evidence for syngenetic precious metal enrichment in an appalachian volcanogenic massive sulfide system the 1806 zone ming mine newfoundland canada the ming deposit baie verte newfoundland canada is an early ordovician bimodal mafic cu au zn ag volcanogenic massive sulfide vms deposit the deposit consists of a number of ore lenses that are stacked in the uppermost part of the rambler rhyolite one of the uppermost lenses the 1806 zone is enriched in au and ag the deposit has been affected by silurian devonian greenschist to amphibolite grade metamorphism and polyphase deformation and this has led to debates as to whether the au ag enrichment in the deposit is syngenetic or a product of a later metamorphic and structural overprint the 1806 zone consists predominantly of discordant sulfide stringer stratabound semimassive to massive sulfides and a weakly mineralized silicified cap zone the ore is largely hosted within the footwall rambler rhyolite that is strongly altered to quartz sericite green mica with sporadic chlorite biotite base and precious metal zoning is developed from the down plunge portion cu au to the up plunge portion cu zn au ag pb of the 1806 zone the ore mineralogy and mineral chemistry are complex and are interpreted to be of an intermediate sulfidation type pyrite and chalcopyrite are the dominant sulfide species with minor to accessory sphalerite galena pyrrhotite and arsenopyrite sulfosalts including ag bearing tennantite tetrahedrite stannite boulangerite and loellingite and precious metal rich phases are common throughout the deposit precious metals occur as 1 mercurian electrum 7 93 20 57 wt hg and 2 various ag phases miargyrite pyrargyrite mercurian stephanite unnamed agcufes phase ag hg au alloys that are more abundant in the up plunge portion of the 1806 zone tellurides and bismuthides are present in trace amounts oxides cassiterite and magnetite are present exclusively in the down plunge portion of the 1806 zone the deposit geometry metals distribution complex ore assemblages abundant sulfosalts and the significant concentration of the epithermal suite of elements e g au ag as hg sb bi in the ore strongly contrast with those of orogenic au deposits and support a syngenetic or synvolcanic origin for precious metals in the ming vms deposit including a possible magmatic input into the 1806 zone ore forming system evidence for a late syndeformation precious metal emplacement via orogenic overprinting is lacking at the 1806 zone and all data point to a syngenetic origin for precious metal enrichment indicating that ordovician appalachian vms deposits are favorable targets for au nevertheless silurian devonian metamorphism and deformation have resulted in textural recrystallization and local remobilization of precious metals and the main fabrics largely control the current geometry of the host succession and of the ming orebody

geochemical and isotopic nd o data from ordovician felsic plutonic and volcanic rocks of the miramichi highlands petrogenetic and metallogenic implications for the bathurst mining camp middle ordovician felsic magmatism contemporaneous with bathurst camp pb zn volcanogenic massive sulphide vms deposits consists of strongly altered volcanic to subvolcanic rocks belonging to the tetagouche group and relativelyunaltered granitoid plutons which are divided into northern central and southern groups within the miramichi highlands calc alkalic felsic volcanic rocks and northern plus central plutons have epsilonnd t values ranging from 8 2 to 1 9 and 4 0 to 0 3 respectively they exhibit within plate type volcanic and transitional i to a type granite geochemical characteristics granitoid rock delta18o values range from 8 0 to 10 1 published granitoid rock pb isotopic compositions overlapunpublished galena data from bathurst vms deposits field geochemical and isotopic evidence indicate that these volcanicand granitoids rocks are consanguineous and mainly derived from proterozoic orolder infracrustal sources alkalic felsic volcanic rocks and associated alkaline basaltic rock

redefinition of the wild bight group newfoundland implications for models of island arc evolution in the exploits subzone the wild bight group and correlative plutonic rocks of the south lake igneous complex comprise one of the accreted ordovician peri gondwanan oceanic terranes of the newfoundland appalachians recent field work and isotopic ages from the eastern wild bight group require that the stratigraphic sequence be redefined a package of bimodal volcanic rocks which forms the oldest part of the group and contains all of its volcanogenic massive sulphide deposits is redefined as the glovers harbour formation this formation is correlative with intra oceanic ophiolitic sequences elsewhere in the exploits subzone previous stratigraphic nomenclature for the upper wild bight group is largely retained although the lithological variation within and spatial distribution of the omega point seal bay brook and pennys brook formations are revised and the side harbour formation is included as part of the seal bay brook formation the upper wild bight group is interpreted to represent a second and distinct arc sequence

lithostratigraphic hydrothermal and tectonic setting of the boundary volcanogenic massive sulfide deposit newfoundland appalachians canada formation by subseafloor replacement in a cambrian rifted arc the boundary volcanogenic massive sulfide vms deposit 0 5 mt 3 5 cu 4 zn 1 pb 34 0 g t ag in the tally pond group central newfoundland represents one of the best preserved subseafloor replacement style vms deposits in the northern appalachian orogen the deposit is hosted within a late cambrian 510 ma volcanic sequence consisting predominantly of rhyolitic flows and associated volcaniclastic rocks footwall strata are dominated by rhyolitic lapilli tuff tuffs lesser rhyolite flows and in situ rhyolite breccias the hanging wall consists of massive quartz bearing flow banded lobe and breccia facies rhyolite the deposit occurs at and below the contact between these two units and comprises pyrite chalcopyrite and lesser sphalerite and other minerals massive mineralization contains abundant clasts of the surrounding host rocks including chlorite sericite quartz altered rhyolite lapilli and ash hydrothermally altered rocks consist of variably intense chlorite with lesser sericite and quartz chlorite alteration occurs in a discordant geometry likely representing hydrothermal upflow zones and chlorite sericite quartz occur as blankets that are parallel to the volcanic stratigraphy likely representing alteration associated with replacement the hanging wall rhyolite flows also contain moderate to intense pervasive quartz and sericite alteration both the hanging wall and footwall are characterized by strong na2o sr depletions k2o mgo fe2o3 ba enrichments high alteration index values e g ba sr chlorite carbonate pyrite index ccpi alteration index ai and enrichments in base metals and volatile metals e g cu zn pb hg the presence of abundant remnant wall rock and host rock clasts within the ore intricate sulfide replacement of laminated porous tuff and sand dikes replacement fronts in host lithofacies and intense alteration in both the footwall and hanging wall where the hanging wall is preserved are all features consistent with formation of the bulk of the boundary deposit via subseafloor replacement the deposit likely formed as a result of cooling of metal bearing hydrothermal fluids mixing with ambient seawater and pore water entrained seawater within the volcanic rocks at a permeability interface between young unlithified highly permeable footwall volcaniclastic rocks and relatively impermeable hanging wall rhyolitic flows in our model this permeability boundary was an important feature that promoted subseafloor replacement within the deposit immobile element systematics of rhyolitic rocks from the boundary deposit lack major differences in primary petrochemistry between hanging wall and footwall strata all rocks from the deposit area are subalkalic with transitional zr y ratios 2 8 4 5 la sm ratios 1 normalized to upper crust and primitive mantle normalized signatures with slightly light rare earth element lree enriched patterns with flat heavy ree hree and negative nb ti and eu anomalies these geochemical features coupled with existing nd pb isotope data zircon inheritance patterns and geologic information are consistent with rhyolitic rocks at the boundary deposit having formed by re melting of arc basement with continental crust or recycled continental crust present in the source region it is likely that the deposit and its associated rhyolitic host rocks formed within a cambrian continental or pericontinental rifted arc along the margin of ganderia within the iapetus ocean

sulphur and lead isotope geochemistry of sulphide minerals from the zn pb cu ag au lemarchant volcanogenic massive sulphide vms deposit newfoundland canada abstract the lemarchant zn pb cu ag au volcanogenic massive sulphide vms deposit in the newfoundland appalachians canada is an important example of a precious metal bearing vms deposit the deposit contains vms and sulphosalt rich mineral assemblages which are paragenetically distinct initial zn pb sulphosalt mineralization was deposited from low temperature 300 c less oxidized hydrothermal fluids with lower sulphur activity in situ microanalyses of pyrite chalcopyrite and galena yield a wide range of 34s values 6 4 to 15 1 sulphides from paragenetically early lower temperature zn pb sulphosalt assemblages have the lowest average 34s values 4 6 whereas the highest 34s values occur in the late stage high temperature cu rich sulphide assemblages variability in 34s occurs in all styles of mineralization and is consistent with s derived from thermochemical reduction of seawater sulphate igneous leaching and potentially disproportionated magmatic so2 although it is difficult to distinguish explicitly between leached igneous and magmatic sources of sulphur mineralogical and geochemical data from lemarchant suggest a possible contribution of magmatic so2 during the deposition of epithermal style mineralization at the earlier stages of deposit formation lead isotope compositions of galena show little variability with style of mineralization suggesting similar pb sources throughout ore deposition most pb at lemarchant is derived from underlying neoproterozoic sandy brook group volcanic rocks with potential input of juvenile pb from the lake ambrose basaltic rocks of the tally pond group and or from more juvenile neoproterozoic basement rocks

regional differences in pb isotopic compositions of feldspars in plutonic rocks of the northern appalachian mountains u s a and canada a geochemical method of terrane correlation feldspar pb isotopic compositions from paleozoic tonalitic to leucogranitic caledonian plutons from the northern appalachian mountains of the u s a and canada range from nonradiogenic to radiogenic relative to the evolution curve of stacey and kramers 1975 pb isotopic values in the feldspars are generally independent of modal and major and trace element contents of the plutons plutons with the least radiogenic pb isotopic signatures northern group have intruded allochthonous rocks closest to the north american craton and plutons with the most radiogenic pb southern group have intruded avalonian basement feldspars from plutons in the central group have intermediate pb isotopic compositions between the northern and southern groups and do not define an isotopically unique group the predominant source of the felsic magmas was the continental lithosphere as indicated by the general pb isotopic similarity of the plutonic feldspars with either grenville or chain lakes basement in the case of the northern group and with avalonian basement rocks in the case of the southern group the source region for plutons in the central group may have contained a mixture of grenvillian and avalonian components plutons in the northern appalachians are as a group more evolved in their pb isotopic compositions relative to caledonian plutons in the british isles

the duck pond and boundary cu zn deposits newfoundland new insights into the ages of host rocks and the timing of vhms mineralization the duck pond cu zn pb ag au deposit in newfoundland is hosted by volcanic rocks of the cambrian tally pond group in the victoria lake supergroup in conjunction with the nearby boundary deposit it contains 4 1 million tonnes of ore at 3 3 cu 5 7 zn 0 9 pb 59 g t ag and 0 9 g t au the deposits are hosted by altered felsic flows tuffs and volcaniclastic sedimentary rocks and the sulphide ores formed in part by pervasive replacement of unconsolidated host rocks u pb geochronological studies confirm a long suspected correlation between the duck pond and boundary deposits which appear to be structurally displaced portions of a much larger mineralizing system developed at 509 3 ma altered aphyric flows in the immediate footwall of the duck pond deposit contained no zircon for dating but footwall stringer style and disseminated mineralization affects rocks as old as 514 3 ma at greater depths below the ore sequence unaltered mafic to felsic volcanic rocks that occur structurally above the o

lead isotope geochemistry of shales from the wolverine volcanogenic massive sulfide deposit yukon implications for pb isotope vectoring in exhalative ore systems combined whole rock lead isotope and high precision trace element data are reported for shales from the wolverine deposit and surrounding prospects e g puck fisher sable to elucidate the source of pb in the shales and their potential utility as an exploration vector shales exhibit distinct variations in time integrated u th pb evolution with proximity to mineralization distal samples resemble the local crustal pb isotope composition of the northern cordilleran continental crust i e shale curve more proximal samples exhibit evidence for hydrothermal activity but were not significantly mineralized they have very high u th and u pb and anomalous present day 206 pb 204pb 20 coincident with elevated y ho zr hf and carbonate alteration these signatures were derived from oxygenated seawater and imprinted on the shales by oxygenated co2 rich hydrothermal fluids that contained uranyl carbonate ions e g uo2 co3 3 4 it is envisioned that this was due to shallow level within 50 m of the seafloor near vent ingress of oxygenated seawater associated with hydrothermal venting a third population of samples is most proximal to mineralization these too have trace element signatures i e high y ho zr hf co2 u enrichment inherited from seawater but they do not exhibit anomalous present day 206pb 204 pb being more juvenile in 206 pb 204 pb 207 pb 204 pb and 208pb 204pb this isotope composition coincides with enrichments in pb zn cu tl sb w and sn cu mo the pb enrichment associated with mineralization effectively buffered these samples from appreciable pb isotope evolution despite overprinting by uranyl carbonate the juvenile pb associated with the shales proximal to mineralization argues for deep penetrative circulation of hydrothermal fluids and leaching of pb from mafic igneous rocks at depth and or influence from juvenile magmas at depth i e magmatic fluids both of these processes were likely critical for the genesis of mineralization at wolverine this study illustrates the utility of quadrupole inductively coupled plasma mass spectrometry icp ms for providing sufficiently precise and accurate pb isotope determinations for district scale metallogenic evaluations furthermore the coupling of solution icp ms pb isotopes with high precision trace element geochemistry from the same digest provides a powerful tool for regional exploration studies for hydrothermal mineralization in shale basins

siliceous sponge communities biological zonation and recent sea level change on the arctic margin ice island results discussion bathymetric profiles bottom camera photographs surface sediment samples and biological samples were obtained through a 44 m long hydrohole in the canadian ice island as it drifted over the canadian polar margin from western ellesmere island to meighen island continuous bathymetric profiles show a 300 km wide shelf with a narrow dissected shallow 200 m inner shelf and a deep 300 800 m sloping outer shelf extensive areas of siliceous sponge communities are present on the seafloor beneath the polar pack ice on the central shelf a clear biological zonation is evident above 130 m large living sponges support a diverse benthic community and form reef mounds up to 10 m high from 130 to 150 m there are few living sponges but extensive mats of sponge spicules are present from 150 to 300 m there are few small living sponges and radiocarbon dating of mud covered spicule mats indicates that formerly extensive sponge communities have died during the past 500 2000 years this zonation may reflec

neoproterozoic and cambrian arc magmatism along the eastern margin of the victoria lake supergroup a remnant of ganderian basement in central newfoundland abstract the eastern margin of the composite and structurally complex victoria lake supergroup has previously been mapped where the silurian rogerson lake conglomeratic rocks unconformably overlie cambrian tally pond volcanic rocks however the recognition that the form of this contact changes between an unconformity and a brittle ductile fault in conjunction with the neoproterozoic age of the crippleback intrusive suite dictate that the above interpretation of the nature of this margin requires revision these discrepancies are resolved by the recognition of a neoproterozoic largely bimodal volcanic sequence sandy brook group which is unconformably overlain by rogerson lake rocks to the east with these combined units in fault contact with the tally pond group to the west the sandy brook group and crippleback intrusive suite form a terrane of ca 563 ma rocks with continental arc like geochemical signatures the distinctly negative nd 563 values for the felsic rocks mean 3 of this terrane imply derivation from a crystalline basement older than the largely pan african crust that underlies contemporaneous volcanic rocks in west avalonia but similar to that inferred for the gander zone thus this terrane is likely to be the leading edge of the peri gondwanan microcontinent ganderia the ca 511 ma tally pond group arc magmatism represent some of the oldest products of iapetean subduction in newfoundland although the tally pond group are only observed to be in fault contact with the ca 50 million year older sandy brook group the high proportion of felsic volcanic rocks sandy brook crippleback age inherited zircons and pb isotopic data all support the inference that the tally pond group was formed on sandy brook crippleback continental crust

mineralogy and mineral chemistry of the metamorphosed and precious metal bearing ming deposit canada abstract the ming deposit in the northwestern canadian appalachians is a metamorphosed bimodal mafic precious metal au ag bearing and cu rich volcanogenic massive sulfide vms deposit consisting of several spatially proximal lenses in a sericite to chlorite altered rhyodacitic footwall the various lenses 1807 zone 1806 zone ming south up plunge ming south down plunge and the lower footwall zone have variations in cu au ag and zn grades that reflect varying physico chemical conditions of ore formation this study describes the complex ore mineralogy of the orebodies and constrains the genesis of the deposit using field methods mineralogy whole rock sulfide geochemistry and micro analytical methods the orebodies are predominantly pyrite chalcopyrite with lesser sphalerite pyrrhotite and trace galena and arsenopyrite with the exception of the lower footwall zone which consists of a high temperature 320 c chalcopyrite pyrrhotite pyrite cubanite assemblage the other orebodies 1806 1807 ming south up plunge and down plunge contain trace amounts of tellurides hessite altaite tsumoite unnamed bismuthtelluride sulfosalts ag poor and ag rich tennantite tetrahedrite meneghinite agsb phases stannite and precious metal phases electrum aghg au alloys the 1807 zone is enriched in te bi and se whereas the 1806 zone is telluride free and contains as sb hg au and ag mineral chemistry of sphalerite shows strong variations in fe content 1 12 11 04 wt intermediate fe 4 33 6 33 wt fe and fe rich 7 327 11 04 wt fe sphalerite are common in all orebodies whereas fe poor sphalerite 1 12 3 57 wt fe occurs exclusively in the 1807 and 1806 zones tennantite tetrahedrite is typically ag poor 0 25 2 19 wt in the 1807 zone but is significantly enriched in ag up to 29 3 wt in the 1806 zone galena in the 1807 zone and ming south orebodies is commonly myrmekitically intergrown with tellurides and has high concentrations of te bi se and ag in contrast galena in the 1806 zone is less enriched in te bi and se but high in ag variations in mineralogy epithermal elements as bi hg sb se sn te and precious metal ag au content and mineral chemistry between the different orebodies indicate that they were formed from predominantly reduced acidic hydrothermal fluids with varying te2 s2 se2 s2 and mbi msb ratios as temperatures steadily decreased from 300 c to

characteristics of gold mineralization in volcanogenic massive sulphide deposits of the notre dame bay area central newfoundland a reconnaissance study of 19 volcanogenic massive sulphide deposits in the notre dame bay area indicates au concentrations of up to 30 ppm betts cove and elevated gold contents 1 ppm au have been found in samples from 10 additional past producers and developed prospects systematic trends in the occurrence of gold are observed in two principal sulphide assemblages polymetallic pyrite sphalerite chalcopyrite galena arsenopyrite assemblages type i and pyrite chalcopyrite sphalerite pyrrhotite assemblages type ii type i assemblages occur in deposits with dominantly felsic host rocks whereas type ii assemblages are restricted to deposits in mafic dominated ophiolite sequences free gold grains were observed in samples from eight different deposits in both type i and type ii assemblages x ray emission spectra and electron microprobe analyses of the gold indicate that most grains are electrum although a au bearing telluride occurs at point leamington ion microprobe analyses indicate that

a tectonic window in central newfoundland geological evidence that the appalachian dunnage zone may be allochthonous in the through hill area of central newfoundland mafic to ultramafic complexes which preserve varying amounts of ophiolite stratigraphy mark the trace of a major fault zone that outcrops in a roughly elliptical pattern the major northeast trending axis is about 60 km and the shorter axis is about 30 km in length the most complete ophiolite stratigraphy is preserved in the coy pond and pipestone pond complexes which have steep dips and face east and west respectively outwards from the centre of the ellipse the ophiolitic rocks are bounded on the outside by rocks typical of the dunnage zone of central newfoundland principally lower to middle ordovician volcanic and volcaniclastic rocks interpreted to be of island arc affinity davidsville victoria lake and baie d espoir groups cold spring pond formation and upper ordovician to silurian clastic sediments botwood group the volcano sedimentary sequences are interpreted to have been deposited on the ophiolite conformably but the contacts are n

mid late ordovician magmatism and metamorphism along the gander margin in central newfoundland fieldwork coupled with u pb dating has clarified the relationships between the exploits and gander derived rocks in central newfoundland during the mid ordovician opening of the exploits back arc basin reinforcing correlation across the peri gondwanan segments of the appalachian caledonian orogen we have separated a new back arc related unit the red cross group from the arc related victoria lake supergroup this group includes 466 3 ma felsic volcanic rock interlayered with alkali basalt enriched mid ocean ridge basalt 457 6 ma gabbro llanvirn caradoc normal mid ocean ridge basalt island arc tholeite limestone black shale and melange locally the red cross group is in parautochthonous contact with low grade gander psammite this contact was overrun by the meelpaeg metamorphic nappe during the devonian the nappe contains gander metapsammite meelpaeg subzone and the coticule bearing howley waters complex exploits which hosts 467 3 ma felsic porphyry the gander and exploits metasediments in the nappe are stitched by arenig llanvirn granite 467 6 ma and 468 3 5 3 ma and caradoc intrusions 458 3 ma and 454 2 ma metamorphic monazite 462 1 ma and titanite 460 3 ma from the nearby mount cormack subzone gander indicate the coeval formation of a low pressure high temperature metamorphic dome the widespread presence of caradoc magmatism suggests that the width of the back arc basin remained relatively narrow

timing and spatial distribution of deformation in the newfoundland appalachians a multi stage collision history van der plmjm b a 1987 timing and spatial distribution of deformation in the newfoundland appalachians a multi stage collision history in h j zwart m martens i van der molen c w passchier c spiers and r l m vissers editors tectonic and structural processes on a macro meso and micro scale tectonophysics 135 15 24 the newfoundland appalachians have been interpreted as an area where lower paleozoic plate convergence culminated in collision between an ordovician volcanic chain and the north american craton in middle ordovician times closure of the intervening proto atlantic iapetus ocean was considered incomplete subsequent deformation gave rise to regional folding and faulting recent studies in the newfoundland dunnage zone have revealed that the deformation history is far more complex than previously recognized large scale thrusting folding and faulting occurred in silurian devonian times furthermore it has been suggested that the dunnage zone is an allochthonous terrane underlain by dominantly continental crust rather than representing remnants of a rooted ocean basin in view of these results a revision of tectonic scenarios and zonal subdivision is warranted and a multi stage collision history will be discussed with emphasis on the spatial distribution and significance of silurian devonian deformation in central newfoundland subduction in lower paleozoic times gave rise to the formation of a volcanic terrane concurrently to the southeast a marginal sea was formed mariana type subduction in middle ordovician times the volcanic terrane collided with the north american craton first stage collision and back arc spreading terminated continued crustal shortening resulted in the formation of a silurian accretionary terrane telescoped marginal sea and its subsequent deformation second stage collision devonian carboniferous strike slip faulting represents the third stage in the collision history the model is applicable to large tracts of the caledonian appalachian chain its main characteristics are a the revised zonal subdivision of the area is based on characteristics of silurian and older rocks rather than middle ordovician and older rocks only b the central part of the orogen represents a telescoped marginal sea that formed to the southeast of the ordovician volcanic chain rather than a remnant of the incompletely closed iapetus ocean c the earliest deformation is progressively younger toward the southeast d the appalachian collision history is a result of the activity of a single deformation regime over a long period of at least 75 ma

variations in style of volcanism and massive sulfide deposition in early to middle ordovician island arc sequences of the newfoundland central mobile belt the newfoundland central mobile belt records the early paleozoic birth development and destruction of the iapetus ocean following opening of the ocean in the cambrian a compressional plate margin developed in the early ordovician and an island arc was formed above an east dipping subduction zone volcanism was active at this plate margin from late tremadocian to early caradocian at which time subduction ceased and the products of the volcanism were blanketed by argillite and flysch the pre caradocian island arc volcanic sequences of the central mobile belt are host to numerous volcanogenic massive sulfide occurrences both the volcanic rocks and the associated massive sulfide occurrences show distinct contrasts across the volcanic belt in the northern part of the belt notre dame bay area submarine dominantly mafic volcanic rocks host pyritic cu zn deposits associated with local felsic domes these sequences pass southward into the victoria river area where volcanic rocks are characterized by laterally extensive felsic pyroclastic sheets which host polymetallic zn pb cu deposits in southern newfoundland the hermitage flexure area partially emergent preponderantly felsic volcanic rocks host pb zn ag massive sulfide mineralization formed during the waning stages of volcanism lead isotope ratios in massive sulfide deposits in the hermitage flexure area are consistently more radiogenic than in deposits hosted by more mafic volcanic sequences to the north this coupled with geologic evidence suggests that these sequences formed under the influence of sialic crustal material it is inferred that the early middle ordovician island arc volcanism in the newfoundland central mobile belt occurred in both oceanic and continental margin settings the compositions and geologic environments of the associated massive sulfide deposits reflect these variations in tectonostratigraphic settings time and space relationships within the volcanic arc during the interval of active volcanism are not entirely clear all early to middle ordovician volcanic rocks in central newfoundland may have formed from contemporaneous volcanic activity if this is the case simultaneous volcanism must have occurred both in oceanic environments and at or near the continental margin alternatively the volcanism may have been slightly diachronous with an early episode of ensimatic mafic volcanism followed by migration of the volcanic centers toward the continental margin the massive sulfide deposits of the pre caradocian island arc exhibit lead isotope ratios which are distinctly more radiogenic than those in the buchans roberts arm and post caradocian cutwell groups this appears to support geologically based inferences that the latter sequences are not part of the main phase of island arc activity in central newfoundland

provenance of exhalites associated with the lemarchant volcanogenic massive sulphide vms deposit central newfoundland canada insights from nd isotopes and lithogeochemistry neodymium isotope data on exhalites and tuffs from the cambrian lemarchant volcanogenic massive sulphide vms deposit provide insights into the tectonic environment of the tally pond group canada new data from exhalites from the lemarchant area show evolved values of end 513 6 0 to 1 8 whereas the associated volcanic rocks have end 513 of 0 4 to 1 4 the lemarchant exhalite end compositions overlap the underlying ganderian neoproterozoic sandy brook group end t 6 5 to 1 9 and crippleback intrusive suite end t 5 9 to 5 2 the evolved nd isotopic signatures suggest that the volcanic rocks of the tally pond group were formed upon ganderian arc basement which itself was possibly built upon or proximal to the gondwanan amazonian margin erosion of older crustal material and tally pond group volcanic rocks together with coeval eruption of the volcanic rocks released nd rich detritus into the water column uptake of eroded detrital and scavenged nd resulted in mixed nd sources juvenile and evolved which are archived in the exhalites the results of this study are not only of significance for occurrences of exhalites within the tally pond group but also have exploration implications for vms districts globally

petrochemistry hydrothermal alteration mineralogy and sulfur isotope geochemistry of the turgeon cu zn volcanogenic massive sulfide deposit northern new brunswick canada the turgeon deposit is a mafic type cu zn volcanogenic massive sulfide vms deposit it is hosted by middle ordovician pillow basalts of the devereaux formation of the fournier group within the elmtree belledune inlier near the bathurst mining camp bmc in northern new brunswick canada the turgeon deposit consists of two cu zn massive sulfide lenses 100m zn 48 49 composed of pyrite chalcopyrite pyrrhotite and sphalerite which are underlain by chalcopyrite pyrite stockwork veins pyrite is overprinted and replaced by chalcopyrite in the stockwork and vent complex sulfide facies where both minerals are enriched in se and co relative to pyrite and chalcopyrite in the massive pyrite and breccia sulfide facies in se and co display a positive covariation with cu whereas zn displays a positive covariation with cd trace element geochemistry indicates that the host rocks are primarily tholeiitic basalts and andesites that have signatures between that of mid ocean ridge basalt and island arc

approaching trophic structure in late jurassic neritic shelves a western tethys example from southern iberia the palaeoenvironmental conditions and trophic structure of a mid outer neritic biota microfossils mainly forams and macroinvertebrate assemblages have been approached in middle oxfordian lowermost kimmeridgian deposits from the prebetic zone betic cordillera in south eastern spain according to relationships between fossil assemblages and lithofacies a general seaward trend is identified which displays decreasing sedimentation rates and nutrient inputs but increasing substrate consistency and presumably depth midshelf terrigenous rich deposits in the external prebetic relate to the highest sedimentation rates and nutrient availability these two parameters correlate with the highest content in vagile benthic calcareous perforate epifaunal forams as well as with potentially deep infaunal forams and infaunal macroinvertebrates outer shelf lumpy deposits in the internal prebetic show the lowest sedimentation rates and nutrient availability and the highest records for macro micro nektonics and planktics in contrast vagile benthic calcareous perforate epifaunal and potentially deep infaunal forams are scarcer in the midshelf environments colonial encrusting forams benthic microbial communities and sessile benthic macro invertebrates increase from the middle to outer shelf trophic analysis structuring through the integration of benthic microbial communities foraminiferal and macroinvertebrate fossil assemblages makes it possible to interpret a a trophic level frame composed of producers and primary and secondary consumers b a main trophic group differentiation in suspension feeders detritus feeders browsers grazers carnivores and scavengers c a preliminary approach to food chain structure supported by suspension feeders deposit feeders and predators active prey selection carnivores and d a food pyramid model which takes into account both recorded fossils and envisaged i e ecologically inferred organisms

upper cambrian to upper ordovician peri gondwanan island arc activity in the victoria lake supergroup central newfoundland tectonic development of the northern ganderian margin the exploits subzone of the newfoundland appalachians comprises remnants of cambro ordovician peri gondwanan arc and back arc complexes that formed within the iapetus ocean the exploits subzone experienced at least two accretionary events as a result of the rapid closure of the main portion of the iapetus tract the penobscot orogeny c 480 ma which juxtaposed the penobscot arc c 513 486 ma with the gander margin and c 450 ma collision of the victoria arc c 473 454 ma with the annieopsquotch accretionary tract that juxtaposed the peri laurentian and peri gondwanan elements along the red indian line the newly recognized pats pond group forms a temporal equivalent to other lower ordovician intra oceanic complexes of the penobscot arc the pats pond group c 487 ma has a geochemical stratigraphy that is consistent with rifting of a volcanic arc an ensialic setting is indicated by low end values end 0 3 to 0 5 near the stratigraphic base and its abundant zircon inheritance c 560 ma and 0 9 1 2 ga the spatial distribution of tremadocian arc back arc complexes indicates that the penobscot arc is best explained in terms of a single east dipping subduction zone this model is favored over west dipping models in that it explains the distribution of the penobscot arc elements continental arc magmatism and the obduction of back arc penobscot ophiolites without requiring subduction of the gander margin or subduction reversal the newly recognized wigwam brook group c 454 ma disconformably overlies the pats pond group and records the youngest known phase of ensialic arc volcanism end 4 1 in the victoria arc which is also related to east dipping subduction thus the penobscot and the overlying victoria arc are reinterpreted in terms of a single relatively long lived east dipping subduction zone beneath the peri gondwanan microcontinent of ganderia the cessation of arc volcanism towards the top of the wigwam brook group and the subsequent syn tectonic sedimentation in the badger group constrain the arrival of the leading edge of ganderia with the ensialic arc complexes to the laurentian margin to c 454 ma

paleomagnetism of the moreton s harbour group northeastern newfoundland appalachians evidence for an early ordovician island arc near the laurentian margin of iapetus paleomagnetic results have been obtained from mafic volcanic units in the upper part of the moreton s harbour group which is part of an accreted island arc terrane that is preserved in the notre dame bay subzone of the central mobile belt of the newfoundland appalachians detailed thermal and alternating field demagnetization reveals a stable characteristic component of magnetization carried by magnetite at a large number of sites in pillow basalts and coeval basaltic dikes the intrusives contain both polarities and a primary age for the characteristic magnetization is indicated by a positive contact test for one of the dikes and by a positive structural test involving a correction for block rotations strike correction the overall mean direction for the characteristic component after tectonic tilt and strike correction flows and intrusives d 171 i 22 k 22 6 95 6 5 pole 29 n 135 e flows d 166 i 22 k 33 2 95 6 5 corresponds to an early ordovician paleolatitude for the arc of 11 s which is indistinguishable from the expected paleolatitude of the north american margin this implies that the arc formed at or near the margin of the craton in contrast the avalon block which formed the other margin of iapetus was widely separated from the arc and the craton at this time the early ordovician paleolatitude of the arc terrane supports a tectonic model in which coeval ophiolitic sequences inboard of the arc were formed in a narrow ocean basin between the arc and the craton subsequent convergence between the arc and laurentia in middle ordovician time resulted in closure of this narrow ocean basin and obduction of the back arc basin oceanic crust onto the ancient margin of the craton thus giving rise to the taconic orogenic pulse in the newfoundland appalachians

sponge ecology on sublittoral hard substrates in a high current velocity area the ecology of sponges on shallow sublittoral hard substrates in little letite passage off deer island bay of fundy new brunswick canada was studied with respect to their areal coverage and orientation to current direction coverage was found to increase with increasing depth and current velocity and was greater on hard substrates than on gravel or cobble substrates the orientation of an individual sponge to the direction of the current was found to be dependent on its morphology with upright species orientated across the current and massive or encrusting species showing a slight orientation parallel to the current direction of the 16 species recorded from little letite passage the two most common were isodictya deichmannae and eumastia sitiens

interpretation of the nitrogen isotopic signal variations in the mauritanian upwelling with a 2d physical biogeochemical model 1 a physical biogeochemical model is used to simulate the evolution of the 15n signal during the last glacial interglacial transition in sedimentary cores offshore from the mauritanian upwelling the biological model is a classical nitrogen based trophic chain model which also computes the nitrogen isotope fractionation the 2d physical primitive equation model simulates the coastal upwelling circulation and is applied for different sea level scenarios the effect of the sea level rise inducing the shelf immersion seems to be a main factor explaining the organic nitrogen flux and isotopic signal variations along the last deglaciation this effect is modulated by an upwelling seasonality that may have been much longer at the last glacial maximum around 10 11 months instead of 4 5 months at present between 15 and 5 5 kyr ago 60 of the sedimentary 15n variations could be explained by this local shelf immersion effect this reconstruction also reproduces the strong isotopic fall occurring between 5 5 kyr and the present

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