structural evolution of the latakia ridge and cyprus basin at the front of the cyprus arc eastern mediterranean sea abstract the active deformation front between the african and anatolian plates in the eastern mediterranean is delineated by the cyprus arc present plate kinematic vectors and earthquake data suggest that the movement along the eastern extent of the cyprus arc is largely sinistral strike slip it is however widely accepted that subduction took place beneath cyprus until the early miocene subduction has since thought to have become impeded by the collision of the eratosthenes seamount with the island of cyprus the deformation front of the cyprus arc is dominated by the latakia ridge a steep narrow high which merges gradually with the lower slope of the broad hecataeus rise in the west and extends to the northern levantine coast in the east where the expression of the ridge changes to a number of narrow northeast trending ridges and basins the latakia ridge has previously been interpreted as either a thrust culmination or a positive flower structure this study uses high resolution marine seismic reflection profiles to delineate the stratigraphic and structural architecture of the deformation front from seismic profiles four stratigraphic units bounded by major basin wide unconformities can be identified these units are eocene lower miocene miocene uppermost miocene messinian and pliocene quaternary the timing of deformation determined from growth stratal architectures on the flanks of the major structures show that two main phases of deformation characterize the structural history of the deformation front each of these phases represents a different kinematic regime a compressional regime dominated during the miocene whereas a strike slip regime dominated in the pliocene quaternary

experimental calibration of the aluminum in hornblende geobarometer with application to long valley caldera california volcanic rocks a new geobarometer based on the al content of igneous hornblendes in equilibrium with melt fluid biotite quartz sanidine plagioclase sphene and magnetite or ilmenite has been calibrated experimentally the calibration was performed by equilibrating the required phase assemblage over the pressure range 2 8 kbar at 740 780c and then analyzing euhedral hornblendes in equilibrium with glass melt experiments were performed on natural samples of both volcanic and plutonic rocks earlier empirical calibrations of this geobarometer relied on analyzing natural hornblendes from plutons with the required phase assemblage and inferring pressure from nearby metamorphic country rocks the experimental calibration differs from the empirical calibrations especially above 5 kbar and shows that the al content of hornblendes in equilibrium with the required phase assemblage is greater for a given total pressure than previously thought the geobarometers uncertainty is dramatically reduced the derived equation is p plus minus 0 5 kbar 3 minus 3 46 plus minus 0 24 4 23 plus minus 0 13 al sup t the geobarometer is applied to post bishop tuff volcanic rocks from long valley caldera california and reveals that most rhyodacites in this complex erupted from depths of about 6 km these eruptions occurred over 500 000 yr suggesting that the rhyodacitic magma reservoir beneath longmore valley had reached a steady p depth t state less

discussion of sea water sound speed determinations available data on the speed of sound in sea water are examined to arrive at a basis for deriving simple equations suitable for most ocean areas extant laboratory data are compared in situ measurements aboard deep submergence vehicles are presented and convergence zone ranges discussed del grosso and mader j acoust soc am 52 961 974 1972 equations appear superior after numerous intercomparisons to serve as a foundation for generating simple sound speed equations

alteration mineralization and radiometric ages of the source pluton at the sangan iron skarn deposit northeastern iran abstract the world class sangan iron skarn deposit with a proven reserve of 1000 mt iron ore 53 fe is located in the khaf kashmar bardaskan volcano plutonic metallogenic belt kkb vpmb of northeastern iran along the e w trending regional doruneh fault north of the lut block skarn mineralization occurs at the contact of the 39 1 0 6 ma to 38 3 0 5 ma middle eocene syenite to syenogranite porphyry source pluton with cretaceous carbonate rocks the source pluton is part of an i type calcalkaline granitoid series with potassium to shoshonitic affinity metaluminous to slightly peraluminous character the granitoids are enriched in lile cs rb ba k th and u and lree la and ce are depleted in hfse nb y ta and ti hree yb and lu and eu which together with the low sr 96 to 362 ppm and la yb n contents suggest a metasomatized slab derived mantel source within the cenozoic volcanoplutonic continental arc of northeaster iran the location of the skarn orebodies is controlled by the regional e w doruneh fault structure and the spatial distribution and the two calcic and magnesian skarns is controlled by the composition of the carbonate protolith that consists of limestone in the west and dolomite in the east the chemistry of the skarn minerals reflects the composition of the protoliths the western skarn is dominated by ca rich calcsilicates that consist of prograde ca rich garnet adr 50 97 grs 0 45 sps alm 2 7 ca fe rich pyroxene hd 75 6 di 20 jo 4 5 k cl f bearing fe ca rich amphibole ferrohastingsite fe 4 4 ca 2 mg 0 5 k 0 4 na 0 3 si 6 5 al 1 8 o 22 cl f oh 2 in endoskarns and retrograde ferroactinolite fe 4 2 ca 2 mgmn 0 04 na 0 1 k 0 06 si 7 8 al 0 2 o 22 f cl oh 2 and fe rich chlorite ripidolite fe 4 3 mg 1 1 ca 0 06 mn 0 01 al 2 8 si 3 o 10 oh 8 in the exoskarns wollasonite plagioclase and k feldspar have been additionally formed together with ferrohastingsite in the endoskarns the eastern magnesian skarn is typically phlogopite rich k 0 9 mg 2 7 fe 0 2 na 0 02 si 2 9 al 1 2 o 10 oh f 2 and consists of prograde forsterite fo 97 0 fa 2 7 diopsidic pyroxene hd 0 2 di 0 88 and retrograde mg rich actinolite mg rich chlorite clinochlore mg 4 5 fe 0 1 k 0 05 al 1 8 si 2 7 o 10 oh 8 serpentine and talc iron mineralization overprints the calcsilicate skarns in both the western and the eastern skarns and is magnesian in the eastern orebodies 3 65 wt mgo the iron ore consists of a number of high grade replacement and magnetite orebodies with minor amounts of pyrrhotite chalcopyrite and pyrite indicating a large scale metasomatic transfer of iron bearing fluids during middle eocene magmatic activity at the kkb vpmb

the lightning creek sill complex cloncurry district northwest queensland a source of fluids for fe oxide cu au mineralization and sodic calcic alteration the lightning creek cu au prospect is hosted by a cogenetic suite of plutonic i type granitoids the dominant rock type is a porphyritic quartz monzodiorite that is intruded by more fractionated rocks including monzogranite and alkali feldspar granite a series of flat lying sills are interpreted to be late stage differentiates based on their timing mineralogy and chemistry in parts of the prospect there is pervasive sodic calcic alteration pyroxene after amphibole albite after k feldspar and oligoclase of the plutonic rocks this alteration predates sill emplacement and is unrelated to veining or fracturing of any kind the presence of small amounts of carbonate in the altered rocks suggests that the fluids were co2 bearing quartz and feldspar separates from these altered rocks have oxygen isotope compositions similar to those from fresh quartz monzodiorite suggesting that the fluids were hot and of magmatic composition sodium and ca were added and k fe cl and cu were stripped during what is interpreted as an autometasomatic event the sills display considerable textural and mineralogical complexity and evolved from equigranular quartzofeldspathic rocks aplites with magmatic chemistry to unusual fe rich rocks albite magnetite quartz that exhibit a range of bizarre spherulitic textures some of the albite and magnetite in the sills is secondary albite forms pseudomorphs after k feldspar na fe ca alteration along sill margins and within sills at the contacts between different textural zones halos of disseminated magnetite clinopyroxene fe ca na alteration are developed adjacent to early magnetite veins fluid inclusion studies indicate that these rocks crystallized at temperatures in excess of 500 c and at pressures in excess of 1 5 kbar the range of spherulitic textures is taken to indicate crystallization under hydrous conditions with the episodic release of a fluid phase this magmatic fluid phase was dominated by h2o co2 and chlorine and underwent phase separation into a co2 rich vapor and a hypersaline brine 33 55 wt nacl equiv the hypersaline fluid was enriched in fe 10 wt and cu 1 wt pixe analysis in addition to na k and ca where this fluid was retained within fe rich portions of the sills it caused ca fe na alteration pyroxene albite magnetite growth at the expense of quartz where the fluid was expelled from the sills it produced quartz magnetite clinopyroxene albite veins broadly coeval with the early magnetite veins although rich in cu these granitoid derived magmatic fluids did not generate significant cu au mineralization perhaps because of the high temperatures involved and or a lack of reduced sulfur in the fluids or host rock however the amount of iron present is estimated from the aeromagnetic anomaly to be in excess of 2 000 million tonnes mt a later generation of calcite chlorite pyrite chalcopyrite veins contain traces of cu au mineralization fluid inclusion and stable isotope work indicate that these veins probably crystallized from cooler 200 c more dilute 15 28 wt nacl equiv fluids perhaps generated by the admixture of a meteoric component the conclusions reached in this study have implications for understanding the genesis of fe oxide cu au deposits and related sodic calcic alteration the study indicates the potential for co2 rich granitoid magmas to evolve hypersaline fe and cu rich fluids capable of causing intense magnetite veining and cu au mineralization autometasomatic sodic calcic alteration of the granitoids may be an important precursor to mineralization contributing fe k cu and cl to the magmatic fluids

kiruna type deposits their origin and relationship to intermediate subvolcanic plutons in the great bear magmatic zone northwest canada magnetite apatite actinolite rocks similar to those at kiruna sweden and the st francois mountains missouri are associated with seven epizonal plutons that intrude andesitic stratovolcanoes of a broadly folded early proterozoic continental magmatic arc located in the northwestern canadian shield the plutons mainly medium grained quartz monzonite monzodiorite diorite iugs sheets and laccoliths 5 to 25 km in diameter are spatially temporally and compositionally related to host andesitic stratovolcanoes they were emplaced at 2 to 3 km depth are compositionally heterogeneous metasomatically altered and had plagioclase as the liquidus phase in addition they have kilometer wide alteration halos comprising an inner zone of nearly complete wall rock albitization an intermediate zone of magnetite apatite actinolite veins pods breccias and wall rock replacement and an outer zone of disseminated sulfides one pluton balachey has a halo that is more or less completely outside the body but another rainy lake has a halo that is partly superimposed over it separation of iron phosphate and silicate melts by liquid immiscibility is not supported by 1 the gradual replacement of plagioclase by chessboard albite toward the roof of the rainy lake pluton 2 the chemical trends in the rainy lake intrusion 3 the mineralogical zoning low temperature mineralogy and replacement textures of the magnetite apatite actinolite and 4 the relationship of the magnetite apatite actinolite veins and bodies to the plutons however all available data are compatible with a deuteric origin it is concluded that high temperature low initial water content and shallow level emplacement by intermediate plutons are necessary for the development of kiruna type deposits

impact and implications of the afro eurasian collision south of cyprus from reflection seismic data abstract the cyprus arc in the eastern mediterranean represents the active collision front between the african and eurasian anatolian plates along the cyprus arc the eratosthenes seamount is believed to have been blocking the northward motion of the african plate since the late pliocene early pleistocene based on a dense grid of 2d reflection seismic profiles covering the eratosthenes seamount and western levant basin offshore cyprus new observations regarding the cyprus arc collision front at the triple transition zone eratosthenes seamount levant basin hecataeus rise are presented the data show that the levant basin is filled with 10 km of sediments of early mesozoic probably jurassic to plio quaternary age with only a localized deformation affecting the miocene oligocene rock units the sediments onlap directly against the steep eastern flank of the eratosthenes seamount to the west and the southern flank of the hecataeus rise to the north the sediments show no deformation that could be associated with collision and are undeformed even very close to the two prominent structures pinching out of the base miocene reflector in the levant basin due to onlapping of the middle miocene reflector indicates uplift of the eratosthenes seamount and the hecataeus rise in contrast to the messinian evaporites north of the eratosthenes seamount the salt in the levant basin even close to the hecataeus rise is tectonically undeformed it is proposed that the eratosthenes seamount the western levant basin and the hecataeus rise act as one tectonic unit this implies that the collision front is located north of this unit and that the hecataeus rise shields the sediments south of it from deformation associated with collision of the african and anatolian plates

mineralization and ore genesis of the qiaoxiahala fe cu au deposit in the northern margin of east junggar terrane central asian orogenic belt constraints from fluid inclusions and stable isotopes abstract the qiaoxiahala fe cu au deposit 1 44 mt ore 43 53 fe 0 55 2 21 cu and 0 13 2 4 g t au is located in the northern margin of east junggar terrane nw china the deposit is hosted in the upper part of the middle devonian beitashan formation mafic and felsic volcanic rocks and sedimentary interbeds and is spatially closely related to local fractures six hypogene hydrothermal stages have been identified including stage i early skarn stage ii late skarn stage iii magnetite mineralization stage iv magnetite pyrite mineralization stage v chalcopyrite mineralization and stage vi late veins these six stages include three major mineralization events as represented by the stage iii magnetite epidote k feldspar quartz calcite stage iv magnetite pyrite garnet quartz calcite and stage v chalcopyrite chlorite assemblages the stage iii magnetite mineralization fluids were likely of high temperature 354 386 c low medium salinity 9 9 14 7 wt nacl equiv mg fe rich and organic rich with lithostatic pressure of 1 3 1 5 kbar and corresponding depth of 4 3 4 8 km oxygen and hydrogen isotopes showed that the 18o rich 9 7 11 2 and d rich 26 3 fluids were possibly modified from the early carboniferous seawater interacting with the beitashan formation organic rich limestone or tuff in comparison the stage iv magnetite pyrite mineralization fluids were likely of medium high temperature 272 453 c low medium salinity 2 9 19 5 wt nacl equiv mg fe rich with pressure of 0 8 1 2 kbar and corresponding depth of 2 6 4 0 km the stage v chalcopyrite mineralization fluids were likely of low medium temperature 186 270 c low medium salinity 1 4 21 8 wt nacl equiv ca or na rich with pressure of 0 4 0 6 kbar and corresponding depth of 1 2 km hydrogen and oxygen isotopic compositions stage iv dwater 141 to 92 18owater 8 9 11 1 stage v dwater 104 18owater 7 2 suggest that the ore fluids were of connate marine origin furthermore stage iv 13cwater values 0 6 to 0 also indicate interactions between seawater and sedimentary wall rocks the negative sulfur isotopic compositions of chalcopyrite and pyrite 4 2 to 0 2 may demonstrate a biogenic sulfur source compared with the arc related iocg deposits in the central andean orogen the qiaoxiahala fe cu au deposit shares many common features in geology mineralization alteration and various sources of fluids indicating a possible iocg like mineralization style and potential to discover other late paleozoic arc related iocg deposits in east junggar

stable isotope evidence for magmatic fluid input during large scale na ca alteration in the cloncurry fe oxide cu au district nw queensland australia sodic calcic alteration is common in mineralized hydrothermal systems yet the relative importance of igneous vs basinal fluid sources remains controversial one of the most extensive volumes of sodic calcic rocks occurs near cloncurry nw queensland and was formed by overlapping hydrothermal systems that were active synchronously with emplacement of mid crustal batholithic granitoids c 1 55 1 50 ga altered rocks contain albite oligoclase actinolite diopside titanite and magnetite alteration was localized by a composite veins and breccias containing crystallized magma intimately intergrown with hydrothermal precipitates b intrusions that host setting a veins and breccias and c extensive breccia and vein systems linked to regional fault systems isotope analyses of actinolites in settings a and b indicate calculated 18oh2o 8 2 to 10 6 and variably depleted dh2o 130 to 54 compared with typical magmatic fluids whereas those from setting c typically indicate calculated 18oh2o 8 0 to 12 8 and dh2o 29 to 99 the lowest dh2o values are interpreted as representing residual fluids after significant 90 open system magmatic degassing overall the stable isotope field geochronological and geobarometric data suggest that these sodic calcic alteration systems were formed by the episodic incursion of magmatic fluids that underwent minor isotopic modification as a result of varying degrees of interaction with country rocks

geochemistry and evolution of ore forming fluids of the yueshan cu au skarn and vein type deposits anhui province south china abstract the yueshan mineral belt is geotectonically located at the centre of the changjiang deep fracture zone or depression of the lower yangtze platform two main types of ore deposits occur in the yueshan orefield cu au fe skarn deposits and cu mo au pb zn hydrothermal vein type deposits almost all deposits of economic interest are concentrated within and around the eastern and northern branches of the yueshan dioritic intrusion in the vicinity of the zongpu and wuhen intrusions there are many cu pb zn au s vein type and a few cu fe au skarn type occurrences fluid inclusion studies show that the ore forming fluids are characterised by a cl s na k chemical association hydrothermal activity associated with the above two deposit types was related to the yueshan intrusion the fluid salinity was high during the mineralisation processes and the fluid also underwent boiling and mixed with meteoric water in comparison the hydrothermal activity related to the zongpu and wuhen intrusions was characterised by low salinity fluids chlorine and sulphur species played an important role in the transport of ore forming components hydrogen and oxygen isotope data also suggest that the ore forming fluids in the yueshan mineral belt consisted of magmatic water mixed in various proportions with meteoric water the enrichment of ore forming components in the magmatic waters resulted from fluid melt partitioning the ore fluids of magmatic origin formed large cu au deposits whereas ore fluids of mixed magmatic meteoric origin formed small to medium sized deposits the sulphur isotopic composition of the skarn and vein type deposits varies from 11 3 to 19 2 and from 4 2 to 10 0 respectively these variations do not appear to have been resulted from changes of physicochemical conditions rather due to compositional variation of sulphur at the source s and by water rock interaction complex water rock interaction between the ore bearing magmatic fluids and sedimentary wall rocks was responsible for sulphur mixing lead and silicon isotopic compositions of the two deposit types and host rocks provide similar indications for the sources and evolution of the ore forming fluids hydrodynamic calculations show that magmatic ore forming fluids were channelled upwards into faults fractures and porous media with velocities of 1 4 m s 9 8 10 1 to 9 8 10 7 m s and 3 6 10 7 to 4 6 10 7 m s respectively a decrease of fluid migration velocity in porous media or tiny fractures in the contact zones between the intrusive rocks and the triassic sedimentary rocks led to the deposition of the ore forming components the major species responsible for cu transport are deduced to have been cucl cucl2 cucl32 and cucloh whereas au was transported as au2 hs 2s2 au hs 2 auhs and auh3sio4 complexes cooling and a decrease in chloride ion concentration caused by fluid boiling and mixing were the principal causes of cu deposition gold deposition was related to decrease of ph total sulphur concentration and fo2 which resulted from fluid boiling and mixing geological and geochemical characteristics of the two deposit types in the yueshan mineral belt suggest that there is a close genetic relationship with the dioritic magmatism geochronological data show that the magmatic activity and the mineralisation took place between 130 and 136 ma and represent a continuous process during the yanshanian time the cooling of the intrusions and the mineralisation event might have lasted about 6 ma the cooling rate of the magmatic intrusions was 80 to 120 c my 1 which permitted sufficient heat supply by magma to the ore forming system

geology and geochemistry of the changlongshan skarn iron deposit anhui province china abstract the changlongshan skarn iron deposit is located in the northeastern part of the tongling fanchang fe cu district anhui province people s republic of china it is a specularite fe2o3 dominated iron deposit hosted in middle carboniferous to lower permian limestones with a drill indicated resource of 28 84 million tons of fe grading 35 9 58 6 both skarns and iron orebodies occur as tabular bodies along bedding parallel faults at some distance from the inferred granitic intrusions prograde skarn alteration consists mainly of andradite and hedenbergite whereas retrograde skarn is characterized by the development of actinolite chlorite and calcite the mineralogy of ores is dominated by specularite magnetite calcite and quartz primary fluid inclusions in garnet consist of aqueous liquid a vapour bubble and a halite crystal microthermometric measurements yield a homogenization temperature range for skarn alteration of 423 to 478 c with a salinity of 34 to 49 wt nacl equivalent fluid inclusions in calcite associated with mineralization generally consist of a vapour bubble and a liquid phase with a rare occurrence of three phase inclusions homogenization temperatures for two phase inclusions vary from 239 c to 303 c with a salinity of 13 to 22 wt nacl equivalent homogenization of three phase inclusions was observed between 264 and 287 c coupled with a salinity of 31 to 36 wt nacl equivalent stable isotope data indicate magmatic water was involved in the early stage of skarn formation 18 o h 2 o 3 7 to 7 6 dh2o 71 3 to 51 2 and a mixed magmatic meteoric water was responsible for the subsequent mineralization 18 o h 2 o 2 1 to 3 1 dh2o 40 1 to 28 1 geological and geochemical evidence obtained in this study supports a metasomatic replacement origin for the changlonshan iron deposit a conclusion contrary to previous syngenetic based interpretation

the southernmost margin of the tethys realm during the mesozoic and cenozoic initial geometry and timing of the inversion processes 1 along the northern border of africa pangea breakup has been diachronic during the jurassic the alpine tethys propagated northeastward from the atlantic to the alps during the permian the neo tethys propagated westward from oman to northwestern arabia then a secondary and late branch of neo tethys gave birth to the east mediterranean basin finally the two oceans connected at end of jurassic times achieving the development of africa northern plate boundary by the late cretaceous convergence between africa and eurasia led to the progressive closure of the tethys realm the continental collision is not completely achieved and the different segments of the confrontation zone maghreb central and east mediterranean zagros and oman expose different stages of the process however we emphasize the existence of synchronous geodynamic events from one end of the system to the other although they do not have the same meaning two of them are particularly important the campanian santonian c s event corresponds to 1 obduction and exhumation of high pressure low temperature metamorphic rocks around the arabian promontory 2 inversion along the margins of the east mediterranean basins and 3 lithosphere buckling in the atlas system maghreb and adjacent sahara platform the middle late eocene mle event corresponds to 1 the onset of collision at the northern corner of arabia 2 the onset of slab retreat in the mediterranean and 3 inversion along the margin of the east mediterranean as well as in the atlas the c s event coincides with a change in plate kinematics resulting in an abrupt increase of convergence velocity the mle event coincides with a period of strong coupling between the africa and eurasia plates and an abrupt decrease of convergence velocity in the middle of the system the central mediterranean seems to escape to the effects of convergence and is the site of quite permanent extensional movements since the triassic

acoustic tomography in the straits of florida variability of the florida current has been monitored via acoustic tomography a reciprocal tomography experiment was conducted in the eastern half of the florida straits during mid october and november 1983 a triangular array of transceivers with leg separations of approximately 45 km was deployed at 27 n the presence of a surface mixed layer in the region allowed for the ducted propagation of acoustic energy in the surface layer a deeper layer was sampled by an unresolved group of refracted bottom reflected ray arrivals incorporating the complete set of arrivals we are able to obtain depth dependent estimates of the temperature field current velocity and relative vorticity the oceanography of the region has been shown to be dominated by the lateral shifting of the surface and subsurface core of the florida current the influx of westward flowing water through the northwest providence channel at 26 n also appears as a large scale signal in the eastern florida straits low frequency fluctuations of temperature current velocity and vorticity occur at periods ranging from several days to nearly 2 weeks and are intimately related to meandering of the florida current system

the role of granites in volcanic hosted massive sulphide ore forming systems an assessment of magmatic hydrothermal contributions assessment of geological geochemical and isotopic data indicates that a significant subgroup of volcanic hosted massive sulphide vhms deposits has a major or dominant magmatic hydrothermal source of ore fluids and metals this group which is typically characterised by high cu and au grades includes deposits such as those in the neoarchean doyon bousquet laronde and cambrian mount lyell districts these deposits are distinguished by aluminous advanced argillic alteration assemblages or metamorphosed equivalents intimately associated with ore zones in many of these deposits 34ssulphide is low with a major population below 3 34ssulphate differs from coexisting seawater and 34ssulphate sulphide 20 30 these characteristics are interpreted as the consequence of disproportionation of magmatic so2 as magmatic hydrothermal fluids ascended and cooled and as a definitive evidence for a significant magmatic hydrothermal contribution other characteristics that we consider diagnostic of significant magmatic hydrothermal input into vhms ore fluids include uniformly high 3 times modern seawater values salinities or very 18o enriched 18o 5 ore fluids we do not consider other criteria e g variable salinity moderately high 18ofluid 2 5 34ssulphide near 0 metal assemblages or a spatial association with porphyry cu or other clearly magmatic hydrothermal deposits that have been used previously to advocate significant magmatic hydrothermal contributions to be diagnostic as they can be produced by non magmatic processes known to occur in vhms mineral systems however in general a small magmatic hydrothermal contribution cannot be excluded in most vhms systems considered conclusive data that imply minimal magmatic hydrothermal contributions are only available in the paleoarchean panorama district where coeval seawater dominated and magmatic hydrothermal systems appear to have been physically separated this district which is characterised by chloritic and sericitic alteration assemblages and lacks aluminous advanced argillic alteration assemblages is typical of many vhms deposits around the world suggesting that for garden variety vhms deposits a significant magmatic hydrothermal contribution is not required other than deposits associated with advanced argillic alteration assemblages the only deposit for which we ascribe a major magmatic hydrothermal contribution is the devonian neves corvo deposit this deposit differs from other deposits in the iberian pyrite belt and around the world in being extremely sn rich with the sn closely associated with cu and in having formed from high 18o rich fluids 18ofluid 8 5 we consider these characteristics particularly the last as diagnostic of a significant magmatic hydrothermal contribution our analysis indicates that two subgroups of vhms deposits have a major magmatic hydrothermal contribution cu au rich deposits with aluminous alteration assemblages and reduced very sn rich deposits in which sn was introduced in a high temperature ore assemblage comparison with normal vhms deposits suggests that these subgroups of vhms deposits may form in specialised tectonic environments the cu au rich deposits appear to form adjacent to magmatic arcs an environment conducive to the generation of hydrous oxidised melts by melting metasomatised mantle in the wedge above the subducting slab this contrasts with the back arc setting of normal vhms deposits in which relatively dry granites in this contribution we use the term granite sensu latto formed by decompression melting drive seawater dominated hydrothermal circulation the tectonic setting of highly sn rich vhms deposits such as neves corvo is less clear however thick continental crust below the ore hosting basin may be critical as it is in other sn deposits

relationship between altered pyroxene diorite and the magnetite mineralization in the chilean iron belt with emphasis on the el algarrobo iron deposits atacama region chile north of el algarrobo one of the four main deposits of the chilean iron belt the iron mineralization magnetite etrmolite actinolite apatite is related to clinoand orthopyroxene diorite intrusions which have crystallized at shallow depth 4km under increasing oxygen fugacities the supercritical fluid phase exsolved during cooling after the consolidation of the plutons 800 900 c results in a h cl and sodic enrichment and in the sequential leaching of fe at less than 700 c then ca and mg between 600 and 500 c from minerals of the primary magmatic diorite assemblage titanomagnetite ilmenite plagioclase an70 40 augite hypersthene as a consequence of the cationic leaching the lower mobility of silica and aluminium and the enrichment in sodium residual altered dioritic rocks present a retromorphic mineral assemblage evolving down to boundary conditions of the greenchist amphibolite facies 450 c fe mg and ca are carried in cationic form associated with cl anions toward cooler rocks where they are precipitated the deposition between 550 and 450 c of magnetite followed iron mineralization paragenesis and occurred in fractured zones located both in altered diorites and contact andesites

petrogenesis of the squirrel hills granite and associated magnetite rich sill and vein complex lightning creek prospect cloncurry district northwest queensland the lightning creek fe oxide cu au prospect is hosted within a mesoproterozoic granitoid batholith composed dominantly of high k calc alkaline porphyritic quartz monzodiorite the quartz monzodiorite contains enclaves of quartz diorite and has been intruded by more felsic granitoids monzogranite and alkali feldspar granite and a series of subhorizontal sills the quartz monzodiorite crystallised at crustal depths in excess of 10 km pnot vert similar4 kb t 800 850 c melt xh2o 4 wt fo2not vert similarnno buffer and was probably fluid saturated xh2o xco2 of 0 5 as might be expected the more fractionated granitoids crystallised at progressively lower temperatures quartz monzonite not vert similar800 c alkali feldspar granite 2 5 kb and temperatures greater than 500 c phase separation occurred in the fluid phase producing in a co2 rich vapour and a metal rich fe cu brine

metallogenic model of the trepca pb zn ag skarn deposit kosovo evidence from fluid inclusions rare earth elements and stable isotope data the trepca pb zn ag skarn deposit 29 mt of ore at 3 45 pb 2 30 zn and 80 g t ag is located in the kopaonik block of the western vardar zone kosovo the mineralization hosted by recrystallized limestone of upper triassic age was structurally and lithologically controlled ore deposition is spatially and temporally related with the postcollisional magmatism of oligocene age 23 26 ma the deposit was formed during two distinct mineralization stages an early prograde closed system and a later retrograde open system stage the prograde mineralization consisting mainly of pyroxenes hd54 100jo0 45di0 45 resulted from the interac tion of magmatic fluids associated with oligocene 23 26 ma postcollisional magmatism whereas there is no direct contact between magmatic rocks and the mineralization the deposit is classified as a distal pb zn ag skarn abundant pyroxene reflects low oxygen fugacity 10 31 bar and anhydrous environment fluid inclu sion data and mineral assemblage limit the prograde stage within a temperature range between 390 and 475 c formation pressure is estimated below 900 bars isotopic composition of aqueous fluid inclusions hosted by hedenbergite d 108 to 130 18o 7 5 8 0 mn enriched mineralogy and high ree content of the host carbonates at the contact with the skarn mineralization suggest that a magmatic fluid was modified during its infiltration through the country rocks the retrograde mineral assemblage comprises ilvaite magnetite arsenopyrite pyrrhotite marcasite pyrite quartz and various carbonates increases in oxygen and sulfur fugacities as well as a hydrous character of min eralization require an open system model the opening of the system is related to phreatomagmatic explosion and formation of the breccia arsenopyrite geothermometer limits the retrograde stage within the temperature range between 350 and 380 c and sulfur fugacity between 10 8 8 and 10 7 2 bars the principal ore minerals galena sphalerite pyrite and minor chalcopyrite were deposited from a mod erately saline ca na chloride fluid at around 350 c according to the isotopic composition of fluid inclusions hosted by sphalerite d 55 to 74 18o 9 6 to 13 6 the fluid responsible for ore deposition was dominantly meteoric in origin the 34s values of the sulfides spanning between 5 5 and 10 point to a magmatic origin of sulfur ore deposition appears to have been largely contemporaneous with the retrograde stage of the skarn development postore stage accompanied the precipitation of significant amount of carbonates including the travertine deposits at the deposit surface mineralogical composition of travertine varies from calcite to siderite and all carbonates contain significant amounts of mn decreased formation temperature and depletion in the ree content point to an influence of ph neutralized cold ground water and dying magmatic system

the jc tin skarn deposit southern yukon territory ii a carbon oxygen hydrogen and sulfur stable isotope study the jc tin deposit is a stanniferous skarn hosted within mississippian sediments intruded by the mid cretaceous seagull batholith the stable isotope compositions of silicate carbonate and sulfide minerals have been used to interpret the evolution of fluid sources during sequential stages of skarn formation the delta 13 c and delta 18 o values of remnant calcite from the earliest contact metamorphic stage 0 rocks are the result of decarbonation of the protolith marble coupled with infiltration of variable amounts of meteoric water garnet pyroxene skarn stage i was produced by predominantly magmatic fluids during initial skarn forming metasomatism stage ii amphibole rich skarn was formed by magmatic water mixed with up to 50 percent meteoric water this meteoric water had undergone stable isotope exchange with the jc granite at a low water to rock ratio as it moved upward along the contact of the granite with the surrounding wall rock the magmatic water component of stage ii fluids is inferred to have moved vertically through the solid cap of the granite before mixing with the exchanged meteoric water stage iii epidote quartz calcite skarn formed in the presence of a fluid consisting of magmatic water which had reequilibrated with the granite cap at temperatures between 350 degrees and 500 degrees c and subsequently mixed with up to 45 percent meteoric water the delta 13 c and delta 13 o values of stage iii calcite suggest the presence of an additional fluid component which had equilibrated with the protolith marble at similarly high temperatures these observations reinforce the hypothesis that originally highly saline stage iii fluids were diluted by low salinity meteoric water at the periphery of the skarn replacement zone and suggest that the surrounding marble horizon may have provided a pathway by which such fluids entered the skarn during formation of stage iv biotite quartz fluorite cassiterite skarn the fluid was predominantly magmatic with no detectable involvement of meteoric water this stage represented a renewed influx of magmatic fluid following the increased involvement of meteoric water during stages ii and iii and may have been related to a discrete episode of aqueous fluid separation from the underlying granitic magma the return to a predominantly magmatic fluid at stage iv is concomitant with an increase in both fluid temperature and salinity relative to stage iii fluids during the fracturing and formation of breccia zones which accompanied formation of stage vi pyrite marcasite carbonate skarn meteoric water which had initially equilibrated at low temperature 13 s values for all skarn sulfide minerals 1 0 to 2 5ppm is consistent with a magmatic source for sulfur throughout skarn formation stage iii and iv mineral pairs which remained in isotopic equilibrium after their initial crystallization yield oxygen isotope geothermometric temperatures consistent with those determined by fluid inclusion microthermometry

ray path identification and acoustic tomography in the straits of florida the florida current which flows through the straits of florida transports a significant fraction of the heat which must be transferred from low to high latitudes in order for the earth to remain in thermal balance while ocean acoustic tomography is an atttactive candidate for monitoring this heat transport its use is dependent on being able to identify individual ray paths all published investigations of tomography have been concerned with deep ocean propagation where experience has shown that paths can be identified propagation in the straits is quite different from deep ocean propagation however the sound speed is such that a ray path which travels modest distances necessarily experiences bottom bounces it is not clear a priori that paths can be identified in the straits we report the results of an investigation of this question using a fast specialized ray tracing program we analyzed the fluctuations in ray path geometry resulting from small perturbations in the bathymetry we found that the topographic features amplify these fluctuations to such a degree that identification of individual rays becomes impossible after only a few bottom bounces consequently there is no adequate interpretive tool for relating an acoustic signal recorded more than a few tens of kilometers from a source to the heat transport i e for carrying out the tomographic inversion we propose a way of overcoming this identification problem based on the use of acoustic profilers

iron oxide copper gold mineralization of the devonian laoshankou deposit xinjiang nw china in the central asian orogenic belt abstract the laoshankou iron oxide cu au iocg deposit 41 km southwest of qinghe city xinjiang nw china is the most important magnetite deposit with economic cu and au metal reserve 3 26 mt fe 33 5 36 4 9 8 kt cu 0 2 0 4 and 0 14 t au 0 5 1 3 g t in the east junggar terrane of the central asian orogenic belt caob the deposit is hosted by volcanic rocks of the middle devonian beitashan formation in this study four hypogene hydrothermal alteration stages have been identified including the ca silicate alteration stage i amphibole epidote magnetite alteration mineralization stage ii pyrite chalcopyrite mineralization stage iii and late hydrothermal veining stage iv mineralogical fluid inclusion including laser raman spectroscopy and mineral sulfur oxygen hydrogen and carbon isotope analyses were carried out to elucidate the nature and origin of the hydrothermal fluids at laoshankou stage i hydrothermal fluids were likely derived from a 590 c magmatic fluid with 18 o water 9 2 9 7 subsequently the magnetite epidote amphibole assemblage may have precipitated from the fluids 530 c formed by the mixing of high temperature magmatic fluids with the seawater that reacted with 18 o rich wall rocks the fluid rock reactions are reflected from the 18 o water 9 6 10 7 and d water 25 5 23 8 values the sub economic stage iii a pyrite epidote quartz garnet mineralization likely occurred at 415 c and was formed by fluids with 34 s fluid 3 7 0 5 d water 110 94 and 18 o water 7 92 8 9 the lower temperature and presence of organic matter of the stage iii a fluids may have reflected the involvement of meteoric water and organic matter from the wall rocks the economic cu mineralization stage iii b was probably formed by the mixing of a meteoric water dominated fluid medium temperature low salinity and na dominated and a ca rich formation water in equilibrium with the volcanic wall rocks medium temperature medium salinity and ca fe mg dominated with 34 s fluid 2 6 18 o water 5 6 5 8 13 c water 3 3 3 1 and d water 92 95 towards the end of the fluid evolution meteoric water incursion may have continued and generated the ore barren low temperature low salinity and na dominated fluids although the laoshankou deposit contains distinct skarn alteration the ore mineral assemblage and ore fluid features indicate that it is not a typical skarn deposit but share many similarities with many central andean iocg deposits we conclude that the iocg ore forming setting in the devonian east junggar was analogous to the cretaceous central andes in that they both occurred during basin inversion in a volcanic arc setting

geochemistry of post 1540 ma granites in the cloncurry district northwest queensland proterozoic fe oxide cu au co mineralization in the cloncuriy district is spatially and temporally related to intrusion of voluminous postpeak metamorphic granites that form most of the williams and naraku batholiths detailed mapping and geochemical study of these granites in the southern part of the district have identified two groups of intrusions that are referred to here as the cloncurry supersuite and eureka supersuite the cloncurry supersuite is composed mainly of monzogranite and syenogranite which consist of quartz plagioclase alkali feldspar hornblende biotite with accessory magnetite titanite apatite and zircon the timing of intrusion of the wiley igneous complex is interpreted to be pre or syn d 3 based on overprinting relationships while hornblende geobarometry suggests an emplacement depth of approximately 14 km the granites are subalkaline high k metaluminous rocks and range from 59 to 74 wt percent sio 2 increasing sio 2 is accompanied by increasing k 2 o rb and th and decreasing mgo fe 2 o 3 feo tio 2 cao p 2 o 5 sr eu zr cu zn ni v and sc this is consistent with fractionation of observed phases including plagioclase amphibole biotite magnetite titanite and apatite the eureka supersuite ranges from diorite to syenogranite in composition more mafic varieties contain pyroxene and hornblende while more felsic varieties contain biotite as the only ferromagnesian silicate sodiccalcic alteration events are closely linked in space and time to intrusion of eureka supersuite magmas the timing of intrusion is interpreted to be pre and post d 3 based on overprinting relationships between different plutons and mylonitic fabrics hornblende geobarometry suggests an emplacement depth of approximately 10 km for the mount angelay igneous complex eureka supersuite granites in the mount angelay igneous complex range from 51 to 76 wt percent sio 2 the granites are alkaline and k 2 o rich leading to their classification as a shoshonite series with increasing sio 2 content tio 2 al 2 o 3 fe 2 o 3 t mno mgo cao p 2 o 5 sr eu cu zn ni v and sc decrease indicating fractionation of observed minerals including apatite magnetite pyroxene hornblende plagioclase and biotite some samples are characterized by very high abundances of k 2 o p 2 o 5 sr ba and light rare earth elements lree compared to other eureka supersuite samples this may reflect their derivation from a source that was variably enriched in incompatible elements compared with many other shoshonitic rocks high k eureka supersuite samples are strongly depleted in sr and to a lesser extent eu and enriched in y and heavy rare earth elements hree this suggests that garnet was not a stable phase in the source region that the source contained plagioclase as a stable phase and or the granites evolved by extensive plagioclase fractionation partial melting in the lower crust to generate post 1540 ma granites was most likely caused by intrusion of basic magma into the crust eureka supersuite magmas were probably derived from partial melting of variably incompatible element enriched gabbroic rocks while cloncurry supersuite magmas were most likely derived from partial melting of more felsic material of dioritic to tonalitic composition

unidirectional solidification textures and their significance in determining relative ages of intrusions at the henderson mine colorado a variety of igneous textures displayed by stocks associated with the henderson molybdenite deposit are interpreted to result from unidirectional growth from the walls of magma chambers inward these igneous textures are present in layers and multilayered sequences consisting of crenulate quartz and feldspar pegmatites crenulate quartz dendritic alkali feldspar and quartz and dendritic and micrographic alkali feldspar quartz intergrowths minerals or intergrowths defining a layer within any one stock consistently terminate or branch inward away from the stock contacts the layers are separated by aplite or aplite porphyry and are most common in the apical and marginal parts of an individual stock layering generally parallels intrusive contacts differences in morphologies of phases among the various layers suggest changing conditions of growth from an undercooled melt and or aqueous solution changes in these physical and chemical conditions as the stock crystallized inward produced the observed textural and compositional layering unidirectional solidification textures can be used to determine the relative ages of individual stocks as well as the approximate orientation of stock contacts in the absence of other independent evidence unidirectional textures can also be used to indicate proximity to an intrusive contact these features are an invaluable aid in detailed mapping of multiple intrusion systems in which the units are compositionally identical or nearly identical

occurrence and origin of marialitic scapolite in the humboldt lopolith n w nevada the occurrence and origin of marialitic scapolite in the humboldt lopolith was investigated in the field and in the laboratory using petrographic and experimental techniques scapolite occurs in three modes as a pervasive replacement of plagioclase and other minerals in gabbro diorite and extrusive rocks as a poikiloblastic mineral in scapolitite dikes and as a fracture filling mineral with analcime albite and sphene in scapolite veins additional secondary minerals associated with scapolite include epidote prehnite hornblende and diopside salite clinopyroxene relations with these minerals suggest that most marialitic scapolite grew at temperatures around 400 c scapolite composition varies from eqan12 to eqan37 containing from 72 to 96 atomic cl in the r position experiments on systems of similar compositions indicate that nacl h2o fluid having more than 40 mol nacl is needed to stabilize the scapolite

a carbonate dominated copper cobalt breccia vein system at the great australia deposit mount isa eastern succession great australia is a small cu co deposit in the eastern succession of the mount isa inlier northern queensland it may be viewed as a carbonate rich member of the globally distributed oxide dominated fe cu au or rare earth element ree or u deposit group it is also a gold poor variant of a group of small to medium sized carbonate dominated vein replacement deposits in the surrounding cloncurry copper gold field known as mount freda style deposits it lies within the proterozoic toole creek volcanics tcv adjacent to and within a major splay of the cloncurry fault which forms a regional tectonic contact with the metasedimentary corella formation and is consequently a fundamental structure in the inlier the deposit has a gangue mineral assemblage of dolomite calcite quartz pyrite ore type 1 transitional to amphibole quartz pyrite ore type 2 with mineralization largely restricted to thick tabular veins and fault zones mineralization that is deeper in the explored deposit within the sheared tcv corella formation contact or in magnetite altered wall rocks is pre dominantly ore type 2 the deposit occurs within a dilational jog that developed during d 3 dextral fault reactivation plunging ore shoots occur at the intersections of this contact with a north south striking fault the main lode forming thick veins strong alteration halos exist around the ore zones within the tcv and are subdivided into a regional pre to syn d 2 albite actinolite alteration sodic calcic i and a local ore related albite actinolite zone sodic calcic ii the latter has a fringing biotite alteration envelope alteration within the corella formation is geochemically similar to but more subdued than that of tcv alteration chalcopyrite bearing secondary fluid inclusions from ore type 1 quartz contain high temperature 450 degrees or 60 degrees c high salinity 45 or 10 wt nacl equiv high f sub o 2 fluids that are interpreted to be syn ore oxygen isotope values of delta 18 o quartz 11 3 13 4ppm indicate that delta 18 o fluid 8 3 to 10 3 per mil consistent with a magmatic to metamorphic source calcite carbon isotope values require delta 13 c fluid 0 3 to 3 7 per mil best explained by a mixture of carbonate sedimentary carbon and magmatic carbon the genetic model involves the emplacement of ore fluids into the previously altered cloncurry fault at high fluid pressures and temperatures initially forming zoned magnetite albite dominant alteration grading out to biotite dominant alteration sodic calcic ii that was contemporaneous with carbonate amphibole magnetite cobaltian pyrite dominant veining and replacement within the dilational jog late in the history of carbonate precipitation sulfate bearing metalliferous fluids were introduced and were rapidly reduced by earlier magnetite biotite and pyrite bearing alteration reduction of fluid sulfate and mineral sulfidation resulted in coprecipitation of chalcopyrite chlorite and minor gold commonly replacing pyrite magnetite biotite amphibole and carbonate

stable isotope evidence for the origin of the mesoproterozoic starra au cu deposit cloncurry district northwest queensland new stable isotope data are consistent with a metasomatic origin for the controversial mesoproterozoic ironstone hosted au cu deposit at starra in the cloncurry district of northwest queensland this supports textural and mineralogical evidence that the ore bearing ironstones formed after the peak of metamorphism and were strongly controlled by brittle ductile deformation three dominant paragenetic stages are recognized these are 1 early widespread na ca metasomatism quartz albite scapolite actinolite 2 localized k fe metasomatism biotite magnetite hematite quartz pyrite and 3 mineralization quartz anhydrite barite hematite calcite gold pyrite chalcopyrite bornite chalcocite chlorite muscovite crosscutting anhydrite veins associated with carbonate or hematite are rare in the upper parts of the system but more common at depths greater than 700 m stage 3 minerals demonstrate that the ore fluid was highly oxidized a restricted range of fe oxide delta 18 o implies isotopically similar fluids were responsible for the magnetite ironstones and later hematite alteration associated with gold and sulfides between 0 2 to 3 3ppm except for one magnetite at 5 4ppm sulfur isotope compositions suggest that pyrite 0 2 to 3 9ppm chalcopyrite 5 8 to 0 7 and 14 6ppm bornite 4 7ppm chalcocite 0 1ppm and anhydrite 1 1 2 4ppm all formed from the same sulfur source anhydrite delta 34 s falls within the sulfide range suggesting that the sulfate inherited its delta 34 s through hydrolytic processes similar to those of some porphyry environments delta 13 c of ore stage carbonates range from 7 3 to 2 2 per mil temperatures based on stage 2 quartz magnetite pairs imply 400 degrees to 500 degrees c for ironstone formation and stage 3 calcite hematite pairs indicate 180 degrees to 330 degrees c for mineralization stage 2 fluid inclusions have homogenization temperatures between 345 degrees and 615 degrees c and salinities of 34 to 52 wt percent nacl equiv stage 3 fluid inclusions homogenized between 225 degrees and 360 degrees c and have salinities of 30 to 42 wt percent nacl equiv calculated delta 18 o fluid compositions for magnetite quartz and hematite calcite average 7 8 per mil and 9 5 per mil respectively fluid compositions for stages 2 and 3 fall within the range for a magmatic or metamorphic fluid however combined stable isotope and fluid inclusion data and thermodynamic considerations suggest a magmatic metasomatic origin for both the magnetite ironstones and the highly oxidized mineral assemblage associated with high grade gold deposition

hydrothermal alteration and mineralization in the neves corvo volcanic hosted massive sulfide deposit portugal ii oxygen hydrogen and carbon isotopes the oxygen hydrogen and carbon isotope compositions of hydrothermally altered rocks and minerals from massive and stockwork ores of the neves corvo volcanic hosted massive sulfide deposit have been used to infer its thermal history and the origins of the hydrothermal fluids quartz and cassiterite separated from the stringer and massive cassiterite ores of the corvo orebody tin corridor have 18o values of 12 5 to 13 6 and 1 4 to 0 4 per mil respectively quartz cassiterite oxygen isotope fractionation indicates temperatures of 174 to 207 c avg 191 c for precipitation of this mineral pair the calculated oxygen isotope composition of the fluid 18oh2o 0 4 to 0 7 avg 0 1 suggests that cassiterite precipitation resulted from extensive mixing of a tin bearing fluid with seawater at sea floor hydrothermal vents the whole rock oxygen isotope composition of the hydrothermally altered felsic volcanic rocks hosting the sulfide stockwork of the corvo orebody varies from the central stockwork chloritic alteration zone i 18o 8 7 9 6 to the peripheral zones sericitic and paragonitic alteration zones iia 18o 11 6 13 1 and iib 18o 11 0 14 1 the 18o values of quartz also increase from alteration zone i avg 13 9 to alteration zone iia avg 14 4 to alteration zone iib avg 15 0 quartz from the hanging wall jasper unit yielded higher 18o values of 15 5 to 17 9 per mil chlorite from alteration zone i has 18o values of 6 1 to 8 4 per mil avg 7 4 sericite has 18o and d values that vary slightly from 18o 9 3 to 10 1 per mil avg 9 9 and d 59 to 47 per mil avg 53 in alteration zone i to 18o 9 8 to 11 4 per mil avg 10 5 and d 50 per mil in alteration zone iia to 18o 9 4 to 11 7 per mil avg 10 6 and d 61 to 36 per mil avg 45 in alteration zone iib siderite associated with waning hydrothermal activity has low 13c values 11 1 to 5 8 suggesting the incorporation of oxidized organic carbon from the footwall sequence and or the addition of magmatic carbon in alteration zone i quartz chlorite fractionation indicates temperatures of 249 to 402 c avg 335 c and 18oh2o values of 6 1 to 10 2 per mil avg 8 3 quartz sericite pairs gave isotopic equilibrium temperatures of 250 to 289 c avg 269 c and 18oh2o values of 5 8 to 7 0 per mil avg 6 4 in alteration zone iia and 170 to 318 c avg 223 c and 18oh2o 1 4 to 8 3 per mil avg 4 5 in alteration zone iib the oxygen isotope data show that in the core of the feeder system alteration zone i the temperature and the 18oh2o values were very high the d values calculated for the ore fluids d 37 to 11 are also significantly lower than seawater outward from the central stockwork alteration zones iia and iib the ore fluid was depleted in 18o and the temperatures were lower the oxygen hydrogen and carbon isotope signatures of the neves corvo ore fluids are best explained by incorporation of magmatic and or metamorphic fluids into a seawater dominated hydrothermal system magmatic fluids in particular were a likely source for the tin and much of the copper in the neves corvo ores

a framework of overprinting orogens based on interpretation of the mount isa deep seismic transect a deep seismic reflection transect and coincident refraction study reveal the crustal structure developed during mesoproterozoic orogenesis preserved in the mount isa inlier of northwest queensland australia geologic interpretation of the reflection data indicates a two stage evolution for east west shortening the first stage involved west directed folding and thrusting above a decollement in the eastern part of the terrane this decollement system was the forehand of an orogenic system rooted east of the present day inlier the second stage is characterized by a network of basement cutting reverse and strike slip faults that dissected the decollement this overprinting system was linked to crustal thickening within the mount isa terrane the refraction profile indicates the crust beneath the inlier is currently approximately 55 km thick rocks with transitional velocities 7 km s in the lower 15 km are interpreted as mafic underplate formed during the pre orogenic rift history of the inlier the refraction profile also reveals two west dipping high velocity layers within the crust evaluating the origin of these layers in light of the kinematics of crustal thickening suggests they are portions of the underplated material thrust to midcrustal levels during the second stage of shortening the overprinting orogenic scenario has implications for the geodynamic evolution of the inlier that should have a direct bearing on mineralizing systems localized by reverse faults developed during the second stage of shortening this basement cutting stage established a linked fault network able to tap deeper crustal circulation during the intrusion of late to postorogenic granitoids

a review of ocean acoustic tomography 1987 1990 the techniques and instruments used in acoustic tomography of the oceans are surveyed and results are summarized sections are devoted to theoretical studies and numerical simulations mesoscale mapping vertical slice tomography flow imaging and nonlinear bias series of tomographic experiments analyses to identify global changes and outstanding problems the forward and inverse problems and ocean physics typical data are presented in tables and graphs and a comprehensive bibliography is provided 72 refs

crystallization of apatite in natural magmas under high pressure hydrous conditions with particular reference to orogenic rock series two separate series of hydrous experiments involving 1 imposing apatite saturation on a series of igneous rock compositions from basanite to rhyolite and 2 crystallizing similar natural rock compositions progressively until apatite appears demonstrate a close dependence between apatite saturation and silica content of the magma and determine p2o5 levels at a given silica value and temperature at which that composition may be expected to crystallize apatite the effect of pressure on apatite solubility is not great and is most significant for silicic compositions

an example of ocean acoustic multipath identification at long range using both travel time and vertical arrival angle a phase coded signal with 62 5 ms time resolution was transmitted for a 22 day period between an acoustic source moored at 1375 m depth and an autonomous acoustic receiver moored at 1333 m depth and at 215 km range the receiver consisted of a four element vertical array with 1 5 wavelengths between elements three strong arrivals were observed excellent agreement was obtained between measured and predicted arrival patterns including both arrival times and arrival angles the first two arrivals were predicted by geometric ray theory the third arrival was nongeometric and associated with a caustic 400 m above the receiver

crystallization and alteration of quartz monzonite iron springs mining district utah relation to associated iron deposits the iron springs mining district of southwestern utah contains the largest iron deposits in the western united states these are related to emplacement at minimum depths of 1 to 2 3 km of three miocene laccoliths of porphyritic quartz monzonite when emplaced the magma was nearly half crystallized on the verge of brittle behavior and contained phenocrysts of plagioclase amphibole biotite and clinopyroxene granophyric dikes in quartz monzonite formed from residual liquid but miarolitic cavities in these dikes are lined with alpha quartz indicating that deposition continued from a volatile rich phase below the solidus pervasive high temperature alteration led to replacement of augite by diopside oxidation of magnetite and ilmenite replacement of amphibole completely and biotite partially by aggregates of diopside alkali feldspars smectite chlorite magnetite ilmenite and calcite albitization of groundmass alkali feldspar exchange of mg for fe and of f for oh in biotite and exchange of f and oh for cl in apatite this alteration produced whole rock enrichment in fe super 3 na and h 2 o and losses in fe super 2 ca and k total fe was effectively unchanged a chilled relatively impermeable margin surrounding the pervasively altered interior of each laccolith was mechanically bonded to wall rock more strongly than to the magmatic interior and deformed with the wall rock during subsequent intrusion and structural readjustment in this peripheral shell clinopyroxene amphibole and biotite were less altered where the roof of each laccolith had a radius of curvature of less than 2 km a heterogeneous jointed zone formed below the peripheral shell in this zone pervasively altered quartz monzonite was fractured by renewed intrusion or by structural readjustment of roof rocks along the resulting joints quartz monzonite was altered to bleached zones selvages during a second stage of alteration within these selvages complete decomposition of biotite that had survived pervasive alteration was accompanied by further growth of diopside albitization of feldspars and dissolution of some apatite unlike early pervasive alteration selvage alteration was fracture controlled and caused strong whole rock depletion in light ree total fe mg p rb y ba and h 2 o super but caused enrichment in na magnetite apatite veins commonly formed along the joint adjacent to zones of selvage joints strata bound orebodies of magnetite hematite and apatite formed in limestone around the three laccoliths iron bearing fluid was derived by subsolidus alteration from quartz monzonite there is no evidence supporting immiscible separation of iron oxide rich liquid from silicate magma mass balance calculations indicate that the fe p s al and mg in the orebodies could have been entirely supplied by selvage alteration of 40 km 3 of quartz monzonite in agreement with the exposed and confidently inferred volume of altered intrusive rock a fourth pluton lacking magnetite veins orebodies and selvages was emplaced closer to the surface and against sandstone and share rather than limestone iron liberated from hydrous mafic phenocrysts in this body was oxidized in place forming disseminated hematite

chemical and stable isotopic compositions of proterozoic metamorphosed evaporites and associated tourmalines from the houxianyu borate deposit eastern liaoning china an integrated major element trace and rare earth element and stable isotope b si o and s study has been carried out on the houxianyu borate deposit eastern liaoning china the present day mineralogy of the deposit is closely similar to that of magnesian skarn deposits and the borates are underlain by granite however the geochemical and isotopic evidence does not favour a skarn type origin in particular the boron isotopic compositions of the borate minerals and associated tourmalines preclude their origin from fluids derived from the granite rather the data are compatible with the borate deposit being a metamorphosed evaporite the mineralogy and chemistry of the deposit are most compatible with a non marineorigin although the high 34s and 11b values suggest that there may have been some marine components to the evaporitic brines overall the premetamorphic origin of the houxianyu borate deposit is similar to that of the tertiary non marine evaporite borate deposits of western turkey there are also similarities with other proterozoic early rifting environments e g the upper proterozoic damaran orogen of south africa that have implications for the structural evolution and mineral potential of the region

le magmatisme de la region de kwyjibo province du grenville canada interet pour les mineralisations de type fer oxydes associees the granitic plutons located north of the kwyjibo property in quebec s grenville province are of mesoproterozoic age and belong to the granitic canatiche complex the rocks in these plutons are calc alkalic k rich and meta to peraluminous they belong to the magnetite series and their trace element characteristics link them to intraplate granites they were emplaced in an anorogenic subvolcanic environment but they subsequently underwent significant ductile deformation the magnetite copper and fluorite showings on the kwyjibo property are polyphased and premetamorphic their formation began with the emplacement of hydraulic magnetite bearing breccias followed by impregnations and veins of chalcopyrite pyrite and fluorite and ended with a late phase of mineralization during which uraninite rare earths and hematite were emplaced along brittle structures the plutons belong to two families biotite amphibole granites and leucogranites the biotite amphibole granites are rich in iron and represent a potential heat and metal source for the first iron oxide phase of mineralization the leucogranites show a primary enrichment in ree rare earth elements f and u carried mainly in y u and ree bearing niobotitanates they are metamict and underwent a postmagmatic alteration that remobilized the uranium and the rare earths the leucogranites could also be a source of rare earths and uranium for the latest mineralizing events

discrimination of productive and nonproductive porphyritic intrusions in the chilean andes a geochemical comparison between productive intrusions those associated with mineralization and nonproductive intrusions those unrelated to mineralization has been made on the basis of over 100 fresh granitoid rocks from the chilean porphyry copper belt the study was carried out on the scale of a mining district el salvador potrerillos then on the scale of a single traverse el salvador chilean coast and finally on the scale of the andes itself the productive intrusions are best characterized by large negative anomalies in y mn th and the heavy rare earth elements a discriminant diagram of y against mno is recommended for predicting whether an apparently fresh intrusion has associated peripheral mineralization the low values of y and mn in productive intrusions can be partly explained by the early crystallization of y and mn rich hydrous phases such as hornblende and by the loss of mn rich fluids from the magma the same elements make useful discriminants in other porphyry copper provinces although the exact position of the discriminant boundary varies from island arcs through continental margin to continental settings

fluid inclusions in epidote minerals and fluid development in epidote bearing rocks the widespread occurrence of epidote minerals in metamorphic and igneous rocks as well as in many ore deposit types makes it a promising candidate for fluid inclusion studies apart from high to very high temperature and low to intermediate pressure conditions epidote minerals are stable over a wide range of pressure and temperature in the continental and oceanic crust e g poli and schmidt 1998 yet fluid inclusion studies on epidote minerals are surprisingly scarce even in fluid saturated environments like certain vein type deposits or hydrothermal volcanic vugs and druses for example epidote minerals are not mentioned in the subject index of roedder s 1984 outstanding summary and review of fluid inclusion studies and occurrences which lists more than sixty different host minerals for fluid inclusions nonetheless more recent studies showed fluid inclusions in epidote minerals to be the only direct witness of the physiochemical and compositional fluid evolution during certain geodynamic processes mainly found in fossil geothermal systems ore deposits and high pressure to ultra high pressure rocks the aim of this review is to outline and summarize some aspects and interpretations of geodynamic processes which are based on temperature t pressure p molar volume v and composition x data from fluid inclusions in epidote minerals as well as associated host minerals from various geological environments the review starts with a chapter on some typical mixed volatile solid fluid equilibria involving epidote minerals which are relevant for the here discussed environments this is followed by a short introduction into the basic concepts of fluid inclusion research and the role of epidote minerals the next section covers fluid inclusion studies on epidote minerals from active and fossil geothermal systems as well as low grade metamorphic rocks and constraints on the p t x properties of the fluids present in these systems this is followed by a short introduction

results from the 1984 marginal ice zone experiment preliminary tomography transmissions implications for marginal ice zone arctic and surface wave tomography during the 1984 marginal ice zone experiment mizex 84 a 224 hz center frequency acoustic tomography sound source was deployed off spitsbergen norway in 1200 m of water over the course of 10 days it transmitted hourly signals that were recorded by receivers at two locations one moving with the ice pack and the other stationary the main purpose of the transmissions was to answer the following questions which are important to the feasibility of acoustic tomography in marginal ice zone miz and arctic regions 1 can the signals be coherently averaged to improve the signal to noise ratio of the multipath arrival peaks 2 are the surface scattering and bottom reflection losses acceptably low 3 are the arrivals identifiable 4 are the arrivals stable and 5 are the arrivals resolvable our data analysis provides generally positive answers indicating that ocean acoustic tomography is feasible in miz regions however the shallow bathymetry in the mizex 84 area increases the difficulty of the problem consistent with the observations of palmer et al 1985 and deferrari and nguyen 1985 in the shallow water of the straits of florida in analyzing the data it was noticed that the phase or travel time fluctuation spectra of surface interacting rays exhibited a shape similar to that of the surface wave frequency spectrum this suggested that tomography could also measure the surface wave field a previously unexplored possibility theoretical expressions are derived in this paper which relate the acoustic fluctuations to standard surface wave descriptors e g the frequency directional spectrum these expressions are then used to compute the surface wave frequency spectra for 2 days of data though these spectra are uncorroborated by other wave spectrum measurements e g wave rider buoys the rms wave heights predicted by the acoustics agree well with rms wave heights estimated by wind force data

tomographic resolution of mesoscale eddies in the marginal ice zone a preliminary study the adequacy of ocean acoustic tomography to resolve mesoscale eddies in the marginal ice zones miz in the vertical plane containing the acoustic multipaths connecting a pair of transceivers is studied using simulation inversions based on realistic eddy profiles obtained from conductivity temperature depth data resolution in this plane is seen to be strongly dependent upon the characteristics of the sound channel for optimal minimum mean square error estimators resolution is directly related to accuracy with better resolution implying higher accuracy for unaided acoustic tomography i e no supplementary measurements using only non bottom interacting paths horizontal and vertical resolution lengths of the order of 40 km and 200 m respectively are found in the upper water column for a transmission range of 150 km the implication is that the horizontal resolution is marginally adequate to resolve miz eddies but the vertical resolution is not since the horizontal scale of the eddies is of the same order whereas the vertical scale is much shorter the incorporation of bottom reflected arrivals is found to improve resolution significantly however the improvement only occurs in the horizontal direction and saturates when more than 14 of these arrivals are included beyond this point additional travel time observations give mostly redundant information on the other hand the disappearance of less stable non bottom interacting ray paths can result in a significant loss of resolution but only vertically the deficiency in vertical resolution is a result of the upward refracting nature of the miz sound channel it is also demonstrated that the inclusion of point temperature measurements on the acoustic transceiver moorings can dramatically increase the vertical resolution of the overall system particularly within a horizontal correlation length of the mooring with the inclusion of satellite radiometry surface temperature measurements adequate vertical resolution is achieved over the entire range considered

a demonstration of ocean acoustic tomography over the past decade oceanographers have become increasingly aware of an intense and compact ocean mesoscale eddy structure the ocean weather that is superimposed on a generally sluggish large scale circulation the ocean climate traditional ship based observing systems are not adequate for monitoring the ocean at mesoscale resolution a 1981 experiment mapped the waters within a 300 300 km square south west of bermuda using a peripheral array of moored midwater acoustic sources and receivers the variable acoustic travel times between all source receiver pairs were used to construct the three dimensional time variable eddy fields using inverse theory preliminary results from inversions are consistent with the shipborne and airborne surveys

vertical seismic profiling of glaciers appraising multi phase mixing models we have investigated the speed of compressional waves in a polythermal glacier by first predicting them from a simple three phase ice air water model derived from a published ground penetrating radar study and then comparing them with field data from four orthogonally orientated walkaway vertical seismic profiles vsps acquired in an 80 m deep borehole drilled in the ablation area of storglaciaren northern sweden the model predicts that the p wave speed increases gradually with depth from 3700 m s 1 at the surface to 3760 m s 1 at 80 m depth and this change is almost wholly caused by a reduction in air content from 3 at the surface to 0 5 at depth changes in p wave speed due to water content variations are small 10 m s 1 the model s seismic cold temperate transition surface cts is characterized by a 0 3 decrease downwards in p wave speed about ten times smaller than the radar cts this lack of sensitivity and the small contrast at the cts makes seismically derived water content estimation very challenging nevertheless for down going direct wave first arrivals for zero and near offset vsp shots we find that the model predicted travel times and field observations agree to within 0 2 ms i e less than the observational uncertainties

co 2 brine immiscibility at high temperatures evidence from calcareous metasedimentary rocks study of fluid inclusions in quartz segregations and in the rock matrix of a calcareous psammite and a carbonate schist suggests that brines containing 23 24 weight percent salt nacl equivalent are immiscible with co2 at the metamorphic conditions of approximately 600 and 6 5 kb the presence of a high temperature solvus between saline brine and co2 is supported by other fluid inclusion studies as well as experimental measurements from the literature as saline brines are common in metamorphic and hydrothermal systems co2 brine immiscibility should play an important role in petrogenesis the fluid inclusions preserved in the quartz segregations probably represent the fluids generated by prograde metamorphic reactions whereas the compositions of the fluids trapped in the rock matrix quartz suggest they have reequilibrated with the matrix minerals during incipient retrograde reactions the isochores from the densest inclusions observed in this study pass close to the inferred peak metamorphic conditions other isochores suggest an episode of deformation and recrystallization at 275 c and 1 4 kb using the density information preserved in all the inclusions a convex downward uplift path on a p t diagram is inferred for these rocks

geochemical evidence for magmatic fluids in porphyry copper mineralization the koloula igneous complex comprises 26 different intrusive phases that have been divided into two major magmatic episodes cycle 1 intrusions 4 5 ma and cycle 2 intrusions 2 4 to 1 5 ma the cycle 2 intrusions are further divided into the inamumu zoned pluton izp which is composed of 6 concentrically disposed quartz diorite and tonalite units and several satellite intrusions the izp is host to porphyry copper mineralization whereas the cycle 1 and cycle 2 satellite intrusions are barren presently exposed mineralization in the izp a system represents the deeply eroded core of a porphyry copper system where widely spaced veinlet alteration envelopes 1 mm thick are separated by large volumes of unaltered rock

amphibolitic cu fe skarn deposits in the central coast of peru monterrosas eliana ra uacute l and condestable are the most important copper mines in the central coast of peru between lat 12 degrees 309 and 14 degrees 309 s their related geologic setting close age relation and similar mineralogy and geochemistry argue in favor of their grouping together as amphibolitic cu fe skarn deposits in the lower cretaceous continental margin 100 to 120 ma incipient rifting accompanied by batholithic gabbrodiorite intrusions at depth gave rise to an elongated trough in which submarine volcanic and sedimentary rocks accumulated skarn deposits developed in association with the intrusive activity are characterized by chalcopyrite concentrations with low ti magnetite and or pyrite in actinolite gangue minor constituents are amphiboles of hastingsitic and tschermakitic varieties apatite pyrrhotite and sodic scapolite copper ores are fracture controlled and hosted by albian gabbrodiorite plutons at monterrosas and eliana volcanogenic strata bound mantos as well as disseminated sulfide stringers and minor veins occur at ra uacute l and condestable in hauterivian to albian volcano sedimentary rocks geochronologic k ar data identify a lower cretaceous episode of metallogenesis for ra uacute l condestable and eliana geologically related iron deposits of hierro acari and marcona are dated as lower cretaceous and upper jurassic respectively petrography and major element chemistry of the gabbrodiorite suite at monterrosas and eliana indicate a low k tholeiitic character with calc alkaline affinities and high na 2 o k 2 o ratios late magmatic and hydrothermal activity developed in the roof zones of the plutons and formed amphibole magnetite chalcopyrite deposits mineralization at eliana involved introduction of cu fe and p along fractures and contacts to form ore shoots the scapolite alteration halo is characterized by si na and ca enrichment the hydrothermal deposits of ra uacute l formed mainly at subvolcanic levels with a dominant seawater component ripley and ohmoto 1977 1979 geologic correlation with eliana and monterrosas indicates that both magmatic and seawater components coincided to form amphibolitic cu fe skarn deposits which span the plutonic and volcanic environments lead isotope compositions of chalcopyrite pyrite and galena define a primitive trend for these skarn deposits compared to that of porphyry cu deposits in southern peru and chile and sn deposits in bolivia the isotopic contrast is interpreted as a result of rifting and extreme crustal thinning during the lower cretaceous along the continental margin of central and southern peru this tectonic and metallogenetic environment continued into northern and central chile where amphibolitic fe and cu deposits of the same age range are known

alteration mineralization and fluid evolution at the eloise cu au deposit cloncurry district northwest queensland australia the eloise deposit 3 1 million metric tons mt 5 5 cu 1 4 g t au and 16 g t ag is hosted by proterozoic rocks of the soldiers cap group in the eastern fold belt of the mount isa inlier the deposit is characterized by very high grade chalcopyrite pyrrhotite rich mineralization hosted by mafic silicate alteration alteration and mineralization lie within and adjacent to a major shear zone the main metasomatism comprised three stages early pervasive albite alteration stage i was overprinted by stage ii hornblende biotite quartz veins and alteration stage iii chalcopyrite pyrrhotite magnetite pyrite calcite quartz chlorite and actinolite replaced and brecciated the earlier mafic silicates the lodes occupy a narrow portion of a zoned mineralized system that is at least 2 km in length magnetite pyrite rich mineralization occurs in the south with chalcopyrite pyrrhotite rich mineralization in the central lode zone and pyrrhotite rich mineralization in the north the system has a distinct chemistry with enriched cu au ag co ni and zn fluid inclusions in pre syn and late to postmineralization veins indicate an evolving fluid history primary inclusions and associated hornblende biotite assemblages in premineralization veins indicate a high temperature fluid 450 degrees 600 degrees c and salinity estimates suggest it was an ultrasaline brine 32 68 wt total salts fluid inclusions in stage iii quartz in mineralized veins display a wide range of homogenization temperatures approximately 100 degrees 500 degrees c and gangue assemblages actinolite chlorite muscovite suggest mineralization was a cooler event 200 degrees 450 degrees c inclusions associated with the mineralization have a lower salinity 30 47 wt total salts than do premineralization inclusions and variable fluid inclusion types occur within the same clusters which may reflect fluid mixing the ultrasaline nature of the fluids and preliminary sulfur isotope results 0 4 2 0ppm suggest the ore fluid was predominantly magmatic metals were carried as chlorocomplexes and h 2 s was the dominant sulfur species important factors in ore deposition were a decrease in temperature and salinity and sulfidation of fe silicates eloise is interpreted to be a structurally controlled distal magmatic hydrothermal vein deposit

the hecataeus rise easternmost mediterranean a structural record of miocene quaternary convergence and incipient continent continent collision at the african anatolian plate boundary abstract the hecataeus rise represents a plateau like structure adjacent to the southern cyprus margin and directly next to the cyprus eratosthenes seamount convergence zone where incipient continent continent collision is believed to occur based on newly acquired seismic reflection and bathymetric data we report on the miocene to quaternary structural evolution of this yet underexplored sector along the african anatolian plate boundary a period of pre messinian compression has significantly deformed the western and southern part of the plateau area offshore continuation of onshore cyprus lineaments attests the existence of a pre messinian structural link between cyprus and the hecataeus rise owing to its relatively elevated position during the messinian salinity crisis the hecataeus rise experienced wide spread messinian erosion and only local deposition of evaporites which were precipitated within small isolated sub basins post messinian convergence was accommodated along the southeastern flank of the hecataeus rise where ne sw trending anticlinal structures experienced reactivation and significant growth a prominent intra pliocene quaternary unconformity in the northwestern part of the plateau area may correlate with the pliocene pleistocene transition and indicates the near synchronous occurrence of several tectonostratigraphic events we suggest that these events represent a chain of structural and depositional changes initiated by incipient collision of eratosthenes seamount with cyprus and the northwestern corner of the hecataeus rise collision derived uplift of cyprus resulted in vertical separation between cyprus and the hecataeus rise and the development of a prominent unconformity in the northwestern part of the plateau area increasing the slopes adjacent to cyprus facilitated more energetic downslope sediment transport expressed by the development of sediment waves and the evolution of a prominent canyon structure at the northeastern limit of the plateau area

crustal structure of the levant basin eastern mediterranean abstract a seismic refraction wide angle reflection experiment was undertaken in the levant basin eastern mediterranean two roughly east west profiles extend from the continental shelf of israel toward the levant basin the northern profile crosses the eratosthenes seamount and the southern profile crosses several distinct magnetic anomalies the marine operation used 16 ocean bottom seismometers deployed along the profiles with an air gun array and explosive charges as energy sources the results of this study strongly suggest the existence of oceanic crust under portions of the levant basin and continental crust under the eratosthenes seamount the seismic refraction data also indicate a large sedimentary sequence 10 14 km thick in the levant basin and below the levant continental margin assuming the crust is of cretaceous age this gives a fairly high sedimentation rate the sequence can be divided into several units a prominent unit is the 4 2 km s layer which is probably composed of the messinian evaporites overlying the evaporitic layer are layers composed of plio pleistocene sediments whose velocity is 2 0 km s the refraction profiles and gravity and magnetic models indicate that a transition from a two layer continental to a single layer oceanic crust takes place along the levant margin the transition in the structure along the southern profile is located beyond the continental margin and it is quite gradual the northern profile north of the carmel structure presents a different structure the continental crust is much thinner there and the transition in the crustal structure is more rapid the crustal thinning begins under western galilee and terminates at the continental slope the results of the present study indicate that the levant basin is composed of distinct crustal units and that the levant continental margin is divided into at least two provinces of different crustal structure

simulated tomographic reconstruction of ocean current profiles in a bottom limited sound channel tomographic reconstruction of the vertical current profile in a bottom limited sound channel requires solving a difficult ray identification problem an approach to deal with this problem is a ray group method in which received arrival pulses are divided into several ray groups according to the characteristics of the arrival patterns the method is validated using numerically simulated reciprocal acoustic transmission in a synthetic ocean in the luzon strait where the kuroshio current has speeds as high as 1 2 m s for both narrowband and broadband signals four ray groups are found for the synthetic data these are chosen based on arrival time the differential travel time is determined by pairing up the reciprocal arrival peaks and then averaging the differential travel times within the selected time windows compared with the narrowband case the estimated broadband differential travel time is more consistent with that computed from the current magnitude in the synthetic ocean the vertical current profile is reconstructed from the broadband differential travel times by a generalized tikhonov regularization approach the data weighting matrix includes observation error in picking and pairing travel times and model parameter error due to path length uncertainty the time series of the reconstructed current agrees with the synthetic ocean current the fractional residual variance is 0 013 for the surface layer and 0 01 for the entire water column the ray group method mitigates the ray identification problem in the bottom limited environment and could offer valuable data regarding the range integrated current velocity

study of a novel range dependent propagation effect with application to the axial injection of signals from the kaneohe source a novel range dependent propagation effect occurs when a source is placed on the seafloor in shallow water with a downward refracting sound speed profile and sound waves propagate down a slope into deep water under these conditions small grazing angle sound waves slide along the bottom downward and outward from the source until they reach the depth of the sound channel axis in deep water where they are detached from the sloping bottom and continue to propagate outward near the sound channel axis this mudslide effect is one of a few robust and predictable acoustic propagation effects that occur in range dependent ocean environments as a consequence of this effect a bottom mounted source in shallow water can inject a significant amount of acoustic energy into the axis of the deep ocean sound channel that can then propagate to very long ranges numerical simulations with a full wave range dependent acoustic model show that the kaneohe experiment had the appropriate source bathymetry and sound speed profiles that allows this effect to operate efficiently this supports the interpretation that some of the near axial acoustic signals received near the coast of california from the bottom mounted source located in shallow water in kaneohe bay oahu hawaii were injected into the sound channel of the deep pacific ocean by this mechanism numerical simulations suggest that the mudslide effect is robust

structures and kinematics in the northeastern mediterranean a study of an irregular plate boundary abstract extensional structures are prominent in the northeastern mediterranean a unique sector of the africa eurasia plate convergence zone to explain this paradoxical situation we analyse here the young tectonics of this region by examining its structural elements and plate kinematics offshore multichannel seismic reflection profiles and onland geology show that the stuctural settings are different on the two sides of the northeastern mediterranean triple junction afr arb ana on the east stuctures controlled by strike slip and by compression coexist whereas on the west compression is not very conspicuous here deep basins separated by a partly submerged ridge are prominent we interpret the ridge which comprises the kyrenia misis andirin unit at its core as a large flower structure which extends from southeastern turkey to cyprus the adana cilicia and the iskenderun latakia mesaoria basins on its flanks are interpreted as due to extension this interpretation agrees with the relative motions between the africa arabia eurasia and anatolia plates in this region analysis of the local plate kinematics reveals that strike slip predominates along the southern boundary of the anatolia plate in this region as a result of anatolia s westward escape east of the triple junction this motion is associated with comparable shortening transverse to the plate boundary whereas west of the triple junction the motion transverse to the plate boundary varies between slight compression to extension depending mainly on the local strike of the plate boundaries these variations calculated from regional data correlate well with the observed structural changes along the northeastern mediterranean sector of the plate convergence zone the structural kinematic analysis explains both the lateral changes in the deformation style and the existence of local extension in the northeastern mediterranean

the influence of meteoric water on skarn formation and late stage hydrothermal alteration at the evciler skarn occurrences kazdag nw turkey abstract skarn ore deposits are generally characterized by two distinctly different alteration styles an early prograde stage with anhydrous minerals such as garnet grossular andradite and pyroxene diopside hedenbergite which forms in the presence of relatively high temperature fluid and a later retrograde stage with hydrous minerals such as epidote amphibole actinolite and chlorite from most to least abundant plus sulfides which forms in the presence of the lower temperature fluid these two alteration stages commonly have been thought to reflect a dominance of magmatic and meteoric water respectively with relevance to the source of ore metals we report data from the evciler au cu skarn deposit kazdag nw anatolia the aim of the analyses was to determine temperatures of formation the extent of equilibration among the mineral phases and or of possible alteration through fluid mineral isotopic exchange stable isotope compositions of anhydrous and hydrous alteration minerals indicate that garnet grossular andradite pyroxene diopside hedenbergite skarn prograde stage was produced by predominantly magmatic fluids during initial skarn forming metasomatism in the study area and actinolite epidote rich skarn retrograde stage was formed by magmatic water mixed with meteoric water the 18 o values of garnet from the evciler district range from 4 6 to 8 2 mean 6 7 18 o values of pyroxene range from 6 2 to 10 3 mean 8 2 18 o values of amphibole range from 6 3 to 8 2 mean 7 4 and the 18 o values of epidote range from 3 3 to 5 1 mean 0 9 however the d values of retrograde alteration minerals such as amphibole and epidote indicate both magmatic and lighter values for evciler skarn deposit that could be explained by mixing with meteoric water we conclude that the isotopic evolution of the hydrothermal fluid can be accounted for by circulation of meteoric water through a convection system heated by the evciler granitoid causing exchange of oxygen isotopes with the granitoid and country rock and possibly involving some admixture of magmatic water

petrogenesis of a mesoproterozoic quartz latite granitoid suite from the roxby downs area south australia abstract mesoproterozoic granitoids from the roxby downs area south australia show a range in composition from mafic quartz monzodiorites 56 sio 2 to felsic granites 71 sio 2 and are interpreted as consanguineous on the basis of similar age isotopic composition and mineralogical and geochemical characteristics these granitoids have geochemical similarities with other mesoproterozoic granitoids the world over including enrichments in k 2 o rb ba th u rare earth elements ree nb y zr and depletions in mgo cao sr cr ni v sc relative to typical phanerozoic calc alkaline granitoids the mafic granitoids have mineralogical textural and geochemical features consistent with an origin as cumulates from a more felsic primary magma and the felsic granites likely represent the fractionated residual melt to this accumulation process none of the granitoids from the batholith preserve the primary magma composition which is deduced to be similar to abundant quartz latite volcanic rocks of the region it is estimated by geochemical modeling that about 27 fractionation of observed phenocrysts from a primary quartz latite is required to produce a typical felsic granite 71 sio 2 production of the primary quartz latite magma was likely the result of partial melting of existing paleoproterozoic crust in response to intrusion into the crust of mantle derived magmas the combination of widespread crustal melting contemporaneous granulite facies metamorphism and mantle derived magmatism suggests involvement of large scale tectonothermal processes in the origin of these granitoids the petrogenesis of these rocks and similar occurrences in laurentia and baltica indicates that processes involving reworking of existing paleoproterozoic crust were similar throughout many continental areas during the mesoproterozoic

internal configuration of the levantine basin from seismic reflection data eastern mediterranean abstract in the easternmost mediterranean the levantine basin is filled by up to 10 km of mesozoic to recent sediments next to the alpine deformation front of the cyprean arc near the junction between africa and arabia away from the deformation front the basin has undergone little deformation for the past 100 ma as evidenced by deep seismic reflection profiles mostly subhorizontal reflections image the undisturbed sedimentation above a possibly paleozoic basement two marked reflections are identified within the sedimentary fill m and k they correspond to unconformities near the deformation front and their laterally equivalent concordant surfaces basinward in the deepest part of the basin there are more than 4 km of tertiary to recent sediments within which the m reflection is well defined above the 1 5 km thick messinian evaporites and beneath the 500 m thick plio quaternary sedimentary sequence pre tertiary sediments reach up to 6 km thick beneath the k reflection and above the top basement reflection they are little deformed and possibly correspond to late jurassic cretaceous age the limit with the cyprean arc deformation front is a sharp tectonic boundary south of the hecateaus rise where the whole sedimentary fill terminates against a subvertical fault zone that can be followed down to more than 14 km depth to the east this limit changes into a 30 km wide zone of strike slip deformation that includes flower structures progressively buried basinward by tertiary to recent syntectonic sediments possibly since paleocene times the basin corresponds to the almost undisturbed part of a larger basin whose northern side has been incorporated within the alpine deformation of the cyprean arc and limited to the east by the dead sea transform system

spatial and temporal zoning of hydrothermal alteration and mineralization in the sossego iron oxide copper gold deposit carajas mineral province brazil paragenesis and stable isotope constraints the sossego iron oxide copper gold deposit 245 mt 1 1 cu 0 28 g t au in the carajas mineral province of brazil consists of two major groups of orebodies pista sequeirinho baiano and sossego curral with distinct alteration assemblages that are separated from each other by a major high angle fault the deposit is located along a regional wnw ese striking shear zone that defines the contact between metavolcano sedimentary units of the 2 76 ga itacaiunas supergroup and tonalitic to trondhjemitic gneisses and migmatites of the 2 8 ga xingu complex the deposit is hosted by granite granophyric granite gabbro and felsic metavolcanic rocks the pista sequeirinho baiano orebodies have undergone regional sodic albite hematite alteration and later sodic calcic actinolite rich alteration associated with the formation of massive magnetite apatite bodies both these alteration assemblages display ductile to ductile brittle fabrics they are cut by spatially restricted zones of potassic biotite and potassium feldspar alteration that grades outward to chlorite rich assemblages the sossego curral orebodies contain weakly developed early albitic alteration and very poorly developed subsequent calcic sodic alteration these orebodies contain well developed potassic alteration assemblages that were formed during brittle deformation that resulted in the formation of breccia bodies breccia matrix commonly displays coarse mineral infill suggestive of growth into open space sulfides in both groups of deposits were precipitated first with potassic alteration and more importantly with a later assemblage of calcite quartz epidote chlorite in the sequeirinho orebodies sulfides range from undeformed to deformed sulfides in the sossego curral orebodies are undeformed very late weakly mineralized hydrolytic alteration is present in the sossego currral orebodies the sulfide assemblage is dominated by chalcopyrite with subsidiary siegenite and millerite pyrrhotite and pyrite are minor constituents of ore in the sequerinho orebodies while pyrite is relatively abundant in the sossego curral bodies oxygen isotope partitioning between mineral pairs constrains temperatures in the deposit spatially and through time in the sequeirinho orebody the early sodic calcic alteration stage was characterized by temperatures exceeding 500 c and delta text 18 text o text h text 2 text o values for the alteration fluid of 6 9 0 9 temperature declines outward and upward from the zone of most intense alteration paragenetically later copper gold mineralization displays markedly lower temperatures 300 c and was characterized by the introduction of 18o depleted hydrothermal fluids 1 8 3 4 the calculated dh2o and delta text 18 text o text h text 2 text o values suggest that the fluids that formed the early calcic sodic alteration assemblage were of formational metamorphic or magmatic origin the decrease of delta text 18 text o text h text 2 text o values through time may reflect influx of surficially derived waters during later alteration and mineralization events influx of such fluids could be related to episodic fluid overpressure resulting in dilution and cooling of the metalliferous fluid causing deposition of metals transported as metal chloride complexes

genesis of the maikhura tungsten tin skarn deposit tajik tien shan insights from petrology mineralogy and fluid inclusion study abstract the maikhura w sn skarn deposit is situated in the gissar segment of the southern tien shan it associates with a late carboniferous early permian composite granitoid pluton which includes earlier ilmenite series transitional metaluminous to peraluminous i type granodiorite and later magnetite series biotite to biotite tourmaline granite leucogranite the oxidized granitic intrusions exhibit a type granite affinity and define a geochemically and genetically distinct group of w sn deposits the deposit incorporates both pyroxene and garnet dominant prograde and retrograde skarns with scheelite and locally magnetite overprinted by highly reduced pyrrhotite stable post skarn mineral assemblages of hydrosilicate and phyllic alteration stages containing scheelite cassiterite and sulfides the fluid inclusions data indicate the involvement of carbonic free aqueous moderately saline 9 9 16 wt nacl eq high pressure 2 1 0 5 kbar hot fluid which was sourced from crystallizing magma and formed prograde calcic skarn this fluid evolved into a sodic chloride slightly less saline 8 6 11 wt nacl eq lower pressure 1 7 0 5 kbar cooler fluids toward the retrograde skarn stage this stage was characterized by deposition of scheelite in association with magnetite the hydrosilicate propylitic alteration was formed from a low salinity ca enriched homogenous aqueous carbonic methane rich fluid at lower temperatures 350 400 c with precipitation of scheelite and cassiterite particularly in phlogopite chlorite oligoclase quartz assemblage corresponding ph decrease explains the trend toward overlapping fields of insoluble cassiterite and scheelite the phyllic alteration assemblages were formed from a boiling aqueous carbonic co2 dominated low salinity fluid at temperatures of 310 250 c and pressure of 1 85 0 1 kbar the alteration evolving from chlorite through muscovite to albite dominant paragenesis indicates a trend toward higher ph less acidic conditions and was accompanied by precipitation of scheelite and cassiterite with further deposition of sulfides a homogeneity of 34s values suggests sulfur isotope homogenization in a magmatic chamber whereas their proximity to the meteorite standard supports a magmatic source of sulfur the depletion in heavy sulfur isotope of sulfides from hydrosilicate propylitic alteration 34s 1 8 to 0 7 to sulfides from phyllic alteration 34s 0 1 to 0 8 is consistent with the evolution from ilmenite series to magnetite series magmatic source

stable isotope thermometry at high temperatures determination of accurate temperatures for geological events has been the grail of stable isotope geochemistry since the seminal 1947 paper by urey in theory this should be simple calibrated mineral pairs are common analysis is rapid and there is no significant pressure correction however in spite of widespread application the promise of reliable thermometry has been elusive stable isotope temperatures in metamorphic and igneous rocks are often controversial is the fractionation between two phases a thermometer speedometer rate dependant hygrometer p h2o dependant or chimera a number of factors have contributed to this uncertainty including incomplete and sometimes conflicting calibration of isotope fractionation factors limited understanding of the kinetics of mineral exchange and the lack of microanalytical techniques this situation has improved dramatically over the past decade permitting reliable and detailed thermal histories to be inferred in a landmark paper bottinga and javoy 1975 empirically calibrated the oxygen isotope fractionation factors among ten rock forming minerals at t 500 c their compilation shows that 84 of analyzed samples contain at least three minerals meeting a concordance test for equilibrium they concluded the great majority of igneous and metamorphic rocks has conserved a state of oxygen isotope exchange equilibrium if correct this bodes well for thermometry however this conclusion was contested by deines 1977 who critically examined the existing data and concluded that less than half of the rocks analyzed to date would yield concordant 18o derived temperatures while seeming irreconcilable both conclusions are based on fact all rocks contain some degree of disequilibrium but many also preserve a thermometric record it is the purpose of this review to discuss the new strategies for reliable isotope thermometry and to explore disequilibrium processes so they may be recognized and properly interpreted the organization of this paper will be to discuss the assumptions

constrains on the origin and history of the eastern mediterranean basin abstract the basin formed along the northern passive margin of gondwanaland as a relict of the mesozoic neotethys in early mesozoic time though direct information from the basin itself is meagre the geology of its passive margins and the regional framework of the tethys evolution constrain the formation and history of the basin the eastern mediterranean and its passive margins are interpreted to have formed as a result of several faulting and continental breakup phases from early permian to middle jurassic times before pangaea s complete disintegration this led to the detachment of the eratosthenes and tauride blocks from the margins of the levant and herodotus basins respectively the latter merged in the northeast with the cyprus basin that extended along arabia s northern margin the main rifting probably occurred in the triassic leading to seafloor spreading in the herodotus and cyprus basins while along the levant margin important rifting also occurred in the jurassic during the initial rifting stages extension perpendicular to the levant margin was important but subsequently the tauride block drifted mainly northward the existence of the passive margins and slopes of the eastern mediterranean is documented at least from the end of the middle jurassic until then the basin was probably narrow 200 300 km but during the main phase of the africa laurasia separation it grew to twice its present width or more this scenario depends critically on the interpretation that the tauride block was originally located next to northeastern africa on the western side of the eratosthenes block plate convergence and consumption of the northern portion of the basin have taken place since mid cretaceous times but the active convergent boundary on its northern side formed only in the neogene by modification of earlier structures some intra plate deformation also took place especially in the neogene but it hardly changed the original configuration of the remaining portion of the basin

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

measurements of gulf stream meandering and evidence of seasonal thermocline development using long range acoustic transmissions abstract phase coded signals with 60 rms resolution were transmitted twice weekly for several months from acoustic sources at 2000 m depth in the sargasso sea to three bottom mounted receives designed as west east and north stations at ranges approximately between 1000 and 2000 km the transmission paths to west and east stations were entirely in the sargasso sea the path to north station crossed the gulf stream and so traversed one of the most time and range dependent environments found anywhere in the ocean arrivals at all three stations were stable and could be identified from range dependent ray traces travel times at west station clearly change is response to the warming of the seasonal thermocline from spring to summer the travel time change with predictions travel time changes at north station primarily respond to the north south meandering of the gulf stream