evidence for a copper bearing fluid in magma erupted at the valley of ten thousand smokes alaska several lines of evidence point to the existence of a pre eruptive fluid phase in the magmas erupted in 1912 at the valley of ten thousand smokes alaska the discovery of rare cu rich bubbles in some melt inclusions is best explained by the random entrapment of a low density fluid phase within growing phenocrysts the h2o s and cl concentrations of the high silica rhyolite are also consistent with fluid saturation in the rhyolite water contents as determined by infrared spectroscopy on doubly polished melt inclusions cluster between 3 5 and 4 5 wt h2o without any apparent differences between magmas vented explosively and effusively these concentrations would be sufficient for h2o saturation at a pressure of 100 mpa though the presence of other volatiles such as co2 and so2 could allow saturation with respect to a fluid phase at higher pressures the s cu and cl contents of the phenocryst assemblages as determined by xrf analyses are too low to account for the decrease in the concentrations of s and cu in the melt and only modest increase in cl with differentiation therefore the behavior of these volatile elements was controlled either by eryptic fractionation if phenocryst phasese or more likely by partitioning into a coexisting fluid phase the presence of this low density phase apparently provided metals such as cu with a volatile phase into which they could partition the concentration of cu in this fluid reached tens to hundreds of times that of the coexisting silicate melt and may have been as rich as 0 05 wt cu the distribution of cu in the magma was also controlled by sulfides such as intermediate solid solution and pyrrhotite which cyrstallized directly from the silicate melt

quantitative morphology of a fringing reef tract from high resolution laser bathymetry southern molokai hawaii high resolution scanning hydrographic operational airborne lidar survey shoals laser determined bathymetric data were used to define the morphology of spur and groove structures on the fringing reef off the south coast of molokai hawaii these data provide a basis for mapping and analyzing morphology of the reef with a level of precision and spatial coverage never before attained an extensive fringing coral reef stretches along the central two thirds of molokai9s south shore 40 km along the east and west ends there is only a thin veneer of living coral with no developed reef complex in total 4800 measurements of spur and groove height and the distance between adjacent spur crests wavelength were obtained along four isobaths between the 5m and 15m isobaths the mean spur height increased from 0 7 m to 1 6 m whereas the mean wavelength increased from 71 m to 104 m reef flat width was found to exponentially decrease with increasing wave energy overall mean spur and groove height and wavelength were shown to be inversely proportional to wave energy in high energy environments spur and groove morphology remains relatively constant across all water depths in low energy environments however spur and groove structures display much greater variation they are relatively small and narrow in shallow depths and develop into much larger and broader features in deeper water therefore it appears that waves exert a primary control on both the small and large scale morphology of the reef off south molokai

volatile exsolution at the dinkidi cu au porphyry deposit philippines a melt inclusion record of the initial ore forming process immiscible phases derived from degassing silicate magmas are considered to be precursors of metal bearing hydrothermal fluids in porphyry deposits the development of melt inclusion techniques provides a window into this critical period of porphyry formation when the cooling decompression and crystallization of silicate melts result in the formation of immiscible phases the record of magmatic to hydrothermal evolution is presented using inclusions in clinopyroxene phenocrysts from the syenitic balut dike one of the host rock lithologies for mineralization at the dinkidi cu au porphyry deposit philippines primary inclusions include silicate glass multiphase aggregates comprising salts silicates sulfates carbonates sulfides and oxides and highly saline aqueous fluids various analyses including in situ laser ablation inductively coupled plasma mass spectrometry of the multiphase inclusions determined elevated concentrations of cl s as tl k na and a number of metals including those that form ore grade deposits e g cu and those that do not e g mo pb zn and w at the dinkidi porphyry deposit silicate melt and multiphase salt rich inclusions in clinopyroxene are interpreted as having originally formed as immiscible phases at magmatic temperatures

a budget of carbonate framework and sediment production kailua bay oahu hawaii abstract sediments of the bay and coastal plain of kailua oahu hawaii are 90 biogenic carbonate produced by destruction of primary reef framework coral and encrusting coralline algae and by direct sedimentation through the biological activity of calcifying organisms the green alga halimeda the branching coralline alga porolithion gardineri molluscs and benthic foraminifera field measurements of benthic community structure gross carbonate production bioerosion and direct sedimentation in 17 physiographic zones in kailua bay are used to calculate modern calcareous sediment production rates in the 12 km2 fringing reef system total gross carbonate productivity by corals and encrusting coralline algae based on mapped percent cover and known growth rates occurs at an average rate of 1 22 0 36 kg m 2 y 1 over hard substrates of the reef platform corresponding to 0 8 0 2 mm y 1 using a bulk density of 1 48 g cm 3 the average of coral and coralline algae coralline algae contributes 42 of the total gross productivity bioerosion of coral and coralline algae facies at and near the reef surface estimated from slabbed reef samples occurs at average rates of 0 10 1 15 kg m 2 y 1 and releases 1 911 436 m3 of unconsolidated carbonate sediment annually mechanical erosion coral breakage likely contributes an additional 315 m3 y 1 carbonate sediment is also produced directly by the green alga halimeda branching coralline algae molluscs and benthic foraminifera at a combined rate of 1 822 200 m3 y 1 using densities specific to sediment origin the total rate of production of unconsolidated carbonate sediment in kailua bay is the sum of these sources amounting to 4 048 635 m3 y 1 normalizing gross sediment production in kg y 1 by reef habitat area in m2 generates average rates of productivity in kg m 2 y 1 that are directly comparable to each other and to the literature such rates can also be employed and tested in other reef settings in kailua bay the total production of calcareous sediment corresponds to an average normalized rate of 0 53 0 19 kg m 2 y 1 with 0 33 0 13 kg m 2 y 1 contributed through erosion of the coralgal framework and 0 20 0 06 kg m 2 y 1 contributed by direct sediment production on the reef surface applying these modern sediment production rates over the 5 000 years that kailua bay has been completely inundated by postglacial sea level rise an estimated 20 2 3 2 106 m3 of unconsolidated carbonate sediment has been produced in the system the volume of sediment stored in the various reef channels and holes in kailua bay is 3 7 0 3 106 m3 or 19 of that produced since 5 000 y bp the volume of sand in the modern beach is 1 0 0 1 106 m3 or 5 of holocene sediment production the volume of carbonate sediment stored in the coastal plain is estimated using core log data and associated radiocarbon ages to be 10 0 1 8 106 m3 or 51 of holocene sediment production the remaining 25 likely represents sediment loss due to the natural processes of dissolution attrition and transport offshore these export terms are not well understood and emphasize the need for sediment dynamics to be incorporated into reef and sediment budgets although sediment production in this reef system is prodigious the rate of new sediment supplied to the beachface is less than 2 of what moves on and off the beach seasonally

holocene reef development where wave energy reduces accommodaton space kailua bay windward oahu hawaii u s a abstract analyses of 32 drill cores obtained from the windward reef of kailua bay oahu hawaii indicate that high wave energy significantly reduced accommodation space for reef development in the holocene and produced variable architecture because of the combined influence of sea level history and wave exposure over a complex antecedent topography a paleostream valley within the late pleistocene insular limestone shelf provided accommodation space for more than 11 m of vertical accretion since sea level flooded the bay 8000 yr bp virtually no net accretion 6 m coral framestone accreted at rates of 2 5 6 0 mm yr in water depths 11 m during the early holocene it abruptly terminated at 4500 yr bp because of wave scour as sea level stabilized more than 4 m of rudstone derived from the upper fore reef accreted at depths of 6 to 13 m below sea level between 4000 and 1500 yr bp coincident with late holocene relative sea level fall variations in the thickness composition and age of these reef facies across spatial scales of 10 1000 m within kailua bay illustrate the importance of antecedent topography and wave related stress in reducing accommodation space for reef development set by sea level although accommodation space of 6 to 17 m has existed through most of the holocene the kailua reef has been unable to catch up to sea level because of persistent high wave stress

shelf stratigraphy and the influence of antecedent substrate on holocene reef development south oahu hawaii abstract paired analyses of drill cores and high resolution seismic reflection data show that development of holocene framework reefs on the oahu hawaii shelf is limited to settings of low wave energy and to the period 8000 to 3000 yr bp a prominent bounding surface that is mapped across much of the oahu shelf is an erosion surface cut into marine isotope stages 5 and 7 limestones that show extensive loss of primary porosity aragonite and mgco3 owing to meteoric and vadose zone diagenesis this acoustic reflector is found exposed at the surface where wave energy is high or in the shallow subsurface below holocene reef and sand sheet deposits where energy is low ship towed video along 30 km of the shelf reveals a steady decrease in limestone accumulation from offshore of honolulu southeast to koko head where the seafloor is characterized by volcanic pavement and or thin sand deposits this may reflect the build up of late pleistocene volcanics associated with the hanauma bay eruption 30 000 7000 yr bp that now comprise the substrate in depths shallow enough to limit reef accretion the absence of significant holocene reef build up on the south oahu shelf is consistent with observations from north facing coasts that lack holocene reefs indicating that holocene reef formation in hawaii is complex and patchy

melt and fluid inclusions from volcanic quartz phenocrysts in the shila gold base metal ore district peru precursors to ore forming epithermal solutions despite the close association with volcanic activity the source of metals and ligands in the epithermal ore deposits is still controversial in order to explore the magmatic hydrothermal connection further silicate melt saline and water rich fluids and co2 vapours are documented that are trapped as inclusions in quartz phenocrysts from dacitic dykes associated with epithermal gold base metal mineralization in the shila district peru melt inclusion characteristics and microthermometric and laser raman fluid inclusion data are presented the investigation of melt and fluid inclusions reveals that the volatile phase of magmas might represent the precursors to the early chlorine rich ore forming epithermal solutions microthermometric investigations in magmatic quartz crystals and data on quartz mineralized veins suggest that the fluid evolution and ore deposition may be the result of several processes including release of an evolving magmatic fluid and or boiling and or mixing

decorrelating remote sensing color bands from bathymetry in optically shallow waters we have developed a simple technique to decorrelate remote sensing color band data from depth in optically shallow water the method linearizes color band data with respect to depth by subtracting an optically deepwater value from the entire waveband under consideration and taking the natural logarithm of the result next this linearized waveband is rotated about the model 2 regression line computed against a bathymetry band the rotated color band is decorrelated from water depth we demonstrate the technique for a small area of kailua bay oahu hi using quickbird multispectral and scanning hydrographic operational airborne lidar survey lidar data results indicate that color band data are effectively decorrelated from depth while bottom reflector variability is maintained thus providing the basis for further analysis of the depth invariant wavebands the primary benefit of our technique is that wavebands are rotated independently preserving relative spectral information

the nature and genesis of gold silver tellurium mineralization in the metaliferi mountains of western romania precious metal au ag and base metal pb zn deposits in the metaliferi mountains of western romania occur in steeply clipping quartz ca mn carbonate veins which are hosted by miocene andesitic stocks and lava flows and surrounding sedimentary rocks the deposits consist predominantly of sulfides pyrite chalcopyrite sphalerite galena sulfosalts of as and sb and a diverse range of au ag tellurides the igneous host rocks have undergone mild pervasive propylitic alteration whereas immediately adjacent to the veins the wall rock alteration assemblages consist of quartz sericite k feldspar calcite and pyrite fluid inclusion stable isotope and thermodynamic data suggest that the majority of the mineralization and hydrothermal alteration in these deposits was caused by loci salinity 0 5 wt nacl equiv medium temperature 200 degrees 300 degrees c near neutral ph 5 6 fluids which underwent occasional boiling the fluid inclusion and stable isotope data support a model in which a metal bearing magmatic fluid was exsolved from a crystallizing calc alkaline melt and ascended to higher levels in the crust undergoing some isotopic exchange with surrounding sedimentary rocks but limited mixing with ground waters although the deposits in this part of the romanian carpathians exhibit many of the geologic characteristics of classic low sulfidation volcanic hosted au ag epithermal deposits they seem to have formed from essentially magmatic waters and there is little evidence for the incorporation of meteoric fluids into the hydrothermal system

depositional processes on oceanic island shelves evidence from storm generated neogene deposits from the mid north atlantic oceanic islands such as the azores in the mid north atlantic are periodically exposed to large storms that often remobilize and transport marine sediments along coastlines and into deeper environments such disruptive events create deposits denominated tempestites whose characteristics reflect the highly dynamic environment in which they were formed tempestites from oceanic islands however are seldom described in the literature and little is known about storm related sediment dynamics affecting oceanic island shelves therefore the geological record of tempestite deposits at oceanic islands can provide invaluable information on the processes of sediment remobilization transport and deposition taking place on insular shelves during and after major storms in santa maria island azores a sequence of neogene tempestite deposits was incorporated in the island edifice by the ongoing volcanic activity thus preserved and later exposed through uplift and erosion because it was overlain by a contemporary coastal lava delta the water depth at the time of deposition could be inferred constituting an excellent case study to gain insight on the still enigmatic processes of insular shelf deposition sedimentological palaeontological petrographic and palaeo water depth information allowed the reconstruction of the depositional environment of these sediments the sequence typifies the characteristics of a tempestite or successive tempestites formed at ca 50 m depth in a steep energetic open insular shelf and with evidence for massive sediment remobilization from the nearshore to the middle or outer shelf the authors claim that cross shelf transport induced by storm events is the main process of sediment deposition acting on steep and narrow shelves subjected to high energetic environments such as the insular shelves of open sea volcanic islands

boiling and vertical mineralization zoning a case study from the apacheta low sulfidation epithermal gold silver deposit southern peru the au ag pb zn apacheta deposit is located in the shila district 600 km southeast of lima in the cordillera occidental of arequipa province southern peru the vein mineralization is found in early to middle miocene calc alkaline lava flows and volcanic breccias both gangue and sulfide mineralization express a typical low sulfidation system assay data show element zoning with base metals enriched at depth and higher concentrations of precious metals in the upper part of the veins three main deposition stages are observed 1 early pyrite and base metal sulfides with minor electrum 1 and acanthite 2 brecciation of this mineral assemblage and cross cutting veinlets with subhedral quartz crystals mn bearing calcite and rhombic adularia crystals and finally 3 veinlets and geodal filling of an assemblage of tennantite tetrahedrite colorless sphalerite 2 galena chalcopyrite electrum 2 fluid inclusions in the mineralized veins display two distinct types aqueous carbonic liquid rich lw c inclusions and aqueous carbonic vapor rich vw c inclusions microthermometric data indicate that the ore minerals were deposited between 300 and 225 c from relatively dilute hydrothermal fluids 0 6 3 4 wt nacl the physical and chemical characteristics of the hydrothermal fluids show a vertical evolution with in particular a drop in temperature and a loss of h2s the presence of adularia and platy calcite and of co existing liquid rich and vapor rich inclusions in the ore stage indicates a boiling event strong h2s enrichment in the vw c inclusions observed at 200 m the abundance of platy calcite and the occurrence of hydrothermal breccia at this level may indicate a zone of intense boiling the vertical element zoning observed in the apacheta deposit thus seems to be directly related to the vertical evolution of hydrothermal fluid characteristics precious metal deposition mainly occurred above the 200 m level below the present day surface in response to a liquid vapor phase separation due to an upward boiling front

critical depth for the survival of coral islands effects on the hawaiian archipelago coral islands drown when sea level rise exceeds the maximum potential of coral reefs to grow upward about 10 millimeters per year during the holocene transgression 18 000 years ago to present sea levels rose at rates of up to 10 to 20 millimeters per year and most coral island reefs situated deeper than a critical depth of30 to 40 meters below present day sea level drowned coral islands that did not drown during the holocene transgression apparently all developed on antecedent foundations shallower than critical depth during low stands in sea level during the pleistocene these islands were elevated and subject to subaerial erosion today in the hawaiian archipelago the depth of drowned banks is inversely related to summit area smaller banks are progressively deeper evidently because of erosional truncation during low sea level stands bank summit area may therefore be an important factor determining the failure or success of coral islands

coastal evolution on volcanic oceanic islands a complex interplay between volcanism erosion sedimentation sea level change and biogenic production abstract the growth and decay of oceanic hotspot volcanoes are intrinsically related to a competition between volcanic construction and erosive destruction and coastlines are at the forefront of such confrontation in this paper we review the several mechanisms that interact and contribute to the development of coastlines on oceanic island volcanoes and how these processes evolve throughout the islands lifetime volcanic constructional processes dominate during the emergent island and subaerial shield building stages during the emergent island stage surtseyan activity prevails and hydroclastic and pyroclastic structures form these structures are generally ephemeral because they can be rapidly obliterated by marine erosion with the onset of the subaerial shield building stage coastal evolution is essentially characterized by rapid but intermittent lateral growth through the formation of lava deltas largely expanding the coastlines until they typically reach their maximum extension with the post shield quiescence in volcanic activity destructive processes gradually take over and coastlines retreat adopting a more prominent profile mass wasting and marine and fluvial erosion reshape the landscape and if conditions are favorable biogenic processes assume a prominent role post erosional volcanic activity may temporarily reverse the balance by renewing coastline expansion but islands inexorably enter in a long battle for survival above sea level reef growth and or uplift may also prolong the island s lifetime above the waves the ultimate fate of most islands however is to be drowned through subsidence and or truncation by marine erosion

vapor transfer prior to the october 2004 eruption of mount st helens washington dome lavas from the 2004 eruption of mount st helens show elevated li contents in plagioclase phenocrysts at the onset of dome growth in october 2004 these cannot be explained by variations in plagioclase melt partitioning but require elevated li contents in coexisting melt a fact confirmed by measurements of li contents as high as 207 g g in coexisting melt inclusions similar li enrichment has been observed in material erupted prior to and during the climactic may 1980 eruption and is likewise best explained via pre eruptive transfer of an exsolved alkali rich vapor phase derived from deeper within the magma transport system unlike 1980 however high li samples from 2004 show no evidence of excess 210pb 226ra implying that measurable li enrichments may occur despite significant differences in the timing and or extent of magmatic degassing diffusion modeling shows that li enrichment occurred within 1 yr before eruption and that magma remained li enriched until immediately before eruption and cooling this short flux time and the very high li contents in ash produced by phreatomagmatic activity prior to the onset of dome extrusion suggest that vapor transfer and accumulation were associated with initiation of the current eruption overall observation of a high li signature in both 1980 and 2004 dacites indicates that li enrichment may be a relatively common phenomenon and may prove useful for petrologic monitoring of mount st helens and other silicic volcanoes lithium diffusion is also sufficiently rapid to constrain vapor transfer on similar time scales to short lived radionuclides

remote sensing of sand distribution patterns across an insular shelf oahu hawaii sandy substrate is important as a resource habitat and dynamic region of the bathymetry we find that sand storage across the insular shelf of oahu hawaii is controlled most strongly by general insular shelf morphology and to a lesser degree by hydrodynamic energy shelf sand is predominantly found in water depths less than or crossing the 10 m contour we use remote sensing to identify and classify 14 037 individual sand deposits in nine study regions a supervised classification algorithm aggregates these into five classes with 14 subclasses almost 63 of all sandy surface area falls into two subclasses of the channels and connected fields class 1 major channels and 2 unchannelized drainage these subclasses connect regions of sediment production to regions of sediment storage on the insular shelf surface this study is the first to quantitatively analyze and classify shelf sand deposits in a high volcanic island coral reef setting

a 15 400 year record of climate variation from a subalpine lacustrine sedimentary sequence in the western nanling mountains in south china abstract multi proxy records of a subalpine lacustrine sequence in daping swamp in the western nanling mountains provide evidence for exploring climate variability in the past 15 400 yr two dry and cool 15 400 14 500 and 13 000 11 000 cal yr bp and one humid and warm interval 14 500 13 200 cal yr bp which we correlate to heinrich event 1 the younger dryas and the bolling allerod event respectively are revealed the early holocene climate 11 000 8000 cal yr bp was characterized by less humid and warm conditions suggesting a weaker asian summer monsoon asm intensity our findings indicate that the holocene optimum occurred between 8000 and 4500 cal yr bp and the most intensified asm appears from 8000 to 7000 cal yr bp after 4500 cal yr bp climate shifted to relatively cool and dry conditions we speculate that five short dry and cool events centered at 11 000 9000 8400 6000 and 3500 cal yr bp were linked to the holocene ice rafting events detected in the north atlantic migration of the itcz and the oceanic atmospheric circulations particularly sst changes in the tropical pacific may play a pivotal role in climate variation of the study region

fluid evolution in the baia mare epithermal gold polymetallic district inner carpathians romania the baia mare district romania represents a complex segment of the neogene quaternary subduction related volcanic chain of the carpathians in this province the calc alkaline volcanism and associated mineralization are closely related to a major strike slip fault and an underlying pluton the ore deposits of the district have many features typical of low sulfidation or adularia sericite epithermal deposits the combination of fluid inclusion microthermometry raman spectroscopy bulk crush leach analysis laser ablation optical emission spectrometry la oes of individual fluid inclusions and stable isotope data has been used to characterize the ore forming solutions involved with gold polymetallic mineralization in three of the largest deposits ore fluids at baia sprie cavnic and sasar deposits had temperatures of 320 to 150 c and salinities in the range 0 21 wt nacl equiv during phreatomagmatic activity fracturing and periods of vein dilation the pressure fluctuations may have caused boiling the hydrothermal fluids were na k li ca chloride solutions with lesser amounts of so4 and f the na k ratios and the stable isotope compositions are consistent with equilibration of the fluids with country rocks at progressively lower temperatures the halogen ratios br cl 103 in the range 0 13 1 21 together with sulfur isotopic systematics 34s 0 3 5 2 per mil are consistent with a dominantly magmatic origin of the solutes and probably of the ore fluids themselves

marine and meteoric diagenesis of pleistocene carbonates from a nearshore submarine terrace oahu hawaii abstract the nearshore slope of oahu consists of a shallowly dipping shelf extending from the shoreline out to the 20 m contour where there is a sharp break in slope down to 30 m limestones recovered in a series of short cores taken from this nearshore terrace are typical of shallow marine reef environments and comprise either a branching coral or massive coral facies the composition as well as shoreward zonation of facies suggests that the terrace represents an in situ fossil reef complex th u ages of in situ corals are all pleistocene and suggest that the bulk of the feature formed during marine oxygen isotope stage 7 later accretion along the seaward front of the terrace occurred during marine oxygen isotope substages 5a and or 5c deposition during these interglacial highstands has not previously been documented in the sea level record on oahu although the diagenetic record in the cored samples is incomplete three periods of diagenesis are identified early shallow marine meteoric and post meteoric shallow marine early shallow marine diagenesis includes cementation by aragonite and mg calcite in an active marine phreatic zone and predominantly micritization in a stagnant marine phreatic zone meteoric processes occurred in the vadose zone and include precipitation of calcite needle fibers meniscus cements micritic networks neomorphism and dissolution all limestones are now in an active marine phreatic zone evidence of post meteoric shallow marine diagenesis is found in last generation mg calcite cements and internal sediments occurring directly on limestone substrates that have otherwise been stabilized to calcite the present seafloor is undergoing extensive biological and physical erosion no holocene limestones were recovered petrographic and geochemical signatures of subaerial exposure and meteoric diagenesis are recognized within the upper several centimeters of all cores thus the present seafloor in the study area is a flooded pleistocene subaerial exposure surface