrite but not with pyrrhotite was used to estimate the minimum mineralization pressure about 1 kbar

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

geology mineralogy and stable isotope geochemistry of the dzuunmod area in northern mongolia constraints for gold ore genesis and sources abstract the dzuunmod area located in the north khentii gold belt nkgb of northern mongolia includes lode gold deposits such as gatsuurt sujigtei and boroo with several minor gold deposits and occurrences they show similar hydrothermal alteration assemblages sericitic siliceous and potassic and ore mineral assemblages pyrite and arsenopyrite with minor amount of galena sphalerite and chalcopyrite gold occurs as native form and invisible gold in pyrite and arsenopyrite the major sulfide minerals are separated into earlier non auriferous stage and later auriferous grains containing invisible gold native gold postdates the major sulfide mineralization gold and arsenic content of pyrite grains indicates that gold exists mainly as solid solution form au 1 in the gatsuurt and boroo deposit whereas gold nanoparticle au0 is present in the sujigtei deposit high co ni and mo ni ratios of pyrite grain suggest a post sedimentary or hydrothermal origin and the ore forming fluid was significantly affected by fluid host rock interactions during mineralization processes large variation of 34s values of pyrite and arsenopyrite from 2 6 to 17 2 indicates that sulfur seems to be mainly derived from a source with heterogeneous sulfur isotope composition even though the role of magmatic sulfur as one of possible sulfur sources cannot be ruled out consistent with geological evidence relatively positive 34s values suggest that sulfidation plays an important role for gold and sulfide precipitation the calculated 18o values of hydrothermal fluid from the measured 18o values of quartz samples from 14 7 to 17 7 indicate a metamorphic derivation of ore forming fluid gold mineralization processes in the dzuunmod area seem to occur several times by multiple input of hydrothermal fluid and fluid host rock interactions the gold deposits in the dzuunmod area are considered to be orogenic gold type influenced by fluid host rock interactions in the deposit area

geodynamics of the western part of the mongolia okhotsk collisional belt trans baikal region russia and mongolia abstract after the western edge of the mongolian microcontinent joined the siberian continent in the region of central mongolia in the earliest permian these two continental blocks remained turned at an angle of about 120 with respect to each other and separated on greater extent of their present day boundary by an enormous gulf of the paleopacific called the mongolia okhotsk ocean closure of this ocean at the early middle jurassic boundary led to the complete collision of siberia and mongolia which by then had already become part of the mongolia north china continent this main collisional episode which lasted through the middle and late jurassic involved thrusting folding and magmatism and produced the mongolia okhotsk belt the onon island arc which was located in the mongolia okhotsk ocean was squeezed between the two major continents inasmuch as the third element the island arc was involved in the collision it is reasonable to distinguish two branches of the mongolia okhotsk suture these branches control the spatial distribution of gold mineralization in the trans baikal region on the southeastern periphery of siberia the crust thickened considerably after the collision and a plateau like uplift formed in the early cretaceous when compression ceased the collisional uplift collapsed and the thrusts were transformed into low angle normal faults the motions on which were responsible for the formation of rift basins and exhumation of metamorphic core complexes

stratigraphic and interregional changes in pennsylvanian coal swamp vegetation environmental inferences abstract quantitative analysis of pennsylvanian coal swamp vegetation provides a means of inferring organization and structure of communities distribution of these communities further provides inferences about environmental factors including paleoclimate our observations are based on in situ structurally preserved peat deposits in coal ball concretions from 32 coal seams in the eastern one half of the united states and from several seams in western europe and on spore assemblages from more than 150 seams there were three times of particularly significant and nearly synchronous vegetational changes in the midcontinent and appalachian coal regions during the pennsylvanian period each was different in kind and magnitude the first marked changes occurred during the early part of the middle pennsylvanian with the fluctuating decline in the high level of lycopod dominance the abundance of cordaites increased there was a rise in the occurrences of the lycopod herbs to form intercalated marshlands and an overall increase in floral diversity changes ensuing from this time also include shifts in dominant species of lycopod trees and a sustained rise in abundance and diversity of tree fern spores the next significant time of change was during the middle part of the middle pennsylvanian representing both a culmination of earlier trends and expansions of cordaites in the midcontinent where there was a maximum change in species without net loss of diversity tree ferns and medullosan pteridosperms attained subdominant levels of abundance and diverse lycopod species dominated except in the atokan desmoinesian transition of the midcontinent the third and sharpest break occurred near the middle late pennsylvanian boundary when extinctionsof the dominant coal swamp lycopods allowed development of tree fern dominance the late pennsylvanian coal swamps apparently were colonized or recolonized mainly by species from outside coal swamps rather than by the survivor populations of the middle pennsylvanian swamps paralleling the changes in floras through the pennsylvanian are changes in preservational aspects of the peat these include a decline in shoot root ratios from approximately 1 to

effects of detrital influx in the pennsylvanian upper freeport peat swamp abstract quartz cathodoluminescence properties and mineralogy of three sets of samples and vegetal and or miospore data from two sets of samples from the upper freeport coal bed west central pennsylvania show that detrital influence from a penecontemporaneous channel is limited to an area less than three km from the channel the sets of samples examined include localities of the coal bed where 1 the coal is thin split by partings and near a penecontemporaneous fluvial channel 2 the coal is relatively thick and located approximately three km from the channel and 3 the coal is thick and located approximately 12 km from the channel samples from locality 1 nearest the channel have relatively high ash yields low temperature ash average 27 3 on a pyrite and calcite free basis and high proportions of quartz and clay minerals the quartz is primarily detrital as determined by cathodoluminescent properties and the ratio of kaolinite to illite is low in addition most of the plant remains and miospores indicate peat forming plants that required low nutrient levels for growth in contrast samples from localities 2 and 3 from the more interior parts of the bed contained predominantly authigenic quartz grains nd yielded low temperature ash values of less than 14 on a pyrite and calcite free basis the low temperature ash contains low concentrations of quartz and clay minerals and the ratio of kaolinite to illite is relatively high although intact core was not available for paleobotanical analyses another core collected within 1 km from locality 3 contained plant types interpreted to have required high nutrient levels for growth these data indicate that mineral formation is dominated by authigenic processes in interior parts of the coal body some of the authigenic quartz may have been derived from herbaceous ferns as indicated by patterns in the palynological and paleobotanical data in contrast detrital processes appeared to be limited to in areas directly adjacent to the penecontemporaneous channel where the coal bed is high in ash split by mineral rich partings and of little or no economic value

gpr stratigraphy of a large active dune on parengarenga sandspit new zealand the parengarenga sandspit figure 1 is new zealand s only coastal source of silica sand for glass manufacturing concerns about the environmental effects of sand extraction from the harbor mouth in the last two decades led the extraction companies to instigate a monitoring program the parengarenga beach dune monitoring program started in 1982 since that time cross profiles have been surveyed twice a year from below chart datum cd to landward of the sparsely vegetated foredune system this is the longest continuous record of beach profile measurement in new zealand and provides important information on the behavior of this coastal spit system parnell 1997 the sedimentary material in parengarenga sandspit consists of 93 5 quartz and has a very uniform fine sandy grain size median 193 microns from near shore to the beach and in the dunes

gilt by association origins of pyritic gold ores in the victory mesothermal gold deposit western australia sulfur isotope data and calculated fluid rock reaction paths constrain the origin of pyritic gold ores in the victory mesothermal gold deposit of western australia pyrite 34s values range from 4 4 to 5 1 and are negatively correlated with gold tenor in mafic host rocks indicating a significant increase in fluid oxidation state accompanied mineralization geologic evidence argues strongly that mineralization occurred with wall rock sulfidation but this process alone cannot produce the degree of fluid oxidation necessary to explain the sulfur isotope range in contrast either carbonation of ferric iron bearing minerals or separation of immiscible fluid phases both of which are consistent with the available geologic data can drive fluid oxidation to the point of aqueous sulfate dominance coupled decreases in gold solubility and sulfide sulfur isotope values that are predicted by such a scenario provide an explanation for the trend between 34s and gold tenor observed at victory because both wall rock carbonation and fluid phase separation involve loss of aqueous sulfide but do not require precipitation of iron sulfides these processes may explain the poor correlation between gold tenor and pyrite abundance in many mesothermal deposits and the occurrence of some gold ores in iron poor rocks

formation of gold deposits a metamorphic devolatilization model a metamorphic devolatilization model can explain the enrichment segregation timing distribution and character of many goldfields such as those found in archean greenstone belts slate belts and other gold only provinces in this genetic model hydrated and carbonated greenschist facies rocks particularly metabasic rocks are devolatilized primarily across the greenschist amphibolite facies boundary in an orogenic setting devolatilization operates on the scale of individual mineral grains extracting not just h2o and co2 but also s and in turn au elevated gold in solution is achieved by complexing with reduced s and by h2co3 weak acid buffering near the optimal fluid ph for gold solubility the buffering is more important than being at the point of maximum gold solubility low salinity ensures low base metal concentrations in the auriferous metamorphic fluid migration of this fluid upwards is via shear zones and or into hydraulic fracture zones in rocks of low tensile strength the geometry of the shear zones dictates the kilometre scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold deposition of gold from solution necessitates breakdown of the gold thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon bearing host rocks and or by sulphidation of wallrocks to generate iron bearing sulphide and precipitated gold as such black slate carbon seams banded iron formation tholeiitic basalt magnetite bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields gold deposition is accompanied by carbonation sulphidation and muscovite biotite alteration where the host rock is of suitable bulk composition the correlation of major gold deposits with rock type even when the gold is primarily in veins argues for rock dominated depositional systems not fluid dominated ones as a consequence a general role in gold deposition for fluid mixing temperature decrease and or fluid pressure decrease and boiling is unlikely although such effects may be involved locally several geological features that are recorded at gold only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process overprinting by higher grade metamorphism and deformation and or palaeo weathering may provide many of the most obvious features of goldfields including their mineralogy geochemistry geometry small scale timing features geophysical response and even mesoscopic gold distribution

comparison of the petrography palynology and paleobotany of the little fire creek coal bed southwestern virginia u s a abstract two continuous cores that penetrated the lower pennsylvanian little fire creek coal bed in the southwestern coal field in southwestern virginia were sampled and x ray radiographed to determine subunit distinctions comparison of petrographic palynologic and paleobotanic data from the same sample sets from the two cores allowed for comparison of compositional data within the little fire creek coal bed the proximate petrographic palynologic and plant tissue data from two sets of samples indicate a high ash gelocollinite and liptinite rich coal consisting of a relatively diverse paleoflora including lycopsid trees small lycopsids tree ferns small ferns pteridosperms seed ferns and rare calamites and cordaites the relatively very high ash yields 3 80 wt the relatively thin subunits 1 28 cm and the large scale vertical variations in palynomorph floras suggest that the study area was at the edge of the paleopea forming environment as a result most of the compositional correspondences are among those components indicative of degradation or decomposition

sand incursion into temperate lithuania and tropical the bahamas maritime vegetation georadar visualization of target rich aeolian lithosomes abstract interaction of windblown sand with maritime vegetation either as dune migration or episodic grain transport is a common phenomenon along many sandy coasts vegetation introduces antecedent surface roughness especially when scaled to the landform height but its role may be concealed if overwhelmed by aeolian incursion and burial where field observations and cores lack detail for characterizing this complex process ground penetrating radar gpr offers continuous visualization of aeolian sequences along the curonian spit lithuania dune reactivation phases resulted in massive invasion of siliciclastic sand triggered by natural perturbations and land clearance massive 30 m high dunes entombed mature pine oak and alder stands and this process is ongoing mid frequency 200 mhz georadar surveys reveal landward dipping lateral accretion surfaces interrupted by high amplitude point source anomalies produced by recently buried trees in tropical regions dense vegetation and potential for rapid lithification of carbonate sand results in more complex internal structures along the windward coast of san salvador island the bahamas a massive dune has buried several generations of maritime scrubland resulting in highly chaotic reflection pattern and high target density on a nearby little exuma island numerous reentrants in aeolianites promoted formation of blowouts and incursion of windblown sand 10 25 m into a silver thatch palm forest high frequency 800 mhz gpr images resolve diffractions from trunks and roots buried by 2 m of oolitic sand basal refection morphology helps differentiate the irregular dune beachrock surface from a smooth palm frond mat aside from detecting and mapping buried vegetation geophysical images capture its effect on sediment accumulation this has the potential for differentiating its effect from other discordant structures within dunes clasts dissolution voids trunk molds burrows and cultural remains

genesis of two different types of gold mineralization in the linglong gold field china constrains from geology fluid inclusions and stable isotope abstract the dongfeng and linglong gold deposits are located in the northwest jiaodong peninsula north china craton the deposits are mainly hosted in the mesozoic granitoids and structurally controlled by the zhaoyuan pingdu fault zone gold mineralization at dongfeng occurs as disseminated ores and sulfide stockworks typically enveloped by broad alteration selvages in contrast mineralization at linglong is characterized by massive auriferous quartz veins with narrow alteration halos three stages of mineralization were identified in both deposits with the early stage represented by quartz pyrite the middle stage by gold quartz pyrite or gold quartz base metal sulfides and the late stage by quartz carbonate pyrite respectively four types of fluid inclusions were distinguished based on petrography microthermometry and laser raman spectroscopy including 1 pure co2 fluid inclusions type i 2 h2o co2 nacl fluid inclusions type ii 3 h2o nacl fluid inclusions type iii and 4 daughter mineral bearing or multiphase fluid inclusions type iv in the dongfeng gold deposit the early and middle stage quartz mainly contains primary type ii fluid inclusions that completely homogenized at temperatures of 276 341 c with salinities of 2 8 11 7 wt nacl equivalent and temperatures of 248 310 c with salinities of 3 3 10 8 wt nacl equivalent respectively a few primary type i fluid inclusions could be observed in the early stage quartz in contrast the late stage quartz contains only the type iii fluid inclusions with homogenization temperatures of 117 219 c and salinities of 0 5 8 5 wt nacl equivalent the estimated pressures for the middle stage fluids are 226 338 mpa suggesting that gold mineralization mainly occurred at paleodepths of deeper than 8 4 12 5 km the mineralization resulted from extensive water rock interaction between the h2o co2 nacl fluids and wallrocks in the first order fault in the linglong gold deposit the early stage quartz mainly contains primary type ii fluid inclusions and a few type i fluid inclusions of which type ii fluid inclusions have salinities of 3 3 7 5 wt nacl equivalent and homogenization temperatures of 271 374 c the middle stage quartz mainly contains all four types of fluid inclusions among which the type ii fluid inclusions yield homogenization temperatures of 251 287 c and salinities of 5 5 10 3 wt nacl equivalent while the type iii fluid inclusions have homogenization temperatures of 244 291 c and salinities of 4 1 13 3 wt nacl equivalent fluid inclusions in the late stage quartz are type iii fluid inclusions with low salinities of 0 3 8 2 wt nacl equivalent and low homogenization temperatures of 103 215 c the trapping pressure estimated for the middle stage fluids is 228 326 mpa suggesting that the gold mineralization mainly occurred at paleodepths of about 8 4 12 1 km precipitation of gold is possibly a consequence of phase separation or boiling of the h2o co2 nacl fluids in response to pressure and temperature fluctuations in the open space of the secondary faults the 34s values of pyrite are similar for the dongfeng and linglong deposits and show a range of 5 8 to 7 0 and 5 9 to 7 4 respectively oxygen and hydrogen stable isotopic analyses for quartz yielded the following results 18o 3 8 to 6 4 and d 90 5 to 82 7 for the dongfeng deposit and 18o 0 0 to 8 9 and d 77 4 to 63 7 for the linglong deposit stable isotope data show that the ore forming fluids of the two gold deposits are of magmatic origin with gradual incorporation of shallower meteoric water during after mineralization