fossil charcoal in cretaceous tertiary boundary strata evidence for catastrophic firestorm and megawave abstract organic matter separated from calcareous sandstone from the upper portion of a deep water tsunami deposit at arroyo el mimbral taumalipas mexico which marks the biostratigraphically defined cretaceous tertiary boundary consists primarily of fossil charcoal including semifusinite and pyrofusinite analytical pyrolysis gas chromatography mass spectrometry revealed the highly aromatic and polyaromatic character of the organic matter assemblage typical of the products of partial combustion the organic matter probably originated as terrestrial vegetation that was caught in a firestorm and subsequently transported far offshore in the backwash of a megawave these data are consistent with the hypothesis of combustion of large masses of vegetation triggered by a giant extraterrestrial impact in the gulf caribbean region probably forming the chicxulub crater in yucatan at the very end of the cretaceous period

late holocene chronology and geomorphic development of fluvial tidal floodplains in the upper reaches of the lower columbia river valley washington and oregon usa abstract the upper reaches of the lower columbia river valley 125 km in length comprise an alluvial system that is transitional between fluvial and fluvial tidal dominance sinuous channels separate elongate islands 1 8 km in length and floodplains 0 5 12 7 km in total width thirty six floodplain overbank deposits are analyzed for age and depth which demonstrate an average sedimentation rate of 1 6 m ka 1 during the last 5 6 ka older core records confirm that long term depositional rates are controlled by relative sea level rise rising floodplain groundwater surfaces which followed relative sea level rise 1 25 m ka 1 submerged isolated floodplain depressions low sedimentation rates in the isolated depressions 0 6 1 1 m ka 1 maintained large ellipsoidal bullseye lakes 7 22 km2 in area dating back to 3 5 4 0 ka increases in the widths of the floodplains and bullseye lakes are associated with broadening of the incised valley 4 13 km width in the portland basin dated basal overbank deposits 0 5 5 0 ka in age and their separation distances establish channel migration rates of 0 3 1 9 km ka 1 shallow burial rates relative to rapid channel migration rates resulted in reworking of late holocene floodplains 50 75 erosion since 5 ka in the upper reaches of the lower columbia river valley

can biomass burning produce a globally significant carbon isotope excursion in the sedimentary record negative carbon isotope excursions have been comprehensively studied in the stratigraphic record but the discussion of causal mechanisms has largely overlooked the potential role of biomass burning the carbon isotopic ratios 13 c of vegetation soil organic matter and peat are significantly lower than atmospheric carbon dioxide co2 and thereby provide a source of low 13 c co2 when combusted in this study the potential role of biomass burning to generate negative carbon isotope excursions associated with greenhouse climates is modeled results indicate that major peat combustion sustained for 1000 yr increases atmospheric co2 from 2 5 present atmospheric levels pal to 4 6 pal and yields a pronounced negative 13 c excursion in the atmosphere 2 4 vegetation 2 4 and the surface ocean 1 2 but not for the deep ocean 0 9 release of co2 initiates a short term warming of the atmosphere up to 14 4 c with a duration of 1628 yr which is consistent with the magnitude and length of an observed toarcian excursion event these results indicate that peat combustion is a plausible mechanism for driving negative 13 c excursions in the rock record even during times of elevated pco2

origin of perylene in ancient sediments and its geological significance the distributions of polycyclic aromatic hydrocarbons pahs in sediments of three upper triassic to middle jurassic sedimentary sequences from the northern carnarvon basin australia have been investigated perylene was found to be a major pah component in the top lower to base middle jurassic sediments that are immature or at low maturity its depth age profiles are not related to the combustion derived pahs that have been believed to be produced during ancient vegetation fires before deposition this suggests a diagenetic origin for perylene the concentration of perylene in the sediments is proportional to the amount of terrestrial input decreasing with distance from the source of land sediments its carbon isotope composition is slightly heavier than higher plant derived pahs but still in the range of the terrestrially sourced pahs including higher plant pahs and combustion derived pahs as suggested previously fungi are proposed to be the major precursor carriers for perylene in sediments based on the facts that 1 perylenequinone structures have been previously suggested to be the natural precursors for perylene 2 perylenequinone pigments exist in many fungal bodies 3 fungi have played an important role during geological processes

the occurrence distribution and sources of polycycic aromatic hydrocarbons in the sediments of the georges river estuary australia concentrations of 13 polycylic aromatic hydrocarbons pah in sediment samples from the georges river estuary n s w have been determined by gas chromatography mass spectrometry gc ms the concentrations of individual pah were in the range of 0 1 5600 g kg m dry weight the average values of pah i i 1300 g kg l dry weight are well above those previously found in other industralized urban areas of australia the highest total pah concentrations in sediments are found in a section of the river which also has the highest concentrations of silt clay and organic matter indicating that the pah distribution may be controlled by sedimentation processes examination of the alkylated and non alkylated pah distributions in sediment extracts suggested that the main source of pah is from combustion products possibly associated with air particles with point source contributions of two ring pah from marinas and other boating activities at some sites

does subduction polarity control metallogeny the mediterranean case the distribution of ore deposit types in different sectors of the circum mediterranean realm that have been affected by subduction processes since the cretaceous varies in space and time sectors involved in w directed subduction sardinia apennines maghrebides internal betics tyrrhenian western eastern carpathians are dominated by relatively low sulphidation epithermal vms deposits orogens formed by ne directed subduction dinarides hellenides pontides anatolides taurides dhpat were initially dominated by pluton related porphyry skarn high sulphidation epithermal associations these distinct metallogenic styles can be related to the systematic tectono magmatic asymmetry of e ne and w directed subduction systems and are analogous to the relationship observed in circum pacific belts exceptions to this simple pattern occurred in the dhpat in the cenozoic when deposit associations typical of both e directed and w directed systems were formed such exceptions are interpreted to reflect superimposition of contrasting subduction trends and inheritance from earlier metallogenic stages apuseni or the interference of subduction processes with subduction unrelated extension hellenides west anatolia

high molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the gulf of california and northeast pacific ocean hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons pah with molecular weights greater than that of coronene 300 da samples from the hydrothermal systems in the guaymas basin gulf of california and in the escanaba trough and middle valley northeastern pacific were analyzed by gas chromatography mass spectrometry and high pressure liquid chromatography with diode array absorbance detection mass spectra and fluorescence spectra were used to characterize the compounds several large pahs with six and more rings were identified among the heavy pah production routes via one ring build up and scholl condensation are proposed to explain the observed structures the variations in pah concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation migration and post depositional alteration

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

geochemistry and tectonic development of cenozoic magmatism in the carpathian pannonian region this review considers the magmatic processes in the carpathian pannonian region cpr from early miocene to recent times as well as the contemporaneous magmatism at its southern boundary in the dinaride and balkans regions this geodynamic system was controlled by the cretaceous to neogene subduction and collision of africa with eurasia especially by adria that generated the alps to the north the dinaride hellenide belt to the east and caused extrusion collision and inversion tectonics in the cpr this long lived subduction system supplied the mantle lithosphere with various subduction components the cpr contains magmatic rocks of highly diverse compositions calc alkaline k alkalic ultrapotassic and na alkalic all generated in response to complex post collisional tectonic processes these processes formed extensional basins in response to an interplay of compression and extension within two microplates alcapa and tisza dacia competition between the different tectonic processes at both local and regional scales caused variations in the associated magmatism mainly as a result of extension and differences in the rheological properties and composition of the lithosphere extension led to disintegration of the microplates that finally developed into two basin systems the pannonian and transylvanian basins the southern border of the cpr is edged by the adria microplate via sava and vardar zones that acted as regional transcurrent tectonic areas during miocene recent times major trace element and isotopic data of post early miocene magmatic rocks from the cpr suggest that subduction components were preserved in the lithospheric mantle after the cretaceous miocene subduction and were reactivated especially by extensional tectonic processes that allowed uprise of the asthenosphere changes in the composition of the mantle through time support geodynamic scenarios of post collision and extension processes linked to the evolution of the main blocks and their boundary relations weak lithospheric blocks i e alcapa and western tisza generated the pannonian basin and the adjacent styrian transdanubian and z rand basins which show high rates of vertical movement accompanied by a range of magmatic compositions strong lithospheric blocks i e dacia were only marginally deformed where strike slip faulting was associated with magmatism and extension at the boundary of adria and tisza dacia strike slip tectonics and core complex extension were associated with small volume miocene magmatism in narrow extensional sedimentary basins or granitoids in core complex detachment systems along older suture zones sava and vardar accommodating the extension in the pannonian basin and afterward pliocene quaternary inversion magmas of various compositions appear to have acted as lubricants in a range of tectonic processes

miocene pliocene tectonic evolution of the slovenian periadriatic fault implications for alpine carpathian extrusion models the periadriatic line pal is a remarkable several hundred kilometer long fault system of the alpine orogen its dextral character was documented by several authors using diverse criteria but detailed kinematics and timing of movements had not been investigated along its whole length structural and paleomagnetic measurements mapping and stratigraphic and sedimentological studies have helped to unravel the miocene pliocene evolution of the slovenian segment of the pal brittle deformation was characterized by nw se to n s compression and perpendicular tension deformation has resulted in dextral strike slip faulting folding and tilting of beds the first transpressional event corresponds to the first phase of lateral extrusion of the east alpine western carpathian northern pannonian block in the early miocene 24 17 5 ma after a short period of transtension during the karpatian 17 5 16 5 ma dextral transpression reoccurred during the middle miocene to pliocene and lasted up to the quaternary middle miocene dextral slip can be connected to the second phase of extrusion the highly deformed rocks within the dextral shear zones show variable clockwise sometimes counterclockwise rotations the mechanism of rotation seems to be complex ranging from regional rotation to local folding due to pure or simple shear domino type rotation

wildfires and seasonal aridity recorded in late cretaceous strata from south eastern arizona usa lithostratigraphic and organic chemostratigraphic studies of fluvial lacustrine sediments in the late cretaceous fort crittenden formation in south eastern arizona usa reveal changes in palaeoclimate and tectonics as well as associated fluctuations in lake level the lower fort crittenden is dominated by marginal wetland to deep water lake deposits whereas the upper fort crittenden is characterized by wetland to deltaic deposits abundance of polycyclic aromatic hydrocarbons pah and reflectance of fusinite substantiate the impact of wildfires within the watershed organic geochemical evidence of wildfires is linked with sedimentological indicators of seasonal aridity suggesting that wildfires were common occurrences sedimentological evidence for seasonal aridity includes mottles and pseudoslickensides on ped structures within wetland mudstones distinct variations in pah assemblages characterized by the number of aromatic rings indicate that there were variations in the intensities of wildfires assuming no variations in the types of fuel fusinite reflectance values are consistent with combustion temperatures from 470 to 550 c observed in modern wildfires

polycyclic aromatic hydrocarbons in ancient sediments and their relationships to palaeoclimate combustion derived and land plant derived polycyclic aromatic hydrocarbons pahs have been investigated for an upper triassic to middle jurassic sedimentary sequence from the northern carnarvon basin western australia the former included fluoranthene pyrene benzofluoranthenes benzo e pyrene and benzo a pyrene and the latter included retene cadalene and simonellite combustion derived pahs are most abundant in the upper triassic and late lower jurassic sediments the abundances of land plant derived markers all maximise in the upper part of the lower jurassic section but vary independently of one another through time the changes in the relative abundances of these markers have been related to the variation of regional climatic conditions especially the changes in humidity and seasonality during the late triassic to middle jurassic times

13c and 18o of wood from the roman siege rampart in masada israel ad 70 73 evidence for a less arid climate for the region the isotopic ratios 13c12c and 18o16o of cellulose from tamarix trees which were used by the roman army as a groundwork of the siege rampart of masada ad 70 73 were compared with ratios measured in present day tamarix trees growing in the masada region and in central israel the ancient tamarix cellulose is depleted in both 13c and 18o compared to cellulose from trees growing in the masada region today similar trends were observed on comparing modern tamarix trees growing in the negev desert with those growing in the temperate climate of central israel considering the factors that can contribute to the observed changes in isotopic composition we conclude that the ancient trees enjoyed less arid environmental conditions during their growth compared to contemporary trees in this desert region this report demonstrates the potential in using combined 18o and 13c analyses of archeological plant material as independent indication of regional climatic change in desert areas where conventional isotopic analyses such as in tree rings are impractical

an integrated biomarker isotopic and palaeoenvironmental study through the late permian event at lusitaniadalen spitsbergen abstract the largest extinction of the phanerozoic occurred near the permian triassic p tr boundary some 252 ma ago several scenarios and drivers have been proposed for this event here we report for the first time an integrated study comprising sedimentological data biomarker distributions abundances and selected stable carbon and hydrogen isotopes along with bulk isotopes 34spyrite 13ccarb 13corg for a late permian section from lusitaniadalen spitsbergen norway sedimentological and geochemical data support a marine transgression and collapse of the marine ecosystem in the late permian strong evidence for waxing and waning of photic zone euxinia throughout the late permian is provided by chlorobiaceae derived biomarkers including 13c data and 34spyrite implying multiple phases of h2s outgassing and potentially several pulses of extinction a rapid decrease in abundance of various land plant biomarkers prior to the marine collapse event indicates a dramatic decline of land plants during the late permian and or increasing distance from palaeoshoreline as a consequence of sea level rise changes in d of selected biomarkers also suggest a change in source of organic matter om or sea level rise we also found biomarker and isotopic evidence for a phytoplanktonic bloom triggered by eutrophication as a consequence of the marine collapse compound specific isotope analyses csia of algal and land plant derived biomarkers as well as 13c of carbonate and bulk om provide strong evidence for synchronous changes in 13c of marine and atmospheric co2 attributed to a 13c depleted source the source could be associated with isotopically depleted methane released from the melting of gas clathrates and or from respired om due to collapse of the marine ecosystem

correlating terrestrial signatures from biomarker distributions δ13c and palynology in fluvio deltaic deposits from nw australia triassic jurassic abstract a multidisciplinary study using molecular and organic isotope geochemistry petrology and palynology has been used to establish palaeoenvironmental conditions of fluvio deltaic deposits from the delambre 1 well western australia triassic jurassic changes in higher plant biomarker distributions correlate with 1 brackish water environments 2 major changes in composition of spore and pollen assemblages 3 variations in types of sedimentary facies and 4 stable carbon isotopic composition of higher plant biomarkers these changes are all consistent with the occurrence of climatic shifts in northwestern australia during triassic jurassic periods established by parrish j t bradshaw m t brakel a t mulholland s m totterdell j m yeates a n 1996 palaeoclimatology of australia during the pangean interval palaeoclimates 1 241 281 the combustion marker benzo e pyrene is abundant in samples that contain pollen from falcisporites australis the decline of f australis and the rapid emergence of assemblages dominated by corollina spp at the end of the triassic marks a rapid pollen spore extinction event at the triassic jurassic boundary there is an increase in relative abundance of the higher plant biomarkers cadalene and simonellite in a prodeltaic facies the 13 c values of between 26 9 and 24 9 for retene are consistent with a source from class i conifer resinites and relate to samples abundant in araucariacian conifers in the early middle jurassic where facies are characterized as pro distal deltaic

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

on the geodynamics of the aegean rift abstract the aegean rift is considered to be either a classic backarc basin or the result of the westward escape of anatolia or the effect of a gravitational collapse of an over thickened lithosphere here these models are questioned we alternatively present a number of geodynamic and magmatic constraints suggesting a simple model for the genesis of the extension as being related to the differential advancement of the upper lithosphere over a heterogeneous lower african plate the greek microplate overrides the ionian oceanic segment of the african plate faster than the anatolian microplate over the thicker levantine more continental segment this setting is evidenced by gps velocity gradient in the hangingwall of the hellenic cyprus subduction system and requires a zone of rifting splitting the hangingwall into two microplates this mechanism is unrelated to the replacement of retreated slab by the asthenosphere as typically occurs in the backarc of west directed subduction zones the supposed greater dehydration of the ionian segment of the slab is providing a larger amount of fluids into the low velocity channel at the top of the asthenosphere allowing a faster decoupling between the greek microplate and the underlying mantle with respect to the anatolian microplate slab ruptures associated with the differential retreat controlled by the inherited lithospheric heterogeneities in the lower plate and the proposed upwelling of the mantle suggested by global circulation models would explain the occurrence and coexistence of slab related and slab unrelated magmatism

1 subduction slab detachment and mineralization the neogene in the apuseni mountains and carpathians abstract the inner carpathians comprise several distinct neogene late stage orogenic pb zn cu ag au ore districts the mineral deposits in these districts are closely related to volcanic and subvolcanic rocks and represent mainly porphyry and epithermal vein deposits which formed within short periods of time in each district here we discuss possible geodynamic and structural controls that suggest why some of the neogene volcanic districts within the carpathians comprise abundant mineralization while others are barren the neogene period has been characterized by an overall geodynamic regime of subduction where primary roll back of the subducted slab and secondary phenomena like slab break off and the development of slab windows could have contributed to the evolution location and type of volcanic activity structural features developing in the overlying lithosphere and visible in the carpathian crust such as transtensional wrench corridors block rotation and relay structures due to extrusion tectonics have probably acted in focusing hydrothermal activity as a result of particular events in the geodynamic evolution and the development of specific structural features mineralization formed during fluid channelling within transtensional wrench settings and during periods of extension related to block rotation in the slovakian ore district of the western carpathians neogene volcanism and associated mineralization were localized by sinistral ne trending wrench corridors which formed part of the extruding alcapa block the baia mare ore district in the eastern carpathians reflects a transtensional wrench setting on distributed oversteps close to the termination of the dragos voda fault there mineralization was spatially controlled by the transtensional dragos voda master fault and associated cross fault systems the golden quadrangle cu au ore district of the southern apuseni mountains reflects an unusual rotated transtensional extensional setting close to the termination of a graben system there fluid flow was probably localized by fault propagation at the inner tip of the graben system the spatial and temporal evolution of the magmatism and its changing geochemical signature from n w to s e strongly suggests a link with the contemporaneous northeastward roll back of the subducted slab and a progressive southeastward detachment during accelerating roll back this geodynamic evolution is further supported by the present day overall and detailed mantle lithospheric density images the present day heat flow patterns the crustal architecture and its interpreted evolution and the spatial and temporal evolution of depocentres around the carpathian arc in contrast to all these features the mineral deposits in the west carpathians east carpathians and apuseni mountains are too synchronous with respect to their individual volcanic history and contrast too much with younger volcanics of similar style but barren in southeastern parts of the carpathians to simply link them directly to the slab evolution in all three districts the presence of magmatic fluids released from shallow plutons and their mixing with meteoric water were critical for mineralization requiring transtensional or extensional local regimes at the time of mineralization possibly following initial compressional regimes these three systems show that mineralization was probably controlled by the superposition of favourable mantle lithospheric conditions and partly independent evolving upper crustal deformation conditions in the 13 to 11 ma period the dominant mineralization formed all across the carpathians and was superimposed on structurally favourable crustal areas with at that time volcanic hydrothermal activity the period may reflect the moment when the upper part of the crust failed under lithospheric extension imposed by the slab evolution this crustal failure would have fragmented the overriding plate possibly breaking up the thermal lid to provoke intensive fluid flow in specific areas and allowed subsequent accelerated tectonic development block rotation and extrusion of a family of sub blocks that are arbitrarily regarded as the tisia dacia or alcapa blocks even though they have lost their internal entity

vascular plant biomarker distributions and stable carbon isotopic signatures from the middle and upper jurassic callovian kimmeridgian strata of staffin bay isle of skye northwest scotland the molecular and stable carbon isotopic composition of higher plant biomarkers was investigated in middle to upper jurassic strata of the isle of skye northwest scotland aromatic hydrocarbons diagnostic of vascular plants were detected in each of nineteen sedimentary rock samples from the early callovian to early kimmeridgian interval a succession rich in fossil fauna including ammonites that define its constituent chronozones the higher plant parameter hpp and higher plant fingerprint hpf calculated from the relative abundance of retene cadalene and 6 isopropyl 1 isohexyl 2 methylnaphthalene ip ihmn exhibit several large fluctuations throughout the skye succession studied these molecular profiles contrast with both 1 the more uniform profiles previously observed in jurassic successions putatively of the same age from other palaeogeographical settings including the carnarvon basin western australia and 2 the steady rise in global sea level during this interval this suggests that the hpf profiles of jurassic marine successions may not be reliable indicators of global climate change our results indicate that other factors such as local tectonism resulting in changes to the relief and landscape of the hinterland likely influenced the palaeoflora and the mode of transport of its detritus into adjacent marine depocentres however the skye succession showed similar 13c profiles of total organic carbon toc comprising mainly fossil wood the vascular plant biomarker retene and a predominant phytoplanktonic biomarker phytane the apparent isotopic relationship between terrigenous and marine derived biomarkers supports a strong coupling of the atmosphere and ocean the maximum isotopic excursion occurs in the cardioceras cordatum ammonite biozone of the early to middle oxfordian which may be indicative of changes in atmospheric and oceanic levels of co2

igneous activity and organic maturation in the midland valley of scotland abstract the general relationship of erich stach s research work to the effects of igneous activity on organic maturation is briefly considered the geological history of the midland valley of scotland is then reviewed as a graben which developed in devonian old red sandstone times and continued to do so as lithospheric tensional stretching was maintained throughout the carboniferous a significant factor in relation to the development of organic maturation was the widespread igneous activity that persisted throughout much of upper palaeozoic times calc alkaline volcanic rocks are a major feature within the molasse type deposits of the old red sandstone after a period of quiescence in later old red sandstone times the continuing tensional stretching initiated or rejuvenated major crustal fractures extensive volcanic sill and dyke activity exercised an important influence on the predominantly shallow water deltaic deposits of the carboniferous alkaline olivine basalts were erupted in the early carboniferous while volcanic activity in the later carboniferous was essentially phreatic two major intrusive episodes occurred the first of alkaline sills in early to mid carboniferous times which were closely related to volcanic plugs and eruptive centres the second in post westphalian times when tholeiitic sills and dykes with no known relationships with any extrusive rocks were injected the effects of this igneous activity on organic maturation can be considered under four headings 1 1 although the general development of maturation of carboniferous organic matter which includes many coal seams and oil shales was controlled to some degree by burial history the regional pattern of igneous activity was also influential thus there is a gradual increase of coalification from east to west in the midland valley which corresponds with an increasing thickness of volcanic pile in the central and westerly parts of the graben suggesting that there may have been a greater regional heat sink in the west during the carboniferous the level of coalification is nowhere particularly high except where affected by intrusions and regional reflectance gradients generally vary between r oil vitrinite 0 2 km to 0 4 km without displaying any consistent pattern 2 2 the post westphalian tholeiitic quartz dolerite midland valley sill which underlies most of the central and eastern parts of the graben has produced extensive reflectance thermal aureoles in the organic matter above and below the intrusion the olivine dolerite and teschenite sills of namurian early westphalian times many of similar thickness to the quartz dolerite intrusions fail to produce significant reflectance thermal aureoles this major difference in organic matter response to the intrusions can only be explained in terms of the initial rank level of the organic matter differences in degree of compaction of the sediments and particularly in the amount of water the sediments contained at the time of intrusion 3 3 maturation of organic matter closely associated with extensive surtseyan type volcanic activity in the eastern part of the graben displays no relationship to the regionally developed coalification in associated sediments although some vitrinite clasts in the pyroclastic deposits have had their reflectances raised to meta anthracitic rank reflectance levels of clasts in tuffs and agglomerates are generally not much raised above the regional reflectance level suggesting incorporation of organic matter in ash streams in which water was an important cooling and protective component 4 4 the close relationship of organic matter of all kinds with volcanic and intrusive igneous rocks has led to a marked increase of parent polycyclic aromatic hydrocarbons pah in the aromatic fractions of organic extracts the source of these hydrocarbons is the combustion and or pyrolysis of organic matter caused by the high temperatures of the igneous materials whether volcanic or intrusive these pah may be directly generated or absorbed from the surrounding environment

plutonism oblique subduction and continental growth an example from the mesozoic of california major episodes of mesozoic plutonism in california correlate with periods of oblique subduction and trench parallel transport of western california along intrabatholithic faults major episodes of plutonism occurred in the late jurassic during left oblique convergence and in the mid cretaceous during right oblique convergence in contrast a conspicuous lull in plutonism but continuation of volcanism in the earliest cretaceous coincides with a time when the north america farallon convergence vector although large in magnitude was oriented perpendicular to the trench this correlation suggests that plutonism is facilitated by strike slip faulting within the batholithic belt one explanation which helps to solve the plutonic room problem is that plutons are passively emplaced at releasing bends in the strike slip faults and volume is conserved by thrusting at the trench if this correlation is generally applicable then it implies that mid crustal plutonism is limited beneath areas in which the convergence vector is subperpendicular to the trench continental growth in such areas may occur dominantly by volcanism

hydrothermal evolution in the calabona porphyry copper system sardinia italy the path to an uneconomic deposit the calabona porphyry copper system is developed in a small relatively deep seated nearly equal 5 km dacitic intrusion located in northwestern sardinia italy early hydrothermal alteration produced a potassic assemblage in the deep and central parts of the complex and a peripheral propylitic halo sodic alteration was subsequently superimposed on the potassic zone and volumetrically dominant phyllic alteration overprinted the apical parts of the intrusion hypogene copper mineralization chalcopyrite and minor bornite was associated with potassic alteration the earliest fluid that circulated in the calabona porphyry complex had high salinity 40 60 wt nacl equiv and is interpreted to have been exsolved directly from the crystallizing magma however major entrapment of this fluid only occurred after it had cooled to temperatures of about 400 degrees c this fluid was responsible for potassic alteration and for precipitation of chalcopyrite and bornite in thin discontinuous group 1 veins and irregular and widely spaced group 2 veins the average cu grade in the potassic zone is between 0 05 and 0 1 percent the circulation of a lower temperature 270 degrees 330 degrees c ca enriched fluid of meteoric origin in the peripheral parts of the system caused propylitic alteration at an intermediate stage of hydrothermal evolution waters of external origin entered the central parts of the system along a network of late fractures group 3 veins or reopened group 2 veins partial mixing of this meteoric formational water with the high salinity fluid already circulating in the system created a fluid characterized by salinities ranging from 2 to 23 wt percent nacl equiv circulation of this mixed fluid at relatively low fluid rock ratios along a prograde thermal path caused sodic alteration the continuous inflow of meteoric water and the general temperature decrease in the system produced progressively more oxidized and acidic fluids which caused phyllic alteration and intense copper leaching late boiling in the apical parts of the phyllic alteration zone favored deposition of chalcopyrite and bornite but did not add significant copper cu grade 0 03 supergene enrichment led to copper grades higher than those in the phyllic zone 0 07 but not enough to permit mining the very low concentration of cu in the calabona deposits is surprising in view of wall rock alteration style of mineralization and a fluid evolution typical of those of many productive porphyry copper systems we propose that this is mainly a consequence of the raltive deep level of emplacement of the intrusion and the dacitic composition of the magma these factors are interpreted to have combined to retard melt saturation with alkali chlorife enriched fluids until late stages of crystallization which restricted the amount of exsolved fluid and cu extracted form the melt as a result overpressuring in the apical parts of the system was limited the related fracture density was low and the system therefore failed to provide the focus for the mineralizing fluids needed to permit bulk concentration of copper to economic levels further reasons for the uneconomic nature of the calabona porphyry were the lack of multiple intrusive events and the sulfide destructive cu leaching effects of phyllic alteration

orogens and slabs vs their direction of subduction abstract subduction zones appear primarily controlled by the polarity of their direction i e w directed or e to nne directed probably due to the westward drift of the lithosphere relative to the asthenosphere the decollement planes behave differently in the two end members in the w directed subduction zone the decollement of the plate to the east is warped and subducted whereas in the e to nne directed it is ramping upward at the surface there are w directed subduction zones that work also in absence of active convergence like the carpathians or the apennines w directed subduction zones have shorter life 30 40 ma than e or ne directed subduction zones even longer than 100 ma the different decollements in the two end members of subduction should control different ptt paths and therefore generate variable metamorphic assemblages in the associated accretionary wedges and orogens these asymmetries also determine different topographic and structural evolutions that are marked by low topography and a fast eastward migrating structural wave along w directed subduction zones whereas the topography and the structure are rapidly growing upward and expanding laterally along the opposite subduction zones the magmatic pair calc alkaline and alkaline tholeiitic volcanic products of the island arc and the back arc basin characterise the w directed subduction zones magmatic rocks associated with e or ne directed subduction zones have higher abundances of incompatible elements and mainly consist of calc alkaline shoshonitic suites with large volumes of batholithic intrusions and porphyry copper ore deposits the subduction zones surrounding the adriatic plate in the central mediterranean confirm the differences among subduction zones as primarily controlled by the geographic polarity of the main direction of the slab the western margin of the adriatic plate contemporaneously overridden and underthrust europe toward the west to generate respectively the alps and the apennines while the eastern margin subducted under the dinarides hellenides these belts confirm the characters of the end members of subduction zones as a function of their geographic polarity similarly to the pacific subduction zones

subduction arc reversal and the origin of porphyry copper gold deposits in island arcs the tertiary quaternary porphyry copper gold deposits of the southwest pacific rim particularly in luzon mainland papua new guinea bougainville guadalcanal and fiji mostly formed after a reversal of arc polarity where this reversal has not occurred e g new zealand and japan porphyry copper gold deposits are absent or scarce hence older porphyry copper gold deposits may be useful clues to tectonic history enrichment of magmas in gold may have resulted from two stage melting the tectonic setting of porphyry copper gold deposits differs from that inferred for volcanic hosted massive sulfide deposits

copper enrichment in arc magmas controlled by overriding plate thickness the characteristics of magmas typically associated with porphyry copper deposits are thought to be imparted in the mantle statistical assessment of over 40 000 geochemical analyses of magmatic rocks formed in subduction zones worldwide however shows that the characteristics of these magmatic rocks are systematically controlled by the thickness of the arc crust

intra orogenic extension driven by gravitational instability carpathian pannonian orogeny the extensional pannonian basin was formed in a few million years during miocene time synchronously with contraction in the surrounding alpine and carpathian orogens this system is characteristic of a class of extensional basins that form in the midst of active orogenic mountain forming belts the mechanism that causes this type of geological event is enigmatic but usually has been associated with subduction we examine a new hypothesis for intra orogenic extensional basin formation in which gravitational spreading of previously thickened crust triggers gravitational instability of the mantle lithosphere a basin is formed by lithospheric extension as shortening and lithospheric downwelling occur in the surrounding mountain belts this mechanism provides a mechanically self consistent explanation for all of the main structural features of the pannonian carpathian system and presents a plausible alternative to the popular view that subduction and slab rollback have driven the development of this basin

distribution of porphyry copper deposits along the western tethyan and andean subduction zones insights from a paleotectonic approach abstract along the western tethyan and andean subduction zones the distribution of cretaceous and cenozoic porphyry cu deposits is not random and shows that they were emplaced in distinct regional clusters to understand the appearance of these clusters within their geodynamical contexts and identify kinematic features which would favor the genesis of porphyry type ore bodies we use a paleotectonic approach two clusters in the aegean balkan carpathian area which were emplaced in upper cretaceous and oligo miocene and two others in the andes which were emplaced in late eocene and miocene are sufficiently well constrained to be studied in detail it appears that they are associated with a specific polyphased kinematic context related to the convergence of tectonic plates this context is characterized by 1 a relatively fast convergence rate shortly followed by 2 a drastic decrease of this rate from these observations and assuming that the major part of plate convergence is accommodated along subduction zones we propose a two phase geodynamic model favoring emplacement of porphyry cu deposits 1 a high melt production in the mantle wedge followed by 2 an extensional regime or at least relaxation of the compressional stress in the upper plate promoting ascension of fertile magmas to the upper crust melt production at depth and the following extensional regime which would be related to variations in convergence rate are thus associated with variations in plate and trench velocities themselves being controlled by both plate kinematics at the surface and slab dynamics in the upper mantle in particular along strike folding behavior of the subducting slab may strongly influence trench velocity changes and the location of porphyry cu deposits metallogenic data suggest that periods of slab retreat which would favor mineralization processes during 40 myrs would be separated by barren periods lasting 10 to 20 myrs corresponding to shorter episodes of trench advance as observed in laboratory experiments these results confirm the control of the geodynamic context and especially subduction dynamics on the genesis of porphyry cu deposits this study also shows that the paleotectonic approach is a promising tool that could help identify geodynamic and tectonic criteria favoring the genesis of various ore deposits

a review of cu dominant mineral systems in the kalatag district east tianshan china abstract the chinese east tianshan is the easternmost sector of the tianshan mountain range in the central asian orogenic belt caob and accommodates several events of magmatism crustal growth and mineralization the kalatag arc is unique in the east tianshan due to its widespread early paleozoic volcanic rocks which offers a special opportunity to study the early paleozoic cu dominant mineral systems in island arc setting in this region nine deposits have been discovered in recent years these deposits occur in paleozoic volcanic rocks between the kalatag fault and kabei fault and can be divided into six mineral systems i e vms cu zn epithermal cu porphyry cu au skarn fe cu magmatic cu ni sulfide and hydrothermally overprinted deposits among them vms epithermal porphyry skarn and magmatic cu ni sulfide mineralization are distributed in the southeastern central northwestern and westernmost kalatag respectively the mineralization and associated intrusive rock ages can be clustered into four episodes in the kalatag arc i e late ordovician silurian ca 450 430 ma middle devonian ca 390 380 ma late carboniferous ca 320 300 ma and permian ca 280 ma here paleozoic granitoids show similar geochemistry and isotopic features all paleozoic granitoids plot in the subalkaline field and predominantly tholeiitic to calc alkaline series with enrichment of large ion lithophile elements and depletion of high field strength elements these granitoids plot in a volcanic arc fields in tectonic discrimination diagrams which are characteristic of an island arc setting the fluid inclusions in porphyry and skarn system are characterized by high temperature high salinity low content of co2 whereas epithermal system represented by low temperature low salinity low content of co2 and the vms system can be described as medium temperature medium low salinity co2 bearing fluid h o isotopic data suggest that ore fluids were sourced from a mixing fluid between magmatic and meteoric water s pb isotopic data show that the sulfur mainly came from magma or ore hosting igneous rocks the yudai porphyry cu au deposit the hongshi epithermal cu deposit and the honghai au rich vms cu zn deposit formed at the same time related to a subduction environment the early paleozoic vms mineralization is generally overprinted by late magmatic hydrothermal fluids which may be due to multiple accretionary orogeny in kalatag island arc we propose that the north dipping subduction of the paleo tianshan ocean or south dipping subduction of the junggar ocean during late ordovician silurian which may led to the development of yudai porphyry copper hongshi epithermal copper and honghai vms copper zinc deposits in the kalatag arc after that north dipping subduction of the paleo tianshan ocean resulted to the formation of the middle devonian ca 390 380 ma and late carboniferous ca 320 300 ma cu mineralization finally the permian ca 280 ma magmatic copper nickel sulfide deposits associated with ultramafic mafic complexes developed in post collisional extension setting part of a large igneous province lip event associated with mantle plume upwelling

mantle wedge asymmetries and geochemical signatures along w and e ne directed subduction zones article i nfo subduction zone kinematics predict that assuming a fixed lower plate the velocity of the subduction equals the velocity of the subduction hinge vs vh in all subduction zones the subduction hinge migrates toward the lower plate however two main types of subduction zones can be distinguished 1 those where the upper plate converges toward the lower plate slower than the subduction hinge mostly w directed and 2 those in which the upper plate converges faster than the subduction hinge generally e or ne directed along the first type there generally is an upward flow of the asthenosphere in the hanging wall of the slab whereas along the opposite second type the mantle is pushed down due to the thickening of the lithosphere the kinematics of w directed subduction zones predict a much thicker asthenospheric mantle wedge larger volumes and faster rates of subduction with respect to the opposite slabs moreover the larger volumes of lithospheric recycling the thicker column of fluids rich hotter mantle wedge all should favour greater volumes of magmatism per unit time the opposite e ne directed subduction zones show a thinner if any asthenospheric mantle wedge due to a thicker upper plate and shallower slab along these settings the mantle wedge where the percolation of slab delivered fluids generates melting mostly involves the cooler lithospheric mantle the subduction rate is smaller andesites are generally dominant and the lithosphere thickens there appears to be a greater contribution to the growth of the continental lithosphere another relevant asymmetry that can be inferred is the slab induced corner flow in the mantle along w directed subduction zones and an upward suction of the mantle along the opposite e or nne directed slabs the upward suction of the mantle inferred at depth along e ne directed subduction zones provides a mechanism for syn subduction alkaline magmatism in the upper plate with or without contemporaneous rifting in the backarc positive 11 ba nd high 143 nd 144 nd characterize w directed subduction zones where a thicker and hotter mantle wedge is present in the hanging wall of the slab however this observation disappears where large amounts of crustal rocks are subducted as along the w directed apennines sub duction zone

tectonic configuration of the apuseni banat timok srednogorie belt balkans south carpathians constrained by high precision r e o s molybdenite ages the apuseni banat timok srednogorie magmatic metallogenic belt abts belt forms a substantial metallogenic province in the balkan south carpathian system in southeastern europe the belt hosts porphyry skarn and epithermal deposits mined since pre roman times generally the deposits prospects and occurrences within the belt are linked to magmatic centers of calc alkaline affinity fifty one rhenium osmium re os ages and re concentration data for molybdenites define systematic geochronologic trends and constrain the geochemical metallogenic evolution of the belt in space and time from these data and additional existing geologic geochemical data a general tectonic history for the belt is proposed mineralization ages in apuseni banat timok and panagyurishte the central district of the larger e w srednogorie zone range from 72 83 81 88 and 87 92 ma respectively and clearly document increasing age from the northwestern districts to the southeastern districts further re os ages suggest rapidly migrating pulses of late cretaceous magmatic hydrothermal activity with construction of deposits in 1 m y districts in 10 m y and the entire 1 500 km belt in 20 m y ages in both timok and panagyurishte show systematic younging while deposit ages in banat and apuseni are less systematic reflecting a restricted evolution of the tectonic system systematic differences are also observed for molybdenite re concentrations on the belt scale re concentrations generally range from hundreds to thousands of parts per million typical of subduction related cu au mo pge porphyry systems associated with the generation of juvenile crust the geochronologic and geochemical trends are compatible with proposed steepening of subducting oceanic slab and relaxation of upper continental plate compression resulting influx of sub continental mantle lithosphere scml and asthenosphere provide a fertile metal source and heat while the subducting slab contributes connate and mineral dehydration fluids which facilitate partial melting and metal leaching of scml and asthenosphere cu au mo pge porphyry deposits may develop where melts are trapped at shallow crustal levels often with associated volcanism and epithermal style deposits south banat timok and panagyurishte mo fe pb zn skarn deposits may develop where felsic melts are trapped adjacent to mesozoic limestones at moderate crustal levels north banat and apuseni systematic spatial variations in deposit style commodity enrichment re os ages and re concentrations support specific tectonic processes that led to ore formation in a post collisional setting subduction of vardar oceanic crust may have stalled causing slab steepening and rollback the slab rollback relaxes compression facilitating and enhancing orogenic collapse of previously thickened balkan south carpathian crust the progression of coupled rollback orogenic collapse is evidenced by the width of late cretaceous extensional basins and northward younging of re os ages from panagyurishte 60 km 92 87 ma to timok 20 km 88 81 ma to apuseni banat 5 km 83 72 ma generation of a well endowed mineral belt such as the abts requires a temporally and spatially restricted window of magmatic hydrothermal activity this window is quickly opened as upper plate compression relaxes thereby inducing melt generation and ingress of melt to higher crustal levels the window is just as quickly closed as upper plate compression is reinstated the transient tectonic state responsible for economic mineralization in the abts belt may be a paleo analogue to transient intervals in the present subduction tectonics of se asia where much mineral wealth has been created in the last few million years

subducted slabs beneath the eastern indonesia tonga region insights from tomography tomographic images of mantle structure beneath the region north and northeast of australia show a number of anomalously fast regions these are interpreted using a recent plate tectonic reconstruction in terms of current and former subduction systems several strong anomalies are related to current subduction the inferred slab lengths and positions are consistent with neogene subduction beneath the new britain and halmahera arcs and at the tonga and the new hebrides trenches where there has been rapid rollback of subduction hinges since about 10 ma there are several deeper flat lying anomalies which are not related to present subduction and we interpret them as former subduction zones overridden by australia since 25ma beneath the bird s head and arafura sea is an anomaly interpreted to be due to north dipping subduction beneath the philippines halmahera arc between 45and 25ma a very large anomaly extending from the papuan peninsula to the new hebrides and from the solomon islands to the east australian margin is interpreted to be the remnant of south dipping subduction beneath the melanesian arc between 45and 25ma this interpretation implies that a flat lying slab can survive for many tens of millions of years at the bottom of the upper mantle in the lower mantle there is a huge anomaly beneath the gulf of carpentaria and east papua new guinea this is located above the position where the tectonic model interprets a change in polarity of subduction from north dipping to south dipping between 45and 25ma we suggest this deep anomaly may be a slab subducted beneath eastern australian during the cretaceous or subducted north of australia during the cenozoic before 45ma the tomography also supports the tectonic interpretation which suggests little neogene subduction beneath western new guinea since no slab is imaged south of the new guinea trench however one subduction zone in the tectonic model and many others that associated with the trobriand trough east of papua new guinea and the miocene maramuni arc is not seen in the tomographic images and may require reconsideration of currently accepted tectonic interpretations 4 2002 elsevier science b v all rights reserved

origin and geodynamic significance of tertiary postcollisional basaltic magmatism in serbia central balkan peninsula abstract tertiary basaltic magmatism in serbia occurred through three episodes i paleocene eocene when mostly east serbian mafic alkaline rocks espemar formed ii oligocene miocene dominated by high k calc alkaline basalts shoshonites hkca sho and ultrapotassic up rocks and iii pliocene episode when rocks similar to ii originated in this study the geodynamics inferred from petrogenesis of the i and ii episodes are discussed the espemar 62 39 ma occur mainly as mantle xenolith bearing basanites their geochemical features such as the ree patterns elevated hfse contents and depleted sr nd isotope signatures indicate a relatively small degree of melting of an isotopically depleted mantle source their mantle normalized trace element patterns are flat to concave and bell shaped characteristic of an oib source free of subduction component 87sr 86sri and 143nd 144ndi isotope ratios 0 7030 0 7047 and 0 5127 0 5129 respectively indicate a depleted source for the espemar similar to the european asthenospheric reservoir ear the hkca sho rocks 30 21 ma occur as basalts basaltic andesites and trachyandesites they show enrichment in lile and depletion in hfse with all the distinctive features of calc alkaline arc type magmatism this is coupled with somewhat enriched sr nd isotope signature 87sr 86sri 0 7047 0 7064 143nd 144ndi 0 5124 0 5126 all these features are characteristic of subduction related metasomatism and fluxing of the hkca sho mantle source with fluids melts released from subducted sedimentary material up rocks 35 21 ma appear as i si rich lamproites and related rocks and ii olivine leucitites and related rocks up rocks have high lile hfse ratios with enrichment for some lile around 1000 primitive mantle troughs at nb and ti and peaks of pb in their mantle normalized patterns they also show highly fractionated ree patterns la yb up to 27 lan up to 400 the isotopic ratios approach crustal values 87sr 86sri 0 7059 0 7115 and 143nd 144ndi 0 5122 0 5126 and that signature is typical for ultrapotassic rocks worldwide the paleocene eocene episode and formation of the espemar is referred to as asthenospheric derived magmatism this magmatism originated through passive riftlike structures related to possible short relaxational phases during predominantly collisional and compressional conditions the oligocene miocene episode and formation of hkca sho and up rocks were dominated by lithospheric controlled magmatism its origin is connected with the activity of a wide dextral wrench corridor generated along the axis of the dinaride orogen which collapsed in response to thickened crust caused by earlier compressional processes to explain conditions of these two magmatic events a three stage geodynamic model has been proposed 1 subduction termination collision stage paleocene eocene 2 collision stage eocene and 3 postcollision collapse stage oligocene early miocene

polycyclic aromatic hydrocarbons of pyrolytic origin in ancient sediments evidence for jurassic vegetation fires abstract polycyclic aromatic hydrocarbon pah distributions in an upper jurassic succession from offshore korea bay basin were consistent with a pyrolytic source being dominated by non alkylated species levels of these pahs were significantly higher in samples containing abundant fusinite macerals which are believed by some to be the product combustion the data were consistent with a pah origin from periodic conflagration throughout the upper jurassic of vegetation adjacent to a tectonically formed lake distribution of pahs exhibited some differences from those of combustion origin in recent and some ancient sediments and were characterized by the dominance of the highly peri condensed compounds benzo e pyrene benzo g h i perylene and coronene this characteristics reflects either preferential formation or preferential preservation under the prevailing sedimentary conditons of the highly peri condensed structures

can earth s rotation and tidal despinning drive plate tectonics abstract we re evaluate the possibility that earth s rotation contributes to plate tectonics on the basis of the following observations 1 plates move along a westerly polarized flow that forms an angle relative to the equator close to the revolution plane of the moon 2 plate boundaries are asymmetric being their geographic polarity the first order controlling parameter unlike recent analysis the slab dip is confirmed to be steeper along w directed subduction zones 3 the global seismicity depends on latitude and correlates with the decadal oscillations of the excess length of day lod 4 the earth s deceleration supplies energy to plate tectonics comparable to the computed budget dissipated by the deformation processes 5 the gutenberg richter law supports that the whole lithosphere is a self organized system in critical state i e a force is acting contemporaneously on all the plates and distributes the energy over the whole lithospheric shell a condition that can be satisfied by a force acting at the astronomical scale assuming an ultra low viscosity layer in the upper asthenosphere the horizontal component of the tidal oscillation and torque would be able to slowly shift the lithosphere relative to the mantle

2 hydrothermal ore deposits related to post orogenic extensional magmatism and core complex formation the rhodope massif of bulgaria and greece abstract the rhodope massif in southern bulgaria and northern greece hosts a range of pb zn ag cu mo and au ag deposits in high grade metamorphic continental sedimentary and igneous rocks following a protracted thrusting history as part of the alpine himalayan collision major late orogenic extension led to the formation of metamorphic core complexes block faulting sedimentary basin formation acid to basic magmatism and hydrothermal activity within a relatively short period of time during the early tertiary large vein and carbonate replacement pb zn deposits hosted by high grade metamorphic rocks in the central rhodopean dome e g the madan ore field are spatially associated with low angle detachment faults as well as local silicic dyke swarms and or ignimbrites ore formation is essentially synchronous with post extensional dome uplift and magmatism which has a dominant crustal magma component according to pb and sr isotope data intermediate and high sulphidation pb zn ag au deposits and minor porphyry cu mo mineralization in the eastern rhodopes are predominantly hosted by veins in shoshonitic to high k calc alkaline volcanic rocks of closely similar age base metal poor high grade gold deposits of low sulphidation character occurring in continental sedimentary rocks of synextensional basins e g ada tepe show a close spatial and temporal relation to detachment faulting prior and during metamorphic core complex formation their formation predates local magmatism but may involve fluids from deep mantle magmas the change in geochemical signatures of palaeogene magmatic rocks from predominantly silicic types in the central rhodopes to strongly fractionated shoshonitic bulgaria to calc alkaline and high k calc alkaline greece magmas in the eastern rhodopes coincides with the enrichment in cu and au relative to pb and zn of the associated ore deposits this trend also correlates with a decrease in the radiogenic pb and sr isotope components of the magmatic rocks from west to east reflecting a reduced crustal contamination of mantle magmas which in turn correlates with a decreasing crustal thickness that can be observed today hydrogen and oxygen isotopic compositions of the related hydrothermal systems show a concomitant increase of magmatic relative to meteoric fluids from the pb zn ag deposits of the central rhodopes to the magmatic rock hosted polymetallic gold deposits of the eastern rhodopes

imaging a relic of complex tectonics the lithosphere asthenosphere structure in the eastern mediterranean the crust and upper mantle structure of the eastern mediterranean is investigated through the nonlinear inversion of raleigh wave dispersion curves extracted from broadband records in the region along two profiles crossing the hellenic and cyprian arcs corresponding density models are constructed consistent with the observed gravity anomalies the modelled profiles exhibit a continental crust type overlain by a thick sedimentary cover and underlain by a thick lithospheric mantle the lithosphere asthenosphere system exhibits features which suggest the presence of upducted asthenosphere exhumed to the north of the hellenic arc where the slab extension is limited to depths of about 220 km

postsubduction porphyry cu au and epithermal au deposits products of remelting of subduction modified lithosphere porphyry cu mo au and some epithermal au deposits are formed from hydrothermal fluids exsolved from cooling water rich calc alkaline magmas emplaced in volcanoplutonic arcs above subduction zones these magmas originate by partial melting of the metasomatized asthenospheric mantle wedge however there is increasing evidence for the existence of a suite of porphyry cu au and epithermal au deposits related to magmas generated after subduction beneath the arc has ceased associated magmas tend to be mildly alkaline relatively sulfur poor and emplaced as isolated complexes rather than in voluminous volcanoplutonic arcs they are likely formed by remelting of previously subduction modified arc lithosphere triggered by postsubduction lithospheric thickening lithospheric extension or mantle lithosphere delamination metasomatized mantle lithosphere or hydrous lower crustal cumulates residual from first stage arc magmatism contain small amounts of chalcophile and siderophile element rich sulfides and constitute a fertile source for hydrous au rich but relatively sulfur poor magmas during later remelting the recognition that porphyry cu au and related epithermal au systems can also form in postsubduction and collisional tectonic settings expands the range of geological environments and geographical terranes that are prospective for such deposits

depositional wedge cycles on evolving plate margin western and northwestern australia the barrow province lies at the transition between the western and northwestern rift domains of the australian continental margin as these domains evolved during the mesozoic five depositional wedge sequences developed in the eastern half of the province each sequence possesses distinct stratigraphic and sedimentological characteristics which differs from the others as a function of proximity direction and style of rift related diastrophism along the evolving margin the first depositional sequence developed during the triassic as part of a regional tethyan facing passive margin clastic wedge this event was followed during the early and middle jurassic by a second more provincial sequence in response to early syn rift fault related subsidence by the callovian a deep anastomosing rift complex had formed and deposition of the third late jurassic cycle was initially very localized confined by the new graben topography however stratigraphic continuity returned during post breakup subsidence of the northwestern margin as subregional depositional systems began to bury the fragmented borderland this cycle was terminated at the close of the jurassic in response to renewed rifting between western australia and greater india sediment stripped from t e uplifted rift shoulders fed the northerly prograding barrow delta system to form a fourth depositional sequence during the late jurassic early neocomian the final cycle commenced as greater india uncoupled from australia during the middle neocomian post breakup subsidence is reflected by a major regional transgression and the development of a second margin wide depositional wedge during the later cretaceous the close temporal and spatial relationship that exists between these cycles and the evolution of the western and northwestern australian continental margin emphasizes the importance of tectonic control upon sedimentation

terrane boundary and spatio temporal distribution of ore deposits in the sanjiang tethyan orogen insights from zircon hf isotopic mapping abstract the sanjiang tethyan orogen sjto of the eastern tethyan tectonic belt in china records a transition from late paleozoic tethys realm to cenozoic continental collision associated with the formation of large metallic mineral deposits this contribution combines geological and hf isotopic data for igneous rocks from the sjto together with the salient features associated with mineralization to gain insights into the crustal architecture and metallogeny integrating the available information from tectonic events sedimentary successions paleobiogeography and paleolatitude based on paleomagnetic data the hf isotopic maps that we construct highlight the changning menglian suture as an important tectonic boundary between the gondwana and cathaysian continents the changning menglian suture separates two distinct hf isotopic domains with an old reworked crustal block to the southwestern part of the sjto and a juvenile crustal block with significant mantle derived components to the northeastern part of the orogen the hf isotopic mapping of the sjto also provides important indications on the location of different deposits the jinshajiang ailaoshan suture appears to have exerted a first order control on the localisation of cenozoic magmatism and intrusion related mineral systems the magmatic source for intrusions in the eastern high ehf low tdmc domain is dominated by mantle components and gave rise to porphyry and porphyry skarn cu mo mineralization in contrast the magma sources for intrusions in the low ehf high tdmc domains contain an old and reworked crustal component and gave rise to granite related sn w mineralization those for the intrusions characterized by variable ehf and tdmc are dominantly reworked older crustal components together with subordinate juvenile material which generated the granite related pb zn cu ag mineralization

global fire at the cretaceous tertiary boundary cretaceous tertiary k t boundary clays from five sites in europe and new zealand are 102 104 fold enriched in elemental c mainly soot which is isotopically uniform and apparently comes from a single global fire the soot layer coincides with the ir layer suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled