geothermometry and geobarometry applied to early proterozoic s type granitoid plutons wopmay orogen northwest territories canada many of the s type granitoid plutons that comprise hepburn and wentzel batholiths of the early proterozoic wopmay orogen contain garnet biotite and rarely cordierite and sillimanite the garnet cordierite and sillimanite are interpreted to be relict crystals brought up from the depth of origin of the magmas

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

evidence of large scale deformation patterns from gps data in the italian subduction boundary abstract we present the velocity field in italy derived from over 300 continuous gps stations operated in the 1998 2009 time span the gps network maps the whole country with a mean inter site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central mediterranean the estimated horizontal and vertical velocity fields show major significant features and also less known second order kinematic features a general uplift characterizes the whole apennines and alpine belts that follow the topographic ridge whereas the po plain shows a gradually increasing subsidence from west to east the apennines belt displays a distinctive extension 50 80 10 9 yr 1 while compressive tectonic regimes characterize northern sicily eastern alps and the northeast front of the northern apennines 25 50 10 9 yr 1 second order deformation patterns on large scale wavelength 100 km have been detected on the accretionary prism of central and southern apennines that are highly correlated with other geophysical data vp anomalies seismic anisotropy etc and related to deep rooted sections 70 100 km marked by different subduction regimes apparently at this scale length the observed deformations are governed by the lithosphere as a whole we interpret these deformations as a result of different subduction mechanisms such as variations of the subduction rollback velocity affecting different segments of the subduction zone and or to mantle flows in proximity of the slab edges further south in central southern sicily we detect a contraction of 1 1 0 2 mm yr that probably accommodates part of the africa eurasia convergence on the outer thrust front of the apennines maghrebides belt this hypothesis agrees with an independent analysis of the seismicity associated to the sicilian basal thrust thought to be still active the itrf2005 estimates of the new gps velocity field are available also in sinex format as supplementary file s1

crustal structure evolution and volcanic unrest of the alban hills central italy the alban hills a quaternary volcanic center lying west of the central apennines 15 25 km southeast of rome last erupted 19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka earthquakes of moderate intensity have been generated there at least since the roman age modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features the phreatomagmatic craters on the west side of the volcano results from seismic tomography allow identification of a low velocity region perhaps still hot or partially molten more than 6 km beneath the youngest craters and a high velocity region probably a solidified magma body beneath the older central volcanic construct thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters the volume of magma accumulation and the amount of maximum uplift was probably at least 40 106 m3 and 40 cm respectively comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift the magma chamber beneath the western alban hills is probably responsible for much of the past 200 ka of eruptive activity is still receiving intermittent batches of magma and is therefore continuing to generate modest levels of volcanic unrest bending of overburden is the most likely cause of the persistent earthquakes which generally have hypocenters above the 6 km deep top of the magma reservoir in this view the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity

calculating velocity fields across plate boundaries from observed shear rates summary a general horizontal velocity field can be expressed uniquely in terms of the velocities at points along a line and an integral function of the 2 d shear rate consequently the relative motion across a plate boundary can be calculated from observed shear rates by taking the velocities along a line within one of the plates to be zero

geochemistry of s type granitic rocks from the reversely zoned castelo branco pluton central portugal abstract the zoned pluton from castelo branco consists of variscan peraluminous s type granitic rocks a muscovite biotite granite in the pluton s core is surrounded successively by biotite muscovite granodiorite porphyritic biotite muscovite granodiorite grading to biotite muscovite granite and finally by muscovite biotite granite id tims u pb ages for zircon and monazite indicate that all phases of the pluton formed at 310 1 ma whole rock analyses show slight variation in 87 sr 86 sr 310 ma between 0 708 and 0 712 nd 310 ma values between 1 and 4 and 18 o values between 12 2 and 13 6 these geological mineralogical geochemical and isotopic data indicate a crustal origin of the suite probably from partial melting of heterogeneous early paleozoic pelitic country rock in detail there is evidence for derivation from different sources but also fractional crystallization linking some of internal plutonic phases least squares analysis of major elements and modelling of trace elements indicate that the porphyritic granodiorite and biotite muscovite granite were derived from the granodiorite magma by fractional crystallization of plagioclase quartz biotite and ilmenite by contrast variation diagrams of major and trace elements in biotite and muscovite the behaviours of ba in microcline and whole rock 18 o the ree patterns of rocks and isotopic data indicate that both muscovite dominant granites were probably originated by two distinct pulses of granite magma

petrology and geochemistry of potassic and ultrapotassic volcanism in central italy petrogenesis and inferences on the evolution of the mantle sources major trace element sr isotopic and mineral chemical data are reported for mafic volcanic rocks mg value 65 from the northern central sector of the potassic volcanic belt of central italy the rocks investigated range from potassic series ks and high k series hks to lamproitic lmp and kamafugitic kam through a transitional series trans thus covering the entire compositional spectrum of potassic and ultrapotassic magmas kam rocks are strongly silica undersaturated and compared with the other rock series have low sio2 al2o3 na2o sc and v and high cao k na na k al ks and hks have high al2o3 cao and variable enrichment in k2o and incompatible elements lmp rocks are saturated in silica and have high sio2 k2o k2o na2 mgo ni and cr and low al2o3 cao na2o sc and v trans rocks display intermediate compositional characteristics between lmp and ks all the rocks under study have fractionated hygromagmaphile element patterns with high lil hfs element values and negative anomalies of ti ta nb and ba negative sr anomalies are observed in the lmp and trans rocks lil elements show overall positive correlations with k2o whereas different trends of sr and hfse vs k2o are defined by lmp trans and ks hks kam 87sr 86sr range from about 0 710 to 0 716 ks hks and kam rocks have similar 87sr 86sr values clustering around 0 710 lmp and trans rocks have the highest 87sr 86sr values geochemical and isotopic data reported for the most primitive italian potassic and ultrapotassic rocks support the hypothesis that the interaction between crustal and mantle reservoirs was a main process in the genesis of italian potassic magmatism simple mass balance calculations exclude however an important role of crustal assimilation during ascent of subcrustal magmas to the surface and indicate that the sources of central italy volcanics underwent contamination with fluids and or melts released by upper crustal material previously brought into the mantle by subduction processes different trends of incompatible elements vs k2o observed in the studied rocks suggest distinct metasomatic processes for the sources of the investigated magmas liquids derived by bulk melting of pelitic sediments are believed to be the most likely contaminants of the source of lmp rocks fluids or melts rich in ca sr and with high lile hfse value and sr isotopic composition around 0 710 are the most likely contaminant of the source region of ks hks and kam volcanics variations in cao na2o and ferromagnesian element abundances and ratios suggest that in some zones the mantle source of potassic magmas experienced partial melting with extraction of basaltic liquids prior to metasomatism

crustal deformation rates in central and eastern u s inferred from gps analysis of continuous gps observations between 1996 and 2000 at 62 stations distributed throughout the central and eastern united states suggests that the area is generally stable seven of the 62 stations show anomalous velocities but there is reason to suspect their monument stability assuming the remaining 55 stations are stable with respect to interior north america we have found the north america itrf97 euler vector 1 88 1 04 n 77 67 0 39 w 0 201 0 004 myr 1 that minimizes the rms station velocity referred to fixed north america all of these velocities are less than 3 2 mm yr 1 motion of several stations suggests the mississippi embayment may be moving southward away from the rest of the continent at a rate of 1 7 0 9 mm yr 1 the motion of the embayment produces a large gradient in velocity which in turn implies the highest seismic moment accumulation rate that we found although the highest rate is only marginally significant the fact that it occurs near new madrid where earthquake risk is thought to be high argues that the anomaly may be real nevertheless the identification of the anomaly remains tentative

accelerated stress buildup on the southern san andreas fault and surrounding regions caused by mojave desert earthquakes a sequence of four mw 6 earthquakes including the 1992 mw 5 7 3 landers and mw 5 7 1 hector mine earthquakes occurred in the mojave desert in the 1990s in close proximity to the southern san andreas fault inducing stress changes on several of its segments we calculate that coseismic slip combined with postseismic relaxation of viscous lower crust and or upper mantle has led to a coulomb stress increase of 2 3 3 5 bar on the san bernardino mountain segment of the southern san andreas fault between 1992 and 2001 with a projected increase of 3 6 4 9 bar by the year 2020 in comparison the calculated coseismic stress increase is 1 8 bar for this segment this accelerated buildup of stresses is predicted to bring the san bernardino mountain segment which last ruptured more than 190 yr ago closer to a potentially major rupture meanwhile we project a net stress decrease of as much as 23 5 bar between 1992 and 2020 for the western coachella valley segment if the fault is governed by low effective friction or an increase of 1 5 bar if the fault is governed by high effective friction coulomb stresses are calculated to decrease on the mojave segment by as much as 21 bar between 1992 and 2020 accelerated stress buildup is also predicted to occur on parts of the san jacinto elsinore and calico faults the pattern of the observed post landers aftershock clustering and the calculated coulomb stress buildup on the calico fault is similar to that noted in the hector mine region prior to the 1999 mw 5 7 1 earthquake these results imply that the stress changes caused by an earthquake may still play a role in triggering future quakes in neighboring crust many years later through viscoelastic processes

physical properties of tuffs from a scientific borehole at alban hills volcanic district central italy recent seismic swarms and hydrothermal activity suggest that the quaternary volcanic complex of the alban hills may pose a threat to the city of rome a 350 m scientific borehole was therefore drilled into this volcanic area to elucidate its inner structure for the first time wire line logs were run in the borehole in order to characterize the physical properties of the rocks and their variations with depth in particular a detailed sonic log was run to measure the p wave velocity from the well head down to 110 m to further investigate velocity changes we carried out laboratory measurements of p and s elastic wave velocities and fluid permeability at effective pressures up to 70 mpa during both increasing and decreasing pressure cycles on selected core samples representative of the main volcanic units specifically we studied samples from two pyroclastic units representative of two classes of volcanic deposits that are representative of the whole succession i a coarse grained well lithified facies pozzolane rosse unit containing abundant mm to cm lava clasts and crystals and ii a fine grained matrix supported pyroclastic deposit tufo pisolitico di trigoria unit with rare lithic lava clasts and sparse pumice elastic wave velocities reveal significant differences between units and indicate how within the same lithology the different degree of lithification and presence of clasts can affect significantly physical property values the mean laboratory value of the p wave velocity for pozzolane rosse and tufo pisolitico di trigoria units is respectively of 3 75 and 3 2 km s at an effective pressure equivalent to that at the depth at which the sonic velocity was measured under increasing effective pressure a profound influence on the transport properties is observed permeability ranges from the order of 10 18 m 2 for the pozzolane rosse unit to the order of 10 15 m 2 for the tufo pisolitico di trigoria unit in good agreement with the shallow aquifer circulating in the shallower units c 2008 elsevier b v all rights reserved

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

lower crustal structure in northern california implications from strain rate variations following the 1906 san francisco earthquake 1 it is well known that geodetic data from a single instant in time cannot uniquely characterize structure or rheology beneath active seismogenic zones nevertheless comparison of spatial and temporal variations in deformation rate with time dependent mechanical models can place valuable constraints on fault zone geometry and rheology we consider postseismic strain rate transients by comparing geodetic data from north of san francisco bay obtained between 1906 and 1995 to predictions from viscoelastic finite element models models include 1 an elastic plate over a viscoelastic half space 2 distributed shear within a viscoelastic layer 3 discrete shear zones within an otherwise elastic layer 4 discrete shear zones in combination with distributed viscoelastic shear and 5 midcrustal detachment surfaces we vary as applicable locking depth elastic thickness depth to the top and bottom of the distributed shear layer distributed shear relaxation time discrete shear zone relaxation time and discrete shear zone width the best fitting physically reasonable elastic plate over viscoelastic half space models 1 do a poor job simultaneously predicting spatial and temporal variations in the data the best fitting distributed shear models 2 do a poor job predicting spatial variations in the deformation rate although they fit the geodetic data recent findings from seismic reflection refraction studies in northern california argue against models with shallow subhorizontal detachments 5 models incorporating discrete shear zones 3 4 provide the best fit to the geodetic data and are consistent with seismic studies that argue for discrete fault zones extending through the entire crust

co2 release variations during the last 2000 years at the colli albani volcano roma italy from speleothems studies abstract the colli albani is the quiescent volcano that dominates the southwestern skyline of roma italy the last eruption occurred during the holocene from the eccentric albano maar along its western slope the volcano is presently affected by cyclic seismic swarms ground uplift and diffuse co 2 degassing the degassing has caused several deadly incidents during the last years and constitutes a major civil protection concern as the volcano slopes are densely inhabited nevertheless the volcano does not have a permanent monitoring network and the background level and anomalous co 2 levels the relationship between the gas release and the seismic and ground deformation activity at the colli albani are still to be defined the aim of this work is to define the historical record of co 2 release evidences of deep co 2 periodic release during the last 2000 years in the area of colli albani volcano roma italy are offered from speleothems studies a roman age stone mine now used for mushroom cultivation is decorated with actively growing speleothems characterised by depositional hiatuses different levels of four stalactites separated by depositional unconformities and several samples from a single depositional cycle belonging to a stalagmite have been dated by u th method and analysed for their o and c isotopic composition eight cycles of deposition have been identified from 90 110 a d to 1350 1370 a d some of which are recognised across different speleothems the age gap dividing different growth layers is in the order of one to few hundred years giving a temporal span for periodic interruption of speleothems deposition o and c isotopic analyses performed on the samples collected from a single cycle the oldest have shown that the composition of the mother solutions was initially mainly meteoric and that a progressive increase in the input of a deep component rich in co 2 up to a proportion of 20 30 occurred just before the interruption of the speleothem deposition this could be due to a progressive increase of the acidity of the water solutions that caused the undersaturation of fluids if we extrapolate this mechanism to the other cycles of deposition being characterised by analogue isotopic compositions we can hypothesise periods of deposition interrupted by episodes of co 2 release which in the colli albani volcano are often recorded in coincidence with earthquakes therefore we have correlated the hiatuses with some of the largest historical earthquakes interesting to the city of rome

nature and origin of proterozoic a type granitic magmatism in the southwestern united states of america the mountain ranges of arizona and adjacent california and nevada contain large areas underlain by proterozoic anorogenic granites comprising the southwesternmost portion of a transcontinental belt of 1 4 1 5 ga old anorogenic complexes that extends across north america northeast into labrador of these a two mica monazite bearing granitic suite resides in central and southeastern arizona as part of a peraluminous subprovince that is bordered on the south southern arizona to sonora and west western arizona and adjacent portions of california and nevada by marginally metaluminous granites bearing biotite sphene hornblende and fluorite all of these 1 4 ga granites are distinctly more potassic iron enriched relative to mg and depleted in ca mg and sr in contrast to typical orogenic granitoids in general the large ion lithophile element enriched composition is a consequence of limited melting of a water deficient crustal source at depths greater than 25 37 km for the peraluminous granites this contrast is less extreme perhaps resulting from a larger degree of melting as a consequence of a greater metasedimentary component and water in its crustal source the anorogenic granitic magmas intruded into the upper crust at depths of 8 17 km or shallower at temperatures up to 790 c the most dramatic variation in the crystallization intensive parameters resides in the oxygen fugacity which spans three orders of magnitude relative to other anorogenic suites all of the magmas crystallized at elevated levels of o2 as reflected in their assignment to the anorogenic magnetite series yet a regionally significant rise in primary o2 levels unmatched elsewhere in the transcontinental belt occurs for plutons in western arizona including the holy moses and hualapai granites the most extreme case is the hualapai granite whose biotite fe fe mg ratios drop due to high o2 to a low of 0 27 down from more typical levels of 0 54 to 0 75 such extreme variations in primary levels of oxygen fugacity must be an indirect imprint of regional changes of the level of oxidation of the lower crust the high fo2 holy moses and hualapai plutons have intruded near the regional boundary between the metaluminous and peraluminous granites and appear to be imaging a major change in the level of oxidation of the lower crust this boundary is also approximately equivalent to significant changes in the nd and pb isotopic compositions of these granites and the metamorphic and magmatic character of the older orogenic terrane on a global scale the crust forming orogenies ended by 1 6 ga ago and the continents entered a long lived era dominated by localized extension and transcontinental intrusion of anorogenic potassic rapakivi granite mafic dike swarms charnockite and anorthosite the absence of orogenic deformation implies that plate consumption became intraoceanic during this time the profuse and widespread nature of the igneous activity has no phanerozoic analogue and is considered to be unique to the proterozoic a crustal overturn model ties the magmatism to heating within a largely undepleted subcontinental mantle the eventual rise of mantle plumes and the transfer of heat into the youthful undifferentiated proterozoic crust subsequent melting and rise of potassic granitic magmas from the lower crust leads to considerable crustal reorganization a process that would continue until both the mantle and crust reached a stable configuration

accidental gas emission from shallow pressurized aquifers at alban hills volcano rome italy geochemical evidence of magmatic degassing abstract recent studies suggested that alban hills rome is a quiescent and not an extinct volcano as it produced holocene eruptions and several lahars until roman times by water overflow from the albano crater lake alban hills are presently characterized by high p co2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover gas consists mostly of co 2 with minor h 2 s and the diffuse co 2 soil flux is locally very high accidental gas blowouts occurred during shallow well drillings tens to hundreds m depth in zones with no surface gas manifestations indicate the presence of gas pressurized aquifers confined underneath impermeable layers within both the volcanic rock pile and the underlying pleistocene loose sediments degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the mesozoic carbonate basement hosting the main aquifer carbon isotopic composition 13 c co2 suggests that co 2 is at least partly originated by thermal decarbonation of these limestones 3 he 4 he isotopic ratio of the gas up to 1 9 ra is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the alban hills volcanic products indicating a possible magmatic source for the gas low r ra values compared to morb and island arc magmas are characteristic of the potassic roman comagmatic province and reflect a deep involvement of crustal material in the magma genesis the lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains

effect of crustal layering upon dislocation modeling slip distribution at depth on a fault may be inferred from the deformation observed on the surface in inverting the surface deformation data to obtain the slip distribution the earth is generally approximated by an elastic half space slip distributions inferred from a half space model may contain artifacts including zones of reversed slip due solely to effects of layering in the real earth this effect is demonstrated for a vertical strike slip fault in an earth consisting of an elastic layer overlying an elastic half space slip on the fault is taken to be independent of the along strike coordinate i e antiplane strain is assumed for a given slip distribution in this model the slip distribution on a similar fault in an elastic half space is found that produces the identical surface deformation comparison of the two slip distributions reveals structure introduced into the half space equivalent slip profile by crustal layering the comparisons suggest that low resolution inversion schemes e g single screw dislocation models are not drastically affected by earth structure but attempts at detailed inversion are likely to produce profiles contaminated by artifacts of earth structure

crystal chemistry of trioctahedral micas in the top sequences of the colli albani volcano roman region central italy abstract trioctahedral mica crystals are frequently found in the volcanoclastic products emplaced during the final stages of the activity of the colli albani volcano roman region central italy in the youngest phreatomagmatic deposits mica is found either as a minor mineral phase in holocrystalline ejecta scoriae and coherent pyroclastics or as loose phenocryst in incoherent pyroclastics based on optical and electron microscope investigations as well as crystal chemical and structural data the micas selected for this study were divided into two groups the first one encompassing brownish fe rich crystals type a phlogopites hereafter referred as t a with 0 68 from a petrological point of view the textural and chemical variations of t a phlogopites are compatible with fractional crystallization processes taking place within the magma chamber t b phlogopites show evidence of a ti oxy substitution mechanism thus suggesting high fo2 conditions textural and paragenetic features observed in t b phlogopite bearing rock samples indicate a genesis by thermal metamorphism of a siliceous dolomitic limestone with the input of a variable amount of a potassic magma possibly the same from which the t a phlogopites formed with the exception of one sample for which a different parental magma is suggested indeed there is an almost continuous spectrum of crystal chemical and structural parameters starting from t b and evolving towards t a phlogopites the t a phlogopites displays complex apparently meaningless relationships in their crystal chemical parameters thus indicating interplay of several substitution mechanisms they possibly formed in polybaric conditions since their cell volumes differ but the total size of the cations hosted in the octahedral sheet is the same

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

gps derived strain rate field within the boundary zones of the eurasian african and arabian plates we use the gps velocity field 1988 1998 for eastern mediterranean and asia minor to determine the crustal deformation strain rate field in an area bounded by 35 n and 43 n and 20 e and 48 e we calculate the normal and shear strain rate components associated with the major faults and compare these qualitatively with seismological data uncertainties in the calculation of the strain rates reach 50 nstrain yr 1 in sparsely observed parts of anatolia whereas we estimate errors 20 nstrain yr 1 in the aegean and marmara regions the largest compressional strain rate components in the eastern part of the study area occur along the greater caucasus mountain front reaching 70 nstrain yr 1 1 nstrain yr 1 0 0317 10 15 s 1 the north anatolian fault zone is the clearest feature in the shear strain rate field it is expressed as a pronounced dextral strike slip fault zone reaching rates of up to 170 nstrain yr 1 this holds true also for the izmit area where the august 17 1999 earthquake occurred central anatolia is almost strain free whereas extension prevails in western anatolia the principal axes of extension vary around the n s direction with strain rates of up to 85 nstrain yr 1 these extensional areas coincide with graben features and normal faulting earthquakes the central and southwestern aegean sea is strain free with values far below 40 nstrain yr 1 the seismic cluster around the dodekanissa islands southeastern aegean sea coincides with nw se oriented extension attaining strain rates of up to 90 nstrain yr 1 this area of extension also exhibits recent active volcanism the entire hellenic arc shows compressional strain rates perpendicular to the arc the pliny strabo troughs along the eastern segment of the arc show left lateral shear strain rates reaching 80 nstrain yr 1 significant extension is found in central greece with a nne ssw oriented maximum of 120 nstrain yr 1 centered around the gulf of corinthos the kephalonia fault zone in nw greece is a distinct dextral fault zone separating apulia from the rapidly moving aegean microplate right lateral shear strain rates reach 150 nstrain yr 1

looking into a volcanic area an overview on the 350 m scientific drilling at colli albani rome italy abstract a 350 m deep borehole was drilled in the colli albani volcanic district central italy in order to understand the shallow crust structure beneath the volcanic complex characterize the rock physical properties especially through in situ measurements and afterward laboratory experiments assess the local present day stress field install a broad band seismometer at depth the borehole is located adjacent to the western rim of the tuscolano artemisio caldera where several phenomena of unrest recently occurred in 1989 90 a seismic swarm affected this area and a related uplift was recognized in addition high gas concentrations mainly co 2 and h 2 s in aquifers and soils caused illnesses and casualties among inhabitants and animals in the past we describe the investigations carried out at the drill site and the results achieved from data analysis wire line drilling produced a complete stratigraphic record of the quaternary volcanic units down to the plio pleistocene sedimentary sequence and geophysical logs allowed a characterization of the rock physical properties from a tectonic point of view data provided by dipmeter and borehole televiewer were used for investigations on the recent and present day stress field and the results are compared to those available in the literature in the volcanic units we recognized two main fracture systems sw and nw dipping several faults intersecting the borehole show planes with oblique striae indicating a prevalent strike slip component of the movement finally borehole breakout analysis defined an active stress field with a e w oriented minimum horizontal component at the end of the drilling a blow out occurred due to pressurized fluids trapped into the sandy unit drilled in the last few meters of the hole sampling these fluids gave an additional value to the borehole providing information about the deep volcanic circulation and its possible connection to a deep seated magma chamber the main results show water with a na hco 3 chemistry and the highest salinity ever recognised in the area electrical conductivity 10 12 ms cm stable o and h isotopes reveal a meteoric origin of water and the absence of tritium points out a long residence time in the aquifer emitted gas is co 2 dominated with n 2 as second most important component helium isotopic composition of the gas allows us to estimate a magmatic component ranging in the interval 40 50 one of the highest in the colli albani carbon isotopes of co 2 0 53 vs pdb suggest that it could derive partly from a magmatic source and partly by the thermal decarbonation of the carbonatic basement

copper partitioning between felsic melt and h2o co2 bearing saline fluids abstract analysis of fluid inclusions from porphyry copper deposits reveals that magmatic vapor and brine are vital for the removal of copper from arc magmas and its transport to the site of ore deposition experiments in melt vapor brine systems allow for investigation of the partitioning of copper between silicate melts and volatile phases at magmatic conditions the presence of co2 affects both the pressure at which a melt saturates with respect to volatile phases therefore the partitioning of copper among felsic rhyolitic melt vapor and brine in co2 bearing experiments was examined to provide insights into copper partitioning and the generation of porphyry copper and related deposits we present results from experiments performed at 800 c and 100 mpa in co2 bearing melt vapor brine systems with x co 2 v b 0 10 and 0 38 the compositions of vapor and brine inclusions and run product glasses were determined during the course of this investigation microthermometric measurements of fluid inclusions show an increase in the salinity of the magmatic brine 65 to 70 wt nacleq and decrease in the salinity of the vapor 3 5 to 1 wt nacleq as x co 2 is increased from 0 10 to 0 38 the partitioning of copper between brine and vapor d cu b v 2 increases from 25 6 at x co 2 0 10 to 100 30 at x co 2 0 38 the partitioning of copper between vapor and melt d cu v m 2 decreases from 9 6 3 3 at x co 2 0 10 to 2 0 8 at x co 2 0 38 these data demonstrate that copper partitioning in sulfur free co2 bearing systems is controlled by the changes in the salinity of the vapor and brine that in turn are functions of x co 2 no change in the apparent equilibrium constants for cu na exchange was observed in fe bearing experiments which supports a salinity dependent model for copper partitioning an existing model mvpart for ore metal partitioning between melt and volatile phases was modified to incorporate partitioning data from co2 bearing experiments the model can be used to predict trends in efficiency of removal of copper from melts into exsolving co2 bearing magmatic volatile phases at a fixed pressure and temperature the co2 mvpart model predicts that co2 rich x co 2 0 38 magmatic vapor will remove half of the available copper from the melt without a contribution from the brine compared to low co2 x co 2 0 10 systems thus periods of co2 rich vapor exsolution are not expected to be associated with efficient removal of copper from shallow felsic melts

viscoelastic earthquake cycle models with deep stress driven creep along the san andreas fault system 1 we develop a two dimensional boundary element earthquake cycle model including deep interseismic creep on vertical strike slip faults in an elastic lithosphere coupled to a viscoelastic asthenosphere uniform slip on the upper part of the fault is prescribed periodically to represent great strike slip earthquakes below the coseismic rupture the fault creeps in response to lithospheric shear stresses within a narrow linear viscous fault zone the model is applied to the gps contemporary velocity field across the carrizo plain and northern san francisco bay segments of the san andreas fault as well as triangulation measurements of postseismic strain following the 1906 san francisco earthquake previous analysis of these data using conventional viscoelastic coupling models without stress driven creep segall 2002 shows that it is necessary to invoke different lithosphere asthenosphere rheology in northern and southern california in order to explain the data we show that with deep stress driven interseismic creep on the san andreas fault the data can be explained with the same rheology for northern and southern california we estimate elastic thickness in the range 44 100 km 95 confidence level fault zone viscosity per unit width of 0 5 8 2 1017 pa s m and asthenosphere relaxation time of 24 622 years 0 1 2 9 1020 pa s for northern and southern california we estimate a slip rate of 21 27 mm yr and recurrence time of 188 315 years for the northern san francisco bay san andreas fault and slip rate of 32 42 mm yr with recurrence time of 247 536 years for the carrizo plain

active detachment faulting in the san francisco bay area measurements of crustal deformation may help determine if mid crustal reflectors imaged at 15 km depth below the san francisco bay area california are active detachment horizons that accommodate strike slip shear and or convergence across the region elastic dislocation models predict distinguishable secular surface displacements for fault geometries involving vertical shear zones or horizontal detachments only where faults step bend or branch along their trace in the southern san francisco bay area the san andreas hayward and calaveras fault zones splay from a single trace of the creeping central segment of the san andreas fault whereas measured horizontal surface displacements in the central and northern bay area are equally well predicted by models of strike slip faults below the major faults and by models involving a detachment a zone of fault normal motion observed in the southern bay area is not well explained by models involving only vertical strike slip faults a model involving detachment slip parallel to the san andreas fault appears more consistent with the observations we find no evidence for significant san andreas fault normal regional contraction or detachment faulting however additional data and better models are required to more confidently constrain the three dimensional active fault architecture

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

deformation during the 12 november 1999 duzce turkey earthquake from gps and insar data only 87 days after the mw 7 5 17 august 1999 izmit earthquake the duzce earthquake ruptured a ca 40 km long adjoining strand of the north anatolian fault naf system to the east we used displacements of 50 global positioning system gps sites together with interferometric synthetic aperture radar insar range change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture postseismic deformation transients from the duzce earth quake and the preceding i zmit event that are included in some of the measurements are corrected for using dislocation models fit to gps data spanning the various time periods nonlinear inversions for fault geometry indicate that the rupture occurred on a ca 54 north dipping oblique normal right lateral fault distributed slip inver sions indicate maximum strike slip near the center of the duzce fault close to the earthquake hypocenter slip magnitude and depth of faulting decrease to the west and east of the hypocenter both gps and insar data suggest that normal slip is restricted to the shallow portion of the rupture the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the naf

the spectrum of ore deposit types volcanic environments alteration halos and related exploration vectors in submarine volcanic successions some examples from australia variations in shape metal content alteration mineralogy and volcanic host rocks of the ore deposits in the two major volcanic hosted massive sulfide vhms districts of eastern australia the cambrian mount read volcanics and the cambro ordovician mount windsor subprovince strongly reflect their volcanic environment conditions of ore formation and hydrothermal alteration processes lens and sheet style polymetallic zinc rich deposits such as rosebery hellyer que river and thalanga are considered to have formed in moderate to relatively deep water environments 500 1 000 m these deposits probably formed either on the sea floor e g hellyer que river or by replacement of porous volcaniclastic units directly below the sea floor e g rosebery the footwall alteration associated with these polymetallic vhms deposits was controlled by host rock permeability and porosity which are in turn related to volcanic facies type degree of fracturing and synvolcanic structural architecture focusing of hydrothermal fluids along synvolcanic structures has resulted in well zoned chlorite sericite footwall alteration pipes within footwall lavas at hellyer on the other hand diffuse fluid flow through very thick pumice breccia at rosebery and hercules has resulted in strata bound sericite dominated footwall alteration zones parallel to the paleosea floor and the ore lenses massive and disseminated pyritic cu au deposits such as those in the mount lyell field and at highway reward formed by subsea floor replacement and are associated with only minor zinc lead massive sulfide ore these deposits formed from higher temperature fluids 300 degrees c in which copper transport is enhanced and are commonly located in felsic volcanic centers dominated by shallow porphyritic intrusions e g highway reward the cu au ore lenses may be strata bound e g mount lyell or crosscutting pipes e g highway reward depending on the structure and permeability characteristics of the felsic volcanic host rocks the presence of high sulfidation alteration minerals e g pyrophyllite zunyite in some of the cu au deposits e g mount lyell field indicates that fluids were relatively acidic and suggests the possibility of magmatic fluid input into the hydrothermal system alteration zonation associated with the cu au vhms deposits is more symmetrical than that of the zn rich deposits with sericite rich alteration extending into the hanging wall in keeping with the subsurface replacement origin of these deposits synvolcanic gold rich deposits with high gold base metal ratios are less common than the cu au and zn rich vhms ore types the gold rich ores e g henty south hercules are strata bound in nature have low sulfide contents and are associated with central zones of intense silicification surrounded by envelopes of sericite pyrite and carbonate alteration volcanological and geochemical studies at henty indicate the gold rich ore formed by the replacement of particular volcanic units deposited in a relatively shallow water environment dominated by volcaniclastic facies lavas and limestones this spectrum of cu au zn rich and au only deposits in the mount read volcanics and the mount windsor subprovince is interpreted to represent a continuum from classic sea floor vhms ores toward those with features more akin to porphyry cu au and epithermal au ag deposits this spectrum relates to the interplay between factors in the submarine volcanic environment and the character of the hydrothermal fluid as follows 1 proportions of volcaniclastic lava and subvolcanic intrusive facies 2 depth of seawater 3 permeability and porosity of volcanic host rocks 4 balance between magmatic components and seawater components in the ore fluid and 5 temperature and acidity of the ore fluid mineralogical lithogeochemical and isotopic studies have revealed a range of alteration vectors useful in exploration for both the zn rich and cu au vhms deposits carbonate and white mica compositional variations are highlighted as important mineralogical vectors thallium and antimony halos may be useful trace element vectors and oxygen and sulfur provide important isotope vectors toward the center of the hydrothermal system

the albano maar lake colli albani volcano italy recent volcanic activity and evidence of pre roman age catastrophic lahar events abstract the evaluation of volcanic hazard in the roman hinterland related to the quiescent colli albani volcano has recently been the subject of renewed attention and several interpretations by many authors however very little was known of the recent history of the volcano making such interpretations rather speculative the most recent activity of colli albani volcano originated from the albano polygenetic maar lake which erupted several phreatomagmatic units the most recent of which the peperino albano ignimbrite has been dated at around 25 ka an area of several square kilometers centered around albano lake is presently the site of shallow and frequent seismic activity and gaseous emission as well as hydrothermal activity and is therefore considered the most prone to geologic hazards this paper presents new stratigraphic and geomorphologic data as well as age determinations that allow rejuvenation of the most recent activity of the colli albani volcano and particularly the albano maar lake to the holocene this study allows for the first time to identify a potential hazard related to the albano maar lake withdrawal interpreted to be related to endogenous causes namely co 2 emission the main results of the study are 1 the peperino albano is not as is generally believed the last phreatomagmatic eruption from the colli albani volcano a previously unrecognized phreatomagmatic surge deposit has been identified overlying the paleosol at the top of the peperino albano and related lahar deposits 2 two lahar deposits separated by paleosols top the stratigraphic succession and are dispersed only to the nw corresponding to the lowest point of the maar rim indicating that catastrophic hydrologic events occurred at the albano lake in recent times rapid and substantial lake level variations and lake withdrawal are reported by roman historians and recorded by the stratigraphy of the albano lake lacustrine sediments 3 microfracturing related to seismic energy release is linked to sudden variation of co 2 flow and upwelling of hydrothermal fluids these occurrences across the lake are the likely causes that triggered during holocene several episodes of lake withdrawal rising the water table and probably triggering convective rollover of the lake water

chemical composition of rock forming minerals in gold related granitoid intrusions southwestern new brunswick canada implications for crystallization conditions volatile exsolution and fluorine chlorine activity chemical composition of rock forming miner als in appalachian siluro devonian granitoid intru sions southwestern new brunswick was systematically determined by electron microprobe the mineral chem ical data together with petrographic examination was used to test magmatic equilibration and to constrain crystallization conditions volatile exsolution and fluo rine chlorine activity of fluids associated with these intrusions mineralogical distinction between late silu rian to early devonian granodioritic to monzogranitic series gms and late devonian granitic series gs rocks is evident although both are subsolvus i type to evolved i type granitoids oxidized to reduced gms rocks consist of quartz plagioclase an 10 k feld spar biotite apatite titanite zircon monazite hornblende pyroxene magnetite ilmenite and sulfide gs rocks comprise quartz k feldspar pla gioclase an 10 mica group minerals zircon mon azite apatite sulfide ilmente magnetite topaz columbite and xenotime inter intrusion and intra intrusion variations in mineral chemistry are in terpreted to reflect petrogenetic processes e g assim ilation and fractional crystallization during granitoid evolution although magmatic equilibration among rock forming minerals are disturbed by subsolidus hy drothermal processes gms rocks appear to have higher magmatic temperatures variable levels of emplacement a range of fo2 i e reduced intrusions 10 16 7 10 13 4 and oxidized intrusions 10 14 0 10 10 5 bars and rela tively low fhf fhcl ratios 10 3 0 10 1 0 in exsolved fluids compared to gs rocks reduced gms intrusions bear higher gold potential and thus may be prospective targets for intrusion related gold systems

experimental determination of au solubility in rhyolite melt and magnetite constraints on magmatic au budgets the solubility of au metal in rhyolite melt and coexisting magnetite has been determined at 800 c 140 mpa and f 0 2 nno in a au metal saturated sulfur free vapor brine silicate melt system whole crystals of magnetite suspended within quenched rhyolite glass were analyzed by la icp ms these data yield a solubility of au in magnetite on the order of 2 g g the solubility of au metal in rhyolite melt hosting the magnetite crystals is on the order of 500 ng g these data indicate a partition coefficient for au between magnetite and melt d m t m e l l au 4 using reasonable estimates of the mass fraction of magnetite that crystallizes in crustal magmatic systems we modeled the proportion of au sequestered by magnetite during fractional crystallization we considered fractionation in two steps the idealized derivation of a rhyolite by fractionation of basalt at depth and the closed system crystallization of the rhyolite in a magma chamber below the site of ore deposition magnetite sequesters 14 54 au from basaltic parent melt that produces a rhyolite melt via crystal fractionation at modal abundances of 1 5 less then 4 au is sequestered from a crystallizing rhyolite melt because of low modal abundances of magnetite 2 our experimental and model results suggest that early crystallization of magnetite can play a mitigating role in the ability of a calc alkaline magmatic system to yield a au rich ore fluid

modes 2d method of detecting strike shift shear zones one of the goals of using the global positioning system gps and other geodetic survey techniques in tectonics has been to detect boundaries such as faults or shear zones between rigid or mildly deforming crustal masses the calculation of infinitesimal strains and rotations with gps data has been widely used to detect shear zones but it has been largely unsuccessful because infinitesimal strain and rotation although useful in many other ways is non diagnostic of shear zones or faults our approach is to work with components of deformation not strain and to design specifically a diagnostic method of detecting shear zones this paper introduces the first part of our method the detection of two dimensional strike shift shear zones modes 2d the modes 2d method has three elements 1 determination of the orientation of a suspected strike shift shear zone by analyzing components of a deformation tensor derived from a data set of displacements in an arbitrary coordinate system 2 resolution of the deformation tensor into the coordinate system parallel and normal to the detected shear zone and 3 exploration of the resolved data set for evidence for a belt of inhomogeneous deformation which is an essential characteristic of a shear zone the operation of modes 2d is illustrated herein with a theoretical survey network across an ideal shear zone developed with a buried dislocation fault and with a survey network afforded by the crossing of the kaynasli viaduct by the 1999 duzce bolu earthquake rupture in turkey

recent terrestrial and satellite observations to model deformations at colli albani volcano central italy the colli albani volcanic complex rome italy has been dominated by episodic eruptions commencing around 561 ka and ending with the most recent activity of the albano maar phase 70 ka earthquakes of moderate intensity gas emissions and significant ground deformations are the recent evidences of a residual activity former geodetic data from leveling surveys gps stations and insar observations tracked ongoing significant uplift of the order of few mm year near the colli albani western flank different uplift rates were detected by each technique in different time spans suggesting also the possibility of sporadic recharge of the hydrothermal system the renewed high precision leveling data from igmi survey carried out in 1997 1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of 3 mm year radar interferograms from alos satellite show uplift rate of 6 mm year southwest of the central sector of the leveling route we have undertaken a joint inversion of the various geodetic data vertical rates from leveling surveys gps site velocities and insar observations acquired by alos satellite using a nonlinear inversion technique to estimate the parameters of a point pressure source possibly capable of explaining the ongoing deformation at colli albani volcano

average regional strain due to slip on numerous faults of different orientations if a region is cut by faults with different orientations and if the faults intersect the boundaries of the region of interest then the average finite rotational strain eij ui xj is given by eij mij v where is the shear modulus v is the volume of the region and mij represents the sum of asymmetric moment tensors mij for each fault mij m0 u n where m0 is the scalar seismic moment and u and n are the unit vectors parallel to the slip vector and perpendicular to the fault plane this result is applicable when the average regional strain occurs primarily by displacements of essentially rigid blocks that together compose the region of interest and hence when both elastic strains and inelastic strains due to folding and bending are small

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

interseismic strain and rotation rates in the northeast mojave domain eastern california 1 the northeast mojave domain a type locality for bookshelf faulting is a region of east striking left lateral faults in the northeast corner of the mojave block a block otherwise dominated by n40 w striking right lateral faults paleomagnetic evidence suggests that blocks within the domain have rotated clockwise about a vertical axis as much as 60 since 12 8 ma schermer et al 1996 in 1994 and again in 2002 the u s geological survey surveyed an array of 14 geodetic monuments distributed across the northeast mojave domain the 2002 survey results were adjusted to remove the coseismic offsets imposed by the nearby hector mine earthquake 16 october 1999 mw 7 1 the adjusted deformation across the array appears to be uniform and can be approximated by the principal strain rates e1 28 9 9 1 n77 2 w 4 8 and e2 48 2 8 9 n12 8 e 4 8 nstrain yr 1 extension reckoned positive and quoted uncertainties are standard deviations that strain accumulation could be released by slip on faults striking n32 w but not by bookshelf faulting on the east striking faults alone the vertical axis rotation rate of the northeast mojave domain as a whole relative to fixed north america is 71 0 6 4 nrad yr 1 4 07 0 37 myr 1 clockwise about twice the maximum tensor shear strain rate the observed rotation rate acting over 12 8 myr would produce a clockwise rotation of 52 1 4 7 exclusive of possible coseismic rotations that rotation is in rough agreement with the paleomagnetic rotation accumulated in the individual fault blocks within the northeast mojave domain since 12 8 ma

porphyry tungsten molybdenum orebodies polymetallic veins and replacement bodies and tin bearing greisen zones in the fire tower zone mount pleasant new brunswick the fire tower zone at mount pleasant contains geologically complex deposits that are associated with two distinct phases of granite an older fine grained granite associated with tungsten molybdenum orebodies and a younger granite porphyry to which tin and polymetallic zones appear to be related based on potassium argon and rubidium strontium isotope analyses both phases of granite and their associated deposits were emplaced at approximately 340 to 330 m y ago geochemically both phases are silica rich aluminous potassic and fluorine rich porphyry tungsten molybdenum orebodies occur mainly in fire tower breccia and to a lesser extent in quartz feldspar porphyry country rock and the fine grained granite which underlies the breccia the orebodies consist of mineralized fractures quartz veinlets and disseminations in breccia matrix wolframite and molybdenite the principal ore minerals occur together with abundant fluorite and arsenopyrite and minor amounts of bismuth and bismuthinite associated greisen type alteration consists of quartz topaz sericite fluorite which grades outward through an assemblage of quartz biotite chlorite topaz into propylitic alteration mainly chlorite sericite crosscutting relationships between mineralized fractures and veinlets indicate that mineralization occurred in multiple stages the earlier stages being more tungsten rich and the later stages more molybdenum rich tin bearing polymetallic veins and replacement bodies in many places spatially related to granite porphyry are superimposed on the porphyry tungsten molybdenum orebodies and surrounding rocks they consist mainly of chlorite abundant fluorite and complex assemblages of disseminated to massive sulfide and oxide minerals some cassiterite rich relatively sulfide poor zones occur also within greisen altered granite porphyry the relationship of these zones to the polymetallic veins and replacement bodies is not clear cassiterite rich greisen occurs typically at deeper levels and may represent either the roots of the higher level polymetallic zones or an entirely separate stage of mineralization the contrast in the styles of mineralization between porphyry tungsten molybdenum ore bodies on the one hand and tin and polymetallic zones on the other is striking formation of the porphyry deposits appears to be related to the development of high fluid pressures associated with crystallization of the underlying fine grained granite magma and subsequent fracturing and breccia formation the tin and polymetallic zones indicate not only a significant change in the composition of the ore forming fluids but also formation at fluid pressures that were either too low or too localized to cause extensive fracturing and brecciation

geochemistry of hybrid granitoid rocks and of their biotites from central northern portugal and their petrogenesis abstract in the area of franzilhal s lourenco and pombal central northern portugal occur rocks ranging from hornblende biotite tonalite to muscovite biotite granite the distribution of some major and trace elements in the rocks and in the biotite shows an apparent calc alkalic trend of differentiation the behaviour of k li rb cs and k rb cr 103 fe3 ni 103 mg li 103 mg cs 103 k ratios of the rocks and of f of biotite cannot be explained by mineral fractionation but can be described in terms of hybridization the tonalite granodiorites and biotite muscovite granite are hybrid rocks formed by assimilation of pelitic sediments and dolomitic marbles by the granite magma the fo2 values range from 10 14 8 to 10 16 3 fo2 attains higher values during the crystallization of hybrid rocks than in the uncontaminated muscovite biotite granite giii magma the fh2o and ph2o values generally increase and the fh2o fhf ratio decreases in the hybrid rocks from tonalite to biotite muscovite bearing granodiorite and is smaller than in the uncontaminated granite magma

viscoelastic shear zone model of a strike slip earthquake cycle i examine the behavior of a two dimensional 2 d strike slip fault system embedded in a 1 d elastic layer schizosphere overlying a uniform viscoelastic half space plastosphere and within the boundaries of a finite width shear zone the viscoelastic coupling model of savage and prescott 1978 considers the viscoelastic response of this system in the absence of the shear zone boundaries to an earthquake occurring within the upper elastic layer steady slip beneath a prescribed depth and the superposition of the responses of multiple earthquakes with characteristic slip occurring at regular intervals so formulated the viscoelastic coupling model predicts that sufficiently long after initiation of the system 1 average fault parallel velocity at any point is the average slip rate of that side of the fault and 2 far field velocities equal the same constant rate because of the sensitivity to the mechanical properties of the schizosphere plastosphere system i e elastic layer thickness plastosphere viscosity this model has been used to infer such properties from measurements of interseismic velocity such inferences exploit the predicted behavior at a known time within the earthquake cycle by modifying the viscoelastic coupling model to satisfy the additional constraint that the absolute velocity at prescribed shear zone boundaries is constant i find that even though the time averaged behavior remains the same the spatiotemporal pattern of surface deformation particularly its temporal variation within an earthquake cycle is markedly different from that predicted by the conventional viscoelastic coupling model these differences are magnified as plastosphere viscosity is reduced or as the recurrence interval of periodic earthquakes is lengthened application to the interseismic velocity field along the mojave section of the san andreas fault suggests that the region behaves mechanically like a 600 km wide shear zone accommodating 50 mrn yr fault parallel motion distributed between the san andreas fault system and eastern california shear zone in the viscoelastic coupling model savage and prescott 1978 time dependent deformation around a strike slip fault zone is realized by loading subsequent rupture and relaxation of a fault present in a schizosphere elastic upper crust overlying a ductile plastosphere assuming a two dimensional 2 d geometry periodic rupture of the fault and identical slip interseismic deformation is obtained as the superposition of viscoelastic relaxation of the plastosphere summed over the infinity of past periodic earthquakes this model yields far field interseismic motions equal to 1 2 of the average slip rate v0 imposed on the fault thus even when no external mechanism is invoked to load the fault i e when the locked portion of the fault penetrates the entire schizosphere the model satisfies the expectation of rigid plate like behavior in the far field in addition when periodic coseismic offsets are factored in the model predicts that the time averaged fault parallel velocity of each point is vol2 depending on location

magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of california effects of assimilation crustal thickness and depth of crystallization in order to better understand geologic fac tors controlling pronounced regional variations in whole rock chemistry mineralogy and mineral chemistry in the batholiths of california we calculate the magmatic intensive variables f hf f h 2 o f hf f hcl and f o 2 regional scale west to east increases in f oh in mafic silicates corresponding to the systematic i wc to i mc and i sc progression reflect orders of magnitude increase in f hf f h 2 o attending pluton crystallization low f hf f h 2 o of formation of western i wc types is consistent with their derivation from low fluorine source rocks in subducted oceanic slabs or the upper mantle in contrast higher f hf f h 2 o of crystallization of i mc and i sc types to the east implies the involvement of 1 progressively greater amounts of continental crustal source material such as biotite bearing metamorphic rocks their unweathered sedimentary derivatives retaining f rich mafic minerals or their fusion products and or 2 source materials which become more f rich toward the continental interior the regional distribution of i mc and i sc types suggests that the precambrian craton of western north america or derivative sediments may extend farther north in california and be morphologically more complex than previously thought from seemingly out of place occurrences of i wc plutons on the eastern slopes of the sierra nevada batholith we infer the existence of regions where precambrian basement was thin or absent in mesozoic time which prevented extensive cratonal contamination of subducted slab or upper mantle derived magmas new methods for estimating t f o 2 relations in the magmas demonstrate that i scr granites crystallize at oxygen fugacities as much as five orders of magnitude lower than those of i wc i mc and i sc types under conditions at or below the maximum stability limit of graphite in equilibrium with a c o h s gas phase the local scale formation of i scr granites in plutonic belts within specific wall rock terranes containing highly reducing sediments or metasediments may occur by contamination of i types with graphitic pelite or in some cases by the direct fusion of this reducing pelitic wall rock the spatial distribution of i scr granite provinces therefore is controlled simply by wall rock lithology amphibole geobarometry demonstrates a general west to east decrease in crystallization pressure across the sierra nevada batholith in contrast the peninsular ranges batholith displays a west to east crystallization pressure increase the bulk of the california batholiths crystallized at pressures less than 4 5 kb and depths less than about 15 19 km in the southern sierra nevada batholith the san gabriels and the eastern peninsular ranges however plutons crystallized at pressures exceeding 6 kb at deep crustal levels 23 km reconstruction of the pre erosion top of the batholith shows that in an east west cross section the central sierra nevada batholith was a horizontal tabular body with an aspect ratio of at least five to one

strain accumulation and rotation in western nevada 1993 2000 1 the positions of 44 gps monuments in an array extending from the sierra nevada at the latitude of reno to near austin nevada have been measured several times in the 1993 2000 interval the western half of the array spans the walker lane belt whereas the eastern half spans the central nevada seismic zone cnsz the principal strain rates in the walker lane belt are 29 6 5 3 nstrain yr 1 n88 4 e 5 4 and 12 8 6 0 nanostrain yr 1 n01 6 w 5 4 extension reckoned positive and the clockwise as seen from above the earth rotation rate about a vertical axis is 13 6 4 0 nrad yr 1 the quoted uncertainties are standard deviations the motion in the walker lane belt can then be represented by a zone striking n35 w subject to 16 8 4 9 nstrain yr 1 extension perpendicular to it and 19 5 4 0 nstrain yr 1 right lateral simple shear across it the n35 w strike of the zone is the same as the direction of the local tangent to the small circle drawn about the pacific north america pole of rotation the principal strain rates for the cnsz are 46 2 11 0 nstrain yr 1 n49 9 w 6 0 and 13 6 6 1 nstrain yr 1 n40 1 e 6 0 and the clockwise rotation rate about a vertical axis is 20 3 6 3 nrad yr 1 the motion across the cnsz can then be represented by a zone striking n12 e subject to 32 6 11 0 nstrain yr 1 extension perpendicular to it and 25 1 6 3 nstrain yr 1 right lateral simple shear across it the n12 e strike of the zone is similar to the strikes of the faults rainbow mountain fairview peak and dixie valley within it

fractionation of li be ga nb ta in sn sb w and bi in the peraluminous early permian variscan granites of the cornubian batholith precursor processes to magmatic hydrothermal mineralisation this study was supported by the european regional development fund and european social fund as part of the convergence funding for cornwall and the isles of scilly supporting a phd for bs combined universities in cornwall project number11200nco5 and the european union horizon 2020 project 641650 fame the la icp ms work was supported by a grant from the natural environment research council nerc ne l001896 1 the cornwall heritage trust are thanked for providing additional funds for analysis the natural history museum london uk are thanked for loan of samples from collection bm 2004 p14 specimen numbers 1 7 8 10 21 23 24 30 and 31 and thin sections p11849 p11851 p11864 p12400 and p12399 samples gg6 gg15 gg28 and gg44 from the study of darbyshire and shepherd 1994 came from peter floyd university of keele steve pendray sharon uren and joe pickles assisted with the sample preparation and analysis at camborne school of mines sam hammond assisted with la icp ms analysis at the open university de lank carnsew and castle an dinas quarries richard scrivener nick leboutillier and ben thompson imerys are thanked for help with sampling karel breiter and one anonymous reviewer are thanked for their generous and constructive comments which have helped to improve the manuscript

nonlinear strain buildup and the earthquake cycle on the san andreas fault two contrasting models of the earthquake deformation cycle on strike slip faults predict significant temporal declines in shear strain rate near the fault accompanied by a progressive broadening of the zone of deformation adjacent to it in the thin lithosphere model transient deformation results from flow in the asthenosphere due to stress relaxation following faulting through most or all of the lithosphere for an earth model with a thick elastic lithosphere plate thickness depth of seismic slip transient motions are due to postearthquake aseisrnic slip below the coseismic fault plane data from the san andreas fault indicate a long term temporal decrease in strain rate that persists for at least 30 years and may extend through the entire earthquake cycle observations support a cycle long rate decrease and a temporal spreading of the deformation profile only if movement cycles on the northern and southern locked sections of the fault are basically similar if so the usually lower strain rates and broader deformation zone currently observed on the southern san andreas represent a later evolutionary stage of the northern locked section where a great earthquake is a more recent occurrence although the data allow some extreme models to be discarded no sufficiently strong constraints exist to decide between the thin and thick lithosphere models regardless of the appropriate model the geodetic observations themselves indicate that strain buildup is sufficiently nonlinear to cause significant departures from recurrence estimates based on linear strain accumulation and the time predictable model

glass rich cordierite biotite rhyodacite valle ninahuisa puno se peru petrological evidence for hybridization of lachlan s type and potassic mafic magmas

strain partitioning and fault slip rates in the northeastern caribbean from gps measurements 1 gps data collected in the dominican republic from 1994 to 2001 show that oblique convergence between the north american and caribbean plates is partitioned between 5 2 2 mm yr 1 of dip slip reverse motion on the north hispaniola thrust approximately n s and 12 8 2 5 mm yr 1 and 9 0 9 0 mm yr 1 of approximately e w left lateral strike slip motion on the septentrional and enriquillo faults 95 confidence the agreement between gps and paleoseimological slip rates on the septentrional fault together with the 770 960 years since the last major earthquake and the 800 1200 years maximum repeat time of major earthquakes may indicate that the septentrional fault is currently in the late phase of its rupture cycle

a review of shallow ore related granites textures volatiles and ore metals shallow texturally complex granites can be associated spatially introduction and temporally with hydrothermal alteration and mineralization granite related ore deposits include porphyry and skarn the formation of a granite related ore deposit represents the confluence type ores and other hydrothermal deposits that are of many chemical and physical geological factors including magma spatially and temporally associated with granitic sensu composition e g concentrations of ore metals chlorine and water lato rocks in this paper i emphasize characteristics magma oxidation state the relative timing of crystallization magma found in porphyry style cu mo au deposits and some ascent magmatic volatile phase exsolution and the depth of em related systems however my treatment here is not meant placement early magmatic crystallization of ore metal rich minerals to cover the full range of granitic rocks and mineralization coupled with late exsolution of the magmatic volatile phase is that make up the granite related ore systems the forpromoted by deeper emplacement levels and lower magmatic water mation of granite related ore deposits by orthomagmatic concentrations and leads to low eyciencies of removal of compatible hydrothermal processes is dependent upon many physical elements from melts into the magmatic volatile phase s water and chemical magmatic factors including but not limited concentrations in the melt and pressures of crystallization can be to the composition and evolution of the associated estimated from phase equilibria and textural relationships of horn magmas the rate of magma ascent the depth and blende in some felsic systems physical factors avect the dynamics geometry of magma emplacement and the local temof fluid magma melt and volatile phase movement which in turn perature and stress fields at the site of magma emavect the size of zones of alteration and mineralization granite placement detailed studies of the igneous rocks textures can record the partial history of some dynamic processes associated with ore deposits can therefore yield critical miarolitic cavities are good evidence for magmatic volatile phase information regarding the source of metals and ligands exsolution both miarolitic cavities and pegmatitic texture exhibit in the ore generative hydrothermal solutions that are evidence for external nucleation of crystals nucleation controlled operative in the formation of granite related ores in this phenomena expressed as variations in granite textures can result review i will present a series of narratives consistent in from a multiplicity of causes including undercooling of the melt my view with prevailing field and experimental data on textural elements such as pegmatite aplite skeletal crystals and the orthomagmatic hydrothermal theory for the genesis graphic textures can form as a result of undercooling interconnected of some granite related deposits volumes of the magmatic volatile phase allow for advection of some high level granites i e those that are emplaced hydrothermal ore fluids through the magma in shallow granitic at depths of 8 km or less represent the crystallized systems miarolitic cavities can be interconnected consistent with remains of magmas that were associated with subvolcanic this hypothesis ore generative hydrothermal systems therefore studies of shallow granites aimed at understanding magmatic evolution and volatile phase exsolution at shallow levels are necessary if we are to understand ore genesis and the deep inputs to present day geothermal systems as well as evaluate hazards associated with the volcanic

recent uplift of the alban hills volcano italy evidence for magmatic inflation first order leveling surveyed in 1951 and 1994 along a line across the alban hills volcano reveals maximum vertical uplift of 30 cm average of 7 mm yr in the region of geologically recent 0 020 0 030 ma explosive activity the uplifted region corresponds to an area where seismic activity is concentrated at depths of 3 6 km uplift exceeding 10 cm is observed over a 14 km wide zone in the center of a 40 km long line with the deformation tapering to zero at both ends of the line data from a few sparse older benchmarks measured in 1891 and 1927 suggest that the deformation in the first half of this century was very small compared to the period 1951 1994 the observed uplift together with increased seismic activity suggest that recent magma injection has occurred in the upper crust beneath the alban hills volcano

gas hazard assessment in a densely inhabited area of colli albani volcano cava dei selci roma the northwestern flank of the colli albani a quaternary volcanic complex near rome is characterised by high pco2 values and rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil the most significant of these zones is cava dei selci where many houses are located very near to the gas emission site the emitted gas consists mainly of co2 up to 98 vol with an appreciable content of h2s 0 8 2 the he and c isotopic composition indicates as for all fluids associated with the quaternary roman and tuscany volcanic provinces the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates an advective co2 flux of 37 tons day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool present in the rainy season in a topographically low central part of the area a co2 soil flux survey with an accumulation chamber carried out in february march 2000 over a 12 000 m2 surface with 242 measurement points gave a total mostly conductive flux of 61 tons day co2 soil flux values vary by four orders of magnitude over a 160 m distance and by one order of magnitude over several metres a fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations six surveys carried out from may 2000 to june 2001 have shown large variations of the total co2 soil flux 8 25 tons day the strong emission of co2 and h2s which are gases denser than air produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man the gas hazard near the houses has been assessed by continuously monitoring the co2 and h2s concentration in the air at 75 cm from the ground by means of two automatic stations certain environmental parameters wind direction and speed atm p t humidity and rainfall were also continuously recorded at both stations h2s and co2 exceeded by several times the recommended concentration thresholds the highest co2 and h2s values were recorded always with wind speeds less than 1 5 m s mostly in the night hours our results indicate that there is a severe gas hazard for people living near the gas emission site of cava dei selci and appropriate precautionary and prevention measures have been recommended both to residents and local authorities

new gps constraints on the kinematics of the apennines subduction abstract we present the velocity field of the italian area derived from continuous gps observations from 2003 to 2007 the gps sites were installed by different institutions and for different purposes they cover the whole country with a mean inter site distance of about 60 km and provide a valuable source of data to map the present day kinematics of the region the absolute itrf2005 rotation poles and rates of eurasia africa and adriatic plates are estimated to study the kinematics along their boundaries in the apennines belt the corsica sardinia block coherently moving as the eurasia plate is used as reference of the upper plate for the apennines subduction zone we apply a simple kinematic model to estimate the rates and spatial pattern of the subduction along the apennines we identify at least four different independently moving lower plates i e the adriatic diverging and internally segmented ionian sicily and africa converging plates with different subduction rates the conservative estimates of the subduction rate are 5 mm yr in the calabrian arc 1 5 mm yr in sicily and 0 9 mm yr in the northern apennines this variegate mixture of behaviors seems to reflect the variable lithospheric thickness and composition of the lower plates inherited from the mesozoic rifting an unexpected along strike contraction is observed along the western side of the central northern apennines velocities are estimated both relative to eurasia and relative to the deep and shallow hotspot reference frames hsrf the hotspot representation seems more coherent with the geophysical and geological constraints along the subduction system in which the adriatic and ionian plates move sw ward and their deeper slab portions provide an obstacle to the opposite relative mantle flow all these patterns better reconcile if the subduction process is conceived as a passive feature controlled by the far field plate velocities and the relative eastward mantle flow acting on a disrupted slab

genesis of the proterozoic mangabeira tin indium mineralization central brazil evidence from geology petrology fluid inclusion and stable isotope data abstract the mangabeira deposit is the only known brazilian tin mineralization with indium it is hosted in the paleo to mesoproterozoic mangabeira within plate granitic massif which has geochemical characteristics of nyf fertile granites the granitic massif is hosted in archean to paleoproterozoic metasedimentary rocks ticunzal formation paleoproterozoic peraluminous granites aurumina suite and a granite gneiss complex the mineralized area comprises evolved li siderophyllite granite topaz albite granite li f rich mica greisens and a quartz topaz rock similar to topazite two types of greisens are recognized in the mineralized area zinnwaldite greisen and li rich muscovite greisen formed by metasomatism of topaz albite granite and li siderophyllite granite respectively cassiterite occurs in the quartz topaz rock and in the greisens indium minerals such as roquesite cuins2 yanomamite inaso4 2h2o and dzhalindite in oh3 and in rich cassiterite sphalerite stannite group minerals and scorodite are more abundant in the quartz topaz rock and are also recognized in albitized biotite granite and in li rich muscovite greisen the host rocks and mineralized zones were subsequently overprinted by the brasiliano orogenic event primary widespread two phase aqueous and rare coeval aqueous carbonic fluid inclusions are preserved in quartz from the topaz albite granite in quartz and topaz from the quartz topaz rock and in cassiterite from the li rich muscovite greisen eutectic temperatures are 25 c to 23 c allowing modeling of the aqueous fluids in the system h2o nacl kcl rare three phase h2o nacl fluid inclusions 45 50 wt nacl equiv are restricted to the topaz albite granite salinities and homogenization temperatures of the aqueous and aqueous carbonic fluid inclusions decrease from the topaz albite granite 15 20 wt nacl equiv 400 c 450 c to the quartz topaz rock 10 15 wt nacl equiv 250 c 350 c and to the greisen 0 5 wt nacl equiv 200 c 250 c secondary fluid inclusions have the same range of salinities as the primary fluid inclusions and homogenize between 150 and 210 c the estimated equilibrium temperatures based on 18o of quartz mica pairs are 610 680 c for the topaz albite granite and 285 370 c for the li rich muscovite greisens these data are coherent with measured fluid inclusion homogenization temperatures temperatures estimated using arsenopyrite geothermometry yield crystallization temperatures of 490 530 c for the quartz topaz rock and 415 505 c for the zinnwaldite greisens the fluids in equilibrium with the topaz albite granite have calculated 18o and d values of 5 6 7 5 and 67 to 58 respectively estimated 18o and d values are mainly 4 8 7 9 and 60 to 30 respectively for the fluids in equilibrium with the quartz topaz rock and zinnwaldite greisen and 3 4 3 9 and 25 to 17 respectively for the li rich muscovite greisen fluid 34s data on arsenopyrite from the quartz topaz rock vary from 1 74 to 0 74 consistent with a magmatic origin for the sulfur the integration of fluid inclusion with oxygen isotopic data allows for estimation of the minimum crystallization pressure at ca 770 bar for the host topaz albite granite which is consistent with its evolved signature based on petrological fluid inclusion and isotope data it is proposed that the greisens and related mangabeira sn in mineralization had a similar hydrothermal genesis which involved exsolution of f rich sn in bearing magmatic fluids from the topaz albite granite early formation of the quartz topaz rock and zinnwaldite greisen progressive cooling and li rich muscovite greisen formation due to interaction with meteoric water the quartz topaz rock is considered to have formed in the magmatic hydrothermal transition the mineralizing saline and co2 bearing fluids are interpreted to be of magmatic origin based on the isotopic data and paragenesis which has been documented as characteristic of the tin mineralization genetically related to proterozoic within plate granitic magmatism in the goias tin province central brazil

phase equilibria of a be u and f enriched vitrophyre from spor mountain utah abstract the equilibrium melting relations of a vitrophyre representative of topaz rhyolites have been experimentally determined in order to constrain the pre eruption temperature and h2o content of topaz rhyolite magmas the vitrophyre sample is strongly enriched in f and incompatible elements and consists of approximately 70 unaltered volcanic glass and 30 crystals of biotite quartz sanidine plagioclase magmatic fluorite and a variety of accessory phases biotite stability is strongly dependent on temperature pressure and ah2o in the melt and is apparently independent of the variations in o2 over the range investigated in this study the thermal stability of biotite increases relative to that of quartz sanidine and plagioclase in water saturated melts as pressure increases from 1 2 to 2 kbar fluorite is stable to temperatures below but within 50 to 75 c of the biotite stability curve and topaz is present in the products of runs at and near the solidus for all fluid conditions investigated the 1 2 wt f in the vitrophyre results in very low solidus temperatures of 525 c for all fluid conditions studied comparison of the experimentally determined crystallization sequence of the vitrophyre with the observed crystallization sequence of the vitrophyre and of the overlying topaz rhyolites indicates that the phenocrysts in the vitrophyre and in the topaz rhyolites crystallized at a pressure 1 kb that the magma contained at least 4 wt water during initial crystallization of biotite and that the magma contained a pre eruption water content of 5 wt

partitioning of f between h2o and co2 fluids and topaz rhyolite melt implications for mineralizing magmatic hydrothermal fluids in f rich granitic systems fluid melt distribution coefficients for f have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of h2o and h2o co2 at pressures of 0 5 to 5 kbar temperatures of 775 1000 c and concentrations of f in the melt ranging from 0 5 to 6 9 wt the major element f and cl concentrations of the starting material and run product glasses were determined by electron microprobe and the concentration of f in the fluid was calculated by mass balance the h2o concentrations of some run product glasses were determined by ion microprobe sims the solubility of melt in the fluid phase increases with increasing f in the system the solubility of h2o in the melt is independent of the f concentration of the system with up to 6 3 wt f in the melt no evidence of immiscible silica and fluoriderich liquids was detected in the hydrous but water undersaturated starting material glasses 8 5 wt f in melt or in the water saturated run product glasses f concentrates in topaz rhyolite melts relative to coexisting fluids at most conditions studied however df wt f in fluid wt f in melt increases strongly with increasing f in the system maximum values of df in this study are significantly larger than those previously reported in the literature linear extrapolation of the data suggests that df is greater than one for water saturated peraluminous granitic melts containing 8 wt f at 800 c and 2 kbar df increases as temperature and as h2o h2o co2 of the fluid increase for topaz rhyolite melts containing 1 wt f and with h2o rich fluids df is independent of changes in pressure from 2 to 5 kbar at 800 c for melts containing 1 wt f and in equilibrium with co2 bearing fluids the concentrations of f in fluid increases with increasing pressure f and lithophile element enriched granites may evolve to compositions containing extreme concentrations of f during the final stages of crystallization if f in the melt exceeds 8 wt df is greater than one and the associated magmatic hydrothermal fluid contains 4 molal f such f enriched fluids may be important in the mass transport of ore constituents i e f mo w sn li be rb cs u th nb ta and b from the magma

eruptive history and petrologic evolution of the albano multiple maar alban hills central italy a comprehensive volcanological study of the albano multiple maar alban hills italy using i 40ar 39ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and ii petrographic observations phase analyses of major and trace elements and sr and o isotopic analyses of the pyroclastic deposits shows that volcanic activity at albano was strongly discontinuous with a first eruptive cycle at 69 1 ka producing at least two eruptions and a second cycle with two peaks at 39 1 and 36 1 ka producing at least four eruptions contrary to previous studies we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 1 ka the activity of albano was fed by a new batch of primary magma compositionally different from that of the older activity of the alban hills moreover the ree and 87sr 86sr data indicate that the albano magma originated from an enriched metasomatized mantle according to the modeled liquid line of descent this magma differentiated under the influence of magma limestone wall rock interaction our detailed eruptive and petrologic reconstruction of the albano maar evolution substantiates the dormant state of the alban hills volcanic district

constraints on the viscosity of the continental crust and mantle from gps measurements and postseismic deformation models in western mongolia 1 we use gps measurements and models of postseismic deformation caused by seven m6 8 to 8 4 earthquakes that occurred in the past 100 years in mongolia to assess the viscosity of the lower crust and upper mantle we find an upper mantle viscosity between 1 1018 and 4 1018 pa s the presence of such a weak mantle is consistent with results from independent seismological and petrological studies that show an abnormally hot upper mantle beneath mongolia the viscosity of the lower crust is less well constrained but a weak lower crust 3 1016 to 2 1017 pa s is preferred by the data using our best fit upper mantle and lower crust viscosities we find that the postseismic effects of viscoelastic relaxation on present day horizontal gps velocities are small 2 mm yr 1 but still persist 100 years after the 1905 m8 4 bolnay earthquake this study shows that the gps velocity field in the baikal mongolia area can be modeled as the sum of 1 a rigid translation and rotation of the whole network 2 a 3 5 mm yr 1 simple shear velocity gradient between the siberian platform to the north and northern china to the south and 3 the contribution of postseismic deformation mostly caused by the 1905 bolnay tsetserleg sequence and by the smaller but more recent 1957 bogd earthquake

inversion of relative motion data for estimates of the velocity gradient field and fault slip abstract a new method is presented for a purely kinematic analysis of relative motion data of crustal deformation we start by developing a general integral formulation that links the relative motion between two positions to the velocity gradient field next fault slip is explicitly incorporated leading to the final observation equation this equation provides a new complete and in practice exact description of the time dependent relation between surface motion and the underlying kinematics the combination of equations belonging to pairs of observation sites e g of a geodetic network leads in a natural way to a linear inverse problem from which the velocity gradient field and slip on active faults can be estimated the method is successfully tested in a synthetic experiment

volcanic unrest of the colli albani central italy detected by gps monitoring test this work has been partially supported by the dept of civil protection project dpc115 v3 colli albani

active deformation in eastern indonesia and the philippines from gps and seismicity data in this study we combine global positioning system gps velocities with information on the style of regional seismicity to obtain a self consistent model velocity and strain rate field for the entire eastern indonesia and philippines region in the process of interpolating 93 previously published gps velocities the style and direction of the seismic strain rate field inferred from earthquakes with m0 1 1020 n m from the harvard centroid moment tensor catalog are used as constraints on the style and direction of model strain rates within the plate boundary zones the style and direction of the seismic strain rate field are found to be self similar for earthquakes up to m0 1 1020 n m equivalent to mw 7 3 our inversion result shows the following the java trench which lacks any significant historic seismicity delineates the australian plate au sunda block sunda plate boundary west of the island of sumba east of sumba convergence is distributed over the back arc and banda sea and there is no subduction at the timor trough suggesting that the northern boundary of the au plate runs north of this part of the banda arc through the banda sea in new guinea most motion is taken up as strike slip deformation in the northern part of the island delineating the pacific plate pa au boundary however some trench normal convergence is occurring at the new guinea trench evidence that the strain is partitioned in order to accommodate oblique pa au motion pa au motion is consistent with nuvel 1a direction but 8 mm yr 1 slower than the nuvel 1a estimate for pa au motion the sulawesi trench and molucca sea delineate zones of high strain rates consistent with high levels of active seismicity the sulawesi trench may take up some of the au sunda motion philippine sea plate motion is in a direction slightly northward of the nuvel ia estimate and is partitioned in some strike slip strain rates along the philippine fault and relatively larger trench normal convergence along the philippine trench and on the philippine mainland in the southern philippines and along the manila trench in the northern philippine islands the high level of strain rate along the manila trench is not released by any significant historic seismic activity for the entire eastern indonesia philippines region seismicity since 1963 has taken up 40 of the total moment rate inferred from our model

recurrence of volcanic activity along the roman comagmatic province tyrrhenian margin of italy and its tectonic significance 1 the roman comagmatic province rcp developed along the nw se striking extensional tyrrhenian margin of italy since middle pleistocene and includes ultrapotassic small eruptive centers and large volcanic districts by means of a review and statistical analysis of a large data set of radiometric ages we demonstrate that in the rcp major eruptive cycles occurred at different volcanic districts almost simultaneously and with an almost constant recurrence time our analysis started with the alban hills volcanic district where a detailed 40ar 39ar chronology of the eruptive cycles has been recently achieved and then extended to include a database of 264 radiometric ages of the rcp volcanics published since 1980 statistical treatment of the data set shows a marked non poissonian behavior of volcanic activity through the whole magmatic province with climax of each major eruptive cycle occurring simultaneously at the different districts approximately every 48 kyr the concomitant eruption of many volcanic districts spreading over a 250 km long chain implies a control mechanism acting at a regional scale after discussing the possible relationship between tectonics sea level changes and volcanic activity we hypothesize that constant rates of slab retreat during middle pleistocene could have been a key factor controlling the rate of magma upwelling and the major cycles of recharge of the magma chambers as a working hypothesis we propose that the duration of the cycles may be related to 1 progressive weakening of the crust due to magma underplating or 2 cyclic injection of convective plumes into the mantle wedge

sub surface dynamics and eruptive styles of maars in the colli albani volcanic district central italy protezione civile italy 2004 2006 agreement with istituto nazionale di geofisica e vulcanologia ingv project v3 1

pinguino in bearing polymetallic vein deposit deseado massif patagonia argentina characteristics of mineralization and ore forming fluids the pinguino deposit located in the low sulfidation epithermal metallogenetical province of the deseado massif patagonia argentina represents a distinct deposit type in the region it evolved through two different mineralization events an early in bearing polymetallic event that introduced in zn pb ag cd au as cu sn w and bi represented by complex sulfide mineralogy and a late ag au quartz rich vein type that crosscut and overprints the early polymetallic mineralization the indium bearing polymetallic mineralization developed in three stages an early cu au in as sn w bi stage ps1 a zn pb ag in cd sb stage ps2 and a late zn in cd ps3 indium concentrations in the polymetallic veins show a wide range 3 4 to 1 184 ppm in the highest indium values up to 1 184 ppm relate to the ps2 mineralization stage and are associated with fe rich sphalerites although significant in enrichment up to 159 ppm is also present in the ps1 paragenesis associated with sn minerals ferrokesterite and cassiterite the hydrothermal alteration associated with the polymetallic mineralization is characterized by advanced argillic alteration within the immediate vein zone and sericitic alteration enveloping the vein zone fluid inclusion studies indicate homogenisation temperatures of 308 2 327 c for ps1 and 255 312 4 c for ps2 and low to moderate salinities 2 to 5 eq wt nacl and 4 to 9 eq wt nacl respectively 34s values of sulfide minerals 0 76 to 3 61 indicate a possible magmatic source for the sulfur in the polymetallic mineralization while pb isotope ratios for the sulfides and magmatic rocks 206pb 204pb 207pb 204pb and 208pb 204pb ratios of 17 379 to 18 502 15 588 to 15 730 and 38 234 to 38 756 respectively are consistent with the possibility that the pb reservoirs for both had the same crustal source spatial relationships hydrothermal alteration styles s and pb isotopic data suggest a probable genetic relation between the polymetallic mineralization and dioritic intrusions that could have been the source of metals and hydrothermal fluids mineralization paragenesis alteration mineralogy geochemical signatures fluid inclusion data and isotopic data confirm that the in bearing polymetallic mineralization from pinguino deposit is a distinct type in comparison with the well known epithermal low sulfidation mineralization from the deseado massif

indium mineralisation in a type granites in southeastern finland insights into mineralogy and partitioning between coexisting minerals abstract several promising exploration targets in the western parts of the wiborg batholith southeastern finland have been studied with respect to zn in ag as sn and cu ores occur both as massive in bearing magnetite sphalerite getmossmalmen as greisen style veins jungfrubergen and as cu dominant polymetallic quartz veins korsvik 1 and 2 sarvlaxviken area the cu dominant chalcopyrite bornite zn poor quartz veins are characterised by high in zn ratios 3000 roquesite cuins2 being a major indium carrier alongside sphalerite chalcopyrite and arsenopyrite in contrast sphalerite is the dominant in carrier in the greisen veins and massive ores characterised by lower in zn ratios

mineralogy and geochemistry of indium bearing polymetallic veins in the sarvlaxviken area lovisa finland abstract a number of polymetallic vein mineralizations of different styles and metal associations including base alloy noble and critical metals have been discovered around the sarvlaxviken bay in the westernmost parts of the mesoproterozoic wiborg batholith south eastern finland the veins occur in two rapakivi granite varieties coarse grained wiborgite and medium grained marviken granite the veins are divided into five groups based on the dominant metal associations the li as w zn mn pb zn and cu as in associations are hosted by wiborgite and are strongly controlled by a nnw trending tectonic pattern that evolved in two main stages the li as w zn mn association generation 1 formed in a typical greisen environment with li bearing mica in significant alteration halos around a narrow quartz vein this greisenization was accompanied by silicification followed by sericitization and chloritization the pb zn association occurs in a similar vein type but without typical high temperature minerals and is considered to have formed at a higher crustal level generations 2a and 2b formed under more brittle conditions leading to fracturing quartz veining and metal precipitation of ore minerals this metal association is characterized by very high contents of cu as and up to 1490 ppm in but with 0 4 zn which leads to very high in zn ratios up to 8400 enabling formation of abundant roquesite the as sn cu and mo bi be associations are hosted by alteration zones without hydrothermal quartz in the marviken granite mineralization with moderately high contents of as sn and cu is associated with greisenization while mineralization with spectacular contents of be as well as high contents of mo and bi is associated with sericitization chloritization and berylification the internal age relations between the wiborgite hosted nnw trending veins show a clear evolution from a typical greisen type environment the li as w zn mn and pb zn associations of generation 1 to cooler and more brittle conditions governing quartz veining and precipitation of ore minerals belonging to the cu as in association generations 2a and 2b the age relations between these wiborgite hosted veins and the veins in the marviken granite are more uncertain but the presence of a ns trending granitic dyke on the eastern side of the sarvlaxviken bay with similar ore fertile geochemical composition as the marviken granite indicates that the tectonically controlled veins formed simultaneously with the emplacement of the marviken granite and associated hydrothermal activity the polymetallic veins in the sarvlaxviken bay are unique for the fennoscandian shield not the least for the locally high indium grades and spectacular roquesite grains there is an obvious exploration potential for similar veins and hence a number of base alloy noble and critical metals also elsewhere in the entire wiborg batholith

viscoelastic coupling model for the earthquake cycle driven from below in a linear system the earthquake cycle can be represented as the sum of a solution which reproduces the earthquake cycle itself viscoelastic coupling model and a solution that provides the driving force we consider two cases one in which the earthquake cycle is driven by stresses transmitted along the schizosphere and a second in which the cycle is driven from below by stresses transmitted along the upper mantle i e the schizosphere and upper mantle respectively act as stress guides in the lithosphere in both cases the driving stress is attributed to steady motion of the stress guide and the upper crust is assumed to be elastic the surface deformation that accumulates during the interseismic interval depends solely upon the earthquake cycle solution viscoelastic coupling model not upon the driving source solution thus geodetic observations of interseismic deformation are insensitive to the source of the driving forces in a linear system in particular the suggestion of bourne et al 1998 that the deformation that accumulates across a transform fault system in the interseismic interval is a replica of the deformation that accumulates in the upper mantle during the same interval does not appear to be correct for linear systems

petrology of the yerington batholith nevada evidence for evolution of porphyry copper ore fluids the jurassic yerington batholith western nevada is a composite pluton that contains several centers of porphyry copper mineralization and is exposed in structural cross section at paleodepths ranging from 0 to 8 km within these exposures the mcleod hill quartz monzodiorite bear quartz monzonite and luhr hill granite form successive intrusions that are in turn volumetrically smaller approximately 75 19 and 6 vol respectively more deeply emplaced tops at 65 km 3 luhr hill granite the low cu content approximately 10 ppm of the granite would allow extraction of approximately 50 ppm cu from it during crystallization these data suggest an orthomagmatic model in which both high and low density saline aqueous fluids formed during exsolution of water from the crystallizing luhr hill granite and from which salts cu fe and s strongly partitioned into the high density ore fluid low density fluids may have risen from the magma as a vapor plume mineralization occurred when fluid overpressures caused fracturing of wall rock and upward intrusion of granite porphyry dikes and high density saline ore fluids both the f sub o 2 path during subsolidus cooling and the deposition of most s as chalcopyrite pyrite in ore suggest that reduction of magmatic s to sulfide may have been a mechanism for oxidation of magmatic ferromagnesian silicate and fe ti oxide minerals

geodetic measurement of tectonic deformation in the santa maria fold and thrust belt california we have analyzed geodetic observations to resolve tectonic deformation across the santa maria fold and thrust belt northwest of santa barbara california the geodetic network forms a braced quadrilateral with 40 km sides whose southwest corner is the vandenberg very long baseline interferometry station the data include 1 historical triangulation from the 1880s 1920s and 1950s 2 electronic distance measurement trilateration from 1971 and 1985 and 3 global positioning system observations from 1986 and 1987 we combine the three different types of data to estimate two dimensional station positions and strain rate parameters simultaneously using a model which constrains the relative velocity field to be linear in space and constant in time we find significant strain rates the maximum compressive strain is oriented n17 e 5 e and the compressive strain rate in this direction is 0 13 0 03 strain yr under the assumption that the unresolved rotational component of the velocity field is zero we estimate that the integrated rate of deformation across the basin is 7 1 mm yr oriented at n03 e 13 this vector can be decomposed into 6 2 mm yr of crustal shortening on the general structural trend of n30 e and 3 1 mm yr of right lateral shear across this axis on the basis of these values and earthquake focal mechanisms in the area we infer that the deformation occurs on northwest trending folds and thrusts within the belt these results are consistent with the rate and direction of deformation across the central california coast ranges inferred by balancing pacific north america plate motion against san andreas slip and basin and range extension they imply that the santa maria fold and thrust belt is the primary active element in transforming motion from the coast ranges to the western transverse ranges and the santa barbara channel