the emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and ph front here we argue that life emerged on earth from a redox and ph front at c 4 2 ga this front occurred where hot c 150 c extremely reduced alkaline bisulphide bearing submarine seepage waters interfaced with the acid warm c 90 c iron bearing hadean ocean the low ph of the ocean was imparted by the ten bars of co 2 considered to dominate the hadean atmosphere hydrosphere disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal fes membrane iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites our hypothesis is that the fes membrane laced with nickel acted as a semipermeable catalytic boundary between the two fluids encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers the ocean provided carbonate phosphate iron nickel and protons the hydrothermal solution was the source of ammonia acetate hs h 2 and tungsten as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde the mean redox potential eh across the membrane with the energy to drive synthesis would have approximated to 300 millivolts the generation of organic anions would have led to an increase in osmotic pressure within the fes bubbles thus osmotic pressure could take over from hydraulic pressure as the driving force for distension budding and reproduction of the bubbles condensation of the organic molecules to polymers particularly organic sulphides was driven by pyrophosphate hydrolysis regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the hadean ocean this was the first use by a metabolizing system of protonmotive force driven by natural aph which also would have amounted to c 300 millivolts protonmotive force is the universal energy transduction mechanism of life taken together with the redox potential across the membrane the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt the role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers this organic take over of the membrane material led to the miniaturization of the metabolizing system information systems to govern replication could have developed penecontemporaneously in this same milieu but iron sulphur and phosphate inorganic components of earliest life continued to be involved in metabolism

textural and stable isotopic evidence for the genesis of the tynagh base metal deposit ireland at the tynagh mine county galway four major stages of mineralization can be recognized that span the diagenetic and postlithification history of the host waulsortian limestones 1 growth of colloform and granular pyrite clots during the early diagenesis of the micritic host 2 rapid geopetal precipitation of microcrystalline sphalerite galena barite and dolomite within a dilatant fracture system that developed as a consequence of the forceful injection of metalliferous fluids into the coherent waulsortian carbonate mudbanks adjacent to the tynagh fault 3 veining and replacement of the host and previously precipitated phases by tennantite chalcopyrite bornite arsenopyrite medium to coarsely crystalline galena and coarse sparry barite and 4 finally precipitation of calcite within veinlets and cavities and dolomitization of large bodies of previously unmineralized waulsortian limestones sulfur isotope ratios indicate that contemporaneous lower carboniferous seawater acted as the source of sulfate for precipitation of barite delta 34 s 21 1 to 17 4ppm stage 1 delta 34 s 3 1 to 15 5ppm and stage 2 delta 34 s 4 1 to 26 0ppm sulfides were precipitated by reduced sulfur generated during open system bacterial reduction of this sea water sulfate source isotopically heavier delta 34 s or 0ppm reduced sulfur of deep seated origin was introduced from the fault zone during stage 3 this mixed with bacteriogenic sulfur migrating into the waulsortian bank limestones to precipitate stage 3 sulfides and sulfosalts delta 34 s 11 1 to 23 0ppm mineralized limestones delta 13 c 2 1 to 4 0ppm delta 18 o 17 6 to 27 1ppm ore stage carbonates delta 13 c 2 8 to 3 4ppm delta 18 o 17 1 to 26 9ppm and postore carbonates delta 13 c 4 0 to 2 6ppm delta 18 o 15 9 to 25 8ppm are depleted in the heavier isotopes of carbon and oxygen with respect to unmineralized limestones delta 13 c 3 1 to 4 1ppm delta 18 o 22 2 to 28 1ppm the depletion in 13 c is attributed to the mixing of host derived carbon with bacterially oxidized carbon and during stage 4 deep seated carbon the 18 o depletion of the mineralized host is a consequence of isotopic exchange with the ore fluids an oxygen isotope fractionation temperature of 200 degrees c and a delta 18 o smow value of 10 5 per mil for the coexisting water is obtained from a single stage 3 quartz albite pair collected from the fault zone if these values are accepted the delta 18 o values of stage 3 carbonates can only be interpreted in terms of mixing of this isotopically heavy water introduced from the fault with isotopically lighter water already present or migrating into the bank limestones

melting of plagioclase quartz assemblages at 2 kbar water pressure the melting of plagioclase and quartz has been investigated at ph2o 2kb a single crystal of plagioclase was surrounded by quartz powder and water a reaction rim consisting of glass and of an rich plagioclase developed around unchanged starting plagioclase microprobe determinations of melt and coexisting plagioclase compositions reveal a strong fractionation of plagioclase components between melt and new plagioclase for example at 850 c the approximate xan of melt is 0 3 and that of plagioclase is 0 8 the temperature interval between beginning of melting and complete melting of cotectic compositions is 100 c or more for quartz plagioclase mixtures with plagioclases between an 40 and an 75 in comparison to the system ab an h2o the plagioclase melting loop is somewhat wider in the investigated system qz ab an h2o but the temperature interval is much smaller 100 c than in the system ab an h2o 200 c the solidus data indicated by the new plagioclase compositions are practically identical with those observed in beginning of melting experiments the results show that fractionation of plagioclase components between partial melts and restite plagioclase can be more pronounced in multi component rocks than in the pure plagioclase system this finding is important for the development of albite rich rocks from more basic compositions

experimental study for noble gas release and exchange under high speed frictional melting abstract isotope ratios of noble gases in certain minerals are believed to be modified easily by their ambient reservoirs when the minerals reach temperatures that are higher than their closure temperatures the thermal history of a rock or a geologic event even a fault movement can therefore be determined quantitatively by application of radiometric dating methods to different minerals however neither traditional k ar nor ar ar dating methods are readily applicable to faulted rocks because in the case of faulting it is difficult to prove that the temperature of an event was greater than the closure temperatures of minerals frictional melting experiments performed on fine grain homogeneous gabbroid with high temperatures induced by frictional heating using a high velocity friction apparatus were performed to test whether rapid fault movement can reset the noble gas isotope ratio of fault rocks the temperature on the artificial fault plane is much higher than the closure temperature of the k ar system as inferred from the calculated cooling age the anticipated rapid equilibration of volatiles during the frictional melting of rocks implies that the noble gas isotope composition ratio was reset to an atmospheric value during this experiment we measured noble gas isotopes in a gabbroid sample using laser fusion analysis the resetting of noble gases is only observed in glass that had melted completely rejuvenation and or apparent increases in the k ar ages were only observed in a narrow 3 mm wide zone around the fault plane which appears to be thermally altered and mechanically fractured in thin sections because of frictional heating such glassy materials called pseudotachylytes sometimes form along the fault plane in natural faults as a result of complete melting of rock induced by frictional heating thus these results suggest that k ar ages of fault activity can be quantitatively obtained from the analysis of pseudotachylytes

broken hill pb zn ag deposit a product of mantle metasomatism broken hill ore deposition occurred during the highest geothermal gradient coeval with an event of bimodal basic rhydacitic volcanism the depositional environment is interpreted as an ensialic rift on the basis of the sedimentary facies ferro and low k tholeiitic basalts and bimodal basic calc alkaline rhyolite rhyodacite volcanism the orebody is of unusual composition characterised by abundant carbonate fluorite and fluorapatite abundant lil k and rb rich premetamorphic alteration assemblages primordial s and pb isotopic values sr isotopes possibly indicating a heterogeneous source s se in the magmatic range and zoning suggestive of cooling of the ore fluid

selective melting processes as inferred from experimentally generated pseudotachylytes abstract high speed friction experiments have been conducted on gabbros and granites to better constrain the process of frictional melting during seismogenic fault motion experiments were done on cylindrical specimens of 25 mm in diameter under a normal stress of 1 0 1 5 mpa and at slip rates up to 2 m s using a rotary shear high speed frictional testing machine the experimentally generated pseudotachylytes consist of a fused glassy matrix with abundant vesicles and angular or sub angular to rounded fragments these locally occur as injected network veins in the fractured rock x ray diffraction analysis has revealed the presence of as much as 40 70 wt glass the mineral contents of clasts in the experimental pseudotachylyte in granite as determined by x ray diffraction analysis indicate that quartz is the most resistant to melting biotite the least and feldspar is intermediate thus the sio2 depletion in natural pseudotachylyte glass is likely to be due to the selective melting of constituent materials during frictional melting

multi proxy dating the millennium eruption of changbaishan to late 946 ce ranking among the largest volcanic eruptions of the common era ce the millennium eruption of changbaishan produced a widely dispersed tephra layer known as the b tm ash which represents an important tie point for palaeoenvironmental studies in east asia hitherto there has been no consensus on its age with estimates spanning at least the tenth century ce here we identify the cosmogenic radiocarbon signal of 775 ce in a subfossil larch engulfed and killed by pyroclastic currents emplaced during the initial rhyolitic phase of the explosive eruption combined with glaciochemical evidence from greenland this enables us to date the eruption to late 946 ce this secure date rules out the possibility that the millennium eruption contributed to the collapse of the bohai kingdom manchuria korea in 926 ce as has previously been hypothesised further despite the magnitude of the eruption we do not see a consequent cooling signal in tree ring based reconstructions of northern hemisphere summer temperatures a tightly constrained date for the millennium eruption improves the prospect for further investigations of historical sources that may shed light on the eruption s impacts and enhances the value of the b tm ash as a chronostratigraphic marker

examples of structural control of hydrothermal mineralization fault zones in epicontinental sedimentary basins a review by compiling data available from progressive geoscientific research and by complementary studies it seems possible for an increasing number of mineral districts to find indications of the regional structural control of hydrothermal ore deposits the relationship between hydrothermal mineralization faulting or fault reactivation and related processes can of course best be examined at the less deformed sedimentary record of ancient epicontinental sedimentary basins there is increasing evidence that the sediment hosted submarine hydrothermal zn pb ba mineralizations such as meggen rammelsberg howards pass and mcarthur river are spatially and genetically related to deep synsedimentarily active fault systems of intracontinental basins or stretched passive continental margins for long periods of basin development the faults provided favorable conduits for episodically released basin dewatering brines which precipitated the leached metals into third order basins situated next to these faults there are many similarities to epigenetic mineralizations which formed either pre syn or postorogenetically from brines leaching the meta sediments and associated magmatites and migrating along fault zones to their near surface trap structures

identification and correlation of visible tephras in the lake suigetsu sg06 sedimentary archive japan chronostratigraphic markers for synchronising of east asian west pacific palaeoclimatic records across the last 150 ka abstract the lake suigetsu sg06 sedimentary archive from honshu island central japan provides a high resolution palaeoenvironmental record including a detailed record of explosive volcanism from japan and south korea thirty visible tephra are recorded within the 73 m long sg06 core which spans the last 150 ka here we describe and characterise these tephras based on major element glass composition which is useful for the identification and correlation of these tephras and the age models of the records in which they are found utilising the large number of radiocarbon measurements n 600 from terrestrial plant macrofossils in the lake suigetsu sg06 record we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka glass compositional data of some of the largest eruptions from japan k ah at aso 4 aso a aso d and ata sampled at proximal outcrops are also presented these data show that the major element glass chemistry is distinctive for many of the visible sg06 tephra units and allows some of the layers to be correlated to known eruptions from volcanoes in japan and south korea namely k ah sg06 0967 u oki sg06 1288 at sg06 2650 aso 4 sg06 4963 sg06 4979 k tz sg06 5181 aso abcd sg06 5287 and ata sg06 5181 the following ages were obtained for the sg06 tephra units 3 966 4 064 cal ka bp 95 4 probability range for the sg06 0588 tephra 10 242 10 329 cal ka bp 95 4 probability range for sg06 1293 19 487 112 sg06 2012 ka bp 2 for sg06 1965 28 425 194 sg06 2012 ka bp 2 for sg06 2504 28 848 196 sg06 2012 ka bp 2 for sg06 2534 29 765 190 sg06 2012 ka bp 2 for sg06 2601 29 775 191 sg06 2012 ka bp 2 for sg06 2602 43 713 156 sg06 2012 ka bp 2 for sg06 3485 46 364 202 sg06 2012 ka bp 2 for sg06 3668 49 974 337 sg06 2012 ka bp 2 for sg06 3912 50 929 378 sg06 2012 ka bp 2 for sg06 3974 and improved ages for two of the most important tephra markers across japan the k ah 7 165 7 303 cal ka bp at 95 4 probability range sg06 0967 and at tephra 30 009 189 sg06 2012 ka bp at 2 sg06 2650

fractal dimension of molten surfaces as a possible parameter to infer the slip weakening distance of faults from natural pseudotachylytes high velocity friction experiments on gabbro and monzodiorite using a rotary shear high velocity friction apparatus have revealed that frictional melting and progressive growth of a molten layer along a fault cause slip weakening eventually reaching a nearly steady state the melting surface at the host rock molten layer interface is initially very flat but it becomes more complex and rounded in shape towards the steady state owing to the selective melting of minerals with lower melting points and the gibbs thomson effect this change in the melting surface topography can be quantitatively expressed by the fractal dimension d as determined by the divider method from about 1 0 near the peak friction to around 1 1 near the steady state friction the ultimate fractal dimension at steady state friction tends to decrease with increasing heat production rate presumably due to more rapid and uniform melting a systematic correlation of d with mechanical behavior of the fault during frictional melting may provide a way of estimating slip weakening distance and heat production rate at steady state friction by measuring d for natural pseudotachylytes on slip surfaces with different displacements the weakening distance is of vital significance in relation to fault instability and the heat production rate is related to the fault strength the experimental studies point to ways to estimate these difficult quantities for natural faults

ash from changbaishan millennium eruption recorded in greenland ice implications for determining the eruption s timing and impact major volcanic eruptions can impact on global climate by injecting large quantities of aerosols and ash into the atmosphere that alter the radiative balance and chemical equilibrium of the stratosphere the millennium eruption of tianchi paektu china north korea was one of the largest late holocene eruptions uncertainty about the precise timing of the eruption has hindered the recognition of its climate impact in palaeoclimate and historical records here we report the compelling identification of the eruption s volcanic signal in greenland ice cores through the association of geochemically characterized volcanic glass represented in by bimodal populations that compare with proximal material from the source eruption the eruption most probably occurred in the a d 940s 7 years after the eldgja eruption on iceland we examine the eruption s potential for climate forcing using the sulfate records from the ice cores and conclude that it was unlikely to have had a global or extraregional impact

depositional ages of the stratiform base metal deposits at mount isa and mcarthur river australia based on u pb zircon dating of concordant tuff horizons potassium rich tuff beds occur interbedded with major stratiform pb zn mineralization in shales and dolomitic shales of the mount isa group northwest queensland and the mcarthur group northern territory these deposits are some 600 km apart yet they exhibit many similarities which together with regional correlations suggest that the deposits formed by similar processes and that the successions developed more or less contemporaneously zircon is sparsely distributed as tiny crystal fragments or phenocrysts in the tuffs and its morphology and u pb systematics affirm that it is primarily of igneous origin u pb zircon data from a tuff in the mineralized h y c pyritic shale member of the mcarthur group give an age of the tuff of 1 690 super 29 sub 25 m y and from a tuff in the mineralized urquhart shale of the mount isa group an age of 1 670 super 20 sub 17 m y these results are consistent with all other geologic controls and are regarded as the best estimates of the depositional ages of the groups the ages of the mount isa and mcarthur groups are thus the same to within the present experimental uncertainties essentially confirming geologic synchrony of these important sedimentary successions pooled whole rock data from several of the mount isa tuff marker beds give an updated rb sr age of about 1 480 m y interpreted as indicating that isotopic exchange and regional metamorphism had essentially ceased by this time

integrating the holocene tephrostratigraphy for east asia using a high resolution cryptotephra study from lake suigetsu sg14 core central japan abstract tephra volcanic ash layers have the potential to synchronise disparate palaeoenvironmental archives on regional to hemispheric scales highly productive arc regions like those in east asia offer a considerable number of widespread isochrons but before records can be confidently correlated using these layers a refined and integrated framework of these eruptive events is required here we present the first high resolution holocene cryptotephra study in east asia using the lake suigetsu sedimentary archive in central japan the holocene tephrostratigraphy has been extended from four to twenty ash layers using cryptotephra extraction techniques which integrates the deposits from explosive eruptions from north korea china south korea and along the japanese arc this lake suigetsu tephrostratigraphy is now the most comprehensive record of east asian volcanism and the linchpin site for correlating sequences across this region major element glass geochemical compositions are presented for the tephra layers in the sequence which have been compared to proximal datasets to correlate them to their volcanic source and specific eruptions this study has significantly extended the ash dispersal of many key holocene marker layers and has identified the first distal occurrence of isochrons from ulleungdo and changbaishan volcanoes utilising the high precision lake suigetsu chronology we are able to provide constrained eruption ages for the tephra layers which can be transferred into other site specific age models containing these markers this new framework indicates that several isochrons stratigraphically bracket abrupt climate intervals in japan and could be used to precisely assess the regional and hemispheric synchronicity of these events

historical tsunami and storm deposits during the last five centuries on the sanriku coast japan abstract nine event deposits in a small alluvial valley along the sanriku coast japan were correlated with historical tsunamis and storms that have been recorded in this region since the 15th century we identified nine sandy layers in 15 geo slices collected at distances ranging from 140 to 260 m from the coast in a lowland back marsh protected from the sea by a high sandy ridge based on their sedimentary characteristics grain size distribution and marine microfossil assemblages namely coccoliths these event layers which were well preserved in their order of deposition were probably either tsunami or storm deposits diatom analysis revealed four stages of paleo environmental change from tidal marsh to wetland the uppermost event layer covering the ground surface is probably the deposit from the 2011 tohoku oki tsunami ages for other event deposits were radiometrically dated using 14 c 137 cs and 210 pb with bayesian estimation the second event layers can be correlated with the 1960 chilean or 1968 aomori oki earthquake tsunamis the candidates for the third event layer are the 1947 catherine and 1948 ione typhoons as well as the candidates for the second event layer the fourth and fifth event layers are likely associated with the 1933 and 1896 sanriku oki earthquake tsunamis four lower event layers can be correlated with historical tsunamis and storms that occurred during the 15th to 18th centuries such as the 1611 sanriku oki earthquake tsunami

challenges of anticipating the 2011 tohoku earthquake and tsunami using coastal geology 1 can the magnitude of a giant earthquake be estimated from paleoseismological data alone attempts to estimate the size of the jogan earthquake of ad 869 whose tsunami affected much of the same coast as the 2011 tohoku tsunami offers an excellent opportunity to address this question which is fundamental to assessing earthquake and tsunami hazards at subduction zones between 2004 and 2010 examining stratigraphy at 399 locations beneath paddy fields along 180 km of coast mainly south of sendai we learned that a tsunami deposit associated with the ad 869 jogan earthquake had run inland at least 1 5 km across multiple coastal lowlands and that one of the lowlands had subsided during the jogan earthquake and an earlier earthquake as well radiocarbon ages just below above sand deposits left by the pre jogan tsunamis suggested recurrence intervals in the range of 500 to 800 years modeling inundation and subsidence we estimated size of the jogan earthquake as moment magnitude 8 4 or larger and a fault rupture area 200 km long we did not consider a longer rupture like the one in 2011 because coastal landform and absence of a volcanic ash layer make any jogan layer difficult to identify along the sanriku coast still sendai tsunami geology might have reduced casualties by improving evacuation maps and informing public awareness campaigns

the genesis of sediment hosted exhalative zinc lead deposits large sediment hosted lead zinc deposits like mount isa mcarthur river navan rammelsberg and sullivan form a distinctive group characterised by stratiform syngenetic sulphide ores that formed in local basins on the sea floor as a result of protracted hydrothermal activity accompanying continental rifting generally there is a development of a sedimentary pre ore phase mineralization often featuring manganese followed by zinc lead iron and chert lower main phase zinc lead lenses are usually almost devoid of copper but cu tenors increase toward the middle or top of the ore sequences hanging wall trace element haloes are common these characteristics are accounted for by deriving the ore solutions from subsurface convective circulation of modified highly saline seawater the circulation is initiated during rifting and driven by a high geothermal gradient as a result of continued extensional strain and cooling of the rock column the brittle to ductile transition zone is depressed and the circulation penetrates to greater depth with time of the ore metals the downward penetrating convection fluids first leach and transport zinc and lead but with increasing temperature are later able to leach and transport some copper unless convective circulation ceases the metal sequence generally reverses as the cooling phase sets in the minimum distance separating major coeval orebodies of this type is 18 km which is a function of the size of the convective systems

subsidence along the central to southern sanriku coast northeast japan near the source region of the 2011 tohoku oki earthquake estimated from the holocene sedimentary succession along a ria coast abstract along the sanriku coast northeast japan discrepancies in crustal movement have been reported between uplift on a scale of 105 years versus subsidence on a scale of 101 102 years well dated holocene incised valley fill sediments provide records of millennial scale vertical crustal movement which is key to understanding the tectonic history in this area previous studies of the age and distribution of early holocene intertidal deposits in incised valleys reported that the southern sanriku coast has subsided during the holocene at an average rate of about 1 mm yr here we studied three sediment cores tgi1 tgi2 and tgi3 collected from the tsugaruishi plain on the central sanriku coast and recognized a holocene deltaic sediment succession in all three cores in core tgi3 from the farthest inland site the intertidal sediment facies deposited from 7500 to 7000 cal bp and the overlying 6 m thick floodplain facies deposited from 7000 to 5000 cal bp are both below the present sea level because a sea level highstand due to hydroisostatic uplift around japan occurred in the mid holocene we inferred that the tsugaruishi plain subsided during the holocene and the estimated subsidence rate 1 1 1 9 mm yr at maximum is consistent with the recently reported subsidence rate along the southern sanriku coast the results of this study confirm that the central to southern sanriku coast is subsiding in contrast to an interpretation based on the study of marine terraces that this part of the coast is uplifting the empirical data presented here will be useful for constructing an earthquake cycle model related to plate subduction

dating pseudotachylyte of the nojima fault using the zircon fission track method 1 the zircon fission track analysis of pseudotachylyte answered how old the nojima fault is which was activated during the 1995 kobe earthquake in japan the time of seismic fault motions at the crustal interior can be constrained by dating pseudotachylyte formation we succeeded in separating zircons from the pseudotachylyte layer of the fault as well as in dating them by the fission track method here we show that the layer has a significantly younger age 56 4 ma than the initial cooling age of the host rock suggesting that the fault was already initiated at 56 ma much older than the previous estimate based on the spatial distribution of sediments around the fault

artificial generation of pseudotachylyte using friction welding apparatus simulation of melting on a fault plane a 150 m thick fused layer of rock has been produced by rotating two metadolerite core faces against each other at 3000 r p m under an axial load of 330 kg for 11 s using friction welding apparatus scanning electron microscopy and electron microprobe analysis reveal that the melt layer comprises sub angular to rounded porphyroclasts of clinopyroxene feldspar and ilmenite 20 m diameter derived from the host metadolerite set within a silicate glass matrix thermal calculations confirm that melting occurred at the rock interface and that mean surface temperatures in excess of 1400 c were attained the fused layer shows many textural similarities with pseudotachylyte described from fault zones morphologically the fused layer consists of a series of stacks of porphyroclasts welded together by melt to form build ups oriented at right angles to the friction surface there is also evidence of gouging ploughing and plucking as well as transfer and adhesion of material having occurred between the rock faces the mean surface velocity attained by the metadolerite 0 24 m s 1 and duration of the experiment are comparable with velocities and rise times of typical single jerk earthquakes occurring during stick slip seismic faulting within brittle crust i e slip rates of 0 1 0 5 m s 1 for say 1 10s in these respects the experiment successfully simulated frictional fusion on a fault plane in the absence of an intergranular fluid power dissipation during the experiment was about mw m 2 comparable only to very low values for earthquakes e g 1 100 mw m 2 for displacement rates of 0 1 0 5 m s 1 at shear stresses of 100 1000 bars this indicates that melting on fault planes during earthquakes should be commonplace field evidence however does not support this contention either pseudotachylyte is not being recognized in exhumed ancient seismic fault zones or melting only occurs under very special circumstances

growth of molten zone as a mechanism of slip weakening of simulated faults in gabbro during frictional melting 1 to understand how frictional melting affects fault instability we performed a series of high velocity friction experiments on gabbro at slip rates of 0 85 1 49 m s 1 at normal stresses of 1 2 2 4 mpa and with displacements up to 124 m experiments have revealed two stages of slip weakening one following the initial slip and the other immediately after the second peak friction the first weakening is associated with flash heating and the second weakening is due to the formation and growth of a molten layer along a simulated fault the two stages of weakening are separated by a marked strengthening regime in which melt patches grow into a thin continuous molten layer at the second peak friction the frictional coefficient decays exponentially from 0 8 1 1 to 0 6 during the second weakening the host rocks are separated completely by a molten layer during this weakening so that the shear resistance is determined by the gross viscosity and shear strain rate of the molten layer melt viscosity increases notably soon after a molten layer forms however a fault weakens despite the increase in melt viscosity and the second weakening is caused by the growth of molten layer resulting in the reduction in shear strain rate of the molten layer very thin melt cannot be squeezed out easily from a fault zone so that the rate of melting would be the most critical factor in controlling the slip weakening distance effect of frictional melting on fault motion can be predicted by solving a stefan problem dealing with moving host rock molten zone boundaries

geochemical applications of noble gases abstract noble gases are unique tracers due to their rarity on earth and their inertness several of their isotopes are produced by nuclear reactions whereas others were trapped when the earth formed they have been widely used for understanding the evolution and structure of the earth dating geological events processes characterizing magma genesis and volcanism in different tectonic environments tracing mantle crust interaction even in non volcanic areas and for monitoring earthquake and volcanic activities some of these topics were presented at the 9th international conferences on gas geochemistry that was held in 2007 in taipei taiwan this special volume includes twelve papers which cover a wide range of applications of noble gases geochemistry such as tracing the thermal evolution of the early earth understanding the mantle source of continental basalts establishing the spatial variations of gas compositions in hot springs and fumaroles from volcanic and forearc areas as well as in key non volcanic areas such as faults and seismic zones and tracing the origin and evolution of ore forming fluids of uranium deposits reproducing the noble gas behavior during faulting and finally using argon as a tracer of large scale geologic processes

mid proterozoic pb pb ages for some himalayan base metal deposits and comparison to deposits in rajasthan nw india abstract lead isotope ratios from three base metal deposits rangpo gorubathan in the eastern lesser himalaya and bageswar in the lesser himalaya of kumaun have been studied the first two deposits generally stratiform and stratabound occur within pelitic psammopelitic wacke type metasediments which are locally carbonaceous the bageswar deposit is hosted by silicified dolomitic carbonate rocks the pb isotope ratios appear to be homogenous in two and heterogenous in one of the deposits model pb pb ages obtained for the rangpo and gorubathan deposits are 1800 ma and for the bageswar deposit 1550 1700 ma dispersion in isotopic ratios reflect the geochemical heterogeneity particularly with respect to larger variation in the composition of pb isotope ratios in the bageswar deposit may be explained by the participation of pb from heterogenous sources pb isotope characteristics of the himalayan deposits are compared with those of a number of base metal deposits in the delhi aravalli belt in rajasthan nw india ore lead from the deposits of both the himalaya and of rajasthan are enriched in 206pb and 207pb however lead in all cases plots on the evolution lines corresponding to sources with higher u pb ratios but the sources of lead in the himalayan deposits had a lower th u ratio the geologic observations as well as the pb isotope compositions are consistent with a sedimentary diagenetic origin of the himalayan base metal deposits

experimental generation of volcanic pseudotachylytes constraining rheology volcanic systems are highly dynamic environments that comprise rocks and magmas which in the process of strain localisation e g in catastrophic flank collapse or dome building events are candidate materials for the occurrence of frictional melting and the formation of pseudotachylytes we evaluate the frictional behaviour of a plagioclase two pyroxene and glass bearing andesite and introduce an approach to constrain the rheology of frictional melts frictional slip at a rate of 1 3 m s under an axial stress of 1 5 mpa induces heating at a rate approximating 130 c per meter of slip and frictional melting of the andesite occurs at 1000 c which corresponds to a peak in shear stress with continuing displacement the shear stress decreases by 25 from the peak strength and stabilises while the temperature equilibrates to 1230 1290 c the shear stress for the system is congruent with a non arrhenian temperature dependent frictional melt rheology exhibiting a non newtonian viscosity evolving from approximately 104 2 to 103 4 pa s post experiment analysis show a gradation from 1 the host rock to 2 an extraordinary zone of unmelted yet viscously deformed material to 3 a thin outer region of chemically heterogeneous protomelts and to 4 an inner region of chemically homogeneous frictionally generated modified melt in the core of the slip zone we discuss the role and identification of frictional melting in volcanic systems and the implication of viscous remobilisation of magmatic plugs during frictional slip of glass bearing volcanic materials

40ar 39ar dating of cataclastic k feldspar a new approach for establishing the chronology of brittle deformation abstract constraining the timing of brittle deformation such as in high angle normal or strike slip faulting is technically challenging in this study we present a new approach of age determinations from cataclastic k feldspars of brittle faults developed in rocks of the tan lu fault zone and from louzidian and liaonan metamorphic core complexes in ne china the attempt is based on field investigations microstructural observations back scattered electron bse imaging electron microprobe analyses x ray diffraction scanning electron microscope sem results and 40ar 39ar step heating of k feldspar separated from brittle fault zones of cataclastic mylonite granite and gneiss sem and bse images of individual k feldspar crystals reveal distinct grain deformation features including grain scale faults fractures and microfractures that occur parallel or perpendicular to each other the 40ar 39ar dating results provide well defined plateau spectra for the cataclastic k feldspar grains in the tan lu fault zone 74 5 1 3 ma and of brecciated gneisses and mylonites that formed at depth in the louzidian and liaonan metamorphic core complexes 120 129 ma and 116 2 ma these data suggest complete resetting of the ar isotope system of the cataclastic k feldspars allowing to constrain the timing of their deformation

sediment geochemistry and base metal sulphide mineralisation in the quidong area southeastern new south wales australia geochemically anomalous pyritic sediments occur directly above a mid silurian unconformity in the quidong area of southeastern new south wales the composition of these sediments reflects derivation from a mixture of a feldspar and mica depleted detritus reworked from underlying quartz rich flysch b mg rich clay or chlorite precipitated from hydrothermal exhalations and c pyrite formed by reaction of iron in clays or oxides with reduced sulphur derived largely from sea water sulphate and possibly a magmatic source three types of base metal sulphide mineralisation occur at quidong including a weak syngenetic concentrations in the pyritic sediments b stratabound and fault controlled bodies of massive sulphides hosted by the pyritic sediments and containing higher grade pb zn and cu and c small vein and cavity fillings of galena barite and other minor sulphides in overlying limestones all types of mineralisation are related to hydrothermal activity which occurred during and after deposition of the pyritic facies the geochemistry of the immediately underlying basement rocks and pb isotope data indicate that the source of the metal bearing fluids was deeper in the crust and probably related to widespread partial melting and magmatic processes the sulphidic sediments and stratabound sulphide deposits represent syngenetic epigenetic sediment hosted mineralisation developed in a shallow marine environment distal from major volcanic centers this style of mineralisation has not previously been described from the region it has some similarities to the irish alpine type spectrum of deposits best known in europe

structurally controlled hydrothermal dolomite reservoir facies an overview structurally controlled hydrothermal dolomite htd reservoir facies and associated productive leached limestones are major hydrocarbon producers in north america and are receiving increased exploration attention globally they include multiple trends in the ordovician locally silurian and devonian of the michigan appalachian and other basins of eastern canada and the united states and in the devonian and mississippian of the western canada sedimentary basin they also occur in jurassic hosts along rifted atlantic margins in the jurassic cretaceous of the arabian gulf region and elsewhere hydrothermal dolomitization is defined as dolomitization occurring under burial conditions commonly at shallow depths by fluids typically very saline with temperature and pressure t and p higher than the ambient t and p of the host formation the latter commonly is limestone proof of a hydrothermal origin for htd reservoir facies requires integration of burial thermal history plots fluid inclusion temperature data and constraints on timing of emplacement hydrothermal dolomite reservoir facies are part of a spectrum of hydrothermal mineral deposits that include sedimentary exhalative lead zinc ore bodies and htd hosted mississippi valley type sulfide deposits all three hydrothermal deposits show a strong structural control by extensional and or strike slip wrench faults with fluid flow typically focused at transtensional and dilational structural sites and in the hanging wall transtensional sags above negative flower structures on wrench faults are favored drilling sites for htd reservoir facies saddle dolomite in both replacive and void filling modes is characteristic of htd facies for many reservoirs matrix replacive dolomite and saddle dolomite appear to have formed near contemporaneously and from the same fluid and temperature conditions the original host facies exerts a major influence on the lateral extent of dolomitization resultant textures pore type and pore volume breccias zebra fabrics shear microfractures and other rock characteristics record short term shear stress and pore fluid pressure transients particularly proximal to active faults high temperature hydrothermal pulses may alter kerogen in host limestones a process designated forced maturation basement highs underlying sandstone and or carbonate aquifers probably overpressured and overlying and internal shale seals and aquitards also may constrain or influence htd emplacement although many questions and uncertainties remain particularly in terms of mg and brine source and mass balance recognition and active exploration of the htd play continues to expand increasing use of three dimensional seismic imagery and seismic anomaly mapping combined with horizontal drilling oblique to linear trends defined by structural sags helps to reduce risk

sulphur isotopic investigation of lower carboniferous vein deposits of the british isles similar characteristics and age data suggest that the pb zn vein deposits hosted by lower palaeozoic and vendian strata of the british isles form a genetically related group coeval with the lower carboniferous carbonatehosted base metal deposits of ireland sulphur isotopic data demonstrate that there were separate sulphide and sulphate sulphur sources for the vein minerals 34s values from minerals in individual vein systems are consistent but there is a large variation between deposits revealing distinctive local sulphur sources the data suggests that sulphide sulphur total range of values of 34sh2s of 6 5 to 18 62 was derived from the underlying strata while the sulphate baryte sulphur source 34sbaryte mainly in the range 12 to 24 was groundwater or surface water that mixed with rising hydrothermal fluids in the upper reaches of the veins

1 66 ga old metamorphosed pbcu deposit in sargipali eastern india manifestations of tidal flat environment and sedex type genesis abstract the metasedimentary rocks and the unusual pb cu mineralization of the sargipali mine area are described and discussed to elucidate the processes involved in their deposition important lines of evidences used for the interpretation of an inter to supratidal flat environment are 1 a general pattern of a shallowing upward sequence from coarse clastics arenaceous through finer clastics argillaceous to carbonate 2 the occurrence of metaconglomerate trough cross bedding and wave ripples within the arenaceous lithostratigraphic unit 3 intercalations of quartzite carbonate skarn dolomite and convolution of chert laminae within the argillaceous lithostratigraphic unit and 4 intercalation of quartz mica chlorite schist laminae within the carbonate lithostratigraphic unit the ores seems to belong to the same environment furthermore in the assessment of the origin of the sargipali ores it is recognized that the orebodies not only represent a sedimentary setting but also show a high pb content and an older age of mineralization than that of deformation metamorphism and granite intrusion along with the lack of stockwork zones wall rock alteration subaerial volcanism and the presence of chert and tourmalinite these features are consistent with a sedex type origin the idea of this origin finds support by yet another observation i e the ore sulphur was mainly derived from the inorganic reduction of the seawater sulphate at more than 300 c while the ore metals were leached from the 238u 204pb enriched singhbhum soda granite of 2200 ma the present study may help in conceiving a new possibility that the sediment hosted pb rich deposits of mvt origin can also be evaluated in terms of the sedex model

variations of noble gas abundances and isotope ratios in a single morb pillow to evaluate variations of noble gas signatures within a single morb pillow caused at its extrusion all noble gas abundances and isotope ratios from he to xe were analyzed in different portions of a pillow basalt from the glassy rim to the interior by slicing off at every 2 5mm in thickness 1 to 7 40ar 36ar and he contents are high in glassy parts and rapidly decrease toward the inner crystallized parts although he 4he is almost uniform among glassy parts 1 to 3 the outermost part 1 has a lower 40ar 36ar than the inner glassy parts 2 and 3 this indicates incorporation of low 40ar 36ar component into the glassy rim from the surrounding materials at its solidification abundances of heavier noble gases especially xe greatly increase toward crystallized parts it could not be explained by incorporation of surrounding noble gases dissolved in the seawater and requires some other component such as fractionated product during crystallization by solid melt partition or derived from fine sediments in order to obtain magmatic signature outermost glassy part should be eliminated as well as crystalline parts

holocene tephrostratigraphic framework and monsoon evolution of east asia key tephra beds for synchronising palaeoclimate records abstract in east asia our understanding of holocene climate change forcing mechanisms and propagation require the precise chronological control of palaeoclimate records to allow robust integration of data sets the existing chronologies predominantly based on 14c method however are not sufficient to constrain key questions about abrupt climate shifts that occur within a century in the transitions between states widely dispersed tephra layers allow precise dating and synchronisation of sedimentary archives providing a chronological framework for integrating records especially where the visible tephra record is complemented by the addition of cryptotephra non visible ash despite significant tephra studies in this region however a comprehensive holocene tephra framework is not available to address this issue we carry out a thorough review on holocene tephra investigations undertaken in japan using widespread tephra beds we present an integrated tephra framework and suggest the way forward for establishing this as a wider approach for east asia the framework is based on twenty two ash layers that are mainly from japan and to a lesser extent china n korea s korea and russia each tephra is assessed in terms of chronology geochemistry and distribution the framework is compared with high resolution palaeoclimate records from east asia using this we demonstrate regional variations in monsoon evolution and more importantly the potential of tephra isochrons in constraining such variations given the scarce identification of tephra layers in those well resolved palaeoclimate records we advocate a more systematic employment of the cryptotephra method which would potentially lead to a significant advance in east asian tephrochronology and the correlation of palaeoclimate archives in the region

contribution to the genesis of the sedex type mineralizations of the rhenish massif germany implications for future pb zn exploration the meggen orebody and the number of subeconomic sediment hosted mineralizations at plettenberg affeln oberhundem and gunterod eastern rhenish massif are considered to be typical members of the large sedex family i e submarine hydrothermal zn pb orebodies examples such as howards pass canada mcarthur river and broken hill australia and navan ireland formed between the middle proterozoic and carboniferous as a consequence of slow continental extension long term elevated heat flow and basin dewatering enhanced and focused along deeply penetrating synsedimentary fault zones volcanic activity bound to these fractures has no direct genetic relationship to sedex mineralization based on structural and detailed stratigraphic correlation and facies analysis it can be shown that all sedex type mineralizations of the rhenish massif are bound to one and the same synsedimentary fault zone named here the balve oberscheld fault zone which was reactivated during variscan compressional and extensional movements the trend of this tectonic lineament termed menden oberscheld lineament can be even recognized on maps depicting crustal gravity patterns and the configuration of the moho illite crystallinity measurements in devonian shales along profiles crosscutting the lineament evidence increased variscan to early post variscan metamorphism in the fault system which already had promoted the synsedimentary heat flow indications were found that the metalliferous brines escaping into the meggen basin were bound to a synsedimentary fault situated at the western margin of the meggen basin the widespread zn pb ba mineralizations and anomalies in the middle to upper givetian shales in the plettenberg affeln area are likewise bound to horst and graben tectonism along the balve oberscheld fault zone based on data from economic and scientific research in the rhenish massif the application of paleostructural methods for future basemetal exploration is discussed

holocene environmental changes and paleo tsunami history in onuma on the southern part of the sanriku coast northeast japan abstract after the 2011 tohoku oki earthquake that occurred off the pacific coast significant problems arose concerning the pacific coastal area sanriku coast such as the lack of the historical and paleo tsunami records and the paradox between long term and short term vertical crustal movements the data necessary to solve the issues are also essential for understanding the mechanisms of tsunami generation and earthquakes and assessing the risk of large low frequency disasters thus we conducted excavation and coring surveys and reconstructed the paleoenvironment at onuma on the southern sanriku coast based on sedimentary facies age data radiocarbon dating and tephra fossils diatoms and mollusks and topography first we discussed the preservation potential of tsunami deposits considering the geomorphologic and geologic evolution of the study area subsequently we identified tsunami deposits and estimated their occurrence ages and inundation height we discovered six tsunami beds deposited during ca 5 1 ka when the preservation potential of tsunami deposits was high in the study site we divided them into two types of deposits sand and gravel these deposits reflect different sources and flow processes of paleo tsunamis therefore we estimated the heights of the paleo tsunamis that is 5 10 m for sand tsunami deposits s1 s3 deposits and 10 m for gravel tsunami deposits g1 g3 deposits the tsunami deposits were dated at 690 1040 bp s1 2240 3310 bp g1 3320 3630 bp g2 3620 4060 bp g3 4030 4400 bp s2 and 4440 5570 bp s3 this approach and the setting of the study site enabled us to evaluate not only the ages of paleo tsunami deposits but also the paleo tsunami heights moreover we estimated the paleo sea level between 8 and 7 ka based on the sedimentary facies and paleoenvironment deduced from the fossil shells and calculated the vertical crustal movement during the holocene at 0 4 to 1 0 mm yr by comparing with the theoretical relative sea level curve this information is significant for reconstructing the tectonic evolution along the subduction zone and for paleogeography to estimate the paleo tsunami magnitudes

the effect of sub seismic fault slip processes on the isotopic signature of clay minerals implications for k ar dating of fault zones abstract clay minerals are abundant in fault gouges and isotope dating of the radiogenic noble gases that they contain may be used to constrain timing of fault initiation reactivation and to estimate recurrence intervals of earthquakes the potential influence of fault slip and ambient temperature on the isotope signature of authigenic clay minerals however remains unknown this study reports measurements of the k ar isotope signature of samples that have been sheared experimentally at sub seismic slip rates within a range of ambient temperatures as well as of samples undergoing standardised clay heating degas experiments in the investigation and comparison of the influence of sub seismic frictional slip and external heating on clay gouge the age data confirm that the sub seismic frictional slip of clay gouge affects the clay microstructures and releases radiogenic 40ar the experimental data indicate that radiogenic 40ar release due to external heating can be disregarded until 350 c which is supported by ar diffusion modelling frictional slip at sub seismic slip rates and at room temperature results in a significant radiogenic 40ar loss of 56 and the remaining clay will inherit 44 of radiogenic 40ar sub seismic frictional slip experiments at imposed elevated temperatures from 150 to 450 c increase the amount of radiogenic 40ar loss and decrease the amount of inherited radiogenic 40ar at a relatively high temperature of 450 c about 16 of radiogenic 40ar will be present in the remaining sample portion reinforcing the importance of rigorous clay grain size separation processes required prior to fault gouge dating

the geochemical signature caused by earthquake propagation in carbonate hosted faults friction laboratory experiments have been performed at sub seismic 0 01 m s to seismic slip rates 1 m s on dolomite gouges of the triassic evaporites which hosted the five mainshocks 5 mw 6 of the 1997 colfiorito earthquakes in the northern apennines italy experimental faults are lubricated as marked falls of the steady state sliding friction coefficients ss 0 2 are observed at seismic slip rates as opposed to values of ss 0 6 attained for sub seismic slip rates at seismic slip rates decarbonation reactions triggered by frictional heating in the experimental slip zone produced 1 new fluid co2 and mineral phases e g mg calcite periclase brucite lime portlandite 2 isotopic fractionation between the reaction products and the reactant mineral phases the variations of total dissolved inorganic carbon tidc in concentration tdic and isotopic composition 13ctidc in a carbonate aquifer with geochemical parameters similar to those of an aquifer located in the seismic belt of the northern apennines have been modelled after an input of earthquake produced co2 modelling results show that variation in 13ctidc can be detected in volumes of groundwater which are about three times larger than those calculated for the variations in tdic for amounts of co2 produced by coseismic decarbonation of 5 wt of the slip zone gouge modelling results show that a detectable geochemical anomaly is obtained if the produced co2 is dissolved into volumes of water comparable to those of the shallower aquifers feeding the springs in the 1997 colfiorito earthquakes area we conclude that the integration of results from laboratory experiments performed at seismic condition and geochemical analyses can potentially aid in the calibration of monitoring strategies of geochemical properties of water in seismically active areas and provide insights into seismic fault zone processes e g constraints on the temperature rise during earthquake propagation

iron ore deposits associated with hormuz evaporitic series in hormuz and pohl salt diapirs hormuzgan province southern iran abstract three types of iron ore including banded ore hydrothermal metasomatic ore and earthy hematite ochre occur in hormuz and pohl salt diapirs primary banded ores of upper neoproterozoic age contain alternating iron rich and silica rich bands which characterized by the presence of folded hematite rich bands and glacial diamictite fragments of quartz dropstone and other clastics hematite as specularite and oligist is the major mineral in the iron rich bands with minor goethite pyrite magnetite and rare siderite textural relationships between the ore and gangue minerals indicate that these ores are rapitan type sedimentary banded iron deposits this is supported by the geochemical data of iron ores such as low concentration of al2o3 tio2 ba v cr co ni cu and other trace elements plus high value of mno fe v and fe ti ratios and ree patterns subsequent to the formation of iron ore deposits an immense thickness of evaporitic rocks was formed in the oceanic marginal basins negative 13c and 18o values of the cap carbonates and strong positive 34s values of the underlying sulfates are similar to the isotopic patterns of ediacaran rapitan type iron deposits due to salt diapirism in the upper mesozoic and cenozoic eras secondary iron deposits were formed by the activation of hot hydrothermal fluids during salt rising high contents of some indicative elements such as sr zr u th pb zn sn w and mo in the metasomatic iron ores showed that they are the products of iron ore remobilization redeposition in a hydrothermal system the nearness of these ores to the fault zones is consistent with the scheme of migration and redeposition of iron compounds as metasomatic deposits under oxidizing conditions finally earthy ochre was formed following the weathering and erosion of pre existent iron ores

40ar 39ar geochronometry of pseudotachylytes by vacuum encapsulation north cascade mountains washington usa to determine a reliable means of dating pseudotachylytes we obtained total gas ages plateau ages and argon retention ages on samples from the north cascade mountains washington quartz ampoule vacuum encapsulation analysis of small grains a few milligrams from six samples allowed evaluation of 39 ar loss through recoil during irradiation and laser ablation on four samples allowed textural control in microlitic samples recoil loss 39 ar ranges from 0 2 to 8 4 the total gas ages incorporating this 39 ar are inconsistent but retention ages are much more internally consistent and within analytical error they match or nearly match plateau ages from most of the microlitic samples at 54 55 ma samples analyzed by laser ablation suggest one episode of faulting and pseudotachylyte formation at 55 59 ma and an earlier episode at ca 80 ma the partly glassy pseudotachylyte yielded laser ablation total gas and retention ages of ca 65 ma the microlitic pseudotachylytes indicate formation close to 55 ma with possible older faulting and pseudotachylyte formation at ca 81 84 ma the good consistency among the retention ages the laser ages with highest precision and especially the plateau dates combined with the ages falling within the anticipated time span provides confidence in the geologic reality of the ages nevertheless it is clear that large clasts and crystal fragments within these particular veins did not completely degas or may have an anomalous inherited radiogenic 40 ar component

an argument against the crush origin of pseudotachylytes based on the analysis of clast size distribution abstract the origin of pseudotachylytes has been controversial since wenk cast doubt on the melt origin of the matrix of pseudotachylytes in 1978 the matrix of this rock is so fine grained that the crush origin of pseudotachylytes revived by wenk cannot easily be denied this paper presents a new line of argument based on the size analysis of clasts contained in pseudotachylytes in felsic granulite from the musgrave range central australia these clasts are definitely crush products produced during the pseudotachylyte generation their sizes as measured on photomicrographs of thin sections obey the size distribution n n r d where n is the cumulative number of clasts with sizes greater than r d is the fractal dimension and n is a constant that depends on the number of measurements d was found to be 1 5 0 05 for the size ranges of 10 2000 m if the matrix of the pseudotachylytes consists mostly of ultrafine crush products they must have formed simultaneously with those coarse crush products the proportion of fine products relative to the coarse clasts can be estimated assuming that a similar size distribution also holds for the fine products the estimated area occupied by fine products in a thin section is of the order of only several percent whereas the measured area of the matix is about 60 thus the major part of the matrix of the pseudotachylytes cannot be regarded as crush products it is also shown that the number of clasts smaller than about 5 m becomes very small perhaps as a result of nearly complete dissolution of fine clasts in a melt however if the ultrafine grained matrix of the pseudotachylytes had formed by crushing during seismogenic fault motion the grain size refinement during the crushing should have occurred jumping the size range of at least 1 5 m this is quite unreasonable and disproves the crush origin for the matrix of pseudotachylytes

high velocity frictional properties of gabbro high velocity friction experiments have been performed on a pair of hollow cylindrical specimens of gabbro initially at room temperature at slip rates from 7 5 mm s to 1 8 m s with total circumferential displacements of 125 to 174 m and at normal stresses to 5 mpa using a rotary shear high speed friction testing machine steady state friction increases slightly with increasing slip rate at slip rates to about 100 mm s velocity strengthening and it decreases markedly with increasing slip rate at higher velocities velocity weakening steady state friction in the velocity weakening regime is lower for the non melting case than the frictional melting case due perhaps to severe thermal fracturing a very large peak friction is always recognized upon the initiation of visible frictional melting presumably owing to the welding of fault surfaces upon the solidification of melt patches frictional properties thus change dramatically with increasing displacement at high velocities and such a non linear effect must be incorporated into the analysis of earthquake initiation processes

the generation at hot springs of sedimentary ore deposits microbialites and life abstract notwithstanding the current fashion which favours an epigenetic origin for what used to be termed sedex deposits there are several lines of evidence to indicate that phanerozoic base metal orebodies of this type have at least some exhalative aspects the fossil polychaete worms which occur in lower carboniferous pyrite mounds at tynagh and silvermines in ireland have affinities to paralvinella an organism that lives attached to hydrothermal chimneys at the juan de fuca hot spring site in the northeast pacific in addition fossil tube worms and their moulds occur both in silica masses underlying the carboniferous giant red dog sulphide orebody in alaska and in devonian barite and base metal deposits in north america and in russia respectively the development of sulphide and carbonate fossil microbialites over exhalative centres further supports generation of some mineral deposits on sea or lake floors carbonate microbialite mounds are also developing today over warm springs and seepages the existence of an environment in which sulphide mineralisation developed at the sea floor has implications also in a different sphere life itself may have emerged in a similar milieu at 4 2 ga from iron monosulphide bubbles a primitive metabolism could have been driven by the high long lived and constant redox potential of 300 mv made available across an iron monosulphide membrane which would have been spontaneously generated where sulphide bearing submarine alkaline springs issued into the acidic iron bearing hadean ocean the alkaline spring provided bisulphide to the iron rich carbonic acid ocean for the precipitation of iron monosulphide bubbles probotryoids as well as acetate shock 1992 the feeder to the biochemical krebs cycle driven in reverse by the high partial pressure of co2 in addition to its scientific significance an understanding of these beginnings may well benefit research into many aspects of economic geology even more extreme redox contrasts are revealed by the presence of sedimentary jasper or iron formation in three of the major carboniferous sulphide orebodies in ireland pyritic sulphide microbialites also grew over some of the associated fossil hot spring sites and may be recognised by their bacteriogenic 34s values 20 to 40 recognition of such fossil hot spring sites could lead to further discoveries of sedex deposits

three important holocene tephras off the pacific coast of the tohoku region northeast japan implications for correlating onshore and offshore event deposits abstract tephra is a product of explosive volcanic eruptions and is deposited and preserved in both terrestrial and marine environments because a tephra is a geologically synchronous deposit tephras constitute important isochrones in the quaternary sequences in and around japan and can be used to correlate onshore and offshore events tephras are considered to be robust time markers connecting the two environments for this comparison it is important to establish a marine tephra catalog we examined a total of 52 marine cores collected from offshore fukushima to south of cape erimo misaki hokkaido to identify the holocene tephras in this region as a result 11 tephras were identified and correlated with known late quaternary tephras among them three holocene tephras are widespread in this region the to a 915 ce and to cu 6 ka tephras from towada caldera north tohoku and the hr fp 6th century tephra from haruna volcano north kanto the to a tephra is distributed in the southern part of the study area the hr fp tephra has a very narrow distribution and is only found offshore of the central sanriku coast the to cu tephra on the other hand shows a wider distribution covering most of the study area these tephras provide important and robust isochrones for correlating offshore and onshore events along the deep japan trench

size distribution of clasts in experimentally produced pseudotachylytes abstract high velocity frictional experiments on monzodiorite at sliding rates of 1 3 m s and at normal stresses of 2 mpa produced dark 100 m thick pseudotachylyte layers on the sliding surfaces the experimentally produced pseudotachylyte contains clasts of various sizes in an ultrafine matrix similar to the texture observed for natural pseudotachylytes the size distribution of clasts in the experimental pseudotachylyte obeys a power law of the form n n 1 r r d where n is the cumulative number of clasts with a size greater than r r and d are material constants and n is a constant that depends on the total number of measurements the total area of ultrafine grained clasts in a thin section estimated from the size distribution is less than 0 5 whereas the actual area of ultrafine matrix is measured as 60 70 of the total product this suggests that the matrix cannot be regarded as a product of only comminution processes consistent with natural pseudotachylytes and that the ratio of actual area of the ultrafine grained matrix to the hole product represents almost the ratio of the melt glass this estimate is consistent with the ratio of glass determined from an x ray diffraction analysis

alternative sources of metals for stratiform copper deposits abstract the controversy between sedimentary and epigenetic emplacement of copper in stratiform copper deposits appears to be subsiding in favour of an essentially synsedimentary enrichment of sulphur e g disseminated pyrite and or sulphates which undergo biogenic reduction to sulphide followed by an early diagenetic addition of copper to the host sediment the source of the copper has yet to be conclusively identified since the copper is deposited upon migrating into reducing zones e g sulphide rich organic bearing black shales and sulphate bearing microbial laminated carbonates the closest source of copper could be the commonly adjacent red beds where oxidising conditions would favour solution of copper in the presence of interstitial brines the thickness of these red bed sections is typically measured in 100 s to 1000 s of metres and they commonly contain abundant immature detrital grains including mafic minerals which could provide sufficient trace element copper to form major ore deposits copper in red beds may also include metal initially absorbed on amorphous iron oxides and released during diagenetic reddening of these oxides to form haematite on the other hand the ubiquitous red beds might be discounted as a principal source of copper and could be considered for the most part to have behaved as permeable beds through which cupriferous solutions from other sources migrated toward the grey beds for example mafic volcanics are found in important quantities in stratigraphic sequences hosting several stratiform copper deposits and could contribute large volumes of metalliferous solutions during metamorphic dehydration alternatively these same volcanic rocks may suggest volcanic associated pene exhalative activity with hydrothermal fluids emptying into subsurface red bed aquifers rather than onto surface sediments as commonly proposed for exhalative models although fluids of 250 c are generally considered necessary to transport copper in significant quantities in sulphide bearing exhalations lower temperatures are sufficient for chloride complexing in the absence of sulphide the large volumes of red beds could also have a major cooling effect on initially hot solutions the pene exhalative model may be closely related to fault bounded hot spring models of the type envisaged for so called shale hosted submarine exhalative base metal deposits

pb isotope evidence on the origin of the west shropsh orefield england pb isotope data on ore galenas from the west shropshire orefield show a significant spread of 20 pb 204 pb values with minor variation in 207pb 204 pb and 208pb 204 pb ratios these indicate that lead was derived from multiple sources some of them uranium enriched and incompletely mixed prior to ore deposition four possible mineralizing agents are considered circulating sea water metamorphic waters basinal brines and convecting formation waters pb isotope data exclude a circulating sea water origin for the mineralization and best support a convecting formation water mineralizing agent a model involving a single fluid tapping multiple lead sources is proposed to explain the observed pb isotope variation

a complete terrestrial radiocarbon record for 11 2 to 52 8 kyr b p radiocarbon 14c provides a way to date material that contains carbon with an age up to 50 000 years and is also an important tracer of the global carbon cycle however the lack of a comprehensive record reflecting atmospheric 14c prior to 12 5 thousand years before the present kyr b p has limited the application of radiocarbon dating of samples from the last glacial period here we report 14c results from lake suigetsu japan 35 35 n 135 53 e which provide a comprehensive record of terrestrial radiocarbon to the present limit of the 14c method the time scale we present in this work allows direct comparison of lake suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels

ferrimagnetic resonance signal produced by frictional heating a new indicator of paleoseismicity 1 high speed fault slips during earthquakes may generate sufficient frictional heat to produce fused fault rocks such as pseudotachylyte we have carried out high speed slip tests using natural fault gouge to judge whether or not frictional heating universally occurs during seismic fault slips in our shearing tests natural fault gouge is put between two cylindrical silica glasses and sheared under a fixed axial stress of 0 61 mpa despite such a low stress near the earth s surface a darkened cohesive material resembling pseudotachylyte is made from the fault gouge along the edge of a circular shear plane when shearing at a high speed of 1500 rpm the maximum slip rate reaches 1 96 m s at the edge electron spin resonance measurements reveal that the darkened cohesive material has a strong ferrimagnetic resonance fmr signal which is derived from bulky trivalent iron ions in ferrimagnetic iron oxides fe2o3 the fmr signal is produced by the thermal dehydration of antiferromagnetic iron oxides feooh in the fault gouge this may be applicable to the detection of past heating during seismic fault slip we thus attempt to reconstruct the temperature of frictional heat generated on the nojima fault plane in the 1995 kobe earthquake m 7 3 by inversion using the fmr signal the computer simulation indicates that the frictional heat generated on the nojima fault plane at 390 m depth may have attained 390 c during the 1995 kobe earthquake the temperature in the fault plane may have returned to its initial state after 1 year this result suggests that a heat flow anomaly generated by faulting may be difficult to detect

hydrothermal pyrite chimneys from the ballynoe baryte deposit silvermines county tipperary ireland we report the discovery of pyrite tubes 0 1 to 20mm in diameter in the ballynoe sedimentary baryte deposit well developed tubes comprise concentric layers of pyrite of contrasting crystal sizes 0 05 to 1 mm thick an outer rim of crystalline baryte 10mm thick commonly coats the tubes where these are not touching the central canals contain myriad pyrite framboids these tubes have characteristics in common with the chimney spires found on the east pacific rise at 21 n from which metal bearing solutions issue at temperatures of up to 380 30 c their presence carries the implication that the baryte deposit was not a distal facies of the silvermines sedimentary pyritic zinc and lead ore but was produced from local hydrothermal exhalations though in a shallower part of the basin than the coeval sulphide deposits which had their own feeders some epigenetic mineralization may be awaiting discovery beneath the feeder sites at ballynoe

kar age determination of late quaternary volcanic rocks using the mass fractionation correction procedure application to the younger ontake volcano central japan abstract we propose an age derivation procedure for the k ar dating method to be applied to late quaternary volcanic rocks of low to medium k 2 o content whose k ar ages calculated by the conventional derivation procedure provide insufficient age information in this procedure which we call the mass fractionation correction procedure mfcp the initial 40 ar 36 ar ratios of the samples are estimated from the stable 38 ar 36 ar ratios determined by the unspiked technique assuming that the initial argon isotope ratios of all the samples should lie on a theoretical mass fractionation line of argon in the atmosphere to examine the usefulness of the mfcp systematic k ar age determinations using this procedure were made on volcanic rocks from the stratigraphically well known younger ontake volcano in central japan which has erupted repeatedly over the past 100 ka the k ar ages determined for these volcanics by this procedure generally have analytical uncertainties within 25 1 level and are consistent with the volcanostratigraphy exceptions were the large phenocrysts in pumice fall deposits these may contain significant amounts of excess 40 ar and we considered them to be unsuitable for accurate k ar age determinations of young volcanic rocks in the cases of lava flows which underlie a widespread fallout tephra the k ar ages determined by the mfcp were consistent with the 14 c age of the tephra 21 22 ka

central irish geology metallogeny a lower carboniferous rifting related exhalative catastrophy the geological background and development of a recently presented irish carboniferous metallogenic model is outlined a new exhalative based interpretation of existing central irish tectonic stratigraphic sedimentological and sulphur isotopic data is shown to be consistent with the model which suggests that stratiform sulphide metallogeny and the central irish waulsortian mudbank complex may be the manifestation of a rifting related exhalative catastrophy in this view sulphur isotope age curves of the whole world ocean may indicate that phases of globally synchronous in the relative sense rifting may have been a feature of the phanerozoic record

sulphur isotopic investigation of vein lead zinc mineralization at tyndrum scotland the tyndrum pb zn veins hosted by late proterozoic quartzites were probably generated in the tournaisian 360 ma by determination of sulphur isotopic ratios of vein minerals three aspects of the tyndrum mineralization were addressed i sulphate sulphur sources ii reduced sulphur source iii isotopic equilibrium in the vein system including geothermometry twelve galenas have 34s values ranging from 3 55 to 6 38 this excludes one value of 11 21 from a large but nearly barren quartz vein other sulphides are enriched or depleted in 34s in the sense expected for isotopic equilibrium although there is no evidence for isotopic equilibrium between the vein minerals the sulphide sulphur source was probably in the dalradian metasediments where disseminated pyrite averages 6 baryte had 34s values averaging 14 and was therefore not in isotopic equilibrium with sulphides a continental groundwater source is most likely

formation of fossil hydrothermal chimneys and mounds from silvermines ireland sulphur isotope analyses reveal that the fossil hydrothermal pyrite mound and tubes at silvermines were produced by the reaction of hydrothermal fe ii with bacteriogenically reduced sulphur species 34s range 18 4 to 42 5 this took place in a brine pool dominated by hyper saline carboniferous seawater this is in contrast to their modern but considerably larger morphological counterparts forming by direct precipitation of hydrothermal sulphides on the east pacific rise at 21 n

the middle valley sulfide deposits northern juan de fuca ridge radiogenic isotope systematics the bent hill and the ore drilling program massive sulfide deposits in middle valley the sediment filled rift valley at the northern juan de fuca ridge are among the largest and richest sulfide deposits on the modern sea floor drilling during ocean drilling program leg 169 allowed a complete hydrothermal system to be sampled for the first time representative samples from this leg were analyzed for radiogenic isotopes sr nd and pb with the objectives of determining the sources of metals in the deposits and the nature of fluid circulation and evolution of the hydrothermal systems samples were chosen both from the sulfide deposits and host units the latter including sediments basaltic flows and sills sr nd and pb isotope compositions of the basalts and sills below the bent hill massive sulfide deposit confirm that both were highly altered by hydrothermal solutions the data also show that the sills are cogenetic petrologically with the underlying basaltic basement pb isotope compositions of the massive sulfides in both sulfide deposits vary within narrow ranges i e 206 pb 204 pb ranges of 18 83 18 89 and 18 77 18 89 for bent hill and ore drilling program respectively which could reflect remobilization replacement and recrystallization of sulfides during formation of the sulfide mounds but also mixing and homogenization during hydrothermal circulation of fluids below the sea floor data for the massive sulfides form elongate clusters between the basalts and the sediment clusters in pb isotope diagrams the most simple explanation for these patterns involves the mixing of pb from a basaltic source 206 pb 204 pb range of 18 64 18 74 with pb from isotopically heterogeneous sediments comprising a hemipelagic component with relatively higher 207 pb 204 pb and 208 pb 204 pb values and a clastic component turbidite with relatively higher 206 pb 204 pb values a third potential source is represented by hydrothermal sulfides present in both the sediments and basalts that have relatively unradiogenic pb isotope ratios 206 pb 204 pb range of 17 83 18 36 implying an old crustal source possibly older than 1 5 ga the overlapping pb isotope compositions of the massive sulfides in the two deposits suggest that the same sources were involved and in similar proportions to form the deposits ore drilling program massive sulfide is extremely enriched in zn compared to bent hill massive sulfide if the metal sources are the same for the two deposits other parameters must have produced the differences between them such as different fluid chemistry temperature or factors at the depositional site pb isotope data for sulfides of the bent hill massive sulfide feeder zone and the stratiform deep copper zone 206 pb 204 pb range of 18 59 18 82 are both much less radiogenic than the massive sulfides and overlap with the field for the underlying basalts the pb isotope ratios a high cu zn ratio and intense alteration of the basalts strongly suggest that the basalts were the main source for the metals in the deep copper zone and related feeder zones rather than a higher sediment influence in the overlying massive sulfides this conclusion is also supported by positive correlations between the pb isotope value and zn cu ratio contents of pb and mo a silicified zone immediately above the deep copper zone may have played a major role in the formation of the deposits by serving as an efficient seal preventing the deep seated fluids to escape to the sea floor as observed even today when the seal formed the fluids were forced to circulate in the lower part of the sedimentary sequence and in the basalts the seal would have insulated this hydrothermal system leading to higher temperatures in the fluids and subsequently to more efficient leaching of metals this model offers an explanation for differences in the pb isotope compositions of the massive sulfides and the underlying deep copper zone and feeder zones

melt origin of fault generated pseudotachylytes demonstrated by textures a petrographic and electron microprobe study of fault generated pseudotachylytes from the outer hebrides thrust zone scotland demonstrates that the textures have resulted from the primary crystallization of a clast laden melt rather than the devitrification of a glass or by crushing and cataclasis the observations are consistent with these pseudotachylytes having formed by frictional fusion followed by rapid quenching implying faulting at shallow crustal depths

documenting large earthquakes similar to the 2011 tohoku oki earthquake from sediments deposited in the japan trench over the past 1500 years abstract the 2011 tohoku oki earthquake and tsunami was the most destructive geohazard in japanese history however little is known of the past recurrence of large earthquakes along the japan trench deep sea turbidites are potential candidates for understanding the history of such earthquakes core samples were collected from three thick turbidite units on the japan trench floor near the epicenter of the 2011 event the uppermost unit unit tt1 consists of amalgamated diatomaceous mud 30 60 cm thick that deposited from turbidity currents triggered by shallow subsurface instability on the lower trench slope associated with strong ground motion during the 2011 tohoku oki earthquake older thick turbidite units units tt2 and tt3 also consist of several amalgamated subunits that contain thick sand layers in their lower parts sedimentological characteristics and tectonic and bathymetric settings of the japan trench floor indicate that these turbidites also originated from two older large earthquakes of potentially similar to the 2011 tohoku oki earthquake a thin tephra layer between units tt2 and tt3 constrains the age of these earthquakes geochemical analysis of volcanic glass shards within the tephra layer indicates that it is correlative to the towada a tephra ad 915 from the towada volcano in northeastern japan the stratigraphy of the japan trench turbidites resembles that of onshore tsunami deposits on the sendai and ishinomaki plains indicating that the cored uppermost succession of the japan trench comprises a 1500 yr old record that includes the sedimentary fingerprint of the historical jogan earthquake of ad 869

generation and crystallization of an amphibolite shear melt an investigation using radial friction welding apparatus a cylinder of amphibolite comprising the assemblage amphibole clinozoisite albite has been frictionally melted using radial friction welding apparatus this was achieved by rotating a steel ring at 750 rpm and a force of 98 kn for 10 s against a stationary steel casing which housed the rock sample the ring penetrated the casing then proceeded to rotate and compress the sample to 95 of its original volume until it cracked at right angles to its length this generated a whole rock silicate melt which injected the crack and on cooling produced glass crystallites and vesicles melting occurred in two stages an initial low pressure melting event with crystallization to augite fe rich anorthite followed by a high pressure melting event with crystallization to fassaitic clinopyroxene it is estimated that pressures of 0 5 gpa rising to 1 gpa were realized at the ring rock interface under these conditions fassaite superseded augite anorthite crystallization due to the increased solubility of ca tschermak s component in clinopyroxene the high pressure event provides a crude analogue for the frictional melting of basic rock at depths of 15 30 km in a seismogenic fault a situation realized along the slip zone between cold descending lithosphere and overlying mantle during subduction

experimental investigations on dating the last earthquake event using osl signals of quartz from fault gouges abstract obtaining a reliable age of the latest seismic slip event along an active fault is important for seismic hazard assessment here we observe changes in the optically stimulated luminescence osl signal of quartz crystals due to frictional heating in artificial fault gouges comprising a mixture of quartz grains and ca bentonite powder the fault gouge was deformed using a high velocity rotary shear apparatus at room temperature and room humidity at a seismic slip rate of 1 31 m s 1 intense slip localization occurred along a very thin layer 300 m thick within the simulated fault zones 1 mm thick the estimated temperature of the slip localized layer sll increased by 475 c from frictional heating the quartz osl signals of the gouges were fully reset most noticeably for the sll in contrast there was rare slip localization at subseismic slip rates 0 06 0 001 m s 1 for which the estimated temperature rise in the sll was 120 c hence the quartz osl signal was not reset under this condition the results suggest that quartz osl dating can be used to constrain the age of the latest seismic event in natural quartz bearing fault zones where a sll occurs

a fossil hydrothermal worm assemblage from the tynagh lead zinc deposit in ireland fossil hydrothermal chimneys were first discovered at silvermines1 ireland subsequent discoveries of fossils associated with mounds and chimneys in sulphide deposits within the ophiolite complexes of cyprus2 and oman3 prove that life forms similar to those colonising active vents on the east pacific rise4 7 were extant 100 myr ago around ridge crest hot springs here i report the discovery of 350 myr old worm like fossils recovered from pyrite chimneys associated with sedimentary exhalative mineralization at tynagh ireland this find suggests that even older examples of life existing at seafloor hot springs may be awaiting discovery

microlite morphology and chemistry in pseudotachylite from the fuyun fault zone china microlites in pseudotachylite veins from the fuyun fault zone northwest china can be divided into four morphological groups simple skeletal dendritic and spherulitic from the margin to the center of microcrystalline and microlitic pseudotachylite veins the size of single crystals or crystal fibers becomes progressively larger from a few m to as much as 15 m the morphologies of microlites vary from simple shapes such as acicular and globular forms to more complex forms such as skeletal dendritic and coarse spherulitic forms in glassy pseudotachylites only simple and fine spherulitic microlites generally smaller than 5 6 m occur these microlites have a varied mineralogy but are mainly made up of plagioclase an20 70 and alkali feldspar including sanidine and anorthoclase as well as clinopyroxene grossular garnet biotite hornblende and some magnetic minerals the biotite and hornblende microlites have a variable ti content generally higher than that of biotite and hornblende frag