molybdenum mineralization in an active geothermal system valles caldera new mexico shallow sub ore grade molybdenite mineralization has been discovered in the active high temperature geothermal system penetrated by continental scientific drilling program corehole vc 2a at sulfur springs in the western ring fracture zone of the valles caldera new mexico this mineralization is hosted by fractured quartz sericitized intracaldera ash flow tuffs younger than 1 12 ma the molybdenite is an unusual poorly crystalline variety that occurs in vuggy veinlets and breccia cements also containing quartz sericite illite pyrite and fluorite as well as local sphalerite rhodochrosite and chalcopyrite fluid inclusion data suggest that this assemblage was deposited from very dilute solutions at temperatures near 200 sup 0 c geochemical modeling indicates that under restricted ph and fo sub 2 conditions at 200 sup 0 c the molybdenite and associated phases would be in equilibrium with hydrothermal fluids now circulating in the deep subsurface the shallow molybdenite zone intersected in vc 2a may be the near surface expression of deep climax type stockwork molybdenum mineralization

magmatic anhydrite in plutonic rocks at the el teniente cu mo deposit chile and the role of sulfur and copper rich magmas in its formation anhydrite occurs along with biotite feldspars quartz fe oxides and sulfides in fine grained igneous rocks that form the small porphyry a stock at el teniente these minerals crystallized together in the space generated by the intrusion of this stock and they do not replace preexisting phases planar crystal boundaries between anhydrite and other phases as well as the fact that plagioclase and biotite are fresh and unaltered also suggest that anhydrite is an igneous phase and not the product of secondary hydrothermal alteration plagioclase is unusually na rich ranging from oligoclase in mafic varieties of these rocks with 20 percent biotite to albite in more felsic samples with 20 percent these unusual anhydrite bearing plutonic rocks which contain up to 3 wt percent s and 0 5 wt percent cu are isotopically similar to all other igneous rocks related to the deposit these rocks formed during a late miocene period of regional compressive deformation with no coeval volcanic activity in the area of the deposit which prevented devolitalization of the oxidized parent magma in the large productive magma chamber inferred to have underlain el teniente at 4 km below the paleosurface this allowed igneous fractionation involving the recharge of mantle derived mafic magmas into the base of the chamber as well as volatile transfer and concentration near its roof to produce the cu and s rich magmas that formed the anhydrite bearing intrusive rocks

travertine deposits of soda dam new mexico and their implications for the age and evolution of the valles caldera hydrothermal system uranium thorium disequilibrium dates and stable isotope analyses of travertine deposits at soda dam new mexico have been used to determine the age and to document the evolution of the valles caldera hydrothermal system soda dam discharges from paleozoic and precambrian rocks in san diego canyon southwest of the caldera and the canyon was filled with several hundred metres of upper bandelier tuff during formation of valles caldera 1 12 ma according to the dates the valles hydrothermal system is at least 106 yr old or nearly as old as the caldera the basic hydrology of the system has thus remained virtually unchanged during this time travertine ages indicate pulses in travertine deposition from 1 0 to 0 48 ma from 0 107 to 0 058 ma and from 0 005 ma to present the volume of various travertine deposits suggests that the hot spring system at soda dam was once larger than it is today possibly discharging as much as 5 to 10 times more fluid of na hco3 cl composition stable isotopes of the travertines indicate however that the hot spring system has probably never been more than about 10 c hotter than the present maximum temperature of 48 c stable isotopes also show that the 13c of co2 and 18o of h2o in hot spring waters has remained relatively constant for 106 yr the similar ages between caldera formation and the onset of large scale hydrothermal circulation and travertine deposition on pre bandelier tuff rocks imply that incision rates by the jemez river in bandelier tuff were relatively rapid as much as 400 m of tuff were cut by the ancestral jemez river in 105 yr or less

geochemistry and isotopes of fluids from sulphur springs valles caldera new mexico abstract detailed geochemistry supported by geologic mapping has been used to investigate sulphur springs an acid sulfate hot spring system that issues from the western flank of the resurgent dome inside valles caldera the most intense activity occurs at the intersection of faults offsetting caldera fill deposits and post caldera rhyolites three geothermal wells in the area have encountered pressures 4 8000 mg l these conditions cause argillic alterations throughout a large area non condensible gases consist of roughly 99 co 2 with minor amounts of h 2 s h 2 and ch 4 empirical gas geothermometry suggests a deep reservoir temperature of 215 to 280 c comparison of 13 c and 18 o between caco 3 from well cuttings and co 2 from fumarole steam indicates a fractionation temperature between 200 and 300 c by decarbonation of hydrothermally altered paleozoic limestone and vein calcite in the reservoir rocks tritium concentrations obtained from steam condensed in a mudpot and deep reservoir fluids baca 13 278 c are 2 1 and 1 0 t u respectively suggesting the steam originates from a reservoir whose water is mostly 50 yrs old deuterium contents of fumarole steam deep reservoir fluid and local meteoric water are practically identical even though 18 o contents range through 4 thus precipitation on the resurgent dome of the caldera could recharge the hydrothermal system by slow percolation from analysis of d and 18 o values between fumarol steam and deep reservoir fluid steam reaches the surface either 1 by vaporizing relatively shallow groundwater at 200 c or 2 by means of a two stage boiling process through an intermediate level reservoir at roughly 200 c although many characteristics of known vapor dominated geothermal systems are found at sulphur springs fundamental differences exist in temperature and pressure of our postulated vapor zone we propose that the reservoir beneath sulphur springs is too small or too poorly confined to sustain a true vapor dominated system and that the sulphur springs system may be a dying vapor dominated system that has practically boiled itself dry

speleothems and mountain uplift ancient speleothems were recovered from caves that today are situated in a high alpine cirque landscape at 2500 m altitude at the northern rim of the european alps u pb ages date speleothem deposition to the early quaternary between 2 16 and 2 12 ma and ca 2 00 ma i e well before the onset of major alpine and northern hemisphere glaciations using a stable isotope based modeling approach we quantitatively estimate the paleoelevation of both the caves and their former catchment area which in turn allows us to calculate rates of rock and surface uplift and hence erosion since 2 ma we show that for the frontal part of the alps rates of rock uplift and erosion were 0 75 and 0 5 mm yr respectively and further suggest that isostatic uplift of mountain peaks of as much as 500 m in response to enhanced glacial erosion occurred during the quaternary this study highlights the potential of u pb dated speleothems for reconstructing paleoaltimetry particularly in calcareous mountain ranges where a standard thermochronologic assessment of exhumation and erosion is generally not feasible

initial results from vc 1 first continental scientific drilling program core hole in valles caldera new mexico valles caldera 1 vc 1 is the first continental scientific drilling program csdp core hole drilled in the valles caldera and the first continuously cored well in the caldera region the objectives of vc 1 were to penetrate a hydrothermal outflow plume near its source to obtain structural and stratigraphie information near the intersection of the ring fracture zone and the precaldera jemez fault zone arid to core the youngest volcanic unit inside the caldera banco bonito obsidian coring of the 856 m well took only 35 days to finish during which all objectives were attained and core recovery exceeded 95 vc 1 penetrates 298 m of moat volcanics and caldera fill ignimbrites 35 m of precaldera volcaniclastic breccia and 523 m of paleozoic carbonates sandstones and shales a previously unknown obsidian flow was encountered at 160 m depth underlying the battleship rock tuff in the caldera moat zone hydrothermal alteration is concentrated in sheared brecciated and fractured zones from the volcaniclastic breccia to total depth with both the intensity and rank of alterations increasing with depth alteration assemblages consist primarily of clays calcite pyrite quartz and chlorite but chalcopyrite and sphalerite have been identified as high as 450 m and molybdenite has been identified in a fractured zone at 847 m carbon 13 and oxygen 18 analyses of core show that the most intense zones of hydrothermal alteration occur in the madera limestone above 550 m and in the madera and sandia formations below 700 m this corresponds with zones of most intense calcite and quartz veining thermal aquifers were penetrated at the 480 540 and 845 m intervals although these intervals are associated with alteration brecciation and veining they are also intervals where clastic layers occur in the paleozoic sedimentary rocks

stratigraphic relations and lithologic variations in the jemez volcanic field new mexico over 100 radiometric dates and recent detailed geologic mapping allow some refinements of the stratigraphic relations of major units and generalization of temporal lithologic variations in the jemez volcanic field volcanism had begun in the area by about 16 5 ma with episodic eruptions of alkaline basalts by 13 ma alkaline volcanism had been replaced with eruptions of more voluminous olivine tholeiite high silica rhyolite derived from melts of lower crust also was erupting by about 13 ma basalt and high silica rhyolite continued to be erupted until about 7 and 6 ma respectively but effusions of dominantly andesitic differentiates of basalt that began as early as about 12 ma volumetrically overshadowed all other eruptive products between 10 and 7 ma from 7 to 3 ma the dominant erupted lithology was dacite which appears to have been generated by mixing of magmas whose compositions are approximated by earlier andesites and high silica rhyolites less than 4 3 ma volcanism was dominated by eruption of rhyolitic tuffs field relations geochemistry and dates specifically indicate the following with regards to stratigraphie relations 1 distinctions among basalt of chamisa mesa paliza canyon formation basalts and lobato basalt for other than geographic reasons are artificial basaltic volcanism was continuous in volcanic field from 13 to 7 ma 2 canovas canyon and bearhead rhyolites form a continuum of high silica rhyolite volcanism from 13 to 6 ma 3 hypabyssal and volcanic rocks of the cochiti mining district probably represent the exhumed interior of a keres group volcano s 4 temporal overlaps exist among the major stratigraphie groups which may imply some genetic relations and 5 the tewa group formation cerro rubio quartz latite may more appropriately be considered part of the tschicoma formation of the polvadera group preliminary analysis of hydrothermal alteration in the context of the volcanic stratigraphy suggests at least three distinct hydrothermal events have occurred in the volcanic field s history

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

an interpretation of the alteration assemblages at sulphur springs valles caldera new mexico sulphur springs located near the western edge of the valles caldera north central new mexico is the only vapor dominated surface manifestation of any significance found in the valles the percolating acid sulfate waters and fumarolic gases have leached and oxidized the country rock near the hot springs to a bleached wasteland the near surface mineral assemblages at 90 c are restricted to one and two phases occurring in contact with a variety of solutions and gases the conditions of local equilibrium at 90 g are approximately halotrichite alunogen log fo2 45 log fs2 12 ph 0 3 szomolnokite pyrite log fo2 46 log fs2 16 ph 0 8 alunite log fo2 50 log fs2 10 ph 1 2 kaolinite sulphur log fo2 53 log fs2 10 ph 1 2 log ak 0 0012 m log asio2 0 0033 m and pyrite log fo2 60 log fs2 19 ph 4 3 this study has demonstrated that local equilibrium is closely approached even under the low temperature and pressure conditions found near the surface

hydrothermal brecciation in the jemez fault zone valles caldera new mexico results from continental scientific drilling program core hole vc 1 an unusual breccia sequence penetrated in the lower 30 m of continental scientific drilling program core hole vc 1 total depth 856 m records a complex hydrothermal history culminating in hydraulic rock rupture and associated alteration at the edge of the quaternary valles caldera the breccias both tectonic and hydrothermal in origin were formed in the jemez fault zone near the intersection of this major regional structure with the caldera s ring fracture margin tectonic breccias in the sequence are contorted crushed and sheared coexisting hydrothermal breccias lack such frictional textures but display matrix flow foliation and prominent clast rounding features characteristic of fluidization these hydrothermal breccias were intensely altered during at least five major stages to quartz illite phengite pyrite aggregates traces of molybdenite occur locally this assemblage indicates interaction with hydrothermal fluid at temperatures in excess of 200 c the extrapolated present maximum temperature of 184 c in the breccia zone therefore represents considerable cooling since these phases were formed fluid inclusions in the breccias also preserve evidence of the prior passage of hotter fluids the inclusions are principally two phase liquid rich secondary in origin and concentrated in hydrothermal quartz older high salinity inclusions unrelated to brecciation homogenize in the temperature range 189 246 c younger inclusions in part of interbreccia origin are low salinity and homogenize in the temperature range 230 283 c locally coexisting liquid and vapor rich inclusions document periodic boiling of the dilute fluids these fluid inclusion data along with the probable age of the hydrothermal breccias 1 5 ma the assumed depth at which they developed about 515 m and the contemporaneous state of stress extensional can be combined to model hydrothermal brecciation at the vc 1 site the minimum fluid pressure pfr required to hydrofracture these rocks was probably about 7 5 mpa 0 0146 mpa m a boiling point versus depth curve based on these pfr values graphically defines the physical conditions prevailing when the breccias were formed when fluid pressure at the assumed depth of brecciation exceeded that curve in response to rapid release of confining pressure possibly augmented by renewed heating flashing hydrothermal fluid fractured the enclosing rock large overpressures most likely induced by sudden seismic cracking of a hydrothermally sealed portion of the jemez fault zone led to local fluidization of the resulting breccias late quartz veining hydrothermal alteration and molybdenite mineralization were probably produced by the fluids responsible for brecciation

mixed layer illite smectite as a paleotemperature indicator in the amethyst vein system creede district colorado usa ordered illite smectite is the most abundant and widespread product of argillic alteration associated with the oligocene epithermal ag pb zn cu au amethyst vein system southwest colorado hydrothermal illite smectites exhibit all reichweite from 1 to 3 and span the composition range from about 25 to about 3 illite the composition and reichweite of illite smectite vary smoothly with distance from the amethyst vein with increasing distance from the vein percent illite and the reichweite decrease when composition temperature relationships of illite smectite from modern geothermal systems are applied to the fossil amethyst system isotherms describing the thermal regime at the time of argillization can be estimated temperatures near 240 c appear to have existed near the amethyst vein these temperatures agree with homogenization temperatures obtained from fluid inclusions in vein minerals the most distal illite smectites sampled about 260 m from the vein indicate temperatures near 110 c estimated thermal gradients are on the order of 0 4 to 1 c per meter although illite smectite composition and structure vary systematically with distance from the amethyst vein there are no systematic trends associated with the numerous smaller veins and veinlets in the hanging wall of the system this indicates that temperatures of both wallrock and the fluids in all but the major amethyst vein were nearly the same during clay formation apparently the hydrothermal system had reached a fairly steady mature thermal state at the time of argillization

rapid glacial erosion at 1 8 ma revealed by 4he 3he thermochronometry alpine glaciation and river incision control the topography of mountain ranges but their relative contributions have been debated for years apatite 4 he 3 he thermochronometry tightly constrains the timing and rate of glacial erosion within one of the largest valleys in the southern coast mountains of british columbia canada five proximate samples require accelerated denudation of the klinaklini valley initiating 1 8 0 2 million years ago ma at least 2 kilometers of overlying rock were removed from the valley at 5 millimeters per year indicating that glacial valley deepening proceeded 6 times as fast as erosion rates before 1 8 ma this intense erosion may be related to a global transition to enhanced climate instability 1 9 ma

plio pleistocene climate evolution trends and transitions in glacial cycle dynamics abstract we describe the evolution of climate system dynamics by examining the climate response to changes in obliquity and precession over the last 5 3 myr in particular we examine changes in the shape of glacial cycles and the power of obliquity and precession response in benthic 18 o when the exponential trend in 18 o variance is removed its spectral power exhibits strong proportional responses to amplitude modulations in orbital forcing over most of the plio pleistocene precession responses correlate with modulations in forcing for the last 5 myr but 41 kyr response is sensitive to obliquity modulation only before 1 4 myr where responses are sensitive to modulations in forcing we demonstrate that glacial cycles are orbitally forced rather than being self sustained or paced by orbital changes the shapes of glacial cycles have several nonlinear properties which may be indicative of glacial interglacial differences in climate sensitivity or response time the saw tooth asymmetry of glacial cycles first appears shortly after the onset of major northern hemisphere glaciation and the relative duration of interglacial stages decreases at 1 4 myr collectively trends in the shape of glacial cycles and the sensitivity of 18 o to obliquity and precession are suggestive of major transitions in climate dynamics at approximately 2 5 and 1 4 myr but show no significant change associated with the appearance of strong 100 kyr cycles during the mid pleistocene transition

multiple low temperature thermochronology constraints on exhumation of the tatra mountains new implication for the complex evolution of the western carpathians in the cenozoic the tectonothermal evolution of the highest mountain range in the carpathian arc the tatra mountains is investigated by zircon and apatite fission track and zircon u th he zhe dating methods in order to unravel the disputed exhumation and geodynamic processes in the western carpathians our data in combination with geological evidences reveal a complex cenozoic history with four major tectonothermal events i a very low grade metamorphism of the crystalline basement at temperatures 240 c due to tectonic burial during the eo alpine collision in the late cretaceous 80 ma ii exhumation and cooling of the basement to temperatures 150 c after burial to 5 9 km depths by the paleogene fore arc basin iv final exhumation of the segmented basement blocks during oligocene miocene 32 11 ma owing to lateral extrusion of the north pannonian plate and its collision with the european foreland the spatial pattern of thermochronological data suggests asymmetric exhumation of the tatra mountains beginning in the northwest at 30 20 ma with low cooling rates 1 5 c ma and propagating toward the major fault bounding the range in the south where the youngest cooling ages 16 9 ma and fastest cooling rates 10 20 c ma are found our data prove that the tatra mountains shared cenozoic evolution of other crystalline core mountains in the western carpathians however the miocene zhe ages suggest that the tatra mountains were buried to the greatest depths in the paleogene early miocene and experienced the greatest amount of miocene exhumation

uranium series age determination of calcite veins vc 1 drill core valles caldera new mexico uranium series analysis sup 238 u sup 234 u sup 230 th of 13 calcite veins from the hydrothermally altered madera limestone in the vc 1 drill core was performed to determine the ages of the veins and their relation to the valles hydrothermal system thermal water from vc 1 and two hot springs in san diego canyon was analyzed for u and sup 234 u sup 238 u to help evaluate the constancy of initial sup 234 u sup 238 u the sup 230 th sup 234 u age of one of the veins is similar to 95 kyr and those of two other veins are similar to 230 and similar to 250 kyr five of the veins have near equilibrium sup 230 th sup 234 u and are probably older than similar to 0 3 m y uranium concentrations in the remaining veins are too low for analysis by the cap alpha spectrometry techniques employed in this study of the five veins near sup 230 th sup 234 u equilibrium suggesting ages greater than similar to 1 0 m y but one has sup 234 u sup 238 u 1 15 suggesting an age between similar to 0 3 and similar to 1 0 m y calculated initial sup 234 u sup 238 u of the veins yielding relatively young ages are neither equal to each other nor to sup 234 u sup 238 u in thermal water from vc 1 indicating inconstancy of initial supmore 234 u sup 238 u tht may be related to variations in groundwater mixing proportions three of the four veins that yield relatively young ages consist of coarse sparry vuggy calcite suggesting that this may be the type of calcite vein which forms under conditions resembling those encountered presently in vc 1 the analytical data are consistent with closed system behavior of u and th in the vc 1 calcite veins copyright american geophysical union 1988 less

glaciation as a destructive and constructive control on mountain building glacial erosion is thought to have an important role in controlling mountain height a common perception is that glaciers are powerful erosive agents inhibiting the ability of active mountains to rise significantly above the elevation of permanent glaciation through a process known as the glacial buzzsaw but now a study of erosion patterns and climate data from the late cenozoic in the glaciated patagonian andes suggests that glaciation can also have the reverse effect in effect making mountains higher at these polar latitudes glaciation acts as a protective layer preserving the uplifting mountains from erosion and allowing them to reach heights well above those predicted had a glacial buzzsaw been active it has been suggested that glacial erosion has an important role in controlling mountain height here spatial and temporal patterns of erosion in the glaciated patagonian andes have been assessed with the help of a low temperature thermochronologic data set the results show that between 38 s and 49 s accelerated erosion at the onset of widespread glaciation limits mountain height but at higher latitudes glaciation protects the landscape from erosion and leads to growth in mountain height and width theoretical analysis predicts that enhanced erosion related to late cenozoic global cooling can act as a first order influence on the internal dynamics of mountain building leading to a reduction in orogen width and height1 2 3 the strongest response is predicted in orogens dominated by highly efficient alpine glacial erosion producing a characteristic pattern of enhanced erosion on the windward flank of the orogen and maximum elevation controlled by glacier equilibrium line altitude3 4 where long term glacier mass gain equals mass loss however acquiring definitive field evidence of an active tectonic response to global climate cooling has been elusive5 here we present an extensive new low temperature thermochronologic data set from the patagonian andes a high latitude active orogen with a well documented late cenozoic tectonic climatic and glacial history data from 38 s to 49 s record a marked acceleration in erosion 7 to 5 myr ago coeval with the onset of major patagonian glaciation6 and retreat of deformation from the easternmost thrust front7 the highest rates and magnitudes of erosion are restricted to the glacial equilibrium line altitude on the windward western flank of the orogen as predicted in models of glaciated critical taper orogens where erosion rate is a function of ice sliding velocity3 8 in contrast towards higher latitudes 49 s to 56 s a transition to older bedrock cooling ages signifies much reduced late cenozoic erosion despite dominantly glacial conditions here since the latest miocene6 the increased height of the orogenic divide at these latitudes well above the equilibrium line altitude leads us to conclude that the southernmost patagonian andes represent the first recognized example of regional glacial protection of an active orogen from erosion leading to constructive growth in orogen height and width

methane origin and oxygen fugacity evolution of the baogutu reduced porphyry cu deposit in the west junggar terrain china most porphyry copper deposits worldwide contain magnetite hematite and anhydrite in equilibrium with hypogene copper iron sulfides chalcopyrite bornite and have fluid inclusions with co2 ch4 that are indicative of high fo2 in contrast the baogutu porphyry cu deposit in the west junggar terrain xinjiang china lacks hematite and anhydrite contains abundant pyrrhotite and ilmenite in equilibrium with copper iron sulfides chalcopyrite and has fluid inclusions with ch4 co2 that are indicative of low fo2 the mineralized intrusive phases at baogutu include the main stage diorite stock and minor late stage diorite porphyry dikes the main stage stock underwent fractional crystallization and country rock assimilation contamination and consists of dominant diorite and minor gabbro and tonalite porphyry the country rocks contain organic carbons 0 21 0 79 wt the 13cvpdb values of the whole rocks 23 1 to 25 8 in the wall rocks suggest a sedimentary organic carbon source the 13cvpdb values of ch4 28 2 to 36 0 and co2 6 8 to 20 0 in fluid inclusions require an organic source of external carbon and equilibration of their 13cco2 ch4 values 8 2 25 0 at elevated temperatures 294 830 c suggesting a significant contribution of thermogenic ch4 mineral composition data on the main stage intrusions such as clinopyroxene hornblende biotite magnetite ilmenite sphene apatite and pyrrhotite suggest that the primary magma at baogutu was oxidized and became reduced after emplacement by contamination with country rocks mineral compositions and fluid inclusion gas compositions suggest that the redox state of the system evolved from logfo2 fmq 1 in the magma stage to logfo2 fmq in the hydrothermal stage though oxidized magma was emplaced initially assimilation contamination of carbonaceous country rocks decreased its fo2 such that exsolved fluids contained abundant ch4 and deposited a reduced assemblage of minerals

hydrothermal alteration in the valles caldera ring fracture zone and core hole vc 1 evidence for multiple hydrothermal systems two types of hydrothermal mineral assemblages kaolinite alunite and sericite chlorite were recognized in outcrop and core samples from the jemez volcanic field new mexico active and fossil acid sulfate hydrothermal activity producing kaolinite alunite alteration occurs along the caldera ring fracture and within the resurgent dome whereas alterations of the chlorite sericite type are mostly confined to subsurface rocks k ar dates on illitic clays 2 m 2 0 25 m and 0 25 m separated from hydrothermally altered samples are used to document hydrothermal episodes in pre caldera rocks of the jemez volcanic field the clay separates are illitic 75 95 illite layers with k2o contents of 8 24 8 95 in the core samples and 4 22 6 67 in the outcrops three episodes of hydrothermal alteration are now recognized in the jemez mountains region based on k ar age dates of illites the earliest event 17 11 ma n 4 occurred within altered and illite rich 90 illite layers lowermost paleozoic rocks in core hole vc 1 and may correlate with the inception of volcanism in the jemez region 16 5 ma illitic clays from altered andesite and rhyolite from the topographic rim of the valles caldera were dated at 8 2 and 6 96 ma suggesting that a hydrothermal event related to the waning stages of the keres group volcanism 13 5 8 ma was responsible for the alteration these dates overlap minimum ages obtained on slightly altered basalt 8 05 ma and andesite lava 7 07 ma from the southern and northwestern topographic rim of the valles caldera respectively ages of 1 21 and 1 34 ma from illite rich 90 illite layers hydrothermally altered paleozoic sandstone at a depth of 479 m in vc 1 suggest hydrothermal activity contemporaneous with the formation of the toledo 1 45 ma and valles 1 12 ma calderas ore minerals of sphalerite chalcopyrite galena barite and molybdenite mineralization occur in the lower half of vc 1 and are related to the toledo and valles caldera forming eruptions

exhumation history of the tatry mountains western carpathians constrained by low temperature thermochronology this study tests alternative models for the growth of the tatry mountains central western carpathians by the application of low temperature thermochronology zircon u th he ages from the north of the range are mostly between 48 to 37 ma and indicate cooling prior to the onset of forearc sedimentation in the region 42 39 ma in contrast zircon u th he ages in the south of the range are around 22 ma apatite fission track ages across the sampled sites range from 20 to 15 ma apatite u th he ages range from 18 to 14 ma with little variation with elevation or horizontal location based on thermal modelling and tectonic reconstructions these miocene ages are interpreted as cooling in the hanging wall of a northward dipping thrust ramp in the current location of the sub tatric fault with cooling rates of 20 c myr at 22 14 ma modeled cooling histories require an abrupt deceleration in cooling after 14 ma to 5 c myr this is associated with termination of deformation in the outer carpathians and is synchronous with the transition of the pannonian basin from a syn rift to a post rift stage and with termination of n s compression in the northern part of the central western carpathians overall the timing of shortening and exhumation is synchronous with the formation of the outer carpathian orogen and so the miocene exhumation of the tatry record retro vergent thrusting at the northern margin of the alcapa microplate

temporal relations of volcanism and hydrothermal systems in two areas of the jemez volcanic field new mexico two hydrothermal alteration events 8 07 ma one sample 6 51 5 60 ma six samples related to the waning stages of late miocene volcanism ge 13 to le 5 8 ma are recognized at the cochiti district southeast jemez mountains most of the k ar dates 0 83 plus minus 0 11 0 66 plus minus 0 21 ma four samples in the hydrothermally altered caldera fill rocks of core hole vc 2a at sulfur springs valles caldera indicate post valles caldera hydrothermal alteration a sample from acid altered landslide debris of postcaldera tuffs from the upper 13 m of the core hole was too young to be dated by the k ar method and is possibly associated with current hot spring activity and the youngest pulses of volcanism oxygen isotope data from illite smectite clays in the cochiti district are zonally distributed and range from minus 2 15 per thousand to plus 7 97 per thousand smow depending upon temperature extent of rock fluid interaction and composition the samples from vc 2a get lighter with depth minus 0 20 per thousand to plus 1 62 per thousand the k ar and oxygen isotope data provide strong evidence that the epithermal quartz vein hosted gold silver mineralization at cochiti and the sub ore grade molybdenite at vc 2a were deposited in the late miocene 5 99 5 60 ma and mid quaternary approximately 0 66 ma respectively by hydrothermal fluids composed primarily of meteoric water

k ar dates of hydrothermal clays from core hole vc 2b valles caldera new mexico and their relation to alteration in a large hydrothermal system abstract seventeen k ar dates were obtained on illitic clays within valles caldera 1 13 ma to investigate the impact of hydrothermal alteration on quaternary to precambrian intracaldera and pre caldera rocks in a large long lived hydrothermal system 1 0 ma to present clay samples came from scientific core hole vc 2b 295 c at 1762 m which was spudded in the sulphur springs thermal area and drilled into the boundary between the central resurgent dome and the western ring fracture zone six illitic clays within quaternary caldera fill debris flow tuffaceous sediment and ash flow tuff 48 to 587 m depth yield ages from 0 35 to 1 09 ma illite from miocene pre caldera sandstone 765 m gives an age of 6 74 ma two dates on illite from sandstones in permian red beds 1008 and 1187 m are 4 33 and 4 07 ma respectively surprisingly three dates on illites from altered andesite pebbles within the red beds 1010 1014 m are 0 95 to 1 06 ma four illite dates on variably altered precambrian quartz monzonite 1615 1762 m range from 2 90 to 276 ma post valles age illite is not correlated with alteration style argillic to propylitic rather post valles ages are uniformly obtained from illites in highly fractured intensely altered caldera fill rocks and the permian volcanic clasts generally finer clay fractions from identical samples yield younger ages plots of 40 ar 36 ar versus 40 k 36 ar and 40 ar versus 40 k for the illites in caldera fill rocks lie close to a 1 ma isochron most illite dates older than valles caldera are difficult to interpret because they correspond to the ages of pre valles volcanic and hydrothermal episodes in the jemez volcanic field 13 ma in addition older dates may be caused by co mingling of different illites during sample preparation or by inherited argon or lost argon in illites from rocks with potentially complex hydrothermal histories however the range of ages obtained from illites in permian sands and pebbles and from precambrian crystalline rocks indicates that valles hydrothermal activity is overwhelming illite produced by earlier geologic events

snežna jama slovenia interdisciplinary dating of cave sediments and implication for landscape evolution caves are important markers of surface evolution since they are as a general rule linked with ancient valley bottoms by their springs however caves can only be dated indirectly by means of the sediments they contain if the sediment is older than common dating methods one has to use multiple dating approaches in order to get meaningful results u th dating palaeomagnetic analysis of flowstone and sediment profiles cosmogenic dating of quartz pebbles and mammalian dating allowed a robust estimate of speleogenesis sediment deposition climatic change at the surface and uplift history on the periadriatic fault line during the plio pleistocene our dates indicate that sne na jama was formed in the upper miocene received its sedimentary deposits during the pliocene in a rather low lying hilly landscape and became inactive due to uplift along the periadriatic and sava faults and climatic changes at the beginning of the quaternary although it is only a single cave the information contained within it makes it an important site of the southern alps

the geochemistry of apatite from the los colorados iron oxide apatite deposit chile implications for ore genesis apatite grains from the los colorados iron oxide apatite ioa deposit the largest ioa deposit in the chilean iron belt cib exhibit significant intracrystalline spatial variability with respect to the concentrations of f cl and oh and trace elements statistical interrogation of the compositional data indicates that individual apatite grains contain spatially discrete f rich and cl rich domains the chemical composition of the f rich domains is consistent with apatite growth from silicate melts whereas the chemical composition of the cl rich domains is consistent with apatite growth from a magmatic hydrothermal fluid that cooled as it percolated outward from the los colorados fault the structural control for emplacement of the ore body into the surrounding brecciated diorite and andesite host rocks apatite in the deposit is intimately intergrown with magnetite and actinolite for which trace element fe h and o stable isotope data indicate a combined magmatic magmatic hydrothermal genesis for the deposit the compositional data for apatite are consistent with a genetic model wherein f rich apatite cores crystallized with magnetite from silicate melt followed by exsolution of a magmatic hydrothermal fluid during decompression of the parent magma experimental studies demonstrate that magmatic hydrothermal volatile phase bubbles preferentially nucleate and grow on the surfaces of apatite and magnetite microlites during decompression of a magma body continued degassing of the melt results in the volatile phase sweeping up apatite and magnetite microlites and forming a magnetite apatite fluid suspension that is buoyant in the magma chamber and ascends from the source magma along faults during regional extension halite saturated fluid inclusions in magnetite which is paragenetically equivalent to apatite at los colorados indicate that the magmatic hydrothermal fluid was a brine which allows this fluid to efficiently scavenge cl p rare earth elements and other fluid compatible elements from the silicate melt during ascent the xcl xf ratio of apatite increases as it grows from the evolving cl rich magmatic hydrothermal fluid during decompression and cooling

geology of the post collisional porphyry copper molybdenum deposit at qulong tibet porphyry deposits are usually thought to form from subduction related calc alkaline magmas in magmatic arc settings although some porphyry deposits also occur in post collisional extensional settings the post collisional deposits remain poorly understood here we describe the igneous geology alteration mineralogy and mineralization history of qulong a newly discovered porphyry cu mo deposit in southern tibet that belongs to the post collisional class the deposit is associated with miocene monzogranite granodiorite intrusions and is hosted partly by jurassic andesitic dacitic volcanic rocks the deposit contains 7 1 mt cu and 0 5 mt mo metal the 19 5 ma granodioritic monzogranitic rongmucuola pluton with diorite enclaves is the earliest miocene intrusive unit it was intruded by a regularly shaped stock p porphyry and then thin dikes x porphyry of monzogranite at about 17 7 ma the main cu mo mineralization is associated with the p porphyry a barren diorite porphyry intruded the p and x porphyries around 15 7 ma petrologic trends of the intrusions suggest that the miocene intrusions have similar origins and probably formed by fractionation of a deeper magma chamber emplacement of miocene porphyries controlled by the qulong anticline is in direct response to the rapid uplift erosion of the gangdese arc batholiths in southern tibet miarolitic cavities and unidirectional solidification textures key evidence for volatile separation have been recognized in the p and x porphyries respectively early potassic alteration characterized by quartz k feldspar anhydrite pervades the p porphyry and rongmucuola pluton laterally this alteration grades into quartz biotite anhydrite k feldspar which affects all miocene intrusions except the latest dioritic porphyry wall rocks of rongmucuola pluton and jurassic andesitic dacitic volcanics within 1 1 5 km of the porphyries are dominated by pervasive potassic alteration an outer halo of propylitic alteration epidote chlorite calcite extends up to 2 km away from the deposit feldspar destructive alteration sericite chlorite clay minerals has overprinted most of the potassic and part of the propylitic alteration the alteration is strongly pervasive in the interior of the porphyry bodies and occurs as vein halos away from the porphyry bodies the earliest quartz k feldspar alteration and veins are barren whereas approximately 60 of the cu reserves is associated with slightly later quartz biotite anhydrite alteration barren assemblages are related to irregular quartz k feldspar anhydrite veins which are truncated by the x porphyry cu sulfide bearing assemblages are associated with discontinuous chalcopyrite biotite and continuous quartz anhydrite chalcopyrite molybdenite veins deposition of cu mo with abundant anhydrite occurred during or between emplacement of closely related porphyries from high temperature magmatically derived fluids and was probably caused by the disproportionation of so

deglaciation chronology and paleoclimate of the pieciu stawow polskich roztoki valley high tatra mountains western carpathians since the last glacial maximum inferred from 36cl exposure dating and glacier climate modelling abstract exposure dating of abraded bedrock surfaces below glacial trimlines in the pieciu stawow polskich roztoki valley using cosmogenic 36 cl has been applied to determine the deglaciation chronology in the study area nineteen rock samples yielded ages between 21 5 and 9 5 ka the spatial distribution of ages provides evidence of progressive downwasting of glaciers within the study area dates of exposure indicate that the onset of ice volume decrease occurred no later than 21 5 ka this provides evidence that the local maximum glaciation occurred in accordance with the global last glacial maximum lgm the first period of deglaciation in the study area was completed around 18 ka further significant loss of ice volume is confirmed between 15 and 13 ka the spatial distribution of chronological data within the pieciu stawow polskich valley indicates post lgm readvances of glaciers around 17 ka and 12 ka using the glacier modelling and paleoclimate proxies from the study area the early late glacial glacier had been stable with a 9 10 c decrease in temperature and 30 50 lower precipitation in relation to modern conditions the subsequent advance took place with temperatures 6 7 c lower and 10 30 less precipitation the timing of the readvances is nearly synchronous with late glacial advances in the european alps southern carpathians and anatolian peninsula this suggests synchronicity of major climatic fluctuations across central europe and the northern margin of the mediterranean basin

tectonics of the jemez lineament in the jemez mountains and rio grande rift the jemez lineament is a ne trending crustal flaw that controlled volcanism and tectonism in the jemez mountains and the rio grande rift zone the fault system associated with the lineament in the rift zone includes from west to east the jemez fault zone southwest of the valles toledo caldera complex a series of ne trending faults on the resurgent dome in the valles caldera a structural discontinuity with a high fracture intensity in the ne jemez mountains and the embudo fault zone in the espanola basin the active western boundary faulting of the espanola basin may have been restricted to the south side of the lineament since the mid miocene the faulting apparently began on the sierrita fault on the east side of the nacimiento mountains in the late oligocene and stepped eastward in the early miocene to the canada de cochiti fault zone at the end of the miocene about 5 ma the active boundary faulting again stepped eastward to the pajarito fault zone on the east side of the jemez mountains the north end of the pajarito fault terminates against the jemez lineament at a point where it changes from a structural discontinuity zone of high fracture intensity on the west to the embudo fault zone on the east major transcurrent movement occurred on the embudo fault zone during the pliocene and has continued at a much slower rate since then the relative sense of displacement changes from right slip on the western part of the fault zone to left slip on the east the kinematics of this faulting probably reflect the combined effects of faster spreading in the espanola basin than the area north of the lineament abiquiu embayment and san luis basin the right step in the rift that juxtaposes the san luis basin against the picuris mountains and counterclockwise rotation of various crustal blocks within the rift zone no strike slip displacements have occurred on the lineament in the central and eastern jemez mountains since at least the mid miocene although movements on the still active jemez fault zone in the western jemez mountains may have a significant strike slip component basaltic volcanism was occurring in the jemez mountains at four discrete vent areas on the lineament between about 15 ma and 10 ma and possibly as late as 7 ma indicating that it was being extended during that time

pre and post exploitation variations in hydrothermal activity in los humeros geothermal field mexico abstract los humeros geothermal field is a remarkable example of the lack of water rock equilibrium significant variations of hydrothermal activity have occurred before and after exploitation started presently discharged water is not in equilibrium with the alteration suite observed in the reservoir rocks hydrothermal minerals identified in core and cuttings define the occurrence of several stages of hydrothermal activity cooling at depth is inferred from fluid inclusion and alteration mineralogy data from the wells located nearby los humeros fault most wells produce a two phase fluid with excess enthalpy this accounts for the high co2 content observed in the discharged fluid sulfur and carbon isotopic data indicate that volatile species in the geothermal fluid have magmatic as well as sedimentary components while strontium isotopic composition shows that calcium is provided by the andesitic rocks that form the reservoir as exploitation of the field started concentration of hcl increased in the discharged fluids this shows that recharge of the reservoir is not enough to balance the output for production and drying out of the field may be taking place at depth the lack of chemical equilibrium and the presence of gases of magmatic origin suggest that los humeros is a relatively young geothermal field related to a recent magmatic intrusion

introduction to special section on the valles caldera and jemez mountains volcanic field the jemez mountains volcanic field new mexico is one of the best known volcanic centers in the world because of pioneering efforts by c s ross r l smith r a bailey and their coworkers in the u s geological survey ross et al 1961 bailey et al 1969 smith et al 1970 the field contains roughly 2000 km3 of basaltic through rhyolitic rocks dominated volumetrically by andesites the most significant activity was formation of the toledo and valles calderas during eruption of over 600 km3 of rhyolitic ash flow tuffs the bandelier tuff during two phases 1 5 and 1 1 m y ago smith and bailey 1966 doell et al 1968 izett et al 1981 many concepts of pyroclastic flows and ignimbrites were based upon work in this volcanic field by ross and smith 1961

geomorphological evidence and 10be exposure ages for the last glacial maximum and deglaciation of the velka and mala studena dolina valleys in the high tatra mountains central europe abstract 10be exposure age chronology of the last glaciation was established in a key area at the southern slopes of the high tatra mts western carpathians in situ produced 10be in moraine boulders glacially transformed bedrock surfaces and rockfall accumulations constrains the timing of the last glacial maximum lgm glacier expansion and provides chronological evidence for the post lgm decay of one of the largest paleoglaciers in the range the uncertainty weighted mean age of 22 0 0 8 ka obtained for the terminal moraine in the forefield of the velka studena dolina valley indicates that the oldest moraine was deposited close to the global lgm this finding confirms that well preserved moraines in the range were formed during the last glacial cycle and that glaciation on the southern flank of the range was more extensive than earlier in the last glacial cycle the maximum glacier extent correlates with late wurmian weichselian glacier phases in the alps the bavarian bohemian forest and the krkonose mts but probably postdates the period of maximum glaciation in the southern carpathians re advance moraines at the mouth of the velka studena dolina valley and in the middle part of the mala studena dolina valley were deposited no later than around 20 5 ka and 15 5 ka respectively the timing of these advances is broadly synchronous within the high tatra mts as well as with glacier advances in the alps bavarian bohemian forest and krkonose mts 10be exposure ages obtained from glacially transformed bedrock surfaces range between 20 5 1 7 ka and 10 7 0 3 ka constraining the onset and the final phase of the deglaciation surface exposure dating of four rockfall accumulations produced uncertainty weighted mean ages of 20 2 1 2 ka 17 0 0 7 ka 16 5 0 4 ka and 15 6 0 7 ka these ages indicate that activation of rock slope failures occurred under paraglacial conditions within a few centuries up to 1400 years after the formation of re advance moraines

alteration in the madera limestone and sandia formation from core hole vc 1 valles caldera new mexico core hole vc 1 penetrated the southwestern ring fracture zone of the 1 1 ma valles caldera and at a depth of 333 m intersected the top of the paleozoic section including the abo formation madera limestone and sandia formation reaching a total depth of 856 m the paleozoic rocks which consist of thin bedded limestone siltstone mudstone sandstone and local conglomerate are overlain by volcanic rocks of the caldera moat that are less than 0 6 ma diagenetic and at least three hydrothermal alteration stages were identified in the madera limestone and sandia formation diagenetic clay alteration was pervasive throughout the sedimentary rocks volcanic activity at 16 5 ma and continuing through the formation of the valles caldera resulted in high thermal gradients which caused recrystallization of diagenetic clay minerals interstratified smectite illite is the most diagnostic clay mineral throughout the section structurally the illite component in the ordered interstratified illite smectite changes gradationally from 70 at the top of the madera limestone to 95 at the base of the section in the sandia formation pyrite that occurs as small clots and lenses as well as finely disseminated is interpreted as being of diagenetic origin especially in organic rich beds low permeability of much of the paleozoic section precluded the deposition of hydrothermal minerals except in fractures and intergranular space in some of the more permeable sandstone and brecciated horizons three stages of hydrothermal mineral deposition are defined stage i is widespread and includes mainly chlorite calcite pyrite and interstratified smectite illite that was formed prior to caldera development at temperatures approximating 200 c stage ii is characterized by quartz sericite and scarce sulfides deposited locally by fluids at approximately 275 c shortly before or at the time of early caldera related volcanism the stage iii hydrothermal event associated with formation of the valles caldera caused complex brecciation accompanied by deposition of phengite and molybdenite at temperatures locally approaching 300 c mostly in rocks underlying the madera limestone during the present drilling program thermal aquifers were encountered at 483 m 113 c 533 m 125 c and 845 m 184 c very close to the stage ii and iii mineralized zones however measured temperatures of the present hydrothermal system are much lower than during the main hydrothermal events good permeability has been maintained in these three levels for a long time while the rest of the madera limestone and sandia formation was sealed by hydrothermal mineral precipitation

hydrothermal alteration in the baca geothermal system redondo dome valles caldera new mexico thermal fluids circulating in the active hydrothermal system of the resurgent redondo dome of the valles caldera have interacted with their diverse host rocks to produce well zoned alteration assemblages which not only help locate permeable fluid channels but also provide insight into the system s thermal history the alteration shows that fluid flow has been confined principally to steeply dipping normal faults and subsidiary fractures as well as thin stratigraphic aquifers permeability along many of these channels has been reduced or locally eliminated by hydrothermal self sealing alteration from the surface through the base of the miocene paliza canyon formation is of three distinctive types argillic propylitic and phyllic argillic alteration forms a blanket above the deep water table in formerly permeable nonwelded tuffs beneath the argillic zone pervasive propylitic alteration is weakly developed in felsic host rocks but locally intense in deep intermediate composition volcanics strong phyllic alteration is commonly but not invariably associated with major active thermal fluid channels phyllic zones yielding no fluid were clearly once permeable but now are hydrothermally sealed high temperature alteration phases at baca are presently found at much lower temperatures we suggest either that isotherms have collapsed due to gradual cooling of the system that they have retreated without overall heat loss due to uplift of the redondo dome that the system has shifted laterally or that it has contracted due to a drop in the water table the deepest well b 12 3423 m in the dome may have penetrated through the base of the active hydrothermal system below a depth of 2440 m in this well hydrothermal veining largely disappears and the rocks resemble those developed by isochemical thermal metamorphism the transition is reflected by temperature logs which show a conductive thermal gradient below 2440 m this depth may mark the dome s neutral plane which separates an upper permeable zone of extensional fracturing from a lower less permeable compressional regime the baca hydrothermal system is similar to those which have formed ore deposits in other calderas particularly creede colorado type epithermal silver base metal veins and stockworks recent scientific drilling has also intersected a deep zone of strong phyllic alteration and molybdenum mineralization in the valles caldera s ring fracture system a setting which localized a large stockwork molybdenite orebody in the nearby questa caldera

microthermometry of fluid inclusions from the vc 1 core hole in valles caldera new mexico fluid inclusions in vein quartz and calcite from core samples of the vc 1 hole were studied with microscope heating freezing and crushing stages all samples originate from hydrothermally altered paleozoic rocks predating formation of the jemez mountains volcanic field and valles caldera most homogenization temperatures th of the liquid rich inclusions are above the present well temperature but some th of primary inclusions from 515 m and those of secondary inclusions from 723 m fit the present well temperature curve measured 10 months after completion of the well the maximum temperature recorded by the primary inclusions is 275 c from hydrothermal quartz in the sandia formation at 811 m depth the total range of th for samples from several depths 90 c indicates cooling from the maximum temperature the salinity of fluid inclusions in hydrothermal quartz and calcite is generally low 1 wt nacl eq high salinity fluid up to 5 wt nacl eq has been found in several calcite veins from the lower part of the madera limestone the salinity decreases with decrease of th of the secondary inclusions and that with lowest th at the lower part of the madera limestone is similar to those from the other depths these data show that early hot water circulation system involved several types of fluid whereas the later one was a homogeneous fluid the salinity of fluid inclusions in detrital quartz presumably inherited inclusions is higher than that in hydrothermal minerals some of these inclusions show extraordinary low temperatures of final melting point of ice about 40 c suggesting that a cacl2 component is present co2 contents in fluid inclusions were estimated by the bubble behavior on crushing crushing results indicate that co2 content of the early fluid is 0 35 wt and that of the later fluid is 0 2 0 3 wt geothermal fluid trapped in the fluid inclusions representing the present temperature regime is comparable in composition to those from the baca geothermal field inside the caldera and to those from hot springs in san diego canyon

abrupt glacial valley incision at 0 8 ma dated from cave deposits in switzerland glacial erosion dramatically alters mountain landscapes but the pace at which glaciers carve a previously fluvial landscape remains poorly defined because long term valley incision rates are difficult to measure here we reconstruct the lowering history of the aare valley switzerland over the past 4 m y by dating cave sediments with cosmogenic 26al and 10be incision accelerated from 120 m m y to 1200 m m y at 0 8 1 0 ma at least 1 m y after the onset of local glaciation rapid incision may have been triggered by lowering of the equilibrium line altitude at the mid pleistocene climate transition

extracting geothermal energy can be hard the initially high expectations of the mid 1970 s for the rapid development of geothermal energy have been lowered one reason is continuing uncertainty about the extraction of geothermal energy drillers can have a good idea of which areas have concentrations of geothermal energy beneath the surface and still have trouble bringing up enough energy to make a power plant worthwhile the extraction problem has been highlighted by the recent termination of a federal geothermal demonstration project at the baca field of the valles caldera new mexico the sixth largest geothermal province in the united states the problem at baca is not necessarily insoluble but it is tending to accentuate industry s cautious approach to geothermal exploration

sulfur evolution of the 1991 pinatubo magmas based on apatite abstract using electron microprobe emp and laser ablation inductively coupled plasma mass spectrometry la icp ms to collect major and rare earth elements ree respectively from apatites from the 1991 mt pinatubo juvenile eruption products we have determined that two statistically distinct populations of apatite exist one population crystallized from the juvenile basaltic melt basalt apatites and the other population crystallized from the main dacitic magma body silicic apatites both populations contain high s apatites 0 7 wt so3 apatite has previously been shown to be a potential monitor for magmatic sulfur contents via numerous proposed coupled substitutions of p5 for s6 however simple apatite melt partitioning cannot account for high s silicic apatites which grew from a silicic melt with an apparent maximum s concentration of 80 ppm disparate apatite morphology i e skeletal and acicular for basalt apatites and euhedral for silicic apatites as well as compositional evidence reveal that high s silicic apatites were not inherited from the juvenile basalt during mingling mixing prior to eruption sulfur gain from neighboring anhydrite phenocrysts can also be ruled out as a source of high sulfur emp sulfur mapping of silicic apatites shows highly irregular patterns of sulfur enrichment that do not correspond with adjacent anhydrite and can be found within apatites hosted by other minerals e g hornblende and fe ti oxides with these data in mind we propose high s silicic apatites from pinatubo and other sulfur rich systems achieved elevated sulfur concentrations during high sulfur fluxing events that originated from underplated basalt during degassing of a so2 rich fluid phase that basalts were indeed sulfur rich and oxidized is here indicated by high s contents of apatites growing in basalt the predominant location of s rich areas of silicic apatite is crystal interiors of apatite inclusions in other mineral phases while large apatite microphenocrysts surrounded by groundmass glass have low sulfur contents this is evidence for placing sulfur fluxing periods long before events that ultimately led to the 1991 eruption

young uplift in the non glaciated parts of the eastern alps abstract we report the first incision rates derived from burial ages of cave sediments from the mur river catchment at the eastern margin of the eastern alps at the transition zone between the alpine orogen and the pannonian basin this river passes through the paleozoic of graz a region of karstifiable rocks called the central styrian karst this river dissects the study area in a north south direction and has left behind an abundance of caves these caves can be grouped into several distinct levels according to their elevation above the present fluvial base level age estimates of abandoned cave levels are constrained by dating fluvial sediments washed into caves during the waning stages of speleogenesis with the terrestrial cosmogenic nuclide method these ages and the elevations of the cave levels relative to the current valley floor are used to infer a very complex history of 4 million years of water table position influenced by the entrenchment and aggradation of the mur river we observe rather low rates of bedrock incision over the last 4 ma in the order of 0 1 mm y with an e folding decrease in this trend to lower rates at younger times we relate this incision history to a tectonic setting where an increase of drainage area of the mur river due to stream piracy in late miocene to pliocene times is linked to surface uplift the later decrease in valley lowering rates is attributed to the rise of the base level related to aggradation of sediments within the valley sediment transport through the valley from the upstream section of the mur river limited the erosional potential of the river to a transport limited state at the later stages of the incision history

valles caldera region new mexico and the emerging continental scientific drilling program valles caldera is best known in recent years as an excellent example of a resurgent caldera smith and bailey 1968 and as the site of a high temperature geothermal system dondanville 1978 however valles caldera and the surrounding jemez mountains volcanic field possess a rich history of geologic research that dates back to the late 1800s through the years the research focus has changed as different economic and scientific factors have exerted their influence early work emphasized mining activity while modern work has stressed volcanology and later geothermal development only in the last 5 years has it been possible to view the region as a dynamic integrated magma hydrothermal system having a complex evolution lasting more than 13 m y gardner et al 1986 goff and nielson 1986 self et al 1986

soft sediment deformation structures in cave deposits and their possible causes kalacka cave tatra mts poland abstract clastic deposits in kalacka cave in the tatra mts show soft sediment deformation structures ssds rare for a cave environments the poorly sorted allochthonous sediments were deposited within a cave sump under a fluvial regime likely due to glacially initiated back flooding during the last glacial the structures include small scale faults normal and reverse folds upright symmetric anticlines low amplitude open folds w vergent folds and fault propagation folds and water escape structures a laboratory experiment is used to assess the possibile liquefaction of a thin soft sediment filling in a limestone tube including calculation of the site effects of resonance frequency and amplification coefficient and the site vulnerability index kg the calculations indicate that seismic waves can be amplified up to 10 times and the expected resonance frequency is 17 05 hz we argue that the observed ssds formed in two stages first brittle and ductile deformation structures developed due to gravity induced slumping next liquefaction produced water escape structures the studied ssds were likely seismically triggered favorable conditions occurred during the withdrawal of the last glacier mis 2 when the sediments were oversaturated and the tatra mts experienced a strong earthquake m7 0 alternatively high frequency microearthquakes could have been triggered by slope failure cutting into kalacka cave

a history of hot dry rock geothermal energy systems abstract this is a short history so far as it can now be assembled of early speculations and observations concerning the existence and origin of natural heat in the earth s crust of some of the many methods proposed to extract and use it and of recent investigations designed to develop and demonstrate such methods it is probably only the preface to a much longer history still to be written of mankind s beneficial use of this one of earth s oldest most plentiful most widespread and secure energy sources

relict landslide development as inferred from speleothem deformation tectonic data and geoelectrics abstract the direct dating of pre and postfaulting dislocated calcite speleothems afforded new insight into slope failure in the tatra mountains in southern poland a multi approach study of the karstic kalacka cave non crevasse type enabled us to infer the slope deformation structure which had been poorly preserved in ground surface topography using combined methods including geomorphological and structural mapping of cave and ground surfaces paleostress analysis near surface electrical resistivity tomography ert and induced polarization methods ip uranium series dating 234u 230th calcite microtexture analysis and stable isotope 18o and 13c analysis here slope deformation began with dilation between 280 7 ka and 265 8 ka and proceeded as deep seated gravitational slope deformations the final stage consisted of dilation rejuvenation and rockfall during the latest pleistocene or holocene post 35 4 ka additionally some dilations are evident beyond the extent of the landslide detected by ert indicating further progradation of slope failure since this failure was initiated during the climatic transition from mis 9 to mis 8 stable isotope analysis of calcite flowstone layers was applied to test climate factors the correlation of calcite microtexture and 18o and 13c compositional changes with the interval of dilation activity indicates that regional environment factors chiefly an increase in precipitation probably contributed to slope destabilization

paleomagnetism and rock magnetism of quaternary volcanic rocks and late paleozoic strata vc 1 core hole valles caldera new mexico with emphasis on remagnetization of late paleozoic strata paleomagnetic and rock magnetic data obtained from azimuthally unoriented core samples collected at approximately 1 to 3 m intervals of continental scientific drilling program core hole vc 1 have prompted reinterpretations of the quaternary volcanic stratigraphy intersected by the bore and have aided in evaluating the thermal regime within late paleozoic strata attending fluid circulation and mineral deposition during and after development of the toledo and valles calderas the results from quaternary units banco bonito obsidian i 35 4 a95 2 8 inclination only determinations n 33 battleship rock tuff d 359 6 i 42 4 a95 2 8 n 5 site means surface sites vc 1 rhyolite i 39 2 a95 12 8 n 7 upper vc 1 tuff i 37 2 a95 10 7 n 13 middle vc 1 tuff i 42 1 a95 2 1 n 39 south mountain rhyolite d 350 9 i 49 9 a95 3 4 n 10 one surface site are consistent with isotopic age data indicating that the entire moat volcanic sequence intersected is less than 650 kyr monitoring of natural remanent magnetization nrm intensity nrm directions directions of magnetizations isolated during progressive demagnetization median destructive forces and rock magnetization parameters has identified systematic variations within the thick banco bonito obsidian and vc 1 tuff units the permian abo formation pennsylvanian to earliest permian madera limestone and pennsylvanian sandia formation typically contain a moderate positive inclination magnetization component abo formation i 52 2 a95 7 4 n 16 madera limestone i 58 4 a95 2 8 n 105 sandia formation i 53 9 a95 4 8 n 21 when residing in magnetite it is usually unblocked in the laboratory by 350 c when carried by hematite it is unblocked by 550 c a moderate negative inclination e g madera and abo strata d 173 1 i 46 6 a95 5 5 n 47 samples assuming a north seeking positive inclination rm providing a useful means of core orientation oppositely directed magnetization is occasionally isolated and removed at higher laboratory unblocking temperatures up to 550 c in magnetite dominated and 600 c in hematite dominated lithologies where present magnetizations of shallower inclination e g madera and abo strata d 160 1 i 10 9 a95 4 4 n 28 are removed over higher ranges of unblocking temperatures and these are probably of late paleozoic age the moderate negative and positive inclination magnetizations are in all likelihood viscous partial thermoremanent magnetizations trms vptrms these were activated at moderate 300 c temperatures between 1 45 and 0 97 ma attending and following the main stages of toledo valles caldera development during the matuyama and at near present downhole temperatures 100 180 c during the brunhes and possibly within the last 10 kyr respectively importantly the preservation of negative inclination rm components in magnetite dominated lithologies of the madera limestone dictates that temperatures during the brunhes chron past 730 kyr did not exceed approximately 300 350 c the inferred temperatures for thermal activation of the vptrms based upon the middleton and schmidt thermal activation curves for both magnetite and hematite derived following walton agree with independent estimates of thermal activity using fluid inclusion and k ar isotopic age determination data during the quaternary the results further illustrate the potential usefulness of thermal activation theories for inferring temperatures of past geologic events especially when they can be applied to magnetizations of similar age residing in both magnetite and hematite and of paleomagnetic and rock magnetic studies in general in continuous coreholes in complex geologic environments

sulfur evolution of oxidized arc magmas as recorded in apatite from a porphyry copper batholith uniformly sulfur rich cores abruptly zoned to sulfur poor rims 1 to 0 2 wt so3 in apatite from the yerington batholith nevada indicate that early magma that is crystal poor oxidizing and sulfate rich evolved to sulfate poor magma via crystallization of anhydrite a mineral observed in magmas from pinatubo and el chichon we predict that the characteristic zonation to sulfur poor rims of apatite in the yerington batholith is common in other oxidized hydrous calc alkaline magmas and can be used to track cryptic anhydrite saturation as well as to monitor sulfur evolution sulfate rich arc magmas such as yerington magmas may crystallize to produce hydrothermal fluids rich in chlorine copper and sulfur and porphyry copper ores

high water contents of magmas and extensive fluid exsolution during the formation of the yulong porphyry cu mo deposit eastern tibet abstract the yulong porphyry cu mo ore district in eastern tibet features a series of eocene felsic porphyry intrusions only one of which is intensively mineralized in this study zircon u pb ages and major and trace element compositions of whole rock samples and in situ accessory minerals zircon apatite and titanite from these various intrusions were analyzed to determine the factors controlling cu mineralization new zircon u pb dating together with published zircon u pb ages suggest that these porphyry intrusions were emplaced over a relatively short period of time 43 9 0 6 ma to 40 9 0 3 ma with the mineralized yulong intrusion emplaced at a late stage of the magmatic activity 41 1 0 3 ma to 40 9 0 3 ma these intrusions have indistinguishable whole rock major and trace element compositions but the mineralized yulong intrusion has higher apatite and titanite la yb ratios average apatite la yb 115 1 28 5 n 52 average titanite la yb 22 4 4 9 n 38 than the earlier subeconomic intrusions average apatite la yb 50 4 12 3 n 72 average titanite la yb 12 4 3 5 n 58 suggesting more fractionation of amphibole from the magmas that sourced it additionally a negative relationship between la yb and cen cen ratios in apatite and titanite are interpreted to reflect increasing oxidation states through magma evolution indistinguishable zircon eun eun values and apatite core so3 contents from the mineralized zircon eun eun 0 69 0 06 n 25 apatite so3 0 65 0 24 wt n 21 and subeconomic intrusions zircon eun eun 0 62 0 05 n 64 apatite so3 0 61 0 27 wt n 15 suggest that the entire magmatic suite was relatively oxidized hydrous and sulfur rich and was therefore fertile for ore formation however apatite crystals from the mineralized yulong intrusion have significantly lower cl contents 0 08 0 03 wt n 72 and higher f cl ratios 47 80 21 97 n 72 than those from the subeconomic intrusions cl 0 29 0 29 wt f cl 12 87 5 16 n 78 these data may reflect more extensive fluid exsolution from the parental magma chamber at the time of emplacement of the mineralizing yulong magmas sudden and voluminous release of volatiles coeval with emplacement of the yulong intrusion was triggered by an as yet unidentified process but possibly including magmatic recharge

climatic limits on landscape development in the northwestern himalaya the interaction between tectonism and erosion produces rugged landscapes in actively deforming regions in the northwestern himalaya the form of the landscape was found to be largely independent of exhumation rates but regional trends in mean and modal elevations hypsometry frequency distribution of altitude and slope distributions were correlated with the extent of glaciation these observations imply that in mountain belts that intersect the snowline glacial and periglacial processes place an upper limit on altitude relief and the development of topography irrespective of the rate of tectonic processes operating

last glacial maximum and lateglacial in the polish high tatra mountains revised deglaciation chronology based on the 10 be exposure age dating abstract deglaciation chronology of the polish high tatra mountains has been reconstructed based on 10 be exposure age dating fifty seven rock samples were collected from boulders located on the terminal and lateral moraines that limit the horizontal extent of the lgm and the lateglacial glaciers in the biala woda and sucha woda catchments the uncertainty weighted mean age of 21 5 2 5 ka obtained for the maximum terminal moraine in the sucha woda valley indicates that the oldest preserved moraines were formed during the global lgm the age population ranges between 15 1 1 0 and 28 3 2 0 ka and suggests that glaciers reached their maximum position lgm i as early as 28 25 ka and the final stabilization of the form occurred much later possibly after melting of buried dead ice the younger glacial oscillation lgm ii occurred no later than 20 5 ka and is represented by well preserved termino lateral moraine systems in the panszczyca valley the first lateglacial stage lg1 in the study area is documented in the rybi potok valley at the rp1 moraine 1300 m a s l which was stable at around 16 6 0 3 ka the younger lg2 stage has no defined absolute age however it is constrained between 16 5 and 15 5 ka by the timing of the lg3 stage this cold event is represented by well formed moraines in the roztoka piec stawow polskich rybi potok and panszczyca valleys of which exposure age indicates their deposition between 15 0 0 5 and 15 6 0 1 ka the lg1 lg2 and lg3 stages likely occurred during the oldest dryas cold stage greenland stadial 2 1a related to the north atlantic cooling heinrich event 1 the youngest glacial oscillation is evidenced by moraines in the pusta and panszczyca valleys these moraines are composed of very large granitic blocks of which exposure ages often exhibit isotope inheritance this is reflected by the youngest p3 moraine in the panszczyca valley with a mean age of deposition close to the lgm the r4 moraine system in the pusta valley however indicates two oscillations phases that occurred at around 13 ka and correlates well with the timing of rp5 moraine formation in the za mnichem valley the lg4 stage is related to the climate cooling during the younger dryas greenland stadial 1 lgm elas reconstructed for the biala woda and sucha woda panszczyca glaciers were located at 1460 1480 m a s l during the oldest dryas stages the ela in the high tatras rose from 1600 to 1650 m a s l in the rybi potok valley and from 1700 to 1800 m a s l in the roztoka piec stawow polskich valley the younger dryas ela depending on glacier s exposition was located between 1950 and 2000 m a s l climate modelling results show that the lgm glaciers maximum advance could have advanced in the high tatras when the mean annual temperature was lower than today by 11 12 c and precipitation was reduced by 40 60 during the lateglacial stages the temperature decrease in the study area changed from 10 c during the oldest dryas to 6 c during the younger dryas and precipitation lowering decreased from 50 to 30 or even 10 respectively compare to modern conditions

oxygen isotope disequilibrium between quartz and sanidine from the bandelier tuff new mexico consistent with a short residence time of phenocrysts in rhyolitic magma abstract oxygen isotope analyses are reported from co existing quartz and feldspar from the bandelier tuff and cerro toledo high silica rhyolitic pyroclastic deposits erupted from the valles caldera new mexico quartz shows little variation outside analytical error but 18 o in feldspar varies over 1 in most samples 18 o 16 o fractionation between quartz and feldspar is significantly less than is predicted for equilibrium at temperatures appropriate for rhyolitic magma in the tshirege upper member of the bandelier tuff isotopic fractionation between mineral pairs is close to equilibrium in the later erupted ignimbrite but non equilibrium in the initial plinian deposit these relationships are interpreted in terms of a model where most phenocrysts are derived from a highly porphyritic carapace around the magma chamber that was disrupted by eruption thus scattering crystals throughout the magma carapace quartz and feldspar are initially isotopically lighter than the bulk aphyric magma due to chemical communication with low 18 o country rock in the meteoric hydrothermal system surrounding the chamber we assume that quartz and feldspar were initially in isotopic equilibrium diffusive re equilibration of crystals begins when the carapace disintegrates and the minerals are immersed in the bulk magma just prior to and during eruption feldspar is isotopically lighter than quartz at equilibrium but responds more rapidly than quartz to an external change due to a higher diffusion coefficient for oxygen hence immersion in the isotopically heavier bulk magma causes feldspar and quartz 18 o values to initially converge over 10 2 years and then diverge over 10 3 10 4 years as first feldspar and then quartz re equilibrate with the new magma higher 18 o variability of feldspar than quartz indicates that the shorter timescale applies to the bandelier and cerro toledo rhyolites two important implications of this interpretation are 1 that the bandelier magmas developed in an aphyric condition and their porphyritic character is an artifact of eruption and 2 that a protective mechanically rigid cognate carapace around a silicic magma chamber may limit interaction with low 18 o hydrothermally altered crust thus hindering the development of significant volumes of low 18 o silicic magma

saalian supercycle mindel riss interglacial and milankovitch s dating abstract there are five pleistocene glacial interglacial cycles recorded in deep sea sediments from the last half million years but only two classic interglacials are recognized on land the dilemma stems from the different understanding and identification of glacials and interglacials in the geologic records on land and in the ocean only those intervals of warm climate that followed a major southward ice sheet advance and were accompanied by a deep penetrating oceanic transgression were recognized in their type areas of northern europe as true interglacials only those ice advances which left moraines farther south than younger ones were recognized as glacials in contrast all intervals reflecting exceptionally low global ice volume high sea level and warm sea surface are taken as interglacials in the deep sea record classic subdivisions are aligned with the glacial interglacial cycles of marine isotope stage stratigraphies by proposed higher order units called supercycles sc bracketed by superterminations st the saalian supercycle sc2 includes glacial cycles c d and e composed of marine isotope stages mis 6 7 8 9 10 and 11 the units mis 7 to mis 11 correspond to the great gross interglacial estimated from the early geologic considerations to be about 240 millennia long penck and bruckner 1909 die alpen im eiszeitalter vols 1 3 christian herman tauchnitz leipzig and determined from astronomic computations to last 235 millennia milankovitch 1941 kanon der erdbestrahlung und seine anwendung auf das eiszeitenproblem academie royale serbe editions speciales section des sciences mathematiques et naturelles tome cxxxiii stamparija mihaila curcica beograd 633pp the current high precision radiometric dating fully confirms the accuracy of milankovitch s determination and the pivotal role of orbital mechanisms in pleistocene climate change

numerical modeling of the development of u shaped valleys by glacial erosion the steep sided valleys and overdeepened basins of alpine landscapes are well known products of glaciation yet relatively little is known about how the dynamics of ice flow and glacial erosion interact to give rise to such landforms by linking a finite element model for ice flow through a glacier cross section with an erosion model it is possible to investigate the development of one of the most striking glacial landforms the u shaped valley in addition to providing a detailed understanding of landform development such modeling provides a way to test current understanding of the controls on glacial sliding and erosion to simulate valley development i first model flow through an initial glacier cross section and calculate the glaciological parameters that govern erosion i then numerically simulate erosion to produce a modified transverse profile for which a new flow field and erosion pattern are computed a number of iterations permits examination of the progressive transformation of cross section form which can be compared with field data model predictions of the cross section flow field are in close accord with data from the athabasca glacier and include marked lateral variations in sliding velocity with an erosion law dependent on basal velocity the model predicts the rapid transformation of a v shaped cross section into a recognizably glacial form over a time period on the order of 10 4 yr and the eventual development of a steady state quasi parabolic glacier cross section better agreement with empirical data from glaciated valleys is obtained by including temporal variations in ice discharge in order to mimic the characteristics of 100 000 yr glacial cycles the high discharge phase dominates form development and at low discharges cross section form is essentially inherited from the central part of the form that developed during the preceding high discharge phase

temporal patterns of tephra alterations in various geologic settings the jemez volcanic field and the adjacent morrison formation in new mexico and colorado abstract authigenic mineral assemblages and temporal constraints of tephra layers altered by hydrothermal activities subaerial weathering and burial diagenesis are described clay size assemblages in the jenez volcanic field the hydrothermal illite smectites in core hole vc 2a range between 0 66 and 0 83 ma for subsurface plio pleistocene tephra deposits 1 14 1 78 ma and interbedded volcaniclastic units whereas similar clays from altered miocene rocks yield ages between 5 6 and 8 1 ma these clays formed during hydrothermal alterations related to the waning phases of the various volcanic episodes of the area clinoptilotites from the zeolitized tephra units from the late jurassic morrison formation gave discordant dates ranging from 154 to 83 ma whereas the illite smectites from the bentonite beds of the same formation yielded two age groups 29 69 38 2 and 53 7 56 ma all the k ar results were interpreted using the k ar isochron method and in most cases the isochron ages are similar to the conventional k ar results the altered tephra layers provide diagnostic regional marker horizons in addition to recording concisely the time of diagenetic processes in various geologic settings