lithofacies associations and evolution of the volcanic host succession to the minifie ore zone ladolam gold deposit lihir island papua new guinea the 46 million ounce ladolam gold deposit the largest alkalic epithermal gold deposit in the world in terms of contained gold is composed of four ore zones minifie lienetz kapit and coastal this detailed lithofacies study of the minifie ore zone recognized three evolutionary stages 1 volcanosedimentary strata part of an alkalic composite volcanic island 2 a porphyry style breccia dike and 3 epithermal style breccias the plio pleistocene volcanosedimentary stratigraphy reflects the transition from subaerial deposition of pyroclastic surge deposits close to vent to a subaqueous quiet depositional environment into which a cryptodome was emplaced the stratigraphy is predominantly composed of polymictic matrix supported breccia and sandstone interbedded with lavas and shallow intrusions the minifie strata have a shallow southward dip as a result of quaternary uplift overprinting the volcanosedimentary stratigraphy are three hydrothermally cemented breccia facies one deposited in the porphyry environment and two deposited in the epithermal environment porphyry style alteration assemblages and a 3 to 5 m wide biotite k feldspar calcite anhydrite cemented breccia dike are focused around the central minifie shear fault the porphyry alteration assemblages are overprinted by shallow level and deeper level epithermal style features the deeper level below the present mining surface 140 m below sea level epithermal vein stockwork is composed of quartz calcite adularia anhydrite cemented breccias and shallowly northward to near horizontal dipping veins that have gold grades of 1 to 60 g t au shallow level epithermal facies adularia quartz pyrite cemented breccias veins and associated alteration host the bulk mineable gold ore and typically yield 4 g t au over 12 m blast hole samples

greenland meltwater as a significant and potentially bioavailable source of iron to the ocean the micronutrient iron is thought to limit primary production in large regions of the global ocean meltwater measurements suggest that the greenland ice sheet serves as a significant source of potentially bioavailable iron to the surrounding coastal ocean

size fractionated iron distribution on the northern gulf of alaska 1 concentrations of soluble 0 4 m and colloidal 0 025 0 4 m fe size fractions were removed from surface waters within the inner and mid shelf as a result the contribution of soluble fe to the total fe concentration increased from the inner shelf to the shelf break slope waters surface water dissolved fe concentrations on the northern goa continental slope were higher than those previously observed in the central goa gyre variations in surface water fe concentrations from spring through summer appear to result from the changes in freshwater discharge and physical processes on the shelf

supergene and hypogene halloysite in a porphyry epithermal environment at cerro la mina chiapas mexico halloysite a phyllosilicate clay mineral chemically similar to but structurally different from kaolinite occurs in a variety of mineral deposit types it is however difficult to identify and dehydrates quite readily when identified in a porphyry or epithermal environment halloysite is often interpreted to be a low temperature polymorph of kaolinite and an indication of supergene processes the occurrence of halloysite in the cerro la mina au cu mo prospect chiapas mexico was investigated to determine if halloysite in porphyry epithermal deposits might also be the product of hypogene processes the prospect consists of quaternary volcaniclastic breccias intruded by monzodiorites and trachyandesites crosscut by a volcanic hydrothermal breccia pipe gold copper molybdenum mineralization at cerro la mina is structurally and lithologically controlled by matrix rich breccia pipes hosting all of the significant alteration and mineralization drilled to date average grades within the prospect are 0 4 ppm au 0 16 cu and 131 ppm mo a total of 100 samples were obtained from 22 diamond drill holes over a range of stratigraphic levels x ray diffraction xrd and swir techniques were employed to identify the different clay minerals found within these samples including halloysite kaolinite dickite and illite identification of halloysite and kaolinite were facilitated by the use of formamide intercalation to produce distinctive peaks for the two minerals in x ray diffractograms halloysite and kaolinite were found to occur from the current erosional surface to depths of over 800 m halloysite occurs as both the hydrated 10a and dehydrated 7a forms within the deposit the morphology of the halloysite present is that of well developed tubes and spheroids results of the study show that halloysite associated with gypsum and jarosite is of supergene origin whereas halloysite occurring with quartz alunite dickite kaolinite and pyrite is of hypogene origin

glacial influence on the geochemistry of riverine iron fluxes to the gulf of alaska and effects of deglaciation riverine iron fe derived from glacial weathering is a critical micronutrient source to ecosystems of the gulf of alaska goa here we demonstrate that the source and chemical nature of riverine fe input to the goa could change dramatically due to the widespread watershed deglaciation that is underway we examine fe size partitioning speciation and isotopic composition in tributaries of the copper river which exemplify a long term goa watershed evolution from one strongly influenced by glacial weathering to a boreal forested watershed iron fluxes from glacierized tributaries bear high suspended sediment and colloidal fe loads of mixed valence silicate species with low concentrations of dissolved fe and dissolved organic carbon doc iron isotopic composition is indicative of mechanical weathering as the fe source conversely fe fluxes from boreal forested systems have higher dissolved fe concentrations corresponding to higher doc concentrations iron colloids and suspended sediment consist of fe hydr oxides and organic complexes these watersheds have an iron isotopic composition indicative of an internal chemical processing source we predict that as the goa watershed evolves due to deglaciation so will the source flux and chemical nature of riverine fe loads which could have significant ramifications for alaskan marine and freshwater ecosystems

the relationship between quaternary volcanism in central mexico and the seismicity and structure of subducted ocean lithosphere late quaternary volcanism in central mexico is related to the subduction of young ocean lithosphere at the middle america trench along arc variations in seismicity volcano structure and composition of volcanic products bear a remarkable correlation with the age and structural framework of the downgoing slab morphological and petrographic characteristics of major volcanoes within the trans mexican volcanic belt tmvb serve to distinguish two calc alkaline subprovinces 1 a western arc averaging 60 km in width associated with aseismic subduction of the rivera plate the main cones of this region are dominated by two pyroxene andesites comprise volumes 70 km 3 and stand less than 3 000 m above sea level 2 a broad central and eastern arc related to subduction of a gently inclined segment of the cocos plate bounded by the rivera transform and the tehuantepec ridge major volcanic edifices possess summit elevations in the range 4 000 to 6 000 m have appropriately larger volumes typically 200 km 3 and are constructed with a high proportion of amphibole bearing lavas the boundary between these subprovinces is marked by a north south oriented structural depression the colima graben and it coincides with a 100 km offset in the volcanic front extensional tectonism in the colima graben accompanied by mixed calc alkaline and alkaline volcanism of potassic affinity is likely related to a hinge type transform fault which marks the cocos rivera plate juncture in the downgoing slab a third segment of ocean floor is presently interacting with continental lithosphere south of the gulf of tehuantepec where quaternary volcanism is weakly developed within a tectonically complex region that marks the diffuse cocos noam caribbean triple junction the northern limit of this triple junction is defined by the seismically active isthmus fault which may be related to alkaline volcanic activity at san andres tuxtla a tectonic reconstruction based on the evolution of oceanic crust reveals that the distribution of intermediate depth earthquakes along the arc is directly dependent upon the age of the subducted slab ocean lithosphere younger than approximately 20 m y is subducted aseismically at convergence rates approaching 9 cm yr the length of the inclined seismic zone indicates that the time constant for thermal relaxation in the slab is approximately 4 m y the tmvb overlies the aseismic extension of this young ocean lithosphere several aspects of this study have a bearing on the segmented nature of converging margins in general 1 the tectonic evolution of the ocean floor may determine the nature of segmentation at the site of subduction 2 the complete record of volcanism in the tmvb over the past million years can be related to the present plate configuration 3 alkaline and calc alkaline volcanism have developed contemporaneously at a converging plate margin 4 lineaments in volcanic arcs may reflect the structural complexity of the crust rather than segment boundaries in the subducted slab

iron solubility driven by speciation in dust sources to the ocean particulate aerosols are thought to be the primary source of iron to the oceans but the factors determining their solubility and thus bioavailability are unclear x ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron

pathways of high latitude dust in the north atlantic abstract the contribution of mineral dust from high latitude sources has remained an under examined feature of the global dust cycle dust events originating at high latitudes can provide inputs of aeolian sediment to regions lying well outside the subtropical dust belt constraining the seasonal variability and preferential pathways of dust from high latitude sources is important for understanding the potential impacts that the dust may have on wider environmental systems such as nearby marine or cryospheric domains this study quantifies dust pathways from two areas exhibiting different emission dynamics in the north and south of iceland which is a prominent northern hemisphere dust source the analysis uses air parcel trajectory modelling and for the first time for high latitude sources explicitly links all trajectory simulations to time specific meteorological observations of suspended dust this approach maximises the potential for trajectories to represent dust and illustrates that trajectory climatologies not limited to dust can grossly overestimate the potential for dust transport preferential pathways emerge that demonstrate the role of iceland in supplying dust to the northern atlantic and sub arctic oceans for dust emitted from northern sources a dominant route exists to the northeast into the norwegian greenland and barents seas although there is also potential for delivery to the north atlantic in summer months from the southern sources the primary pathway extends into the north atlantic with a high density of trajectories extending as far south as 50 n particularly in spring and summer common to both southern and northern sources is a pathway to the west southwest of iceland into the denmark strait and towards greenland for trajectories simulated at 500 m the vertical development of dust plumes from iceland is limited likely due to the stable air masses of the region suppressing the potential for vertical motion trajectories rarely ascend high enough to reach the central portions of the greenland ice sheet the overall distribution of trajectories suggests that contributions of icelandic dust are relatively more important for neighbouring marine environments than the cryosphere

recent glacier mass changes in the gulf of alaska region from grace mascon solutions the mass changes of the gulf of alaska goa glaciers are computed from the gravity recovery and climate experiment grace inter satellite range rate data for the period april 2003 september 2007 through the application of unique processing techniques and a surface mass concentration mascon parameterization the mass variations in the goa glacier regions have been estimated at high temporal 10 day and spatial 2 2 arc degrees resolution the mascon solutions are directly estimated from a reduction of the grace k band inter satellite range rate data and unlike previous grace solutions for the goa glaciers do not exhibit contamination by leakage from mass change occurring outside the region of interest the mascon solutions reveal considerable temporal and spatial variation within the goa glacier region with the largest negative mass balances observed in the st elias mountains including the yakutat and glacier bay regions the most rapid losses occurred during the 2004 melt season due to record temperatures in alaska during that year the total mass balance of the goa glacier region was 84 5 gt a 1 contributing 0 23 0 01 mm a 1 to global sea level rise from april 2003 through march 2007 highlighting the large seasonal and interannual variability of the goa glaciers the rate determined over the period april 2003 march 2006 is 102 5 gt a 1 which includes the anomalously high temperatures of 2004 and does not include the large 2007 winter balance year snowfall the mascon solutions agree well with regional patterns of glacier mass loss determined from aircraft altimetry and in situ measurements

glacial flour dust storms in the gulf of alaska hydrologic and meteorological controls and their importance as a source of bioavailable iron 1 iron is an essential micronutrient that limits primary productivity in much of the ocean including the gulf of alaska goa however the processes that transport iron to the ocean surface are poorly quantified we combine satellite and meteorological data to provide the first description of widespread dust transport from coastal alaska into the goa dust is frequently transported from glacially derived sediment at the mouths of several rivers the most prominent of which is the copper river these dust events occur most frequently in autumn when coastal river levels are low and riverbed sediments are exposed the dust plumes are transported several hundred kilometers beyond the continental shelf into iron limited waters we estimate the mass of dust transported from the copper river valley during one 2006 dust event to be between 25 80 ktons based on conservative estimates this equates to a soluble iron loading of 30 200 tons we suggest the soluble fe flux from dust originating in glaciofluvial sediment deposits from the entire goa coastline is two to three times larger and is comparable to the annual fe flux to goa surface waters from eddies of coastal origin given that glaciers are retreating in the coastal goa region and in other locations it is important to examine whether fluxes of dust are increasing from glacierized landscapes to the ocean and to assess the impact of associated fe on marine ecosystems

hydrothermal alteration and mineralization of the galore creek alkalic cu au porphyry deposit northwestern british columbia canada the late triassic galore creek porphyry district is the largest accumulation of cu au prospects in british columbia canada in terms of contained metal the principal economic resource is the central zone deposit it comprises three high grade centers the au rich north and south gold lenses and the cu dominated central replacement zone alteration footprints ore shells and porphyry intrusions in these centers dip 45 to 60 to the west in the north gold lens and southwest in the south gold lens and central replacement zone indicative of significant postmineral tilting this inclination created an oblique vertical expression of the central zone at surface and at depth providing a 700 m depth profile through the deposit galore creek is considered to be the end member of the silica undersaturated class of alkalic porphyry cu au deposits it displays a unique hydrothermal alteration footprint generally devoid of quartz veining despite the lack of crosscutting veins a paragenetic sequence of several discrete potassic and calcic alteration events has been established during main stage alteration two mineralization events occurred that formed the economic resource in the central zone highly oxidizing fluids derived from porphyritic syenite to monzonite intrusions produced initial potassic alteration and sulfide mineralization in the north gold lens and south gold lens cu au ore shells are characterized by a gold rich core dominated by bornite associated with hematite dusted orthoclase specular hematite and anhydrite the second period of hydrothermal activity caused brecciation and calcic alteration in the central replacement zone the calcic fluids formed hydrothermal cement grading from ti rich andraditic to grossularitic garnet in the core of the breccia to a diopside and magnetite dominated assemblage at the margins calcic alteration also formed in the surrounding host rock this alteration event was followed by potassic alteration and mineralization characterized by biotite anhydrite and chalcopyrite in the cu rich ore shell of the central replacement zone most of the au is hosted in bornite that is spatially associated with oxidized reddened rock units dominated by an alteration assemblage of orthoclase hematite specular hematite garnet anhydrite high grade cu in the central zone is related to abundant chalcopyrite that has commonly replaced an assemblage of biotite magnetite diopside this distinct spatial separation strongly suggests that the local redox environment within the wall rocks governed sulfide and gold distributions the switch from early au rich mineralization to late stage cu dominated mineralization appears to have been controlled by varying redox conditions within the magma the change from more oxidized alteration assemblages fe3 fe2 to more reduced assemblages fe3 fe2 is indicative of a change in oxidation potential that may have propelled sulfide saturation in the magma and thus the subsequent depletion of most of the au

using mineral chemistry to aid exploration a case study from the resolution porphyry cu mo deposit arizona the giant high grade resolution porphyry cu mo deposit in the superior district of arizona is hosted in proterozoic and paleozoic basement and in an overlying cretaceous volcaniclastic breccia and sandstone package resolution has a central domain of potassic alteration that extends more than 1 km outboard of the ore zone overlapping with a propylitic halo characterized by epidote chlorite and pyrite that is particularly well developed in the laramide volcaniclastic rocks and proterozoic dolerite sills the potassic and propylitic assemblages were overprinted in the upper parts of the deposit by intense phyllic and advanced argillic alteration the district was disrupted by tertiary basin and range extension and the fault block containing resolution and its cretaceous host succession was buried under thick mid miocene dacitic volcanic cover obscuring the geologic geophysical and geochemical footprint of the deposit to test the potential of propylitic mineral chemistry analyses to aid in the detection of concealed porphyry deposits a blind test was conducted using a suite of epidote chlorite pyrite altered laramide volcaniclastic rocks and proterozoic dolerites collected from the propylitic halo with samples taken from two domains located to the north and south and above the resolution ore zone laser ablation inductively coupled plasma mass spectrometry la icp ms data of epidote provided indications of deposit fertility and proximity competition for chalcophile elements as sb pb between coexisting pyrite and epidote grains led to a subdued as sb fertility response in epidote consistent with epidote collected between 0 7 and 1 5 km from the center of a large porphyry deposit temperature sensitive trace elements in chlorite provided coherent spatial zonation patterns implying a heat source centered at depth between the two sample clusters and application of chlorite proximitor calculations based on la icp ms analyses provided a precisely defined drill target in this location in three dimensions drilling of this target would have resulted in the discovery of resolution confirming that epidote and chlorite mineral chemistry can potentially add value to porphyry exploration under cover

the transition from porphyry to epithermal style gold mineralization at ladolam lihir island papua new guinea a reconnaissance study the exceptionally large gold resource at ladolam 1 300 metric tons of gold lihir island resulted from the transition of an early stage low grade porphyry gold system to a low sulfidation epithermal gold event this transition was probably triggered by rapid decompression during the partial slope failure of luise stratovolcano and accompanied by the ingress of seawater the original porphyry stage is indicated by remnant hydrothermal breccia clasts of strongly biotite magnetite altered monzodiorite with disseminated pyrite chalcopyrite and poorly developed pyrite quartz stockwork veins the breccias are overprinted by biotite magnetite alteration and their matrix is strongly mineralized with disseminated auriferous pyrite the breccias are cut by late stage epithermal quartz chalcedony illite adularia pyrite veins and associated illite adularia alteration that locally contain bonanza gold grades of up to 120 g t isotope data suggest a magmatic source of sulfur in the gold bearing fluids at ladolam electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 001 0230 y

triassic jurassic silica undersaturated and silica saturated alkalic intrusions in the cordillera of british columbia implications for arc magmatism alkalic igneous rocks of early mesozoic age are found in both the quesnel and stikine terranes in the canadian cordillera and include both silica undersaturated and silica saturated types the saturated complexes are most abundant in quesnellia and are multiphase complexes dominated by monzonite to diorite intrusions undersaturated complexes are distributed through both terranes are dominated by syenite with lesser monzonite and pyroxenite and when present as a single intrusion are characterized by concentric zoning igneous layering and planar mineral fabrics both types of complex are associated with cu au mineralization accompanied by potassic and distinctive sodic and calc potassic alteration assemblages although undersaturated and saturated alkalic intrusions are petrographically distinct a petrogenetic association is suggested by their spatial coincidence in some districts and similarities in their tectonic environment and associated alteration the undersaturated complexes represent a distinctive suite of alkalic intrusion with magmatic arc affinities and their emplacement into both stikinia and quesnellia between 210 and 200 ma suggests that these terranes were either linked at that time or have shared unusual but similar magma generating tectonic events at identical times

strike slip faults and k alkaline volcanism at el chichon volcano southeastern mexico abstract el chichon volcano is located in the northern part of the state of chiapas in southeastern mexico the volcano is situated within the transcurrent fault province characterized by a series of rising and sinking blocks bounded by sinistral strike slip faults the basement around el chichon is a sequence of jurassic evaporates cretaceous limestones and tertiary terrigenous rocks folded into open and an echelon structures the main structures in the area are the la union and caimba anticlines and the buena vista syncline the region is cross cut by two conjugate fault systems a dextral strike slip n s trending set and a sinistral strike slip e w set the most significant fault of the latter system is the san juan fault which controlled the emplacement of a basaltic dike near the village of chapultenango some 1 1 ma ago and the activity of el chichon during the last 0 2 ma additionally a series of n45 e trending faults chapultengo fault system have produced a half graben geometry of blocks on top of which el chichon has been emplaced microstructures such as slickensides tension fractures layer parallel slip stylolites and macro and meso folds of the sedimentary rocks indicate that during the late miocene the el chichon area was affected by a maximum principal stress 1 oriented n70 e a minimum principal stress 3 oriented n20 w and a vertical intermediate principal stress this stress pattern indicates that the area underwent a strike slip motion that produced widespread deformation the occurrence of crustal earthquakes

evidence for magmatic hydrothermal fluids and ore forming processes in epithermal and porphyry deposits of the baguio district philippines the baguio district contains a diverse array of epithermal porphyry and skarn deposits together with a large broadly strata bound advanced argillic lithocap magmatism mineralization and alteration occurred in response to subduction of the south china sea plate and the scarborough ridge beneath northern luzon over the past 3 m y rapid uplift and exhumation resulted in epithermal veins overprinting several porphyry cu au deposits most of the epithermal au ag deposits of the baguio district including antamok and acupan the two largest au deposits are intermediate sulfidation state quartz carbonate adularia illite base metal sulfide veins that contain electrum and minor au ag tellurides in contrast high sulfidation mineralization at kelly includes enargite tennantite electrum and precious metal tellurides and is associated with advanced argillic alteration although the mineralizing fluids that formed the porphyry and epithermal deposits had distinct temperatures and salinities stable and radiogenic data provide evidence for direct magmatic contributions into each deposit type the epithermal mineralizing fluids were dilute generally 600 c hypersaline brines 30 to 70 wt nacl equiv and low density vapor sulfur isotope compositions of sulfides in the porphyry skarn and intermediate sulfidation epithermal veins of the southern and central baguio district are mostly between 1 and 6 per mil consistent with a predominance of h2s in the mineralizing fluids i e reducing conditions in contrast sulfides from the high sulfidation porphyry and intermediate sulfidation deposits located adjacent to the baguio lithocap mostly have negative sulfur isotope values 6 9 to 0 8 consistent with oxidizing so42 predominant mineralizing fluids intermediate sulfidation epithermal veins at acupan have crosscut a well mineralized porphyry cu au stock work at ampucao the two deposits cannot be distinguished on the basis of radiometric age determinations ampucao 0 51 0 26 ma acupan 0 65 0 07 ma and are interpreted to be cogenetic with telescoping of the two environments caused by the rapid uplift and exhumation associated with ridge subduction measured 34ssulfide 1 1 to 6 6 34ssulfate 10 4 to 31 8 values and initial strontium ratios of anhydrite 0 70378 0 70385 are consistent with identical and predominantly magmatic sources of these components for the ampucao porphyry and acupan epithermal veins helium isotopes provide further evidence of mantle derived components in the epithermal veins r ra values of 6 0 and 6 7 oxygen deuterium and carbon isotopes provide evidence for predominantly magmatic water at ampucao and for hybrid magmatic meteoric waters at acupan that precipitated precious metals due to boiling the proportion of magmatic water relative to meteoric water and precious metal grades both decreased with time during epithermal vein formation at acupan the common observation of cross cutting relationships between porphyry and epithermal veins observed throughout the baguio district imply that the evolution of porphyry style to intermediate sulfidation style mineralization was a common phenomenon in this region and contributed significantly to its rich metal endowment

modeling the formation of advanced argillic lithocaps volcanic vapor condensation above porphyry intrusions hypogene advanced argillic alteration typically quartz alunite with halos of kaolinite dickite and roots of pyrophyllite diaspore forms in the epithermal environment from condensates of magmatic vapor that contain so2 and hcl which exsolved from an underlying intrusive source the most aggressive nearly isochemical leaching of the host rock by the most acidic condensate commonly ph 1 leaves residual silica that recrystallizes to quartz within the flow channel at a high condensate rock ratio forming the core of alteration the alteration characteristically flares upward along feeder structures and if a permeable lithologic unit is intersected the alteration zones mushroom to form a subhorizontal blanket due to lateral flow where subsequently mineralized the residual quartz commonly with a vuggy texture that reflects the texture of the original lithology has higher au and cu grades than the quartz alunite halo tonnage in these high sulfidation systems may develop within the subhorizontal lithocap although the highest grades are typically confined to the structurally controlled feeders we modeled a typical volcanic vapor condensate starting with the measured composition of 877 c fumaroles from satsuma iwojima rhyolite dome japan as it cooled and reacted with a host rhyolite the predicted hydrothermal mineralogy reproduces the alteration pattern observed in lithocaps that host high sulfidation deposits the modeling confirms that aluminum rich minerals pyrophyllite diaspore locally andalusite are stable at higher temperature at depth whereas at lower temperature and shallower depth na and k alunite become stable at the lowest temperature 10 1 and where so2 h2s in the original volcanic vapor this so2 dominant composition is typical of andesitic to rhyolitic volcanoes the reason for this mineral transition and the upward flare widening of the alteration zone along structures is related to the dissociation and increased reactivity of h2so4 and hcl as the temperature decreases below 200 c only quartz pyrite native s and anhydrite are stable hence the formation of the dominant quartz from the silica residue a further check on our modeling is the observation that the calculated composition of the condensate after reaction with fresh satsuma iwojima rhyolite and alteration minerals and cooling to 100 c is similar within a factor of two to that of acidic springs with ph 1 that discharge around satsuma iwojima and other active volcanoes the most extensive lithocap alteration residual quartz and or quartz alunite is commonly offset from the surface projection of the causative intrusion this observation can be explained by a combination of two factors hydrology and temperature due to hydraulic gradients at shallow depths in a volcanic edifice the acidic condensate tends to flow along permeable lithologic units away from the locus of the high temperature vapor plume which rises directly over the intrusion where lateral flow occurs the most intense leaching and widespread advanced argillic alteration which develops largely at temperatures of 200 to 250 c based on our modeling will form away from the near surface projection of the intrusion which is the area of highest surface temperature due to ascent of the vapor plume this potential for lithocap alteration to form on the shoulder of the underlying causative intrusion must be assessed when exploring for high sulfidation ore the highest ore grades are commonly related to structures that are proximal to the parent intrusion but they are unlikely to lie directly over the intrusion in addition identifying the most likely location of the source intrusion will help the explorer to efficiently assess any potential for deeper porphyry style mineralization

geology and genesis of the cerro la mina porphyry high sulfidation au cu mo prospect mexico the cerro la mina au cu mo porphyry high sulfidation prospect is located in chiapas state southeastern mexico outside of the major metallogenic provinces of mexico the prospect is hosted by pleistocene alkaline volcanic rocks of the chiapanecan volcanic arc that formed in a complex triple junction tectonic setting cerro la mina s stratigraphy comprises pyroclastic flows that were intruded by monzodiorites and diorites at 1 04 0 04 ma u pb zircon and that were overlain by debris flows and synvolcanic trachyandesite domes the volcanic stratigraphy of cerro la mina is dominated by pyroclastic flows and rare basalts that are cut by the cerro la mina breccia pipe a matrix rich granular vertically oriented downward tapering polymict lithic rock unit that is host to all of the significant alteration and mineralization a nw trending sinistral wrench fault which was active throughout the history of cerro la mina is responsible for dismembering the prospect after mineralization the magmatic hydrothermal system was composed of early porphyry style potassic veins quartz k feldspar biotite and stage 1 pyrite that are preserved in clasts within the breccia pipe suggesting that brecciation disrupted an embryonic porphyry system late potassic alteration occurred after the formation of the breccia pipe as its matrix is strongly k feldspar altered hydrothermal fluids then produced phyllic alteration composed of quartz muscovite illite illite smectite and chlorite that is associated with stage 2 pyrite chalcopyrite molybdenite quartz veins an unusual zoned pattern of advanced argillic argillic alteration overprinted potassic and phyllic alteration this zoning included a low temperature 120 c quartz dickite kaolinite pyrophyllite alunite that occurs from 250 m to the present day surface the advanced argillic argillic altered rocks host the most significant au cu mineralization which is associated with stage 3 marcasite sphalerite galena and barite and stage 4 arsenian pyrite enargite covellite the magmatic hydrothermal system at cerro la mina began sometime between monzodiorite emplacement 1 04 0 04 ma zircon u pb and the precipitation of porphyry stage 2 molybdenite at 780 10 ka re os 40ar 39ar dating of biotite 689 13 ka records the age at which the hydrothermal system cooled below the biotite closure temperature of 300 c and provides a maximum estimate for the onset of advanced argillic argillic alteration sulfur isotope results of sulfides 2 5 to 4 9 mean 0 7 n 20 and a sulfate barite 10 5 n 1 suggest a magmatic source of sulfur for all four stages of mineralization the lack of residual quartz rare alunite and anomalous halloysite kaolinite alteration may be explained by the high acid buffering capacity of alkaline volcanic host rocks high co2 contents of the alkaline magma and or potentially by a highly reduced magmatic hydrothermal fluid at the regional metallogenic scale the cerro la mina prospect along with the nearby santa fe mine and campamento deposit represent parts of a porphyry copper system specifically a porphyry high sulfidation proximal skarn and intermediate sulfidation deposit respectively the characteristics of cerro la mina i e anomalous halloysite kaolinite alteration broaden the window for additional discoveries to be made in the porphyry epithermal environment

the geochemistry of loess asian and north american deposits compared abstract loess is widely distributed over asia and north america and constitutes one of the most important surficial deposits that serve as terrestrial records of the quaternary the oldest pleistocene loess in china is likely 2 6 ma thus spanning much or all of the pleistocene in north america most loess is no older than the penultimate glacial period with the exception of alaska where the record may go back to 3 0 ma on both continents loess deposits date primarily to glacial periods and interglacial or interstadial periods are represented by paleosols both glacial and non glacial sources of silts that comprise the bulk of loess deposits are found on both continents although loess has been considered to be representative of the average upper continental crust there are regionally distinctive compositions of loess in both asia and north america loess deposits in asia from yakutia tajikistan and china have compositionally distinct major element compositions due to varying abundances of silicate minerals carbonate minerals and clay minerals in north america loess in the mississippi river valley the great plains and alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments trace element geochemistry sc th zr and the rare earth elements also shows regional diversity of loess bodies in both asia and north america on both continents most loess bodies show significant contributions from later cycle altered sedimentary rocks as opposed to direct derivation from igneous rocks further some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average upper crustal felsic rocks intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials ratios of soluble to insoluble elements show depletions in paleosols due to chemical weathering losses of calcite dolomite plagioclase mica apatite and smectite in asia and north america the last interglacial paleosol is more weathered than equivalent modern soils which could be due either to a climate that was warmer and more humid a longer period of pedogenesis or both in asia early pleistocene loess and paleosols are both more weathered than those from the middle and late pleistocene forming prior to a mid pleistocene aridification of asia from uplift of the tibetan plateau understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation past temperature and moisture regimes and even tectonic processes

cordilleran ice sheet growth fueled primary productivity in the gulf of alaska northeast pacific ocean fertilization of the ocean by eolian dust and icebergs is an effective mechanism to enhance primary productivity in particular high nutrient low chlorophyll hnlc areas where phytoplankton growth is critically iron limited such as the subarctic pacific ocean and the southern ocean are proposed to respond to increases in bioavailable fe supply with enhanced phytoplankton productivity and carbon export to the seafloor while fe fertilization from dust is widely acknowledged to explain a higher export production during glacial periods in the southern ocean paleoceanographic records supporting links between productivity and eolian dust and or icebergs in the north pacific are scarce by combining independent proxies indicative of ice sheet dynamics and ocean productivity from a single marine sedimentary record integrated ocean drilling program iodp site u1417 we present a comprehensive data set of phytoplankton response to different fertilization mechanisms in the subarctic northeast pacific between 1 5 and 0 5 ma including the mid pleistocene transition importantly the timing of the fertilization events is more strongly controlled by local ice sheet extent than by glacial interglacial climate variability our findings indicate that fertilization by glacigenic debris results in productivity events in hnlc areas adjacent to ice sheets and that this mechanism may represent an important yet rarely considered driver of phytoplankton growth

dissolution of aerosol iron in the surface waters of the north pacific and north atlantic oceans as determined by a semicontinuous flow through reactor method aerosol iron dissolution in oceanic waters is determined with a semicontinuous batch leaching method in this procedure aerosol samples that were collected from the marine boundary layer were leached in an all teflon flow through reaction chamber by multiple aliquots of similar to 40 ml 0 4 mu m filtered oceanic surface water collected using ultraclean techniques each aliquot of seawater is permitted to leach the aerosol sample in the reaction chamber for a predetermined time before the seawater solution is separated from the aerosol sample by a 0 4 mu m nucleopore filter membrane a new aliquot of seawater is then added to the leaching chamber to continue leaching the same aerosol particles retained on the filter the procedure is repeated with progressive increases in leaching time the method allows the fe released from the aerosol particles to be continuously removed from the system before saturating the complexation capacity of the seawater leaching solution or adsorbing onto the leaching chamber wall this method results in accurate measurements of seawater dissolvable labile aerosol fe that is independent of the total aerosol fe concentrations in the sample the aerosol fe solubility determined using this method ranges from 3 5 1 5 for the north atlantic during september 2005 to 5 7 2 0 for the north pacific during april 2005 and april 2006

seasonally resolved diatom δ18o records from the west antarctic peninsula over the last deglaciation understanding the response of the antarctic ice sheets during the rapid climatic change that accompanied the last deglaciation has implications for establishing the susceptibility of these regions to future 21st century warming a unique diatom 18o record derived from a high resolution deglacial seasonally laminated core section off the west antarctic peninsula wap is presented here by extracting and analysing single species samples from individual laminae season specific isotope records were separately generated to show changes in glacial discharge to the coastal margin during spring and summer months as well as documenting significant intra annual seasonal variability during the deglaciation with increased discharge occurring in summer relative to spring further intra seasonal variations are apparent between individual taxa linked to the environment that individual diatom species live in whilst deglacial 18o are typically lower than those for the holocene indicating glacial discharge to the core site peaked at this time inter annual and inter seasonal alternations in excess of 3 suggest significant variability in the magnitude of these inputs these deglacial variations in glacial discharge are considerably greater than those seen in the modern day water column and would have altered both the supply of oceanic warmth to the wap as well as regional marine atmospheric interactions in constraining changes in glacial discharge over the last deglaciation the records provide a future framework for investigating links between annually resolved records of glacial dynamics and ocean climate variability along the wap

surface winds across eastern and midcontinental north america during the last glacial maximum a new data model assessment abstract last glacial maximum lgm proxy evidence of surface wind direction across eastern and midcontinental north america comes primarily from loess and dune deposits and overwhelmingly suggests surface winds had a strong westerly component however the season of sediment deposition and the temporal scale of wind information preserved in these deposits remains uncertain furthermore paleoclimate model simulations over the last several decades have indicated a predominance of easterly winds across this region due to the presence of an anticyclone over the laurentide ice sheet as well as katabatic winds flowing off the ice sheet and over the adjacent land surface here we reassess model data near surface wind direction agreement using nine general circulation models participating in the lgm experiment of the third paleoclimate model intercomparison project pmip3 and a compilation of previously published paleowind directions from loess and dune deposits dating to the lgm we find the highest overall model proxy data agreement in winter december february indicating predominantly westerly winds across the region in the lgm model simulations we also find high zonal and meridional wind direction agreement in spring march may and fall september november in many models winter spring and fall also have faster mean daily near surface wind speeds in the lgm simulations relative to pre industrial control simulations thus this model data assessment suggests lgm aeolian deposition in the study region likely occurred dominantly in these three seasons at times when local conditions favorable for aeolian deflation coincided with high wind speed events models that agree best with the proxy data have strengthened aleutian and icelandic low pressure systems and a weakened laurentide high pressure system which constrains the spatial footprint of the laurentide high to the ice sheet reducing northeasterly winds near the ice sheet margin a weaker laurentide high in turn coincides with warmer surface temperatures over the ice sheet and the north atlantic the strength and location of semi permanent pressure systems were thus key controls on surface wind direction across midcontinental and eastern north america during the lgm

mineralogy as a critical factor of dust iron solubility 1 to understand the impact of dust deposition on ocean primary productivity the evaluation of dust input is not sufficient and the soluble iron supply is also needed measurements of iron in aerosols suggest a much higher solubility than in soil implying substantial atmospheric processing of chemical or physical nature here we have investigated the effect of the mineralogy on iron solubility we have measured iron solubility from some minerals commonly found in dust clay feldspar and iron hydr oxides firstly we observe a greater solubility of iron resulting from clays 4 in comparison to iron hydr oxides 1 independently of specific surface of minerals secondly by considering amount of dissolved iron and the mineralogical composition of dust our results indicate that dissolved iron fraction mainly comes from clay dissolution in contrast to that assumed in some biogeochemical models in consequence it appears that iron solubility is closely linked to the mineralogical composition of aerosol

geology and geochronology of the tiegelongnan porphyry epithermal cu au deposit tibet china formation exhumation and preservation history abstract the tiegelongnan rongna deposit is a giant porphyry epithermal cu au deposit within the duolong porphyry district in the south qiangtang terrane central western tibet china the deposit is centered on multiphase granodiorite porphyry gp intrusions intruded in jurassic sandstone phase 1 and 2 gp are associated with biotite and sericite alteration whereas gp3 and 4 occur in middle and shallow parts of the deposit affected by sericite and advanced argillic alteration alunite kaolinite dickite pyrophyllite sericite alteration is pervasive in the deep part of the deposit replacing biotite alteration and hosting porphyry stage chalcopyrite bornite pyrite molybdenite mineralization advanced argillic alterationis associated with epithermal stage high sulfidation tennantite enargite bornite and digenite mineralization overprints the sericite and biotite alteration from the shallow part of the deposit the top of the tiegelongnan hydrothermal system was weathered with a layer of supergene oxidation and enrichment zone exhumated and covered by andesite and gravel muscovite sampled from deep sericite alteration yields a 40ar 39ar age of 120 9 0 8 ma which is consistent with previously reported hydrothermal biotite 40ar 39ar age of 121 1 0 6 ma molybdenite re os ages of 121 2 0 6 and 119 0 1 4 ma and gp 1 and 2 zircon u pb ages of 121 5 1 5 120 2 1 0 ma la icp ms results and 118 7 0 9 ma sims result phase 3 gp 3 yields a ca id tims zircon u pb age of 119 9 0 2 ma which constrains the age of porphyry magmatic hydrothermal events the porphyry system was then unroofed weathered and superimposed by discrete stages of advanced argillic alteration and high sulfidation mineralization two pulses of alunite events yield 40ar 39ar ages of 116 3 0 8 ma and 111 7 1 0 ma which represent the principal epithermal alteration and mineralization ages at tiegelongnan the first alunite pulse age is consistent with younger porphyry gp4 age of 116 2 0 4 ma zircon la icp ms age weathering and exhumation of the porphyry epithermal deposit were continuing until the cover of andesite at 110 ma and by post andesite gravel the andesite was affected by a younger weak hydrothermal alteration at 108 7 0 7 ma constrained by a muscovite 40ar 39ar age another barren alunite yields a 40ar 39ar age of 100 6 2 0 ma which may represent the youngest hydrothermal event the long life span discrete hydrothermal activities from 120 to 100 ma in the tiegelongnan deposit is consistent with the long lasting tectonic magmatic events of the bangong nujiang suture zone the discrete epithermal mineralization events at tiegelongan are younger than the porphyry mineralization events which is analogous to several other epithermal deposits worldwide the 10 m y exhumation history at tiegelongan is slower than the typical and rapid erosion history of 1 2 m y porphyry deposits in low altitude tropical climates regions and during a specific abrupt uplift pulse in the andean region the slow exhumation at tiegelongnan is interpreted to be an integrated result of an arid climate environment relatively flat topography and a slow uplift condition during cretaceous in central western tibet

mineralization u pb geochronology and stable isotope geochemistry of the lower main zone of the lorraine deposit north central british columbia a replacement style alkalic cu au porphyry the lower main zone of the lorraine alkalic porphyry cu au district bc canada is hosted in an intrusive complex that comprises pre and late mineral biotite pyroxenites monzonites and syenites some of the biotite pyroxenites have interstitial sulfides which appear similar to net textured sulfides in magmatic ore deposits however the pyroxenites have undergone several stages of hydrothermal alteration main stage mineralization produced sulfide zonation patterns consisting of a bornite chalcocite or bornite chalcopyrite core grading outward to domains of chalcopyrite chalcopyrite pyrite and a peripheral domain of pyrite with minor chalcopyrite syenite in the inner bornite chalcopyrite zone typically contains abundant turbid k feldspar 70 whereas syenite marginal to the bornite chalcopyrite core contains less k feldspar 50 70 indicating an increase in k metasomatism of syenites toward the core of the deposit main stage mineralization predominantly occurs as fine grained disseminated sulfides in syenite biotite pyroxenite and fine grained k feldspar biotite rock textural analyses have shown that 1 primary magmatic diopside in contact with sulfides has corroded and actinolite altered margins suggesting alteration of primary minerals 2 scalloped relicts of biotite and diopside occur as inclusions in sulfides implying that sulfides have replaced primary minerals and 3 the deposit scale sulfide zonation patterns overprinted numerous rock types including the biotite pyroxenites that contain interstitial sulfides these results provide evidence for replacement style mineralization at lorraine where primary magmatic biotite and diopside were totally or partially replaced by sulfide minerals during main stage alteration u pb zircon dates from pre and late mineral syenite dikes show that the timing of main stage mineralization occurred between 178 8 and 176 0 ma lorraine is hosted within the quesnel island arc terrane and mineralization and magmatism at lorraine postdate accretion of the quesnel terrane to ancestral north america by approximately 7 to 10 m y the lorraine deposit represents the youngest known alkalic cu au porphyry deposit within the quesnel terrane and appears to coincide with the last gasp of alkalic magmatism within the quesnel terrane during the mesozoic

eolian dust input to the subarctic north pacific eolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high nutrient low chlorophyll status of the subarctic north pacific we map the spatial distribution of dust input using three different geochemical tracers of eolian dust 4he 232th and rare earth elements in combination with grain size distribution data from a set of core top sediments covering the entire subarctic north pacific using the suite of geochemical proxies to fingerprint different lithogenic components we deconvolve eolian dust input from other lithogenic inputs such as volcanic ash ice rafted debris riverine and hemipelagic input while the open ocean sites far away from the volcanic arcs are dominantly composed of pure eolian dust lithogenic components other than eolian dust play a more crucial role along the arcs in sites dominated by dust eolian dust input appears to be characterized by a nearly uniform grain size mode at 4 m applying the 230th normalization technique our proxies yield a consistent pattern of uniform dust fluxes of 1 2 g m2 yr across the subarctic north pacific elevated eolian dust fluxes of 2 4 g m2 yr characterize the westernmost region off japan and the southern kurile islands south of 45 n and west of 165 e along the main pathway of the westerly winds the core top based dust flux reconstruction is consistent with recent estimates based on dissolved thorium isotope concentrations in seawater from the subarctic north pacific the dust flux pattern compares well with state of the art dust model predictions in the western and central subarctic north pacific but we find that dust fluxes are higher than modeled fluxes by 0 5 1 g m2 yr in the northwest northeast and eastern subarctic north pacific our results provide an important benchmark for biogeochemical models and a robust approach for downcore studies testing dust induced iron fertilization of past changes in biological productivity in the subarctic north pacific

gravity and seismicity analyses of the el chichon volcano chiapas mexico subduction induced compressional stress lateral displacement faults probably linked to the nw extension of the polochic motagua fault system and local magma emplacement create a complex geological setting for the el chichon volcano

mapping advanced argillic alteration at cuprite nevada using imaging spectroscopy mineral maps based on airborne visible infrared imaging spectrometer aviris data were used to study late miocene advanced argillic alteration at cuprite nevada distributions of fe bearing minerals clays micas sulfates and carbonates were mapped using the tetracorder spectral shape matching system the al content of white micas increases toward altered areas and near intrusive rocks alunite composition varies from pure k to intimate mixtures of na k endmembers with subpixel occurrences of huangite the ca analogue of alunite intimately mixed na k alunite marks areas of relatively lower alteration temperature whereas co occurring na alunite and dickite may delineate relict hydrothermal conduits the presence of dickite halloysite and well ordered kaolinite but absence of disordered kaolinite is consistent with acidic conditions during hydrothermal alteration partial lichen cover on opal spectrally mimics chalcedony limiting its detection to lichen free areas pods of buddingtonite are remnants of initial quartz adularia smectite alteration thus spectral maps provide a synoptic view of the surface mineralogy and define a previously unrecognized early steam heated hydrothermal event faulting and episodes of hydrothermal alteration at cuprite were intimately linked to upper plate movements above the silver peak lone mountain detachment and growth collapse and resurgence of the nearby stonewall mountain volcanic complex between 8 and 5 ma isotopic dating indicates that hydrothermal activity started at least by 7 61 ma and ended by about 6 2 ma spectral and stable isotope data suggest that cuprite is a late miocene low sulfidation adularia sericite type hot spring deposit overprinted by late stage steam heated advanced argillic alteration formed along the margin of the stonewall mountain caldera

seafloor hydrothermal clay alteration at jade in the back arc okinawa trough mineralogy geochemistry and isotope characteristics seafloor hydrothermal activity at jade has resulted in extensive alteration of the host epiclastic sediments and pumiceous tuffs forming mica kaolins kaolinite and halloysite mg rich chlorite talc montmorillonite and a mixed layer mineral of dioctahedral chlorite and montmorillonite chl mont clay mineral assemblages show a vertical variation which reflects variable amounts of cold seawater incorporated into hot hydrothermal fluids in subsurface sediments and tuff however mixing alone cannot explain the occurrence of abundant kaolin minerals at jade the formation of kaolin minerals requires much more acidic fluid than expected from simple mixing of hydrothermal fluids and cold seawater low ph values are likely attained by oxidation of h2s either dissolved in the hydrothermal fluid or released from the fluid during decompression the fluid reaching the seafloor is discharged into cold seawater which caused precipitation of sulfides close to vents and native sulfur and barite at the margins of the vent areas halloysite barite and anhydrite show sr isotope compositions similar to marine sr indicating the derivation of marine sr directly from seawater or by the dissolution of calcareous nannoplanktons the isotopic compositions of kaolinite 18o 7 4 d 23 chl mont 18o 7 0 d 32 and mica 18o 5 4 to 9 9 d 30 to 26 suggest fluids of a heated seawater origin the o isotopic data yielded formation temperatures of 170 c for kaolinite 61 to 110 c for halloysite and 145 to 238 c for mica barite 34s values 21 0 to 22 5 are very similar to the marine sulfate value confirming that the barite formation took place due to mixing of ba bearing hydrothermal fluids and sulfate rich seawater native sulfur shows a large variation in 34s in one hand specimen probably because of rapid disequilibrium precipitation of s during fluid exhalation on the seafloor sulfur in hydrothermal fluids is usually consumed to form metal sulfides therefore abundant native sulfur at jade suggests high h2s metals ratios of the hydrothermal fluids the alteration assemblages and isotopic data of hydrothermal minerals from jade are very similar to those of kuroko type barite deposits of middle miocene age which formed from fluids of high s metals ratios at less than 200 c at jade there is only one black smoker actively discharging high temperature 320 c fluid but there are many fossil sulfide chimneys and mounds in the area the mineralogy and high au and cu in these precipitates suggest highly metalliferous hydrothermal activity in the past these activities likely resulted in discharge of hydrothermal plumes and fall outs of sulfides and sulfates on the seafloor these fall outs were incorporated in sediments far from the vent areas they are now recorded as high metal contents in sediments with no petrographic and mineralogical evidence of in situ hydrothermal activity some are high as 8 100 ppm for cu 12 500 ppm for zn 1 000 ppm for as 100 ppm for ag and 21 000 ppm for pb detrital grains of montmorillonite in such sediments are coated with fe oxyhydroxides during the suspension in seawater before settling on the seafloor the depths of such metal anomalies in sediments suggest high levels of metalliferous hydrothermal activities from 1 800 to 300 ybp

the 1982 eruptions of el chichon volcano mexico stratigraphy of pyroclastic deposits abstract following a repose period of 500 to 600 years el chichon volcano in se mexico erupted explosively during the months of march and april 1982 three major eruptions involving trachyandesite magma injected ash into the stratosphere on 29 march at 0515 gmt and on 4 april at 0139 and 1110 gmt the first major eruption generated only tephra fall which was dispersed ene in the troposphere over the yucatan peninsula and wsw in the stratosphere towards the pacific ocean the second eruption produced tephra fall and pyroelastic surges and pyroclastic flows by repeated collapse of a lithicrich eruption column the surge and flow activity devastated a roughly circular area 153 km 2 around el chichon to a distance of about 6 km from the vent nine villages within the zone were either partially or completely destroyed and loss of human life was perhaps as high as 2000 pyroclastic flows and surges were also generated during the third eruption although ash fall was the primary activity as a result of both the second and third eruptions tephra was transported ene in the troposphere and wsw in the stratosphere the total volume of material ejected during the three major eruptions 0 50 km 3 d r e is represented by tephra fall 0 37 km 3 pyroclastic surges 0 09 km 3 and pyroclastic flows and debris flows 0 04 km 3 as a result of the eruptions a new 1 km wide and 300 m deep crater was formed by the disruption and excavation of a pre existing summit dome

iron transport by mesoscale haida eddies in the gulf of alaska abstract a two year study of the iron distributions in anticyclonic mesoscale haida eddies of the eastern north pacific ocean has shown that such eddies are a major source of iron to the high nitrate low chlorophyll hnlc waters of the central gulf of alaska basin these eddies which are typically about 100 km in diameter form off the west coast of canada in winter and then track roughly westward into the open ocean therefore they carry large quantities of iron rich coastal waters into iron limited waters of the oligotrophic gyre when the eddies had first formed their dissolved iron concentrations were nearly two orders of magnitude higher than is typically observed at station papa 50 n 145 w 3 n m versus less than 0 05 n m and the total iron in the eddies surface waters 10 40 m was more than 13 n m higher than open ocean waters of the alaska gyre 14 n m versus 0 5 n m while the overall iron content of the eddies decreased rapidly during the first year after they formed the eddy we were able to track the longest still contained 1 5 2 times more iron than the surrounding waters 16 months after its formation therefore although iron concentrations in the surface mixed layers of the eddies drop to levels observed outside very rapidly within 4 months upward transport along isopycnals and upwelling due to eddy decay as well as vertical advective and diffusive transports typical of north pacific waters probably provide steady fluxes of iron into the euphotic zone from the still iron rich eddy core waters throughout the lifetime of the eddy

application of apatite u th he thermochronometry to the determination of the sense and amount of vertical fault displacement at the chuquicamata porphyry copper deposit chile chuquicamata is the world s largest porphyry copper deposit notwithstanding the fact that a portion of the orebody has been faulted off by postmineralization movement along the west fault in order to locate the missing portion of the orebody in the vertical dimension a study was designed to estimate the sense and amount of vertical displacement along this major structure by measuring the u th he and fission track ages of vertically distributed apatite samples from each of the crustal blocks fortuna and chuquicamata intrusive complexes bordering the fault apatite u th he ages range from 32 to 16 ma whereas apatite fission track ages range from 33 to 28 ma reflecting the lower closure temperature of the u th he thermochronology method approximately 75 degrees vs approximately 125 degrees c for cooling rates of approximately 10 degrees c m y the u th he ages decrease systematically with depth in both blocks however the age elevation curve for the western fortuna block is shifted vertically with respect to the eastern chuquicamata block indicating that the postmineralization denudation was significantly greater to the west the minimum vertical displacement along the west fault is estimated to be 600 or 100 m implying that the missing portion of the chuquicamata deposit should be located at a present day elevation of at least 3 600 m the new apatite ages combined with previous thermochronometric data rb sr u pb ar ar reveal rapid cooling rates approximately 100 degrees c m y for the chuquicamata deposit following emplacement at about 35 ma thereby indicating that the cu mineralization took place at a depth of less than 4 km

sulfur isotopic zonation in the cadia district southeastern australia exploration significance and implications for the genesis of alkalic porphyry gold copper deposits the alkalic porphyry gold copper deposits of the cadia district occur in the eastern lachlan fold belt of new south wales australia the district comprises four porphyry deposits ridgeway cadia quarry cadia hill and cadia east and two iron copper gold skarn deposits big cadia and little cadia almost 1 000 tonnes of contained gold and more than four million tonnes of copper have been discovered in these systems making cadia the world s largest known alkalic porphyry district in terms of contained gold porphyry gold copper ore at cadia is associated with quartz monzonite intrusive complexes and is hosted by central stockwork and sheeted quartz sulfide carbonate vein systems the cadia porphyry deposits are characterized by cores of potassic and or calc potassic alteration assemblages and peripheral halos of propylitic alteration with late stage phyllic alteration mostly restricted to fault zones hematite dusting is an important component of the propylitic alteration assemblage and has produced a distinctive reddening of feldspar minerals in the volcanic wall rocks around the mineralized centers sulfide mineralization is strongly zoned at ridgeway and cadia east with bornite rich cores surrounded by chalcopyrite rich halos and peripheral zones of pyrite mineralization the cadia hill and cadia quarry deposits have chalcopyrite rich cores and pyrite rich halos and cadia hill contains a high level bornite rich zone distinctive sulfur isotopic zonation patterns have been identified at ridgeway cadia hill and cadia east the deposit cores are characterized by low 34ssulfide values 10 to 4 consistent with sulfide precipitation from an oxidized sulfate predominant magmatic fluid at 450 to 400 c pyrite grains that occur in the propylitic alteration halos typically have 34ssulfide values near 0 there is a gradual increase in 34ssulfide values outwards from the deposit cores through the propylitic halos water rock interaction during propylitic alteration caused magmatic sulfate reduction and concomitant oxidation of ferrous iron bearing minerals resulting in enrichment of 34s in pyrite and also producing the distinctive reddened hematite rich alteration halos to the cadia deposits these results show that sulfur isotope analyses have potential applications in the exploration of alkalic porphyry style deposits with zones of depleted 34ssulfide values most prospective for high grade mineralization

asian dustfall in the st elias mountains yukon canada in april 2001 a major atmospheric dustfall event occurred in the st elias mountains yukon territory canada field samples were collected and analyzed for particle size mineralogy chemical composition and sr nd and pb isotopes dusts found above 3000 m had their source in the gobi desert region of northern china and inner mongolia and were transported to the yukon following a series of major dust storms that took place in early april dusts found below 3000 m had local yukon or mixed source s the asian dusts had a modal volume diameter of 4 m typical of far traveled mineral aerosols however larger 10 m particles were also found at 5000 m suggesting a very rapid trans pacific transport in the mid troposphere we estimate that the april 2001 event deposited from 5500 to 6335 tons of dust over an area of 21 000 km2 in the southwestern yukon most of which probably fell within a week our findings are consistent with instrumental observations and model simulations of the april 2001 event while the dust cloud was reportedly mixed with volatile pollutants from asia we found no evidence of metal pollution associated with the dustfall in the yukon our findings contribute to clarify the dynamics and the geochemical impact of asian dust long range transport events and to better estimate eolian fluxes of dustborne elements e g fe to the ocean associated with such events they may also assist in identifying past asian dust events in ice cores drilled from the st elias mountains icefields to develop a long term record of their frequency magnitude and source s

a synoptic survey of young mesoscale eddies in the eastern gulf of alaska eddies in the gulf of alaska are important sources of coastal water and associated nutrients iron and biota to the high nutrient low chlorophyll central gulf of alaska three primary eddy formation regions along the eastern boundary of the gulf have been identified from south to north haida sitka and yakutat in the spring of 2005 three eddies one of each type were sampled soon after their formation the subsurface eddy core water in all three eddies was defined by high iron concentrations and low dissolved oxygen compared with surrounding basin water the sitka and yakutat core waters also exhibited a subsurface temperature maximum mesothermal water coincident in depth with the iron maximum suggesting that eddies may play a role in the formation of temperature inversions observed throughout the gulf of alaska the data suggest different formation regions with the yakutat eddy forming in shallow shelf water with riverine input while the sitka and haida eddies appear to form in deeper water

endeavour 26 north a porphyry copper gold deposit in the late ordovician shoshonitic goonumbla volcanic complex new south wales australia endeavour 26 north is the largest of 12 pipelike porphyry cu au deposits found near parkes in central west new south wales within the late ordovician goonumbla volcanic complex the dominant volcanic rocks of the complex the goonumbla volcanics are latitic flows and volcanic breccias which are overlain by the trachytic wombin volcanics the volcanic rocks are characterized by high k 2 o and high k 2 o na 2 o ratios which are typical of the shoshonite association as well as an enrichment in large ion lithophile elements and a low concentration of high field strength elements the nelungaloo volcanics form an early ordovician nonshoshonitic volcanic substrate to the complex which initially developed in a submarine and subsequently subaerial setting the 87 sr 66 sr epsilon nd and pb isotope data indicate the magmas were derived from mantle sources the shoshonitic magmas may be products of high pressure fractionation in the subcontinental lithosphere the porphyry deposits are associated with a gravity low which is taken to reflect a subvolcanic chamber beneath the center of the complex all deposits are located within a pronounced circular feature in the aeromagnetic data that is interpreted as the margin of a collapsed caldera dioritic to monzonitic stocks which in part define the caldera rim represent a resurgent phase of magmatism the endeavour 31 stock which was part of this phase is ringed by six porphyry cu au deposits including endeavour 26 north the deposits are centered on fingerlike quartz monzonite porphyries which cut the endeavour 31 stock at depth geochemical anomalies of cu and zn in the bedrock define the size of the alteration system associated with the stock in part the distribution of the cu au deposits is controlled by the endeavour lineament in comparison to most other volcanic and intrusive rocks of the goonumbla volcanic complex the endeavour

productivity and sedimentary δ15n variability for the last 17 000 years along the northern gulf of alaska continental slope 1 biogenic opal organic carbon organic matter stable isotope and trace metal data from a well dated high resolution jumbo piston core ew0408 85jc 59 33 3 n 144 9 21 w 682 m water depth recovered from the northern gulf of alaska continental slope reveal changes in productivity and nutrient utilization over the last 17 000 years maximum values of opal concentration 10 occur during the deglacial bolling allerod b a interval and earliest holocene 11 2 to 10 8 cal ka bp moderate values 6 occur during the younger dryas 13 0 to 11 2 cal ka bp and holocene and minimum values 3 5 occur during the late glacial interval lgi when converted to opal mass accumulation rates the highest values 5000 g cm 2 kyr 1 occur during the lgi prior to 16 7 cal ka bp which points to a strong influence by lgi glacimarine sedimentation regimes similar patterns are also observed in total organic carbon and cadmium paleoproductivity proxies mid holocene peaks in the terrestrial organic matter fraction at 5 5 4 7 3 5 and 1 2 cal ka bp indicate periods of enhanced delivery of glaciomarine sediments by the alaska coastal current the b a and earliest holocene intervals are laminated and enrichments of redox sensitive elements suggest dysoxic to anoxic conditions in the water column the laminations are also associated with mildly enriched sedimentary 15n ratios indicating a link between productivity nitrogen cycle dynamics and sedimentary anoxia after applying a correction for terrestrial 15n contributions based on end member mixing models of terrestrial and marine organic matter the resulting b a marine 15n 6 3 0 4 ratios are consistent with either mild denitrification or increased nitrate utilization these findings can be explained by increased micronutrient fe availability during episodes of rapid rising sea level that released iron from the previously subaerial coastal plain iron input from enhanced terrestrial runoff and or the intermittent presence of seasonal sea ice resulting from altered ocean atmospheric circulation during the b a in the gulf of alaska

geology mineralization alteration and structural evolution of the el teniente porphyry cu mo deposit sir the el teniente cu mo deposit in central chile is an extraordinary accumulation of cu mo ore fig 1 and we welcome the opportunity provided by skewes and stern 2007 to discuss and clarify several important issues regarding its classification and interpretation and to address several incorrect assertions that they make regarding our manuscript cannell et al 2005 we have interpreted el teniente to be a typical porphyry deposit in terms of its alteration assemblages vein and breccia styles and spatial and temporal relationships between cu mo mineralization and felsic porphyries skewes and stern 2007 dispute our claims that mineralization occurred primarily in veins and was related to felsic intrusive activity they also take issue with our interpretations of the various geochronological datasets from el teniente and our classification of el teniente as a porphyry cu mo deposit we address each of these in turn below in order to facilitate the following discussion table 1 correlates the geologic nomenclature of skewes and stern 2007 with that of cannell et al 2005 figures 1 and 2 illustrate the location of the main geologic units on underground mine level 6 at el teniente also shown on figure 1 are the approximate locations of the hypogene sulfide mineral zones figure 2 shows the block model of mo grades in the mine for more details of geologic relationships at el teniente refer to figure 4 of cannell et al 2005 and figures 4 and 5 of skewes et al 2002 although the dacite porphyry dike is shown as a single unit on figure 1 note that rojas 2002 2003 mapped multiple phases within this composite intrusive body skewes and stern 2007 criticized our use of what they assert to be an outdated map of hypogene mineralization

volcan el chichon mexico pre 1982 s rich eruptive activity abstract mapping and sampling of the interior of el chichon volcano was made possible by the exposures of the 1982 explosion crater the 1 km diameter 200 m deep crater exposes rocks produced during several eruptive episodes volcanic domes talus breccias plinian airfall deposits and pyroclastic flow deposits of compositionally similar alkalic hornblende trachyandesites with phenocrysts of anhydrite all of the rocks except those leached of anhydrite have extremely high s contents el chichon consists of a volcanic dome complex airfall debris and pyroclastic outflow sheets prior to 1982 its last major activity was about 650 100 yr b p

the iron isotopic composition of subglacial streams draining the greenland ice sheet abstract in this study we present the first measurements of iron fe stable isotopic composition 56 fe of subglacial streams draining the greenland ice sheet gis we measure the 56 fe values 56 fe 56 fe 54 fe sample 56 fe 54 fe standard 1 10 3 of both dissolved and suspended sediment fe in subglacial outflows from five distinct land terminating glaciers suspended sediments have 56 fe values that lie within the crustal array 56 fe 0 in contrast the 56 fe values of dissolved fe in subglacial outflows are consistently less than 0 reaching a minimum of 2 1 in the outflow from the russell glacier the 56 fe values of dissolved fe vary geographically and on daily time scales major element chemistry and mineral saturation state modeling suggest that incongruent silicate weathering and sulfide oxidation are the likely drivers of subglacial stream fe chemistry and that the extent of chemical weathering influences the 56 fe of dissolved fe the largest difference in 56 fe between dissolved and suspended load is 2 1 and occurs in the subglacial system from the russell glacier southwest gis major element chemistry indicates this outflow to be the least chemically weathered while more mature subglacial systems i e that exhibit greater extents of subglacial weathering have dissolved loads with 56 fe that are indistinguishable from suspended sediments 56 fe suspended dissolved 0 ultimately the dissolved fe generated in some subglacial systems from the gis is a previously unrecognized source of isotopically light fe into the hydrosphere the data illustrate that the dissolved fe supplied by subglacial weathering can have variable 56 fe values depending on the degree of chemical weathering thus fe isotopes have potential as a proxy for subglacial chemical weathering intensity or mode finally based on our regional fe concentration measurements from each glacial outflow we estimate a flux weighted continental scale dissolved iron export of 2 1 gg fe yr 1 to the coastal ocean which is within the range of previous estimates

geology and isotope geochemistry of the wainaulo cu au porphyry deposit namosi district fiji the late miocene calc alkalic wainaulo cu au porphyry deposit of the namosi district fiji hosts distinct styles of alteration and mineralization that overlapped to produce a substantial porphyry cu au resource the early stages produced medium grade cu low grade au and concentric calc potassic to propylitic alteration that is zoned around the early stage diorite intrusions discrete zones of high grade cu and au and calc sodic alteration were then superimposed during the intrusion of the main stage quartz diorites and the formation of quartz sulfide and epidote sulfide veins as the magmatic hydrothermal system waned lower cu and au grades with a weaker intensity of calc sodic alteration and lower density of veins were produced coincident with emplacement of subsequent quartz diorite intrusions late stage anhydrite pyrite veins and chlorite illite alteration overprinted the quartz diorite intrusive complex the final hydrothermal event consisted of argillic alteration that was concentrated in and around steeply dipping ene trending shears these structures appear to have controlled the emplacement of the quartz diorite complex and distribution of high grade cu au mineralization suggesting they were active during the pre and synmineralization stages stable and radiogenic isotopic data provide evidence for direct seawater contributions to the magmatichydrothermal system measured 34ssulfide 5 0 to 3 8 and 34ssulfate 9 0 16 8 values are consistent with a predominantly magmatic source whereas an elevated bulk sulfur composition 6 7 suggests mixing with an isotopically heavy fluid e g seawater estimates of dfluid derived from epidote 9 1 to 11 3 and 18ofluid from epidote and anhydrite 0 2 to 4 7 approach that of vienna standard mean ocean water and the initial sr isotope ratios of epidote 0 70364 0 70378 suggest a component of seawater sr ranging from 3 2 to 5 8 these results are consistent with the inferred submarine paleogeographic setting and may explain the abundance of albite and epidote rich alteration assemblages at wainaulo

contributions from glacially derived sediment to the global iron oxyhydr oxide cycle implications for iron delivery to the oceans estimates of glacial sediment delivery to the oceans have been derived from fluxes of meltwater runoff and iceberg calving and their sediment loads the combined total 2900 tg yr 1 of the suspended sediment load in meltwaters 1400 tg yr 1 and the sediment delivered by icebergs 1500 tg yr 1 are within the range of earlier estimates high resolution microscopic observations show that suspended sediments from glacial meltwaters supraglacial and proglacial sediments and sediments in basal ice from arctic alpine and antarctic locations all contain iron oxyhydr oxide nanoparticles which are poorly crystalline typically 5 nm in diameter and which occur as single grains or aggregates that may be isolated or attached to sediment grains nanoparticles with these characteristics are potentially bioavailable a global model comparing the sources and sinks of iron present as oxyhydr oxides indicates that sediment delivered by icebergs is a significant source of iron to the open oceans beyond the continental shelf iceberg delivery of sediment containing iron as oxyhydr oxides during the last glacial maximum may have been sufficient to fertilise the increase in oceanic productivity required to drawdown atmospheric co2 to the levels observed in ice cores

reos dating of molybdenites from ore deposits in japan implication for the closure temperature of the reos system for molybdenite and the cooling history of molybdenum ore deposits abstract rhenium and osmium abundances were determined on molybdenites from eighteen ore deposits in japan fifteen vein type a skarn type a greisen type and a pegmatite type deposit re os ages obtained for molybdenites from northeastern central and southwestern japan are 100 130 ma 50 75 ma and ca 10 ma respectively reflecting the ages of regional igneous activities in individual areas for vein type ore deposits re os ages for molybdenites agree with rb sr whole rock ages of host granitoids while they are 3 12 ma older than k ar mineral ages of the host rocks on the other hand re os ages of molybdenites from skarn pegmatite and greisen type ore deposits agree with k ar ages of the host rocks the comparison of re os ages for molybdenites with rb sr and k ar ages of host rocks in vein type deposits suggests that re os closure temperature for vein molybdenite is close to whole rock rb sr closure temperature for host granitic rocks i e roughly estimated to be around 500 c and higher than k ar closure temperature for host granodiorites i e 230 370 c if the thermal history of vein molybdenites is essentially equivalent to that of host rocks one possible explanation for age discrepancies of 3 12 ma between re os ages for molybdenites and k ar ages for the wall rocks observed in vein type molybdenum deposits is that later thermal events after formation of molybdenum ores may reset k ar ages hydrothermal alteration might have occurred in such a temperature condition as to disturb k ar mineral systems in wall rocks and made them younger but not the re os system in molybdenite the other explanation might be that the age discrepancies correspond to a cooling interval from ca 500 to 300 c of host granitoid on the other hand the agreement of re os ages of molybdenites and k ar ages of host rocks in skarn pegmatite and greisen type deposits in this study indicates no later disturbance for k ar system in the wall rock or the rapid cooling of the ore and wall rocks after the formation of molybdenite deposits

isotope geochemistry of the northeast zone mount polley alkalic cu au ag porphyry deposit british columbia a case for carbonate assimilation mount polley is a late triassic 205 ma alkalic porphyry cu au ag deposit 226 3 thousand tonnes t cu 21 5 t au and 65 1 t ag hosted by silica undersaturated to silica saturated monzonitic intrusions of the mount polley complex located in british columbia canada the northeast ore zone at mount polley is hosted by magmatic hydrothermal breccia copper and precious metals occur in sulfide minerals primarily as coarse to fine grained breccia cement local wall rocks include equigranular to porphyritic diorite monzodiorite and monzonite alteration breccia cement and veins of the northeast ore zone formed in five paragenetic stages prebreccia stage 1 brecciation and main stage mineralization stage 2 late stage mineralization stage 3 unmineralized postbreccia dikes and veins stage 4 and epithermal style veins stage 5 intense pervasive k and fe metasomatism calcite and calc silicate alteration occurred prior to brecciation caused by the intrusion of megacrystic k feldspar phyric monzonite stage 2 fluids were silica undersaturated high temperature 350 c co2 enriched and of near neutral to alkaline ph potassic sodic and calc potassic assemblages precipitated with mineralization during stage 2 with moderate temperatures at the deposit periphery and in stages 3 and 4 evidence for more acidic and lower temperature conditions is preserved in stage 5 veins the 34ssulfide isotope compositions of stages 2 and 3 chalcopyrite pyrite and bornite range from 7 1 to 1 4 sulfur isotope compositions of anhydrite and gypsum are mostly between 6 2 and 9 8 these values together with the presence of hematite are consistent with deposition from an oxidized sulfate dominant high temperature magmatic hydrothermal fluid limited sulfur isotope geothermometry indicates that cu sulfides precipitated at temperatures from 480 to 250 c hydrothermal calcite occurs in all paragenetic stages at mount polley calcite 13c values range from 0 2 to 10 5 and 18o values from 4 0 to 20 9 the enriched c o isotope values are not consistent with simple precipitation from an entirely magmatic source of hydrothermal fluid interaction of the fluid and or magma with limestone is considered a likely process to explain the c and o isotope signature lead isotope data suggest mixing of mantle and crustal sources during mineralization main stage chalcopyrite and pyrite as well as late stage galena have 206 204pb values of 18 77 to 18 92 207 204pb of 15 56 to 15 59 and 208 204pb of 38 22 to 38 32 strontium isotope data 0 70331 0 70371 provide evidence of a strongly depleted mantle source of sr with minor crustal input epsilon nd values for main stage apatite range between 5 9 and 6 5 also indicating a depleted mantle source stage 5 carbonate 206 204pb values of 18 96 to 19 04 207 204pb of 15 57 to 15 59 and 208 204pb of 38 26 to 38 36 suggest superposition of an epithermal system onto the northeast ore zone potentially as late as 100 m y after breccia formation the data presented are consistent with the hypothesis that the silica undersaturated alkalic mount polley complex formed due to carbonate assimilation prior to mineralization this process can explain the 13c 18o isotope data calcite precipitation concurrent with cu au mineralization and silica undersaturation of the magma the co2 released during assimilation of carbonate also could have promoted magmatic hydrothermal brecciation silica undersaturated alkalic porphyry systems may preferentially form in arc terranes built on a carbonate bearing substrate

seismicity and tectonics of the subducted cocos plate we have examined teleseismic earthquake locations reported by the international seismological centre isc for the middle america region and selected 220 as the most reliable these hypocenters and other data are used to delineate the deep structure of the subducted cocos plate the results indicate that the subducted plate consists of three major segments segment i extends from the panama fracture zone to the nicoya peninsula the structure of this segment is poorly defined segment ii is the largest and best defined segment this segment consists of two parts iia and iib part iia extends from the nicoya peninsula to western guatemala and is very well defined and continuous in structure its strike follows the curvature of the trench and dips at about 60 part iib extends from western guatemala to orizaba mexico the dip of this part of the segment decreases slightly toward the northwest and its strike is more northward than that of the trench segment iii extends from orizaba to the rivera fracture zone and is not well defined due to a lack of earthquake activity beneath about 100 km its orientation differs markedly from segment ii and strikes somewhat more westward than the trench between parts iia and iib of segment ii the subducted plate seems to be continuous bending smoothly to accommodate the change in geometry local network data from costa rica suggest there may be a tear between segments i and ii between segments ii and iii there is a gap in the hypocenters which makes it difficult to define the boundary the change in geometry between these two segments indicates that there may be a tear and two strike slip focal mechanisms in the region support this conclusion we find no convincing evidence supporting the existence of segments smaller than the three described above if there is smaller scale segmentation in the shallow part of the subducting plate the plate must still maintain enough continuity to appear continuous at greater depths there is no evidence for any major tear in the subducted plate associated directly with either the tehuantepec ridge or the orozco fracture zone the shallow subduction at the northwestern end of segment ii may be related to the bouyancy of the tehuantepec ridge the cocos ridge is probably directly responsible for the change in geometry between segments i and ii and may even be slowing or stopping subduction in segment i the structure of the subducted plate in segment ii and the changes in the character of volcanism along the arc can be related to the relative motion of the north american and caribbean plates the present geometry of part iib of segment ii is more consistent with the probable configuration of the trench about 7 ma ago than with the present configuration indicating that the north american plate is overriding the subduction zone appendices 2 3 and 4 are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b84 009 2 50

atmospheric deposition of glacial iron in the gulf of alaska impacted by the position of the aleutian low our understanding of glacial flour dust storm delivery of iron to the gulf of alaska goa is limited here we interpret concurrent time series satellite meteorological and aerosol geochemical data from the goa to examine how interannual variability in regional weather patterns impacts offshore aerosol glacial fe deposition in 2011 when a northerly aleutian low al was persistent during fall dust emission was suppressed and highly intermittent due to prevalent wet conditions low winds and a deep early season snowpack conversely in 2012 frequent and prolonged fall dust storms and high offshore glacial fe transport were driven by dry conditions and strong offshore winds generated by persistent strong high pressure over the alaskan interior and bering sea and a southerly al twenty five fold interannual variability in regional offshore glacial aerosol fe deposition indicates that glacial dust s impact on goa nutrient budgets is highly dynamic and particularly sensitive to regional climate forcing

iron flux induced by haida eddies in the gulf of alaska 1 mesoscale anticyclonic haida eddies are proposed to deliver a substantial amount of iron into the gulf of alaska goa central gyre where surface waters experience high nitrate low chlorophyll conditions in this study we calculate an averaged upwelling flux of dissolved iron into the euphotic zone 100 m of 1 17 mol m 2 d 1 based on observed iron profiles and modeled eddy dynamics and resultant vertical velocities this estimated eddy derived iron supply rate is comparable with new estimates of pulsed iron fertilization rates from rare volcanic ash deposition events despite the relatively small area affected by haida eddies they are estimated to contribute about 4 6 106 moles of dissolved iron yearly to the goa which is equivalent to the annual atmospheric dust deposition haida eddies therefore represent a major iron source that should strongly influence the regional biological productivity and carbon budget of the goa

ultra high resolution snapshots of three multi decadal periods in an antarctic ice core we offer the first sub seasonal view of glacial age archives from the siple dome a sdma ice core using the ultra high resolution capabilities of a newly developed laser ablation inductively coupled plasma mass spectrometry la icp ms 121 m sampling resolution system capable of conducting multi element glaciochemical analysis our ultra high resolution data demonstrates that 1 the sdma ice core record can be annually dated based on seasonality in chemical inputs at a depth not previously possible using previous glaciochemical sampling methods 2 winter accumulation at the sd site was greater than summer accumulation during the three late glacial periods selected 15 3 17 3 21 4 ka ago in this study and 3 resulting annual layer thicknesses results show greater variability than the current sd ice core depth age model brook and others 2005 possibly due to depositional effects such as wind scouring and or decadal variability in snow accumulation that is not captured by the resolution of the current depth age model

the ridgeway gold copper deposit a high grade alkalic porphyry deposit in the lachlan fold belt new south wales australia ridgeway is a high grade gold copper porphyry deposit 54 mt at 2 5 g t au and 0 77 cu related to an alkalic intrusive complex of monzonitic composition the deposit occurs within the cadia district of new south wales australia which consists of a cluster of four late ordovician gold copper porphyry deposits and two iron copper gold skarn deposits with a combined gold resource in excess of 574 metric tonnes t the deposits lie on a 7 km long northwest oriented corridor of alteration and mineralization transverse to the axis of the postulated volcanic arc alteration and mineralization at ridgeway are zoned around a vertically attenuated intrusive complex of monzodioritic to quartz monzonitic composition distinct styles of veining and alteration are related to different intrusive phases of the monzonite complex with the intensity of alteration and grade of mineralization decreasing from early to late mineral intrusions early mineral intrusions are associated with intense actinolite magnetite biotite calc potassic alteration and up to four stages of high grade quartz magnetite sulfide veining bornite is the most abundant sulfide formed during early stage alteration and correlates well with gold moderate to weak intensity orthoclase biotite plus or minus magnetite potassic alteration accompanies the inter and late mineral intrusions this alteration being associated with chalcopyrite and pyrite rich quartz orthoclase veins propylitic and sodic albite pyrite alteration assemblages are peripheral to and locally overprint the potassic alteration phyllic alteration is restricted to the margins of late stage faults the fluid inclusion assemblage comprises one and two salt bearing brine inclusions in addition to aqueous liquid vapor inclusions of low to moderate salinity no low density vapor rich inclusions are present indicating that the fluids from which the quartz veins precipitated did not enter the liquid vapor field of the h2o nacl system the brine inclusions undergo final homogenization to liquid via halite dissolution this phenomenon in addition to the absence of low density vapor inclusions suggests that the mineralizing fluids at ridgeway were nonboiling hypersaline brines that exsolved directly from the crystallizing magma the presence of mineralized aplitic vein dikes and comb quartz layering are interpreted to indicate that the early and transitional stages of mineralization at ridgeway formed at the transition between magmatic and hydrothermal conditions

primary igneous anhydrite progress since its recognition in the 1982 el chichon trachyandesite abstract primary igneous anhydrite was first identified in 1982 el chichon pumices analysis of the sulfur budget for the eruption provided compelling evidence that the pre eruptive magma contained a significant gas phase at 7 km depth in order to account for the excess gas release of 5 9 million tons of so2 to the stratosphere by the eruption primary igneous anhydrite and a larger excess gas release of 20 million tons of so2 were noted for the significantly larger eruption of mount pinatubo in 1991 for which a separate gas phase at 7 9 km depth was also required by the sulfur budget pumices from both eruptions have mineral assemblages dominated by plagioclase and hornblende with minor biotite and show evidence for co nucleation and mutual inclusions of anhydrite and apatite both magmas were also very water rich and highly oxidized with oxygen fugacities 1 log unit above the synthetic ni nio buffer furthering the similarities between these two eruptions ion microprobe analyses of sulfur isotopic compositions of anhydrites in pumices from el chichon and mount pinatubo both showed that individual crystals are isotopically homogeneous but inter crystalline variations in 34s are well beyond analytical error this study reviews the history of thought regarding primary igneous anhydrite ten volcanic and plutonic analogues to the el chichon and mount pinatubo magmas are discussed all were similarly water rich and highly oxidized magmas hornblende is the dominant mafic phenocryst in all but one plutonic example in that case so much early anhydrite precipitated that no calcium remained to form hornblende biotite is very abundant in that exceptional plutonic case and is present in six of the other examples with primary igneous anhydrite sphene is known as an indicator mineral of high magmatic oxygen fugacity it was present in the 1982 el chichon pumices and in 6 of the other anhydrite bearing samples hornblende and biotite phenocrysts are also characteristic of the intermediate to felsic plutonic rocks that typically host porphyry cu deposits such magmas are also known to be water rich and highly oxidized a close spatial and petrogenetic connection exists between magmas with primary igneous anhydrite and magmatic hydrothermal ore deposits

exploration tools for linked porphyry and epithermal deposits example from the mankayan intrusion centered cu au district luzon philippines the mankayan mineral district of northern luzon philippines hosts several significant ore deposits and prospects of various types within an area of similar to 25 km 2 including the far southeast porphyry cu au deposit the lepanto high sulfidation epithermal cu au deposit the victoria intermediate sulfidation epithermal au ag vein deposit the teresa epithermal au ag vein deposit the guinaoang porphyry cu au deposit and the buaki old palidan porphyry cu au prospects all having formed in a period of about 2 m y from similar to 3 ma the geologic units include 1 a basement composed of late cretaceous to middle miocene metavolcanic rocks volcaniclastic rocks 2 the miocene 12 to 13 ma tonalitic bagon intrusive complex 3 the pliocene similar to 2 2 to 1 8 ma imbanguila dacite porphyry and pyroclastic rocks and 4 postmineralization cover rocks including die similar to 1 2 to 1 0 ma bato dacite porphyry and pyroclastic rocks and the similar to 0 02 ma lapangan tuff extensive advanced argillic alteration crops out for similar to 7 kin along the inconformity between the basement rocks and the imbanguila dacite formation consists of quartz alunite pyrophyllite or diaspore with local zones of silicic alteration and a halo of dickite kaolinite the alteration and its subhorizontal geometry indicate that it is a lithocap or coalesced lithocaps the northwest striking portion is similar to 4 km long and hosts the lepanto enargite au ore deposit also controlled by the lepanto fault the lepanto epithermal deposit is related to the underlying far southeast porphyry the quartz alunite alteration halo of lepanto is contemporaneous with the similar to 1 4 ma potassic alteration of the porphyry there are also silicic advanced argillic alteration patches similar to 600 m above the far southeast orebody at the present surface these are interpreted to be perched alteration there is no systematic mineralogical or textural zoning in the lepanto lithocap that indicates direction to the intrusive source most surface samples of the lithocap contain less than 50 ppb au despite many being less than a few hundred meters from underground cu au ore this study found that several characteristics of the lepanto lithocap change systematically with distance from the causative intrusion the alunite absorption peak at similar to 1 480 nm in the short wavelength infrared swir spectrum shifts to higher wavelengths where the sample is closer to the intrusive center due to higher na and lower k content in the alunite published experimental studies indicate that high na na k is related to higher formation temperature high ca alunite including huangite also occurs at locations proximal to the intrusive center alunite mineral composition analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms indicates that the pb content decreases toward the intrusive center whereas sr la sr ph and la pb increase markedly whole rock compositions using only nonmineralized taken as cu similar to 350 m above the upper extent of the veins an airborne geophysics survey indicates that the far southeast orebody is associated with a wide zone of demagnetization due to extensive magnetite destructive phyllic alteration such low magnetic anomalies on the margin of a large lithocap elsewhere may deserve attention the directional indicators and mineralization signatures found in this study have the potential to indicate direction to the intrusive center during exploration of similar porphyry epithermal districts

episodic deposition of illinois valley peoria silt in association with lake michigan lobe fluctuations during the last glacial maximum the chronology and cause of millennial depositional oscillations within last glacial loess of the central lowlands of the united states are uncertain here we present a new age model that indicates the peoria silt along the illinois river valley accumulated episodically from 28 500 to 16 000 cal yr bp as the lake michigan lobe margin fluctuated within northeastern illinois the age model indicates accelerated loess deposition coincident with regional glacial advances during the local last glacial maximum a weakly developed paleosol the jules geosol represents a period of significantly slower deposition from 23 700 to 22 000 cal yr bp a gastropod assemblage based reconstruction of mean july temperature shows temperatures 6 10 c cooler than modern during peoria silt deposition stable oxygen and carbon isotope values 18 o and 13 c of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the jules geosol suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors however a decrease in 18 o values occurred between 26 000 and 24 000 cal yr bp synchronous with the lake michigan lobe s southernmost advance this 18 o decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period

simulation of the frictional stick slip instability a lattice solid model capable of simulating rock friction fracture and the associated seismic wave radiation is developed in order to study the origin of the stick slip instability that is responsible for earthquakes the model consists of a lattice of interacting particles in order to study the effect of surface roughness on the frictional behavior of elastic blocks being rubbed past one another the simplest possible particle interactions were specified corresponding to radially dependent elastic brittle bonds the model material can therefore be considered as round elastic grains with negligible friction between their surfaces although breaking of the bonds can occur fracturing energy is not considered stick slip behavior is observed in a numerical experiment involving 2d blocks with rough surfaces being rubbed past one another at a constant rate slip is initiated when two interlocking asperities push past one another exciting a slip pulse the pulse fronts propagate with speeds ranging from the rayleigh wave speed up to a value between the shear and compressional wave speeds in agreement with field observations and theoretical analyses of mode ii rupture slip rates are comparable to seismic rates in the initial part of one slip pulse whose front propagates at the rayleigh wave speed however the slip rate is an order of magnitude higher in the main part of pulses possibly because of the simplified model description that neglected intrinsic friction and the high rates at which the blocks were driven or alternatively uncertainty in slip rates obtained through the inversion of seismograms particle trajectories during slip have motions normal to the fault indicating that the fault surfaces jump apart during the passage of the slip pulse normal motion is expected as the asperities on the two surfaces ride over one another the form of the particle trajectories is similar to those observed in stick slip experiments involving foam rubber blocks bruneet al 1993 additional work is required to determine whether the slip pulses relate to the interface waves proposed by brune and co workers to explain the heat flow paradox and whether they are capable of inducing a significant local reduction in the normal stress it is hoped that the progressive development of the lattice solid model will lead to realistic simulations of earthquake dynamics and ultimately provide clues as to whether or not earthquakes are predictable

diurnal dynamics of minor and trace elements in stream water draining dongkemadi glacier on the tibetan plateau and its environmental implications abstract global warming has resulted in rapid glacier retreat on the tibetan plateau tp and the impacts of glacier melting on downstream ecosystems remain largely unknown minor and trace elements in stream water draining dongkemadi glacier dg were examined during the ablation season of 2013 dominant ions and elements are hco 3 ca 2 fe and sr water chemistry is controlled by the weathering of calcite oxidation of pyrite and dissolution of evaporites correlations suggests the hydrological e g meltwater generation and routing water residence time and physicochemical e g sorption precipitation oversaturation controls on species concentrations the distribution of metals is featured by the mixture of soluble metal and non metal ligand complexes and free monovalent and divalent ions downstream increased concentrations and or fluxes of some metals and metalloid e g cr cu and as suggest potential environmental impacts discharge normalized cation denudation rate 372 meq m 3 in the dg basin is larger than those from alpine and polar glaciers suggesting a stronger weathering of carbonate with greater abundance on the tp in comparison to other mountain and polar glacial catchments the maximum fe concentration exceeds the usepa guideline and al zn and pb are close to or of the same order of magnitude as liminal values this implies that the tp may face a challenge of ecosystem health and environmental issue in a warming climate

geochronology of the porphyry copper deposits and related mineralization of mexico k ar dating demonstrates that all but eight of 41 dated porphyry copper and related ore deposits of mexico were emplaced during the laramide episode of maximum plate convergence one older deposit is related to the jurassic volcanic arc of western north america one is pre laramide cretaceous four are oligocene in age and two late cenozoic deposits are within the modern trans mexican chiapenecan volcanic arc thirty three of the deposits lie within a long narrow belt that continues into arizona and new mexico and widens from 100 km to over 300 km in the region of maximum extension in the southern basin and range province eighty five percent of the deposits were emplaced during the eastward transgression of the cordilleran volcanic arc in middle cretaceous through eocene time the occurrence of the porphyry copper deposits of mexico appears to be independent of the terrane intruded and the copper content of the wall rocks where the wall rocks predate the volcanic arc which is syngenetic with the porphy

vertical and lateral variation of mineralogy and chemistry in the early jurassic mt milligan alkalic porphyry au cu deposit british columbia canada the moderately tilted and faulted early jurassic mt milligan au cu deposit provides a cross section view of the hydrothermal alteration sulfide mineralogy and geochemical zonation of a silica saturated alkalic porphyry system over a vertical distance approaching 700 m magnetite bearing potassic alteration and associated au cu form a core to the system in the central monzonitic stock and adjacent basaltic trachyandesite host rock lateral to the high temperature core are sodic calcic and inner and outer propylitic alteration assemblages chalcopyrite dominates the high temperature potassic core whereas pyrite is the predominant sulfide within and outboard from the sodic calcic assemblage a funnel shaped remnant of carbonate rich phyllic alteration of the host supracrustal rocks in the fault bounded 66 zone represents the upper auriferous alteration in the alkalic porphyry au cu system alteration mineral assemblage s isotope ranging from 34s 5 relative to canon diablo troilite in the core to 34s 0 5 in the periphery and limited fluid inclusion data suggest mineralization at the au cu alkalic porphyry system was derived from an oxidized co2 bearing magmatic fluid that rose upward along the margins and through the magnetite breccia stock laterally from the au cu mineralized potassic core magmatic fluid evolved through water rock interaction mixing with an external fluid as shown by a shift in calculated 87sr 86sr for alteration minerals to values higher than magmatic values declining temperature or some combination of all variations in trace element concentrations of epidote v mn sb zr as and bi and pyrite mn as zr pb and bi across the deposit show a local high degree of variability but general increases or decreases in overall trends in their median values are inferred to reflect the hydrothermal evolution of the system pistachite ratios of epidote show an outward decrease in ferric iron as recorded in the pistachite ratio changing from ps36 to ps25 suggesting less oxidizing conditions on the system periphery additionally light rare earth elements in epidote fractionate toward the core of the deposit and the height of positive eu anomalies also appears to have a similar spatial trend in pyrite there is a general increase in trace element concentration toward the epidote pyrite rich outer propylitic assemblage forming the system periphery alteration mineralogy and trace element signatures indicate the southeastern portion of the deposit the 66 zone is a down dropped segment from higher in the paleohydrothermal system s isotope signatures of sulfides within and surrounding the stratiform upper trachyte unit in the 66 zone indicate structural channeling of oxidizing fluids that likely were the distal and cooler expression of more oxidizing magmatic derived hydrothermal fluids responsible for potassic alteration and au cu in the subjacent magnetite breccia zone the main orebody

constraints on magma degassing beneath the far southeast porphyry cu au deposit philippines k silicate alteration in the far southeast fse porphyry cu au introduction deposit formed at 1 4 ma concentric to dikes of quartz diorite magmas become saturated with volatile components as porphyry at 2 km paleodepth the hydrothermal system consisted they ascend in the crust and either erupt or crystallize of magmatic hypersaline liquid and vapor at 550 c and 50 at depth saturated magmas that remain at depth exsolve mpa lithostatic pressure advanced argillic alteration formed at an aqueous fluid that forms a hydrothermal system on the same time over the deposit at 1 km paleodepth from acidic separation from the magma chamber burnham 1979 condensates of the vapor at 1 3 ma k silicate alteration was although part of the exsolved fluid a low density vapor overprinted by 350 c magmatic liquid 5 wt nacl equiv may discharge to the surface from passively degassing at hydrostatic pressure sericite alteration and much of the cu au volcanoes hedenquist 1995 part will remain at depth mineralization formed at this later stage evolution of the magmatic and this dense residual magmatic liquid may be asfluid composition was simulated with a magma chamber cryssociated with hydrothermal mineralization in the portallization model homogeneous crystallization during early stage phyry ore environment hedenquist lowenstern convection is assumed whereas at 50 vol crystals the chamber 1994 becomes stagnant and crystallizes from rim to core over a narrow in this paper we use evidence from a porphyry ore crystallization interval the model calculation based on a magma deposit in the philippines to determine the composition chamber with 2 km thickness at 6 km depth 150 mpa and of the fluid that exsolved from the deeper parent magma 800 c saturated melt composition at 30 vol crystals 5 the evolving composition of the magmatic fluid at the wt h2o 0 2 wt cl and dd of 40 can reproduce the depth of the ore body can then be used to place constraints chemical and isotopic compositions of the early and late magmatic on the nature of the evolved magma chamber far below fluids the most critical factor controlling the compositional evolution the porphyry ore body this approach differs from that of the model hydrothermal system is the transition from convective of other studies where a portion of the parent magma to stagnant magma chamber crystallization there is also a sharp chamber is available to study directly e g at yerington decrease in the rate of fluid exsolution associated with this transition nevada dilles 1987 which can account for the thermal collapse of the fse porphyry the far southeast fse porphyry cu au deposit system from k silicate to sericite alteration and overlying lepanto epithermal cu au ore body are

petrology of philippine geothermal systems and the application of alteration mineralogy to their assessment abstract philippine geothermal systems occur in the vicinity of large holocene calc alkaline volcanic complexes wells drilled in these areas encountered multiple intrusions the latest dikes are the subsurface manifestations of the youngest heat source commonly at least two hydrothermal regimes are juxtaposed in a single area with the latest being in equilibrium with the present temperature and chemical regime alteration by neutral ph water is pervasive and abundant a contact metamorphic aureole also occurs near intrusives alteration due to acid sulfate fluids is generally confined to permeable structures neutral ph alteration is divided into four zones on the basis of key clay minerals and two subzones are defined by calc silicates these are the smectite ambient to 180 c transition 180 230 c illite 230 320 c and biotite 270 340 c zones subzones are defined by epidote 250 340 c and amphibole 280 340 c the four main zones of acid alteration are kaolinite ambient to 120 c dickite kaolinite 120 200 c dickite pyrophyllite 200 250 c and pyrophyllite illite 230 320 c where relict high temperature alteration reaches the surface the area being drilled is usually the outflow zone of the present system these hydrothermal mineral assemblages are used 1 as geothermometers 2 to assist in determining the depth at which the production casing will be set during drilling 3 to estimate fluid ph and other chemical parameters 4 to predict possible corrosion and scaling tendencies of the fluids 5 as a measure of permeability and possible cold water influx into wells 6 as a guide to field hydrology and 7 to estimate roughly the thickness of the eroded overburden

genesis of the late triassic southwest zone breccia hosted alkalic porphyry cu au deposit galore creek british columbia canada the late triassic southwest zone alkalic porphyry cu au deposit in the galore creek district northwestern british columbia is hosted in hydrothermally cemented breccias that overprinted older matrix rich breccia and megacrystic orthoclase phyric syenite and monzonite dikes synmineralization cemented breccias and biotite phyric monzodiorite dikes are localized at the contact of the matrix rich breccia and host syenite and monzonite dikes as well as in crosscutting faults regional shortening tilted the southwest zone deposit so that the cemented breccias now dip 50 to 60 southwest four paragenetic stages formed the deposit a premineralization stage 1 consists of the emplacement of coherent syenite and monzonite host rocks that are cut by a matrix rich breccia the synmineralization stage 2 produced potassic altered rocks and phlogopite magnetite k feldspar cemented breccia and veins and most of the cu fe sulfides a halo of stage 2 diopside magnetite grandite phlogopite calcic potassic veins and altered rocks formed around the potassic domains and cu ore zones alteration during stage 2 probably formed at temperatures of about 500 to 425 c from oxidized saline magmatic hydrothermal fluids contemporaneous high aca2 ah 2 conditions peripheral to the potassic domains are required to form the marginal calcic potassic and calcic assemblages the potassic and calcic potassic alteration domains were overprinted by propylitic and calcic alteration assemblages due to the retrograde influx of an admixture of cooler magmatic and nonmagmatic fluids sphene from a stage 2 calcic potassic vein yielded a 202 8 2 1 ma age u pb shrimp rg that is interpreted to reflect the approximate time of hydrothermal alteration late mineralization stage 3 alteration overprinted the cemented breccias and comprises sericite anhydrite sericitic grandite calcic and chlorite epidote carbonate pyrite propylitic assemblages localized late mineralization and cu poor stage 4 k feldspar fe carbonate specularite carbonate potassic and quartz pyrite veins quartz veins cut stage 2 and 3 assemblages chalcopyrite and bornite dominate the core of the deposit and grade outward to chalcopyrite pyrite and to pyrite chalcopyrite flanked by a pyrite only halo the core of the system is cu au rich grading outward to an au enriched cu poor halo coincident with pyrite bearing propylitic alteration gold copper ratios increase upward within stage 2 potassic zones and outward from the core variations in ph redox and temperature along and across fluid flow paths best explain the change to higher au cu values upward and away from the cu rich potassic domains

porphyry deposits of the northwestern cordillera of north america edited by t g schroeter special volume 46 canadian institute of mining metallurgy and petroleum montreal 1995 888 pp canadian 95 plus 15 handling isbn 0 919086 56 x

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

estuarine removal of glacial iron and implications for iron fluxes to the ocean while recent work demonstrates that glacial meltwater provides a substantial and relatively labile flux of the micronutrient iron to oceans the role of high latitude estuary environments as a potential sink of glacial iron is unknown here we present the first quantitative description of iron removal in a meltwater dominated estuary we find that 85 of dissolved fe is removed in the low salinity region of the estuary along with 41 of total dissolvable iron associated with glacial flour we couple these findings with hydrologic and geochemical data from gulf of alaska goa glacierized catchments to calculate meltwater derived fluxes of size and species partitioned fe to the goa iron flux data indicate that labile iron in the glacial flour and associated fe minerals dominate the meltwater contribution to the fe budget of the goa as such goa nutrient cycles and related ecosystems could be strongly influenced by continued ice loss in its watershed

holocene evolution of diatom and silicoflagellate paleoceanography in slocum arm a fjord in southeastern alaska abstract diatom and silicoflagellate assemblages in cores ew0408 47jc 47tc 46mc 57 34 5278 n 136 3 7764 w 114 m water depth taken from the outer portion of slocum arm a post glacial fjord in southeastern alaska reveal the paleoclimatic and paleoceanographic evolution of the eastern margin of the gulf of alaska goa during the past 10 000 years between 10 and 6 8 cal ka periods of low salinity and cool water conditions alternated with brief intervals marked by the increased influx of oceanic more saline and likely warmer waters increased surface water stability characterized by a middle holocene interval between 6 8 and 3 2 cal ka is typified by increased abundances of northeastern pacific thalassiosira spp that are indicative of spring coastal blooms and decreased abundances of warm and higher salinity oceanic diatoms at 3 2 cal ka an abrupt increase in both the relative contribution of oceanic diatoms and silicoflagellates suggestive of cooler upwelling conditions occurred in the 47jc record a stepwise increase in alkenone sea surface temperature in northern goa core ew0408 85jc and increase in southern sourced precipitation in the carbonate 18 o record of jellybean lake yukon present evidence that this 3 2 cal ka event coincided with the onset of enhanced positive pacific decadal oscillation like pdo conditions in the goa these positive pdo like conditions persisted until 1 0 cal ka and were followed by high amplitude fluctuations in the relative abundance of diatom and silicoflagellate assemblages

observations of a kenai eddy and a sitka eddy in the northern gulf of alaska 1 mesoscale eddies in the gulf of alaska are thought to contribute to the shelf slope exchange of nutrients and plankton enhancing biological production we report on a study of two anticyclonic mesoscale eddies in this region observed through in situ sampling during august and september 2007 both eddies exhibited in their cores s profiles with warmer fresher water relative to the properties of the ambient basin water between 150 and 300 m depths hydrographic properties and satellite altimetry data were analyzed to identify likely formation regions for each feature one eddy sampled near yakutat alaska originated in the sitka formation region 221 223 e the second eddy sampled south of kodiak island originated near the kenai peninsula southeast of the kennedy and stevenson entrances to cook inlet an area not previously studied as a formation region subsequent analysis of 16 years of satellite altimeter data from 1992 to 2008 with an algorithm designed to identify and track eddies revealed approximately six kenai eddies that have formed in this region although this number constitutes only 3 2 of the 188 eddies identified by the algorithm during this period it represents 15 4 of the 39 eddies that formed in or propagated westward into the alaskan stream

numerical simulation of earthquake faults with gouge toward a comprehensive explanation for the heat flow paradox the particle based lattice solid model is used to simulate transform faults with and without fault gouge stick slip frictional behavior is observed in two dimensional numerical experiments of model faults both with and without gouge when no gouge is present the fault is strong and the heat generation and stress drops are correspondingly high in disaccord with observations surrounding the heat flow paradox in contrast when a gouge is specified the fault is weak and the heat generation as well as stress drops are low in quantitative agreement with observational constraints the heat flow is low on average and during short periods of aseismic creep seismic efficiencies are compatible with observationally based bounds counter intuitively the fault strength decreases as the intrinsic friction between particles is increased beyond a given threshold the mechanism for low fault strength and heat is rolling and jostling of fault gouge grains during slip this allows macroscopic movement of the fault with only minimal slip between surfaces of the gouge grains as this dynamical mechanism operates during seismic and aseismic slip it provides an explanation for the lack of a heat flow anomaly in both the seismic and creeping parts of the san andreas fault the simulation results provide the first comprehensive and quantitative possible explanation of the heat flow paradox and suggest that fault gouge plays a fundamental role on the dynamics of earthquake faults whether rolling and jostling of fault gouge particles provides the explanation for the heat flow paradox in nature remains to be validated by observation evidence

seasonal and spatial variabilities in northern gulf of alaska surface water iron concentrations driven by shelf sediment resuspension glacial meltwater a yakutat eddy and dust phytoplankton growth in the gulf of alaska goa is limited by iron fe yet fe sources are poorly constrained we examine the temporal and spatial distributions of fe and its sources in the goa based on data from three cruises carried out in 2010 from the copper river ak mouth to beyond the shelf break april data are the first to describe late winter fe behavior before surface water nitrate depletion began sediment resuspension during winter and spring storms generated high total dissolvable fe tdfe concentrations of 1000 nmol kg 1 along the entire continental shelf which decreased beyond the shelf break in july high tdfe concentrations were similar on the shelf but more spatially variable and driven by low salinity glacial meltwater conversely dissolved fe dfe concentrations in surface waters were far lower and more seasonally consistent ranging from 4 nmol kg 1 in nearshore waters to 0 6 1 5 nmol kg 1 seaward of the shelf break during april and july despite dramatic depletion of nitrate over that period the reasonably constant dfe concentrations are likely maintained during the year across the shelf by complexation by strong organic ligands coupled with ample supply of labile particulate fe the april dfe data can be simulated using a simple numerical model that assumes a dfe flux from shelf sediments horizontal transport by eddy diffusion and removal by scavenging given how global change is altering many processes impacting the fe cycle additional studies are needed to examine controls on dfe in the gulf of alaska

endeavour copper gold porphyry deposits northparkes new south wales intrusive history and fluid evolution four economic porphyry copper gold deposits endeavour 22 26 27 and 48 occur within the late ordovician goonumbla volcanic complex of central west new south wales australia together these deposits have a combined ore reserve of 63 6 million metric tons mt at 1 1 percent copper and 0 5 g t gold mineralization is centered in narrow pipelike quartz monzonite porphyry qmp intrusive complexes we have recognized at least nine intrusive phases within the endeavour deposits these are in order of emplacement as follows a premineral equigranular monzodiorite early mineral equigranular to weakly porphyritic biotite quartz monzonite bqm stocks and dikes synmineral k feldspar qmp k qmp pipes and dikes late mineral augite biotite k feldspar qmp ka qmp intrusions and biotite qmp b qmp dikes and postmineral basaltic trachyandesite dikes augite monzonite porphyry dikes and basaltic dikes early stage biotite magnetite and propylitic alteration of the host volcanic rocks and k feldspar alteration of the bqm occurred at each deposit during the intrusion of the bqm stocks and early mineral b qmp dikes transitional stage unidirectional solidification textures and other related anisotropic textures formed mostly during the emplacement of k qmp and ka qmp intrusions main stage sulfide mineralization at all four deposits is spatially and temporally associated with the k qmp and to a lesser extent ka qmp intrusions and their associated k feldspar and sericite hematite alteration assemblages and is characterized by multiple generations of stockwork and sheeted quartz k feldspar bornite chalcopyrite and gold bearing veins late stage sericite quartz copper sulfide carbonate hematite alteration and vein assemblages formed prior to the emplacement of the postmineral intrusions weak to moderate postmineral propylitic alteration assemblages were the last alteration event related to the qmp intrusive complexes intrusive activity and associated biotite alteration occurred between 446 and 437 ma based on 40ar 39ar analyses of biotite and hornblende based on microthermometric analyses of fluid inclusions from early transitional main and late stage veins the endeavour deposits formed at depths between 1 000 and 1 700 m below the paleosurface with a lithostatic pressure regime prevailing throughout the early transitional and main stages and near hydrostatic pressures during the late stage sericitic events the first three stages were dominated by high temperature 460 550 c magmatic hydrothermal brines with salinities of 55 to 60 wt percent nacl kcl equiv although the late stage fluids were cooler 350 400 c and less saline 40 wt nacl equiv their compositions are consistent with the magmatic hydrothermal origin indicated by previous oxygen and hydrogen isotope studies confirming that the endeavour porphyry deposits are representatives of the orthomagmatic end member of the porphyry continuum

controls on deglacial changes in biogenic fluxes in the north pacific ocean the subarctic north pacific ocean holds a large co2 reservoir that is currently isolated from the atmosphere by a low salinity layer it has recently been hypothesized that the reorganization of these high co2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation this reorganization would leave some imprint on paleo productivity records here we present 230th normalized biogenic fluxes from an intermediate depth sediment core in the northwest pacific rc10 196 54 7 n 177 1 e 1007 m and place them within the context of a synthesis of previously published biogenic flux data from 49 deep sea cores north of 20 n ranging from 420 to 3968 m water depth the 230th normalized opal carbonate and organic carbon fluxes from rc10 196 peak approximately 13 000 calendar years bp during the bolling allerod b a period our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period increased somewhat in the northwest pacific during heinrich event 1 and reached a maximum across the entire north pacific during the b a period we evaluate several mechanisms as possible drivers of deglacial change in biogenic fluxes in the north pacific including changes in preservation sediment focusing sea ice extent iron inputs stratification and circulation shifts initiated in the north atlantic and north pacific our analysis suggests that while micronutrient sources likely contributed to some of the observed changes the heterogeneity in timing of glaciogenic retreat and sea level make these mechanisms unlikely causes of region wide contemporaneous peaks in export production we argue that paleoobservations are most consistent with ventilation increases in both the north pacific during h1 and north atlantic during b a being the primary drivers of increases in biogenic flux during the deglaciation as respectively they were likely to bring nutrients to the surface via increased vertical mixing and shoaling of the global thermocline