a middle cambrian trilobite faunule from the meguma group of nova scotia the meguma group of southern nova scotia is a thick succession of mostly deep water siliciclastic sedimentray rocks of uncertain age previous fossil finds have been in the halifax formation of the upper part of the sequence and have provided early ordovician ages a newly discovered trilobite bearing bed from the underlying goldenville formation yields middle cambrian taxa of acado baltic affinity specimens belonging to paradoxides s l agraulos dorypyge and ellipsocephalidae indicate that the meguma group is an exotic succession with faunal similarity to the adjacent avalon terrane and to middle cambrian successions in europe the middle east and west africa

sedimentary pyrite a window into the microbial past early diagenetic pyrite forms as a result of microbial processes in sediments but has received little attention as a potential source of microbial fossils sedimentary pyrite grains archean to jurassic in age were examined by scanning and transmission electron microscopy tem ion milling was essential for the preparation of electron transparent tem samples most pyrite grains revealed coccoid rod shaped and even filamentous features that are interpreted as microbial identification of microbial remains in sedimentary pyrite may greatly expand our knowledge of microbial life in the sedimentary record combined with geochemical characterization the study of pyritized microbes in the geologic record may in the future enable us to interpret changes in geochemical signatures more realistically in terms of different sulfate reducing communities sedimentary pyrite grains may also represent a good prospect to further our knowledge of past life on mars

the precious metal rich south hercules mineralization western tasmania a possible subsea floor replacement volcanic hosted massive sulfide deposit south hercules is a newly delineated disseminated to semimassive base metal sulfide deposit with significant gold and silver grades the deposit lies a kilometer along strike south from the hercules mine a 2 0 mt polymetallic massive sulfide deposit in the mount read volcanics belt western tasmania the mineralization and alteration at the south hercules deposit has been divided into two major facies the mineralized sulfide facies and the carbonate facies the carbonate facies interfingers with and surrounds the upper part of the sulfide facies the mineralized sulfide facies includes three zones a massive pyrite or barite zone a siliceous or stringer sulfide zone and a sphalerite galena or pyrite zone the carbonate facies also consists of three zones a blebby carbonate chlorite zone a massive carbonate zone and a cherty carbonate zone the massive pyrite or barite zone contains significant gold grades and occurs mostly at the top of the sulfide facies this zone is characterized by colloform aggregates of pyrite and compact massive pyrite in chert the siliceous or stringer sulfide zone is a silicified and sericitized tuffaceous shale with disseminated to stringer pb zn mineralization the massive sphalerite galena or pyrite zone contains subordinate gold and silver and occurs as thin lenses toward the base of the sulfide facies significant zinc and lead values occur throughout the mineralized sulfide facies with the highest values occurring along stratigraphically controlled layers copper values are conspicuously low throughout the south hercules deposit rarely exceeding 0 5 percent the carbonate facies is conspicuous by its lack of significant precious metal and base metal grades mineragraphic investigations indicate that electrum occurs in two general associations with pyrite and with other sulfides such as sphalerite galena and tetrahedrite the electrum locked in the pyrite euhedra is generally fine grained 5 40 mu m whereas the electrum associated with other sulfides displays a range between 5 and 200 mu m microprobe analysis indicates that the fineness 1 000 au au ag wt for gold in the deposit ranges from 427 to 965 the delta 18 o isotope composition of the carbonate varies from 9 8 to 16 7 per mil and the delta 13 c values range from 3 5 to 0 6 per mil the calculated isotopic composition of the ore fluid at 150 degrees and 250 degrees c is consistent with derivation from evolved seawater sulfur isotope analyses of selected samples from the mineralized facies give delta 34 s values of 8 2 to 14 1 per mil which is in the same range as values from the rosebery deposit and consistent with values of sulfur derived from cambrian seawater the form texture mineralogy stable isotopes and fluid inclusion data for the south hercules deposit suggest that it was formed largely by a subsea floor replacement process from relatively low temperature 150 degrees 250 degrees c near neutral fluids the very low copper content and relatively high au ag pb zn ratio of the ores support a low temperature environment in which gold was transported as the au hs 2 super complex and pb and zn were transported as chloride complexes

laser microprobe sulphur isotope analysis of arsenopyrite experimental calibration and application to the boliden au cu as massive sulphide deposit abstract metamorphic remobilization of arsenopyrite rich ores is a globally important process which can lead to significant concentrations of gold in order to understand this and related processes relations of sulphur isotopes can give a number of important clues to resolve such relations in detail we have successfully calibrated and applied a laser combustion system for in situ analysis of sulphur isotopic compositions of arsenopyrite experimental calibration of the laser fractionation factor 0 4 was obtained by using compositionally and isotopically homogeneous natural samples from ore deposits at boliden sweden and freiberg germany subsequent to detailed microscopic study the s isotope ratios of these samples were measured by conventional and laser combustion techniques the present application to different types of arsenopyrite in the palaeoproterozoic metamorphosed vhms ores of the boliden au cu as deposit skellefte district northern sweden shows that the sulphur isotope composition of arsenopyrite is essentially unmodified during medium grade metamorphic recrystallization and remobilization here massive arsenopyrite ore is crosscut by later veins that carry a complex quartz sulphosalt sulphide assemblage the latter ore type is markedly au rich compared to the host ore and thus of significant economic interest we find that both ore types exhibit very similar sulphur isotope compositions ca 2 to 3 v cdt which is similar to most massive sulphide deposits in the skellefte district thus the crosscutting au rich vein ore has inherited the sulphur isotope composition from sulphur liberated by metamorphic reactions affecting the massive ore and most likely also inherited the au through this mechanism the latter finding clearly has important implications both for the general discussion on and the prospecting for similar high grade au ores in this world class mining region

sulfur isotope and trace element data from ore sulfides in the noranda district abitibi canada implications for volcanogenic massive sulfide deposit genesis we examine models for volcanogenic massive sulfide vms mineralization in the 2 7 ga noranda camp abitibi subprovince superior province canada using a combination of multiple sulfur isotope and trace element data from ore sulfide minerals the noranda camp is a well preserved vms deposit rich area that is thought to represent a collapsed volcanic caldera due to its economic value the camp has been studied extensively providing a robust geological framework within which to assess the new data presented in this study we explore previously proposed controls on mineralization within the noranda camp and in particular the exceptional au rich horne and quemont deposits we present multiple sulfur isotope and trace element compositional data for sulfide separates representing 25 different vms deposits and showings within the noranda camp multiple sulfur isotope data for this study have 34sv cdt values of between 1 9 and 2 5 and 33sv cdt values of between 0 59 and 0 03 we interpret the negative 33s values to be due to a contribution of sulfur that originated as seawater sulfate to form the ore sulfides of the noranda camp vms deposits the contribution of seawater sulfate increased with the collapse and subsequent evolution of the noranda caldera an inference supported by select trace and major element analyses in particular higher concentrations of se occur in samples with 33s values closer to 0 as well as lower fe zn ratios in sphalerite suggesting lower pressures and temperatures of formation we also report a relationship between average au grade and 33s values within au rich vms deposits of the noranda camp whereby higher gold grades are associated with near zero 33s values from this we infer a dominance of igneous sulfur in the gold rich deposits either leached from the volcanic pile and or directly degassed from an associated intrusion

two types of outer fan lobe sequence from the late precambrian kongsfjord formation submarine fan finnmark north norway abstract a comparison of outer fan sections from different parts of the kongsfjord formation submarine fan has revealed two types of outer fan lobe sequence designated type i and type ii both types of lobe sequence contain lobes including lobe fringe deposits that are between 2 m and 15 m thick although type i lobes are generally less than 10 m thick there are no obvious differences in bed thickness grain size or other sedimentary attributes the distinction between type i and type ii lobes is based primarily upon their vertical frequency within fan fringe deposits type i lobes are separated by lobe fringe plus fan fringe deposits of similar thickness therefore in vertical sections the lobes are regularly spaced type ii lobes occur sporadically within sections where lobe fringe plu fan fringe deposits vary from tens of centimeters to 70 m in the two representative sections that illustrate the typological differences type i lobes plus lobe fringe deposits comprise 60 percent of the section compared to 22 percent for the type ii lobe sequences type i lobe sequences are interpreted as the result of regular lobe switching immediately downfan from the middle fan channels within a relatively proximal outer fan environment type ii lobe sequences are interpreted as a consequence of sporadic progradation of lobes in a relatively distal fan environment that usually received fan fringe sedimentation type i lobes represent regular and stable deposition controlled by intrafan intrabasinal processes whereas type ii lobes developed because of relatively catastrophic intrafan e g major channel relocation or extrafan source control processes this distinction may serve as a proximality indicator in outer fan successions

rcm e and amie studies of the harang reversal formation during a steady magnetospheric convection event this paper presents the results of a modeling study on the formation of the harang reversal hr during a steady magnetospheric convection event the harang reversal is identified as the boundary of the northward and southward electric field in the nightside auroral zone using the assimilative mapping of ionospheric electrodynamics amie procedure we simulate the event with the rice convection model equilibrium rcm e by adjusting its boundary conditions to approximately match time history of events and macroscale interactions during substorms themis and goes observations in the nightside magnetosphere our results show that the hr is collocated with an upward region 1 field aligned current where converging ionospheric currents cause a southward northward electric field on the poleward equatorward side of the hr our results also indicate that the electric field reversal is slightly poleward of the ionospheric east west current reversal and is to the northeast of the ground magnetic reversal which is consistent with previous observations we also test the sensitivity of the hr formation to a variety of parameters in the rcm e simulations we find that 1 the reduction of the flux tube entropy parameter pv5 3 near the midnight sector plays a major role in the formation of the hr 2 a run carried out assuming uniform conductance produced the same major features as the run with more realistic precipitation enhanced conductance and 3 the detailed pattern of the polar cap potential distribution plays a minor role but its dawn dusk asymmetry significantly controls the location of the hr with respect to midnight the rcm e simulations also predict pv5 3 and flow distributions associated with the magnetospheric source of the hr in the plasma sheet which can be further tested against observations

distribution of region 1 and 2 currents in the quiet and substorm time plasma sheet from themis observations although earth s region 1 and 2 currents are related to activities such as substorm initiation their magnetospheric origin remains unclear utilizing the triangular configuration of themis probes at 8 12 re downtail we seek the origin of nightside region 1 and 2 currents our statistical study reveals that both kinds of currents exist in the plasma sheet during quiet and active times region 2 currents are deep inside the plasma sheet region 1 currents which are farther away from the neutral sheet extend to the plasma sheet boundary layer at geomagnetic quiet times the separation between the two currents is located 2 5 re from the neutral sheet during substorms the separation migrates towards away from the neutral sheet as the plasma sheet thins thickens these findings suggest that the plasma sheet is a source of region 1 and 2 currents and its deformation is associated with redistribution of fac sources in the magnetotail

relation of substorm pre onset arc to large scale field aligned current distribution 1 substorm auroral onset often occurs along a pre existing arc that is associated with an enhanced upward field aligned current fac to determine the location of the upward fac of the pre onset arc relative to the large scale region 1 r1 and 2 r2 facs we present coordinated observations of the themis all sky imagers and champ satellite where champ passed over relatively stable pre onset arcs within the 30 min period before substorm auroral onset we found that the upward fac corresponding to the pre onset arc is latitudinally separated from the upward r1 fac within the onset mlt range in contrast the arc is located near the r1 r2 boundary to the west and east of the onset mlt range this mlt dependence suggests that an east west oriented upward fac sheet forms within the downward r2 fac as a precursor fac signature for substorm auroral onset

sediment flow and deformation sfd layers evidence for intrastratal flow in laminated muddy sediments of the triassic osawa formation northeast japan abstract thin chaotic layers containing abundant intraformational mud clasts are found in the offshore laminated mudstone of the triassic osawa formation in northeast japan the geometry and internal structures of the layers are somewhat similar to those of slump slide or debris flow deposits however the layers have both upper and lower erosional contacts projections of host sediments and mud clasts with planed surfaces are identified beneath the upper contact of the layers closely packed sheet form or ellipsoidal mud clasts are embedded in a poorly sorted fine to coarse grained sandy matrix some mud clasts are tightly folded or show imbricated stacking internal layering structures are also well developed in the layers the above features strongly suggest soft sediment deformation as horizontal displacement of sand and mud under buried conditions here we term these layers sediment flow and deformation sfd layers deformation layers with similar attributes have been identified by some prior authors as in the case of flow of liquefied and or fluidized host sand and clastic sill intrusion however the sfd layers described herein have more complex structure indicating advanced deformation occurrence of the sfd layers is stratigraphically limited to the uppermost part of the osawa formation which is overlain by sand rich submarine fan deposits the fukkoshi formation it suggests that the stress field caused by differential loading of overlying deposits facilitated intrastratal flow and sill intrusions of sand the vertical confinement was also controlled by the anisotropy in physical properties such as tensile strength of laminated mud and or conditions of gentle slope

fossil contourites a critical review abstract despite three decades of study there is still great controversy over the recognition and interpretation of fossil contourites exposed in ancient series on land in order to best examine this problem we briefly review the evidence from modern systems including the many examples of cenozoic contourites that have been recovered from dsdp odp drilling on major drifts in the present day oceans the range of contourite facies described from both deep water 2000 m and mid water 300 2000 m drifts are mostly fine grained bioturbated and homogeneous often with a distinct bedding cyclicity and with some coarser grained sandy contourites developed under higher energy bottom currents there are also a number of current controlled sediment bodies that have formed in outer shelf upper slope settings 50 300 m under the influence of counter currents underflows and major surface currents these are not considered contourites sensu stricto but may be mistaken as such in ancient examples the most commonly described fossil contourites in the literature have been interpreted by the authors concerned as bottom current reworked turbidites however a critical review suggests that these are the facies most subject to misinterpretation and many of the sediments claimed as fossil contourites are almost certainly fine grained turbidites whereas others were more likely formed under outer shelf upper slope current systems there remain very few ancient examples that are more closely comparable to modern contourites these include the cretaceous talme yafe formation in israel the ordovician jiuxi drift in china and parts of the paleogene lefkara formation cyprus and the neogene misaki formation in japan we present a set of possible criteria for the recognition of fossil contourites and bottom current reworked turbidites

geochemical characteristics of pyrite in the dabaozhuang deposit in the middle lower yangtze river metallogenic belt eastern china abstract dabaozhuang is a pyrite deposit in the luzong volcanic basin eastern china and has similar exhalation sedimentary features to volcanic massive sulfide deposits vms which commonly form in seawater to better understand the ore forming process of this special type of deposit we employed shrimp si and la icp ms to measure sulfur isotope and trace element compositions of anhydrite and four types of pyrite from the dabaozhuang deposit shrimp in situ sulfur isotope analysis indicates a narrow range in 34s of anhydrite 21 0 21 7 and variable ranges for pyrite 9 9 10 7 for pyrite vein in the deep py i 9 2 to 2 0 for cyclic annular and oval shaped pyrite in massive ore py ii 3 1 5 3 for massive or disseminated pyrite in the footwall tuff and hematite py iii and 29 7 to 30 4 for euhedral and coarse pyrite in the carbonate cement py iv 33s and 36s in four types of pyrite have no abnormal values indicating that sulfur isotope fractionation is mainly controlled by thermochemical sulfate reduction tsr the higher 34s values in type i pyrite and anhydrite indicate a mixing process of magmatic fluid and evaporates at depth py ii and iv have negative 34s data indicating the formation temperature of pyrite decreases because of the mixing of lake water 34s values in py iii are close to magmatic sulfur which shows the igneous sulfur tuff is an important sulfur source for the disseminated mineralization cobalt and ni content also show that the formation temperature of py i is highest and py iv is lowest this research indicates that the vms like deposits could be formed in continental volcanic lakes and are genetically related to so42 rich ioa iron oxide apatite deposits

substorm triggering by poleward boundary intensification and related equatorward propagation 1 recently a revised auroral substorm onset sequence has been proposed in which onset is preceded by a poleward boundary intensification pbi and subsequent equatorward propagation of n s aligned auroral features to breakup arc latitudes we reanalyzed 20 randomly selected samples of the nishimura et al 2010 251 event database and show in greater detail to what degree the observed features in this subset of events are consistent with the proposed scenario to assess the sensitivity of space based imagers for seeing this scenario we calibrated the absolute responsivity of the themis ground based imagers we also show that although not suitable for studies from apogee image fuv imagers can also observe a consistent scenario from a lower altitude we conclude that in some cases pbis and subsequent plasma flows can be effective in providing a trigger if the inner magnetosphere is ready to produce a substorm

quaternary mud turbidites from the south shetland trench west antarctica recognition and implications for turbidite facies modelling a piston core from the basinal part depth of 5188 m of the south shetland trench west antarctica yielded a terrigenous mud section 11 m long which can be subdivided with great precision into turbidite and hemipelagite layers mud turbidites mean bed thickness 44 cm alternate regularly with and are best distinguishable from their hemipelagite host mean bed thickness 17 cm by the following features i sharp basal contacts ii terrigenous sand free textures except basal well sorted silt laminae and the absence of outsized ice rafted components iii a laminated little to non bioturbated internal structure iv distinct textural and compositional grading and v marked steps on water content and sediment density logs mud turbidites recovered from the south shetland trench differ from an earlier model mud turbidite sequence by their i excessive about six times larger bed thickness ii complex internal organization manifested in multiple repetitions up to four of the same structural interval s in sequential or nonsequential order iii distinctive very fine grained cap of highly porous clay rich in fragments of siliceous biogenics iv widespread zones of penesyndepositional deformation and v evidence of flow reversals these features are interpreted to record deposition from large muddy turbidity currents subjected to flow transformations including soliton and or seiche related reversals induced by ponding and interactions of the flow with the topographical confinements of the trench it is concluded that contained muddy turbidites cannot be adequately modelled using published sequences differentiation of single model and contained mud turbidites offers obvious advantages in basin analysis and in understanding the plethora of turbidity current related depositional mechanisms of deep sea mud

effects of temperature sulfur and oxygen fugacity on the composition of sphalerite from submarine hydrothermal vents experimental studies have shown that temperature pressure sulfur fugacity fs2 and oxygen fugacity fo2 influence the fe content of sphalerite we present compositional in situ data on sphalerite from submarine volcanic hosted massive sulfide vhms ores of hydrothermal vents from different plate tectonic settings and with variable host rock compositions sphalerite from sediment hosted vents has systematically higher s contents and fe zn ratios than those of the sediment starved vents reflecting an influence of fs2 and fo2 on fe partitioning between fluid and sphalerite the fe zn ratios of sphalerite from sediment starved vent systems apparently increase systematically with the fluid temperatures of the corresponding vents we conclude that the composition of sphalerite can be used to 1 distinguish between sediment hosted and sediment starved hydrothermal processes and 2 estimate minimum fluid temperatures of sphalerite precipitation from inactive sediment starved hydrothermal vent sites and fossil vhms deposits

rcm e simulation of substorm growth phase arc associated with large scale adiabatic convection 1 substorm auroral breakup often occurs on a longitudinally elongated arc at the end of a growth phase we present an idealized high resolution simulation with the rice convection model equilibrium rcm e to investigate how large scale adiabatic convection under equilibrium conditions can give rise to an auroral arc we find that a thin arc that maps to the magnetic transition region at r 8 re emerges in the late growth phase the simulation implies that the arc in the premidnight sector is associated with a sheet of additional region 1 sense field aligned current fac just poleward of the main region 2 fac while the arc in the postmidnight sector is associated with the poleward portion of the main upward region 2 fac explanations for the location and the thickness of the arc are proposed based on the simulation

large scale current systems and ground magnetic disturbance during deep substorm injections 1 we present a detailed analysis of the large scale current systems and their effects on the ground magnetic field disturbance for an idealized substorm event simulated with the equilibrium version of the rice convection model the objective of this study is to evaluate how well the bubble injection picture can account for some classic features of the substorm expansion phase the entropy depletion inside the bubble is intentionally designed to be so severe that it can penetrate deep into geosynchronous orbit the results are summarized as follows 1 both the region 1 sense and region 2 sense field aligned currents facs intensify substantially the former resembles the substorm current wedge and flows along the eastern and western edges of the bubble the latter is connected to the enhanced partial ring current in the magnetosphere associated with a dipolarization front earthward of the bubble in the ionosphere these two pairs of facs are mostly interconnected via pedersen currents 2 the horizontal ionospheric currents show a significant westward electrojet peaked at the equatorward edge of the footprint of the bubble the estimated ground magnetic disturbance is consistent with the typical features at various locations relative to the center of the westward electrojet 3 a prominent harang reversal like boundary is seen in both ground h disturbance and plasma flow pattern appearing in the westward portion of the equatorward edge of the bubble footprint with a latitudinal extent of 5 and a longitudinal extent of the half width of the bubble 4 the dramatic dipolarization inside the bubble causes the ionospheric map of the inner plasma sheet to exhibit a bulge like structure which may be related to auroral poleward expansion 5 the remarkable appearance of the westward electrojet harang reversal like boundary and poleward expansion starts when the bubble reaches the magnetic transition region from tail like to dipole like configuration we also estimate the horizontal and vertical currents using magnetograms at tens of ground stations for a deep injection substorm event occurred on april 9 2008 resulting in a picture that is qualitatively consistent with the simulation based on the simulations and the observations an overall picture of the ionospheric dynamics and its magnetospheric drivers during deep bubble injections is obtained

rcm e simulation of a thin arc preceded by a north south aligned auroral streamer the time history of events and macroscale interactions during substorms themis all sky imager data have recently revealed a repeatable sequence that occurs during many auroral substorms in which a newly formed thin arc is preceded by an equatorward propagating streamer the paper aims at modeling this sequence using the rice convection model equilibrium the simulation shows a thin arc arising when a plasma sheet bubble with its pv5 3 reduced to the transition region value arrives at the magnetic transition region the modeled thin arc consists of two parts the one east of the streamer is the result of the bubble pushing high pv5 3 flux tubes ahead of it strengthening the upward region 2 current and the one west of the streamer is associated with westward drifting bubble particles sliding along the transition region the model predicts that 1 the westward and eastward leading edges of the thin arc propagate azimuthally at a speed of 0 5 2 7 km s and 2 the streamer induced thin arc is accompanied by classic signatures of bubble injections

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

width and structure of mesoscale optical auroral arcs arc widths were calculated for 3126 stable auroral arcs observed by an all sky camera located in gillam manitoba the camera is filtered to accept 5577 a emissions and has a single pixel spatial resolution of 1 7 km at zenith the measured mean width of stable mesoscale arcs located within 5 of magnetic zenith is 18 km with a standard deviation of 9 km the width distribution exhibits a steep cutoff below 8 km when combined with studies of small scale auroral structure this cutoff suggests a gap in the occurrence of arcs with widths of order 1 km this feature of the arc width spectrum argues against the notion of a turbulent cascade of energy from larger to small scales residuals from the gaussian fits are only about 3 of the arc amplitude on average indicating little sub structure within arcs at scales down to the measurement resolution

erratum to variations of sulphur isotope signatures in sulphides from the metamorphosed ming cu au volcanogenic massive sulphide deposit newfoundland appalachians canada the ming deposit is an early ordovician bimodal mafic cu au volcanogenic massive sulphide vms deposit in the newfoundland appalachians that was metamorphosed to upper greenschist lower amphibolite facies conditions and deformed in the silurian and devonian the ming deposit consists of several spatially proximal ore bodies of which the 1806 zone 1807 zone ming south up plunge and down plunge and the lower footwall zone are the focus of this paper the ore bodies have similar stratigraphic sequences the ore bodies can be divided into 1 a silicified horizon that caps the massive sulphides 2 semi massive to massive sulphides and 3 sulphide mineralization in a rhyodacitic footwall sulphide mineralization in a rhyodacitic footwall includes a sulphide stringers immediately below the semi massive to massive sulphides and b chalcopyrite pyrrhotite pyrite stringers distally from semi massive to massive sulphides in the lower footwall zone pyrite chalcopyrite pyrrhotite arsenopyrite and galena were analysed by in situ secondary ion mass spectrometry sims for sulphur isotope compositions the isotopic signatures of pyrite chalcopyrite pyrrhotite and arsenopyrite fall within a limited range of 2 8 to 12 0 for semi massive to massive sulphides and sulphide mineralization in the footwall the silicified horizon capping the semi massive to massive sulphides has higher 34s 5 8 19 6 especially for pyrrhotite mean 17 2 2 2 n 8 the sulphur isotope composition of galena is more heterogeneous especially within semi massive to massive sulphides and sulphide stringers ranging from 0 8 to 17 3 mean 6 1 4 3 n 35 and 7 6 to 17 1 mean 13 7 5 3 n 3 respectively geothermometric calculations give insufficient formation and metamorphism temperatures for neighbouring mineral pairs because sulphides were not in isotopic equilibrium while deposited in early ordovician or re equilibrated during silurian devonian metamorphism respectively therefore original isotopic compositions of sulphides at the ming deposit have been preserved modelling of the source of sulphur shows that 1 reduced seawater sulphate and 2 sulphur leached from igneous wall rock and or derived from magmatic fluids are the main sources of sulphur in the ming deposit the influence of igneous sulphur igneous wall rock magmatic fluids increases with temperature and is an important sulphur source for the semi massive to massive sulphides and footwall mineralization in addition to a contribution from thermochemical sulphate reduction tsr of seawater it is difficult to distinguish between sulphur leached from igneous rocks and magmatic fluid related sulphur and it is possible that both sources contributed to the ores at the ming deposit in addition to igneous sulphur the heavy isotopes of the silicified horizon are consistent with the sulphur in this horizon being derived only from thermochemical sulphate reduction of early ordovician seawater sulphate

discussion of geochemical signature of ordovician mn rich sedimentary rocks on the avalonian shelf 11appears in canadian journal of earth sciences 2011 48 4 703 718 doi 10 1139 e10 092 the paper geochemical signature of ordovician mn rich sedimentary rocks on the avalonian shelf romer et al published in 2011 describes six samples of which four are from the meguma supergroup of nova scotia previous work indicates that these samples are cambrian and that they were deposited in a deep water turbidite basin megumia not on the avalonian shelf the geochemical data support models for mn concentration involving oxidation and reduction in a sedimentary environment but do not constrain water depth likely correlatives are in the cambrian of north wales and not in the european localities sampled by the authors

origin of deep water fine grained sediments as revealed from the lower cretaceous rifting basin sequence in the lingshan island yellow sea eastern china abstract understanding the sediment dynamics responsible for the deposition of fine grained sediments is essential for studying fine grained sediment origin and its distribution which is of a great significance for unconventional oil and gas exploration and development fine grained sediments from a lower cretaceous rift basin sequence in the lingshan island the middle of the dengta section in the lingshandao formation were studied on the basis of detailed outcrop investigation thin section observation and laboratory measurements seven types of lithofacies and three lithofacies associations were identified in the fine grained sediment sequence the sediment dynamics were deduced from a comprehensive examination and interpretcation of the sedimentary structures and lithofacies associations the fine grained sediments in the research area belong to a silt dominated subclass which is composed mainly of thin bedded siltstones with normal grading and mudstones with horizontal lamination suspension settling is responsible for the development of horizontal lamination in some mudstone the bouma like lithofacies associations are developed by downslope fine grained turbidity currents the hybrid event bed like lithofacies associations are formed by hybrid flow while turbidity currents transformed to muddy debris flows downslope the interbedded thin sandstone and mudstone banded lithofacies associations may be resulted from a downslope transitional flow between a turbidity current and a muddy debris flow the vertical facies stacking patterns of the fine grained sediment sequence indicatec that the fine grained gravity flow may have been evolved from a transitional flow to a debris flow then to a low density turbidity flow and finally to a hybrid flow lithofacies associations deposited by hybrid flow and transitional flow are potential sweet spots for unconventional oil and gas exploration in such fine grained sediment formation

sulfur isotope characteristics of metamorphosed zn cu volcanogenic massive sulfides in the areachap group northern cape province south africa zn and cu rich massive sulfide ores of volcanogenic origin volcanogenic massive sulfide vms deposits occur as stratiform stratabound lenses of variable size hosted by gneisses amphibolites and schists of the areachap group in the northern cape province of south africa the areachap group represents the highly deformed and metamorphosed remnants of a mesoproterozoic volcanic arc that was accreted onto the western margin of the kaapvaal craton during the 1 0 1 2 ga namaquan orogeny sulfur isotope data 34s are presented for 57 sulfide separates and one barite sample from five massive sulfide occurrences in the areachap group although sulfides from each site have distinct sulfur isotope values all 34s values fall within a very limited range 3 0 to 8 5 barite has a 34s value of 18 5 very different from that of associated sulfides at one of the studied sites kantienpan a distinct increase in 34s of sulfides is observed from the massive sulfide lens into the disseminated sulfides associated with a distinct footwall alteration zone sulfide sulfide and sulfide barite mineral pairs which recrystallized together during amphibolite and lower granulite facies metamorphism are not in isotopic equilibrium sulfur isotope characteristics of sulfides and sulfates of the zn cu ores in the areachap group are however very similar to base metal sulfide accumulations associated with modern volcanic arcs and unsedimented mid ocean ridges it is thus concluded that profound recrystallization and textural reconstitution associated with high grade regional metamorphism of the massive sulfide ores of the areachap group did not result in extensive sulfur isotopic homogenization this is similar to observations in other metamorphosed vms deposit districts and confirms that massive sulfide ores remain effectively a closed system for sulfur isotopes for both sulfides and sulfates during metamorphism