source scaling relationship for m 4 6 8 9 earthquakes specifically for earthquakes in the collision zone of taiwan we investigated the source scaling of earthquakes mw 4 6 8 9 mostly from the taiwan orogenic belt and made a global compilation of source parameters to examine the scaling self similarity finite fault slip models 12 dip slip and 7 strike slip using mainly dense strong motion data and teleseismic data from taiwan were utilized seven additional earthquakes m 7 were included for further ex amination of scaling of large events we determined the effective length and width for the scaling study was m0 l 2 and m0 l 3 for the events less than and larger than the seismic moment of 10 20 nm respectively regardless of the fault types suggesting a nonself similar scaling for small to moderate events and a self similar scaling for large events although the events showed variation in stress drops with the exception of three events with high stress drops most of the events had stress drops of 10 100 bars the observed bilinear relation is well explained by the derived magnitude area equation of shaw 2009 when we considered only events with stress drops of 10 100 bars and a seismogenic thickness of 35 km the bilinear feature of the regressed magnitude area scaling holds for ruptured areas up to about 1000 km 2 for our seismogenic thickness of 35 km for the events having rupture areas larger than that the average slip becomes proportional to the rupture length the distinct high stress drop events from blind faults in the western foothill of taiwan yield local high peak ground accelerations pgas when compared to the next generation attenuation model regardless of the relative small magnitudes of these events the high pgas give the region higher seismic hazard potential and thus require special attention for seismic hazard mitigation

evidence of early generation of liquid hydrocarbon from suberinite as visible under the microscope the early generation of liquid hydrocarbons from suberinite can be clearly observed under the microscope the generation of this oil like material mainly in the form of exsudatinite from the maceral suberinite occurs at a maturity level of about 0 4 vitrinite reflectance hydrocarbons appear to be naturally expelled from coal initially through sweating and agglomeration of suberinite which subsequently forms exsudatinite it is suggested that extensive expulsion of exsudatinite causes cracks to develop in vitrinite whereas limited expulsion of exsudatinite will only impregnate the vitrinite matrix if cracks are formed it is possible they could progressively develop to form an exsudatinite crack network the formation of such a network is believed to represent an effective way of hydrocarbon expulsion from coal source rocks

genesis of the mandongshan gold deposit xinjiang nw china t p ƒs2 and phase equilibria constraints from the au as fe s system abstract the mandongshan gold deposit located in the west junggar xinjiang china is hosted in early carboniferous basalt and tuff ore bodies mainly consist of gold bearing hydrothermal veins mineralized basalt and tuff with disseminated sulfides hydrothermal process could be identified based on ore petrographic studies quartz albite sulfide native gold stage i arsenopyrite calcite native gold ii and pyrite calcite iii microthermometric and laser raman spectroscopic analysis of fluid inclusions in quartz demonstrate the ore forming fluid at stage i was moderate temperature 360 398 c low salinity 0 5 5 1 wt nacl equiv and h 2 o ch 4 dominant which evolved to low salinity 0 2 1 2 wt nacl equiv with insignificant content of ch 4 at 219 267 c stage iii contents of ore elements as au cu sb ba cs rb in mineralized basalt are higher than those in fresh basalt phase analysis for the au as fe s system using supcrt92 software package with the updated database of slop98 dat indicates that a decrease of h 2 s activity and oxygen fugacity caused by phase separation and fluid rock reactions induced native gold precipitation at stage i the decrease of h 2 s activity triggered by arsenopyrite crystallization caused native gold deposition at stage ii

selection of earthquake scaling relationships for seismic hazard analysis a fundamentally important but typically abbreviated component of seismic hazard analysis is the selection of earthquake scaling relationships these are typically regressions of historical earthquake datasets in which magnitude is estimated from parameters such as fault rupture length and area the mix of historical data from different tectonic environments and the different forms of the regression equations can result in large differences in magnitude estimates for a given fault rupture length or area we compile a worldwide set of regressions and make a first order shortlisting of regressions according to their relevance to a range of tectonic regimes plate tectonic setting and fault slip type in existence around the world regression relevance is based largely on the geographical distribution age and quantity quality of earthquake data used to develop them our compilation is limited to regressions of magnitude or seismic moment on fault rupture area or length and our shortlisted regressions show a large magnitude range up to a full magnitude unit for a given rupture length or area across the various tectonic regimes these large differences in magnitude estimates underline the importance of choosing regressions carefully for seismic hazard application in different tectonic environments

generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

cordilleran epithermal cu zn pb au ag mineralization in the colquijirca district central peru deposit scale mineralogical patterns at colquijirca central peru a miocene diatreme dome complex is associated in space and time with several large epithermal polymetallic cu zn pb au ag deposits of the cordilleran class of these deposits smelter and colquijirca located in the northern sector of the district are part of a continuously mineralized northsouth corridor that extends for nearly 4 km outward from the diatreme dome complex and to depths of 1 km below surface this corridor is zoned from cu au ores in its inner parts smelter deposit to peripheral zn pb ag ores colquijirca deposit the smelter colquijirca corridor has undergone minor erosion providing a good example of a nearly intact paleo epithermal system of the cordilleran class this description of the hypogene mineralogical patterns of the smelter colquijirca corridor leads to the proposal that they are the result of superimposition in time and space of three main stages during an early quartzpyrite stage in which basically no economic ore deposition occurred carbonate rocks surrounding the marcapunta diatreme dome complex were replaced by quartz and pyrite this was followed by the main ore stage which was largely superimposed on the quartz pyrite replacements and produced zonation of ore minerals and metals along much of the smelter colquijirca corridor the zoning from cu ores to zn pb ores is complex and comprises a number of distinct and well defined zones that display abrupt or gradual interfaces between zones from internal to external parts these zones consist mainly of the following mineral associations and assemblages 1 enargite luzonite pyrite colusite tennantite goldfieldite ferberite gold silver tellurides bismuthinite gold alunite zunyite kaolinite dickite smectite illite sericite quartz 2 enargite pyrite quartz bismuthinite alunite dickite kaolinite smectite illite sericite 3 bornite pyrite quartz alunite dickite kaolinite barite 4 tennantite barite dickite kaolinite chalcopyrite bi and or ag bearing minerals 5 chalcopyrite sphalerite galena pyrite quartz dickite kaolinite barite 6 sphalerite galena pyrite hematite kaolinite siderite magnetite marcasite 7 zn bearing carbonate zone and 8 a barren outer zone consisting mainly of calcite the crosscutting relationships and zoning patterns indicate that during the main ore stage the inner cu zones progressively overprinted the zn pb zones evidence for the subsequent contraction of the mineralization front is also recognized a mainly fault controlled late ore stage was the last recognized episode of mineralization in the smelter colquijirca corridor related to the deposition of chalcocite digenite and covellite as veinlets cutting and replacing the different cu bearing zones of the main ore stage it is not economically important the different mineral associations and assemblages provide insights into the chemistry of the hydrothermal fluids particularly that of the main ore stage the acidity and oxidation state of the main ore stage fluids varied considerably prior to significant interaction with the host rock this is best observed in the enargite bearing zones in which most acidic fluids formed alunite zunyite enargite bearing assemblages and less acidic fluids formed smectite illite enargite and muscovite enargite bearing assemblages the common kaolinite dickite enargite assemblage was related to a fluid with intermediate character between these two end member styles the significant fluctuations in the acidity of the ore fluids in the central parts of the mineralizing system are interpreted to reflect mixing between variable amounts of acidic and oxidized magmatic vapor derived fluids and less acidic low to moderate saline ore forming fluids of magmatic origin

geochemical and petrographic characterization of humic coals considered as possible oil source rocks abstract recently several groups of authors have argued that coals should be considered as possible source rocks for oil as well as being source rocks for gas the present study was undertaken with the objective of evaluating the various methods of characterization of maturation levels and oil potentials of coals from within the oil window it was found that the degree of maturation of a coal could not be specified exactly no matter what parameter describing coal rank was used this lack of precision obviously makes it difficult to compare coals especially from the point of view of their petroleum potential which varies during the course of coalification furthermore quantitative evalution of the oil potential of coals is difficult particularly the present day petrographic concept of exinite does not seem very well adapted to this quantitative evaluation differences in oil potential might in fact be better explained by the relative proportions of the various vitrinite macerals which are present rather than by the proportion of exinite in the coal

trace metals in pyrite and marcasite from the agua rica porphyry high sulfidation epithermal deposit catamarca argentina textural features and metal zoning at the porphyry to epithermal transition abstract agua rica is a world class cu mo au deposit located in catamarca argentina in which the porphyry and high sulfidation epithermal stages are juxtaposed due to the telescoping of the mineralizing system pyrite is the most abundant sulfide in the analyzed section of the deposit and shows variations in textures and trace metal content determined by la icpms between the porphyry and epithermal stages pyrite from the porphyry stage is fine grained and depleted in most trace elements analyzed except for traces of co up to 276 ppm and ni up to 131 ppm pyrite from the epithermal stage is texturally complex compositionally heterogeneous and the trace metal content varies with depth and within sub stages of mineralization at an intermediate depth 2625 m epithermal pyrite from the cement of the jig saw and clast supported hydrothermal breccias are enriched in cu up to 2961 ppm that correlates with the highest cu grades in the section this pyrite contains micro inclusions of sulfosalt minerals as inferred by la icpms elemental mapping and individual spot ablation profiles they are zoned and show a co rich core an intermediate zone enriched in cu and an outer rim rich in zn at shallower levels 3000 m epithermal pyrite cements in the heterolithic hydrothermal breccia are unusually rich in trace metals that correlate with the highest pb zn au and ag grades the ore stage pyrite occurs as either successive colloform bands on earlier co bearing cores or as veinlets infill the colloform pyrite bands and veinlets are as poor

geology and geochronology of naruo large porphyry breccia cu deposit in the duolong district tibet abstract the duolong district is located in the south qiangtang terrane of tibet and is the most significant ore cluster within the bangongco nujiang metallogenic belt duolong contains one giant three large and two medium to small sized porphyry epithermal breccia copper deposits and several other mineralized porphyry bodies all deposits are closely associated with early cretaceous 123 115 ma intermediate felsic intrusions naruo is a poorly studied porphyry breccia copper deposit in the north of the duolong district hydrothermal alteration surrounding the ore bearing granodiorite at naruo is characterized by an inner potassic zone and an outer propylitic zone overlapped locally by minor phyllic and argillic alteration assemblages a detailed paragenetic study has identified five distinct hydrothermal veins m a b c d within the porphyry system hydrothermal b veins are strongly related to copper mineralization strong propylitic alteration is also observed throughout the hydrothermal breccias identified at naruo sandstone breccia diorite bearing breccia and granodiorite bearing breccia were identified according to the distribution and composition of clasts u pb zircon dating has determined the ages of the ore bearing granodiorite 121 6 1 3 ma and a barren intrusion 115 5 1 1 ma within the porphyry system diorite clasts 122 3 0 9 ma and later diorite matrix 120 5 1 0 ma in the hydrothermal breccia system suggesting that with the exception of the late barren intrusion they all belong to the same mineralizing event at duolong the geological and geochemical evidence presented in this study suggest that the porphyry and breccia systems may have originated from the same magma source but are now spatially independent

regional difference in scaling laws for large earthquakes and its tectonic implication we compiled 67 large earthquakes which occurred at and around plate boundaries for the last 140 yrs and classified them into four groups interplate strike slip events intraplate strike slip events underthrust events at island arc subduction zones and underthrust events at continental margin subduction zones for each group of earthquakes we examined relations between seismic moment m 0 fault length l fault width w and average fault slip d and found the following scaling laws in the case of interplate strike slip events the well known l cubed dependence of seismic moment breaks down when l exceeds 30 km because the extent of the seismogenic zone is limited in depth 12 km for large events l 30 km d and m 0 increase with l as d overline delta tau l mu left alpha l beta right and m 0 overline delta tau w l 2 left alpha l beta right respectively where the mean fault width bar w is 12 km and the mean stress drop overline delta tau is 1 8 mpa here and are structural parameters for intraplate strike slip events we obtained nearly the same relations except for significantly higher stress drop 3 1 mpa the difference in stress drop between interplate and intraplate events may be ascribed to the difference in stress accumulation rates and thus the recurrence time of earthquakes in the case of underthrust events at island arc subduction zones we also found the saturation of fault width bar w 120km and the breakaway from the l cubed dependence of m 0 for events larger than l 200 km if we consider the average dip angle of plate boundaries at island arc subduction zones to be 20 30 this indicates that the extent of the seismogenic zone in depth is limited to 40 60 km in the case of continental margin subduction zones on the other hand we could not find the saturation of fault width nor the breakaway from the l cubed dependence of m 0 from the analysis of the present data set w 200 km l 1000 km for sufficiently large earthquakes in general the downward rupture growth is limited to a certain depth due to the existence of a ductile unstressed region which extends under the brittle seismogenic zone since the brittle ductile transition occurs at 300 400 c the difference in the lower limit of the seismogenic zones between tectonically different regions may be attributed to the difference in thermal state there

scaling relationships of source parameters of inland crustal earthquakes in tectonically active regions we examined the scaling relationships of inland crustal earthquakes occurring in tectonically active regions such as the japanese islands two important points related to reliable scaling relationships are discussed empirically the objective estimation of source parameters such as the seismic moment and rupture area and the regionality of the scaling rupture areas are objectively estimated by trimming heterogeneous slip distributions obtained from waveform inversion two trimming procedures have been proposed to determine effective rupture areas by somerville et al seismol res lett 70 59 80 1999 and thingbaijam and mai bull seismol soc am 106 1802 1816 2016 we confirmed that both trimmed rupture areas agree well with each other when applied to the same dataset the source scaling characteristics are known to depend on the seismotectonic regime we investigate the source scaling relationships of inland crustal earthquakes in japan using source parameters obtained from 36 slip models for 22 recent events mw 5 4 7 1 by waveform inversion analysis we confirmed that the source scaling relationships consisting of two stages were almost the same as those obtained for crustal earthquakes on the us west coast by hanks and bakun bull seismol soc am 92 1841 1846 2002 for larger earthquakes mw 7 4 in seismically active regions tajima et al zisin2 j seismol soc jpn 66 31 45 2013 found saturation of fault displacements showing the third stage combining the earthquake data of mw 5 4 7 1 in this study with those of mw 7 0 8 0 compiled by murotani et al pure appl geophys 172 1371 1381 2015 we conclude that the scaling relationship for rupture area versus seismic moment coincides with the three stage source scaling relationship using source parameters extracted from waveform inversions

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the application of famm fluorescence alteration of multiple macerals analyses for evaluating rank of parana basin coals brazil abstract combining vitrinite reflectance vr and fluorescence alteration of multiple macerals famm analyses provide insights into the chemical nature of vitrinites i e perhydrous vs orthohydrous vs subhydrous compositions in permian gondwana coals of the parana basin brazil the famm derived equivalent vr eqvr values and relationships with vr can be determined according to calibration curves based largely on permian gondwana coals of eastern australia the analytical results indicate that vitrinites in the parana basin coals studied generally range from orthohydrous to perhydrous with interpreted vr suppression ranging up to 0 2 absolute for the most perhydrous case the eqvr values of the santa catarina coals which range from about 0 85 to 0 95 differ from vr values by about 0 10 0 15 absolute potentially having significant implications on coal utilization the causes of vitrinite reflectance suppression in the parana basin coals are as yet poorly understood but are likely to be related to a combination of factors

recipe for predicting strong ground motion from crustal earthquake scenarios we developed a recipe for predicting strong ground motions based on a characterization of the source model for future crustal earthquakes from recent developments of waveform inversion of strong motion data used to estimate the rupture process we have inferred that strong ground motion is primarily related to the slip heterogeneity inside the source rather than average slip in the entire rupture area asperities are characterized as regions that have large slip relative to the average slip on the rupture area the asperity areas as well as the total rupture area scale with seismic moment we determined that the areas of strong motion generation approximately coincide with the asperity areas based on the scaling relationships the deductive source model for the prediction of strong ground motions is characterized by three kinds of parameters outer inner and extra fault parameters the outer fault parameters are defined as entire rupture area and total seismic moment the inner fault parameters are defined as slip heterogeneity inside the source area of asperities and stress drop on each asperity based on the multiple asperity model the pattern of rupture nucleation and termination are the extra fault parameters that are related to geomorphology of active faults we have examined the validity of the earthquake sources constructed by our recipe by comparing simulated and observed ground motions from recent inland crustal earthquakes such as the 1995 kobe and 2005 fukuoka earthquakes

coal as a source rock for oil a review the geological debate about whether and to what extent humic coals have sourced oil is likely to continue for some time despite some important advances in our knowledge of the processes involved it is clear that not only liptinites but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification some liptinites especially alginite cutinite and suberinite contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are therefore more oil prone it is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed review of the distribution of oil prone coals in time and space reveals that most are jurassic tertiary with key examples from australia new zealand and indonesia methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals results are not entirely consistent among the different approaches and there is much overlap in the ranges of degradation but it seems probable that in the natural environment vitrinites begin to generate early followed by labile liptinites such as suberinite then cutinite sporinite and finally alginite petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro techniques especially fluorescence and infrared ir spectroscopy or bulk techniques such as elemental analysis and 13c nmr spectroscopy the latter three techniques enable a measure of the polymethylene component of the coal which now appears to be one of the best available approaches for determining petroleum potential no method of experimental simulation of petroleum generation from coals is without criticism and comparative results are highly variable however hydrous pyrolysis confined pyrolysis and forms of open system hydrous pyrolysis approach acceptable simulations whether and to what degree generated liquid hydrocarbons are expelled has long been the central problem in oil from coal studies the structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained recent studies show the pores are not interconnected combined with a dynamic model of pore generation it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries the main reason for poor expulsion is the adsorption of oil on the organic macromolecule which may be overcome 1 if coals are thin and interbedded with clastic sediments or 2 if the coals are very hydrogen rich and generate large quantities of oil the existence of oil in vitrinite is attested to by solvent extractions fluorescence properties and by microscopic observations of oil and bitumen experimental simulation of expulsion of oil from coals has only recently been attempted the relative timing of release of generated co2 and ch4 could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear as it is universally agreed that dispersed organic matter dom in some shales readily generates and expels petroleum it is curious that few consistent geochemical differences have been found between coal macerals and dom in interbedded shales unambiguous evidence of expulsion from coals is limited and in particular only a few commercial oil discoveries can be confidently correlated to coals these include upper cretaceous fruitland formation coals in the usa from which oil is produced new zealand tertiary coals and middle jurassic coals from the danish north sea it is likely that coals have at least contributed to significant oil discoveries in the gippsland basin australia in the turpan basin china and in the kutei and ardjuna basins in indonesia but this remains unproven early reports that early jurassic coals in mid norway were a major source of the reservoired oils have been shown to be inaccurate none of the proposed rules of thumb for generation or expulsion of petroleum from coals seem particularly robust decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information the assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain

the cristal zinc prospect amazonas region northern peru part i new insights on the sulfide mineralization in the bongara province the cristal zn prospect consists of a mixed sulfide and nonsulfide mineralization located in the bongara province amazonas region northern peru the mineralization is hosted by carbonate rocks of the pucara group deposited in a mesozoic extensional basin on the western margin of the brazilian guyana shield zinc sulfides at cristal occur in the roots of the nonsulfide concentrations and are locally present also nearer to surface the sulfide mineralization postdates two hydrothermal dolomitization phases dol1 and dol2 and the sulfides occur mainly in veins cavity fillings or as disseminated mineralization within sparry to saddle dolomite they mostly consist of dark brown sphalerite intergrown with smaller amounts of pyrite sphalerite shows a distinct fe zonation with average ca 7 wt fe max ca 12 wt fe and is ge rich mean concentration of 142 ppm galena is rare the cristal sphalerite has sulfur isotopic compositions of 34s 14 to 15 vcdt oxygen isotopic compositions of dolomites are 18o 24 4 to 24 7 vsmow for dol1 and 18 4 to 22 for dol2 34s and 18o values of cristal sulfides and dolomites are similar to those observed in two mississippi valley type mvt deposits located ca 20 30 km south of the cristal prospect namely the florida canyon and florcita deposits this could be consistent with one or more events within a same mvt mineralizing system acting at the district scale the pb isotope compositions of sphalerite from two different areas of the prospect named cristal s s and charlita north define two distinct data point clusters centered around averages of 206pb 204pb 18 850 0 002 207pb 204pb 15 685 0 002 208pb 204pb 38 752 0 004 and 206pb 204pb 19 042 0 002 207pb 204pb 15 712 0 002 208pb 204pb 39 080 0 004 respectively this difference requires distinct metal bearing hydrothermal pulses in the mineralized area and or distinct pb sources the pb isotopic compositions of the cristal s s and charlita north sulfides are intermediate between the compositions of galena from the san vicente and shalipayco mvt deposits and record a contribution from an old crustal component the paleozoic basement which has pb isotopic ratios roughly matching those of dolomites and sulfides from cristal and charlita north areas represents the most reliable candidate to be an end member source of the metals of the cristal sulfide mineralization the second end member could be an igneous source isotopically identical to the late paleozoic to early mesozoic intrusives of the peruvian eastern cordillera or the triassic volcanic rocks occurring within the mitu group

heterogeneous melt and hypersaline liquid inclusions in shallow porphyry type mineralization as markers of the magmatic hydrothermal transition cerro de pasco district peru recently identified occurrences of porphyry style mineralization evidence the link of the world s second largest known epithermal base metal cerro de pasco deposit peru to a porphyry system emplaced at depth they consist of i quartz monzonite dykes and ii the south western part of the large diatreme dome complex adjacent to the main ore bodies of cerro de pasco and iii stockwork of banded quartz magnetite chalcopyrite pyrite porphyry type veinlets crosscutting trachyte porphyritic intrusion cropping out at surface in the central part of the diatreme dome complex the latter porphyry type mineralization observed at the same erosion level as the main epithermal base metal carbonate replacement ore bodies is the subject of this work geological constraints indicate a shallow emplacement level depth 1 km p 270 bar implying rather unusual low pressure and high temperature environment for the formation of porphyry style mineralization the banded porphyry type veinlets record a multiphase history of formation with two successive high temperature n600 c stages followed by a lower temperature b350 c stage more than 90 of the quartz in veinlets precipitates during the first two high temperature stages stage 1 is characterized by the entrapment in hydrothermal quartz of inclusions containing variable proportions of both silicate melt and metal rich hypersaline n90 wt nacl eq liquid hereafter referred to as heterogeneous silicate melt inclusions hsmis the latter are rarely described in porphyry type mineralization we suggest that during stage 1 the inclusions result from heterogeneous entrapment of an evolved hydrous rhyolitic melt mixed with a hypersaline fluid phase at low pressure 270 bar and high temperature n600 c the stage 2 is marked by the entrapment of metaland sulfur rich hypersaline liquid inclusions with salinity around 70 wt nacl eq originated from the adiabatic ascent of magmatic hypersaline fluids transferred fromdeeper parts of the system the lower temperature stage 3 is characterized by an important temperature drop from n600 c to b350 c as revealed bymicrothermometry of aqueous two phase liquid vapor l v inclusions quartz textures revealed by sem cl imaging allowascribing the sulfide precipitation to the low temperaturemineralization stage 3 in situ sims 18o 16o isotope analyses of quartz across the veinlets are indicative of a magmatic signature of the fluids during the first two stages while quartz from stage 3 has oxygen isotopic compositions suggestive of minor contribution of meteoric waters to a predominantly magmatic aqueous fluid 10 vol of meteoric input which probably triggered cu fe sulfide precipitation in the stockwork high metal and sulfur contents of hsmis and hypersaline liquid inclusions determined by la icp ms are interpreted to represent the fluid composition prior to the main sulfide precipitation event the similar pb zn ratio of the bulk ore extracted from the epithermal ore bodies at cerro de pasco and the hsmis and hypersaline liquid inclusions suggest a common source of the fluids associated with the different mineralization styles at cerro de pasco

13c nuclear magnetic resonance studies of kerogen from cretaceous black shales thermally altered by basaltic intrusions and laboratory simulations cretaceous black shales from dsdp leg 41 site 368 in the eastern atlantic ocean were thermally altered during the miocene by an intrusive basalt the sediments overlying and underlying the intrusive body were subjected to high temperatures up to 500 c and as a result their kerogen was significantly altered the extent of this alteration has been determined by examination by means of 13c nuclear magnetic resonance using cross polarization magic angle spinning cp mas results indicate that the kerogen becomes progressively more aromatic in the vicinity of the intrusive body laboratory heating experiments simulating the thermal effects of the basaltic intrusion produced similar results on unaltered shale from the drill core the 13c cp mas results appear to provide a good measure of thermal alteration

oil generating coals of the san juan basin new mexico and colorado u s a abstract coal beds of the upper cretaceous fruitland formation in the san juan basin of northwestern new mexico and southwestern colorado have significant liquid hydrocarbon generation potential as indicated by typical rock eval hydrogen indexes in the range of 200 400 mg hydrocarbon g organic carbon type ii and iii organic matter small non commercial quantities of oil have been produced from the coal beds at several locations the oils are characterized by high pristane phytane ca 4 and pristane n c17 ratios ca 1 2 abundant c21 alkanes in the c10 fraction with a slight predominance of odd carbon numbered n alkanes abundant branched chain alkanes in the c15 region and a predominance of methylcyclohexane in the c4 c10 fraction the oils are indigenous to the fruitland formation coals and probably migrated at thermal maturities corresponding to vitrinite reflectance values in the range 0 7 0 8 although the oils found to date are not present in commercial amounts these findings illustrate the potential of some coals to generate and expel oil under conditions of moderate thermal heating

carboniferous orogenic gold deposits at pataz eastern andeancordillera peru geological and structural framework paragenesis alteration and 40ar 39ar geochronology the pataz province forms the central part of a 160 km long orogenic gold belt extending along the eastern andean cordillera in northern peru and has produced a total of 6 million ounces moz gold from vein type deposits during the last 100 yr the deposits present several recurrent and typical field characteristics including 1 at a regional scale location of the mineralization in low order structures within a 1 to 5 km wide structural corridor east of a major north northwest striking lineament and in spatial association with the northnorthwest striking margins of the 330 to 327 ma pataz batholith 2 at the mine scale strong lithological controls of the vein geometries and styles the lodes occurring as fairly continuous 5 km long quartz veins inside or along the margins of the batholith or as branching and bedding concordant narrow ore shoots within adjacent folded ordovician turbidite sequences 3 consistent orientations of veins in particular within the batholith where more than 80 percent of the quartz veins are emplaced in north to northwest striking eastdipping brittle ductile deformation zones 4 a consistent au ag as fe pb zn cu sb bi te w metal association and a sulfide rich paragenetic sequence with a first stage composed of milky quartz pyrite arsenopyrite and ankerite and a second stage of blue gray microgranular quartz galena sphalerite chalcopyrite sb sulfosalts electrum and native gold followed by barren calcite dolomite quartz veinlets and 5 hydrothermal alteration of the vein wall rocks consisting of pervasive muscovite alteration with minor chlorite carbonate minerals and pyrite associated with strong bleaching in plutonic rocks and of weak muscovite and chlorite alteration in sedimentary rocks structural analysis of the deposits outlines four synchronous sets of mineralized fractures in the pataz district the predominant north to northwest striking east to northeast dipping system which is generally located in reactivated reverse faults accounts for more than 80 percent of the gold resource of the district three subordinate systems include in decreasing order of economic importance 1 east west striking flat extensional veins 2 bedding concordant veinlets in east west striking and north dipping to north south striking and east dipping limbs of long wavelength folds in ordovician sedimentary rocks and 3 weakly mineralized roughly east west striking sinistral vertical faults the vein orientations of the four structural sets are compatible with a triaxial strain model with the main shortening axis p oriented at 080 15 an intermediate axis oriented at 165 00 and a subvertical extensional t axis oriented at 255 80 under these conditions the richest ore shoots are preferentially sited in sinistral pull aparts which occur at the intersection of either north south striking lodes or extensional lodes with roughly east west striking vertical faults 40ar 39ar dating of the granodiorite monzogranite bodies of the pataz batholith provides good plateau ages at 329 2 1 4 and 328 1 1 2 ma for biotite separates which are similar to a published 329 ma u pb age for the granodiorite a muscovite and a biotite sample from an aplite dike yielded plateau ages at 322 1 2 8 and 325 4 1 4 ma respectively muscovite samples from alteration intimately associated with the gold mineralization yielded three 40ar 39ar spectra with low temperature staircase shaped patterns followed by plateau segments at 314 to 312 ma these ages analytically indistinguishable at the 2 level are considered to be the most probable ages for the mineralization event three other plateaulike ages between 305 and 288 ma have been obtained and are interpreted to reflect partial argon loss during late fluid circulation associated with the intrusion of late cretaceous monzonite porphyries the age determinations are inconsistent with a genetic link between the 314 to 312 ma pataz gold deposits and the 330 to 327 ma calc alkaline pataz batholith or with the 327 to 319 ma aplite dikes or the late cretaceous porphyry magmatism instead the overall homogeneity of the structural mineralogical and geochemical characteristics of the deposits over the 160 km long mineralized belt and the geotectonic evolution suggest that gold mineralization is linked to a large scale thermal event that occurred in a thickened collisional belt undergoing uplift tectonics

germanium enrichment in supergene settings evidence from the cristal nonsulfide zn prospect bongara district northern peru supergene nonsulfide ores form from the weathering of sulfide mineralization given the geochemical affinity of ge to si4 and fe3 weathering of ge bearing sulfides could potentially lead to ge enrichments in silicate and fe oxy hydroxide minerals although bulk rock ge concentrations in supergene nonsulfide deposits are rarely reported here we present the results of an investigation into ge concentrations and deportment in the cristal supergene zn nonsulfide prospect bongara northern peru which formed from the weathering of a preexisting mississippi valley type mvt sulfide deposit material examined in this study originates from drillcore recovered from oxidized zn rich bodies 15 20 m thick containing 5 45 wt zn and ge concentrations 100 ppm microanalysis and laser ablation icp ms show that precursor sphalerite is rich in both fe mean fe 8 19 wt and ge mean ge 142 ppm using the mineral geothermometer ggimfis geothermometer for ga ge in mn and fe in sphalerite proposed by frenzel et al ore geol rev 76 52 78 2016 sphalerite trace element data from the cristal prospect suggest a possible formation temperature tggimfis of 225 50 c anomalously high for a mvt deposit germanium concentrations measured in both goethite mean values 100 to 229 ppm max 511 ppm and hemimorphite mean values 39 to 137 ppm max 258 ppm are similar to concentrations measured in hypogene sphalerite additionally the ge concentrations recorded in bulk rock analyses of sphalerite bearing and oxidized samples are also similar a persistent warm humid climate is interpreted for the region resulting in the development of an oxidation zone favoring the formation of abundant zn hydrosilicates and fe hydroxides both able to incorporate ge in their crystal structure in this scenario ge has been prevented from dispersion during the weathering of the ge bearing sulfide bodies and remains in the resultant nonsulfide ore

geochemical evidence for mudstone as the possible major oil source rock in the jurassic turpan basin northwest china abstract geologists and geochemists have debated whether hydrocarbons from jurassic coal measures are derived from the mudstones or the coals themselves this paper identifies mudstones as the possible major source rock of hydrocarbons in the jurassic basins in northwest china the turpan basin is used as a representative model mudstones in the middle lower jurassic are very well developed in the basin and have an average genetic potential from 2 to 4 mg g the vitrinite reflectance of the source rocks ranges from 0 6 to 1 3 exhibiting sufficient thermal maturity to generate oil and gas biomarkers in crude oils from the basin are similar to those in mudstones from the coal bearing strata with a low tricyclic terpane cheilanthane content a relatively high content of low carbon number less than c22 tricyclic terpanes and a low content of high carbon number tricyclic terpanes relatively high ratios of ts tm and c29 ts 17 h c29 norhopane and low ratios of tm 17 h c30 hopane and 17 h c31 homohopane 17 h c30 hopane these characteristics and the distribution of steranes and terpanes in the crude oil and mudstone differ significantly from those of the jurassic coals and carbonaceous shales of the basin indicating mudstone is possibly the major source rock of the oils in the turpan basin

source mechanisms of three moderate california earthquakes of july 1986 abstract we studied the source processes of three moderate size earthquakes in california the m s 6 0 event of july 8 1986 near palm springs the m s 5 8 shock of july 13 1986 offshore of oceanside and the m s 6 2 event of july 21 1986 in the chalfant valley on the east side of the sierra nevada the centroidal source parameters are estimated by inversion of long period p and sh waves recorded at teleseismic distances by seismographs of worldwide networks a more detailed description of the source is then obtained by analyzing broadband seismograms the north palm springs earthquake had a simple rupture process most of the seismic moment was released in the first 3 sec in a single step the strike of the source fault plane follows the average trend of the banning fault and its dip agrees with the dip of the fault plane delineated by the aftershocks the faulting mechanism of the main shock is right lateral strike slip with a sizable reverse component that is consistent with uplift north of the banning fault the earthquake offshore of oceanside had a slightly more complex rupture process the far field source time function consists of two pulses that represent the release of most of the moment in the first 3 sec the source mechanism indicates reverse faulting with the compressional axis trending northeast almost perpendicular to the trend of mapped faults offshore the event does not appear to be associated with major mapped faults in the area but the strike of one of the nodal planes agrees with the trend of the major mapped faults offshore and its mechanism is consistent with the missing component of plate convergence not taken up by the onshore strike slip fault systems and the idea of a weak san andreas fault system the rupture process of the chalfant valley earthquake was yet more complicated the source time function indicates that in a 4 sec time window three asperities were broken the source mechanism indicates right lateral strike slip faulting with a small normal faulting component on a fault that dips approximately 50 southwest earthquake activity suggests that presently the deformation in the northern part of the owens valley which includes the chalfant valley is dominated by conjugate strike slip faults which strike obliquely to the main range bounding normal faults the waveforms indicate the presence of a low velocity zone at a depth of about 20 km in the crust in the chalfant valley a synthesis of information from waveform modeling first motion fault plane solutions and aftershock distributions indicates that the nucleation and or termination of rupture for the north palm springs and the chalfant valley events were controlled by preexisting fault geometry

centroid moment tensor solutions for 35 earthquakes in western north america 1977 1983 abstract seismic records from the gdsn sro asro dwwssn rstn and ida networks were used to obtain long period t 45 sec focal mechanisms for 35 earthquakes in western north america longitude 140 to 110 latitude 30 to 60 employing the centroid moment tensor method of dziewonski et al 1981 and dziewonski and woodhouse 1983 the same algorithm was applied to all events the smallest m 0 6 4 10 23 dyne cm being an aftershock to the 1979 imperial valley california earthquake and the largest m 0 8 5 10 26 dyne cm the 1980 eureka california earthquake all events were analyzed with and without the constraint m r m r 0 on the moment tensor an ad hoc criterion on the relative variance reduction was employed to determine a favored solution our solutions show general agreement with other published results as well as with tectonic structures agreement with results obtained using the abundant local and regional data confirms the adequacy of the method in determining long period source parameters and verifies its applicability in regions where local and regional data are scarce or nonexistent in some cases disagreement between our solution and results from first motion studies appears to be related to source complexities our moment tensor represents the total stress release of the composite event a consistent westward movement of the centroid locations reflects lateral heterogeneities in the crust and mantle

pyrolysis gas chromatography of asphaltenes and kerogens from source rocks and coals a comparative structural study abstract pyrolysis gas chromatography of asphaltenes isolated from source rock and coal extracts and the corresponding kerogens show the same general pyrolysis characteristics while the pyrograms of asphaltenes associated with type i and ii kerogens are dominated by an aliphatic n alkene n alkane homology the pyrolysates of coal asphaltenes show a high abundance of aromatics the asphaltene pyrolysates differ from those of the related kerogens principally in that the relative abundance of isoprenoids and long chain hydrocarbons is higher in the asphaltene pyrograms these differences were minimized with increasing maturity suggesting comparable structures for mature asphaltenes and kerogens and that pyrolysis of asphaltenes should be integrated with other methods which are used in source rock geochemistry

immature oil and condensate modification of hydrocarbon generation model for terrestrial organic matter petroleum has been found in canadian frontier basins in reservoirs which have undergone low levels of thermal alteration vitrinite reflectance 0 6 ro paraffin indices stable carbon and hydrogen isotope contents pristane to nc17 ratios and diterpenoid biologic markers have been used to assess the level of maturity of the hydrocarbons in the reservoir independently of the level of maturity of the reservoir itself and of the surrounding shale units in the tertiary of the beaufort mackenzie basin naphthenic oils and condensates have been generated from terrestrially derived organic matter in source rocks juxtaposed with the reservoir at reflectance levels of 0 4 to 0 6 ro however condensates discovered in reservoirs which are th rmally immature on the labrador shelf have undergone extensive vertical migration and can be classed as conventional mature to overmature condensates hydrocarbons discovered in the lower cretaceous of the beaufort mackenzie basin and also those of the scotian shelf are more or less in place in that they are at a level of thermal alteration about equivalent to that of the reservoirs in which they are trapped the source for the early oils and condensates is considered to be resinite occurring dispersed in coal fragments the proportion of resinite liptinite and vitrinite in the organic matter of terrestrial source rocks strongly controls both the level of thermal alteration necessary for the section to function as an effective source rock and the ultimate product gas oil or condensate which will be generated

a multidisciplinary study of invisible gold in arsenopyrite from four mesothermal gold deposits in siberia russian federation characterization of gold in four siberian mesothermal gold deposits was done through a multidisciplinary investigation including ore microscopy inaa sims epma and 197 au moessbauer spectroscopy the deposits are olympiada and veduga in the enisei mountain range and nezhdaninskoye and sentachan in the verkhoyansk kolyma area in which vein and disseminated orebodies are hosted by sedimentary sequences metamorphosed to amphibolite olympiada and greenschist facies ore minerals include arsenopyrite and pyrrhotite or pyrite as major constituents with minor scheelite and sphalerite chalcopyrite and native gold as minor constituents with or aurostibite galena gudmundite tetrahedrite stibnite and berthierite some of the gold mineralization is metallurgically refractory in all four deposits largely due to the presence of invisible gold in arsenopyrite and to a lesser extent in pyrite several generations of arsenopyrite are recognized in the auriferous zones of the veduga nezhdaninskoye and sentachan deposits textural observations indicate late deposition of native gold with respect to arsenopyrite no evidence was found of arsenopyrite recrystallization and the crystallization of native gold is considered to result from an evolution of fluids rather than redeposition of gold wide variations in the gold contents of arsenopyrite occur within deposits within samples and within individual grains inna analyses of individual arsenopyrite grains 30 70 mu m in size show that the gold concentration ranges from 197 au moessbauer spectra of arsenopyrite concentrates from the veduga nezhdaninskoye and sentachan deposits exhibit mainly a component with isomer shifts between 3 3 and 3 6 mm s which is interpreted as strong evidence of the presence of chemically bound gold in the arsenopyrite crystal structure the spectra of samples from the veduga deposit also contain minor amounts of native gold for which negative isomer shifts near 1 2 mm s are expected metallic gold dominates in the 197 au moessbauer spectra of samples from the olympiada deposit but varying amounts of chemically bound gold are also visible in the spectra some attributed to aurostibite it is concluded that the ores from these deposits are refractory partly because the gold occurs in arsenopyrite as chemically bound gold as well as submicroscopic metallic particles probably as small as 2 nm this study also shows that au bearing arsenopyrite is usually depleted in as with respect to its stoichiometric composition but correlation of au enrichment to fe deficiency was not found it is inferred from 197 au moessbauer spectroscopy that substitution of fe super 3 for au super 3 is most likely the temporal change in different modes of gold occurrence i e as native gold or invisibly in sulfides in the mineralized zones and veins is interpreted to result from an evolution of fluids rather than to be a recrystallization phenomenon dissemination of au bearing sulfides within the altered halos infers that a pervasive fluid rock interaction was an effective mechanism for deposition of minerals and gold absorption of gold complexes onto sulfide surfaces is also suggested to have played an important role in the deposition of native gold during the latest episodes in the formation of the deposits

cyclic dilution of magmatic metal rich hypersaline fluids by magmatic low salinity fluid a major process generating the giant epithermal polymetallic deposit of cerro de pasco peru the giant mid miocene cerro de pasco cordilleran polymetallic zn pb ag cu bi deposit in central peru formed during three successive mineralization stages resulting in low to high sulfidation mineral associations emplaced at a paleodepth from 500 to 1 500 m 1 pyrrhotite pipes grading outward to sphalerite and galena replacement bodies stage a 2 deep quartz pyrite veins stage b1 and a funnel shaped massive replacement body of pyrite quartz stage b2 with quartz sericite kaolinite alteration and 3 well zoned zn pb bi ag cu carbonate replacement orebodies stage c1 and e w trending cu ag au zn pb enargite pyrite veins stage c2 stages c1 and c2 are accompanied by advanced argillic alteration field evidence indicates that the epithermal polymetallic mineralization has formed in the shallow part of a porphyry system a detailed microthermometric and laser ablation inductively coupled plasma mass spectrometry la icpms study of fluid inclusions hosted in gangue and using near infrared microscopy opaque ore minerals from the different mineralization stages as well as available bulk and in situ secondary ion mass spectrometry sims stable isotopic data allow reconstruction of the evolution and tracing of the source s of the mineralizing fluids fluid inclusions are two phase l v homogenize to liquid at moderate temperatures 220 280 c in stages a b1 b2 and c2 and down to 150 c in stage c1 and show a wide salinity range 1 2 19 wt nacl equiv with no evidence of phase separation fluids during mineralization stages a b1 b2 and c1 are the result of mixing between a moderate salinity metal rich magmatic fluid and a low salinity fluid at the shallow site of deposition the moderate salinity metal rich magmatic fluid cannot be interpreted as an evolved intermediate density fluid or its boiling product due to its salinity up to 19 wt nacl equiv its high base metal concentration 1 wt mn fe zn and pb and its high li b as and sb contents up to several thousands of ppm the obtained results suggest that the moderate salinity metal rich magmatic fluid results from mixing at depth between metal rich hypersaline fluids and low salinity magmatic fluids exsolved late in the lifetime of the magmatic hydrothermal system the moderate salinity metal rich magmatic fluid resulting from this deep mixing rose to the epithermal environment where it in turn mixed with low salinity fluids that were stored below the paleowater table and had similar temperatures to the moderate salinity fluid in contrast enargite pyrite veins of stage c2 were formed by the ascent of co2 bearing contracted vapor like fluids that subsequently mixed with cold meteoric water no interaction with the moderate salinity metal rich magmatic fluids has been registered in stage c2 the similarity between fluid compositions and evolution during stages a b1 b2 and c1 contrasts with their significantly different mineral assemblages that are rather controlled by changing fo2 ph fs2 and temperature trace element la icp ms analyses of sphalerite pyrite and enargite also reveal important compositional differences the trace elements in the measured minerals reside to a significant extent in micro to nanoscale solid sulfide and or sulfosalt inclusions a direct correlation between fluid composition recorded in the studied fluid inclusion assemblages and the measured trace element composition of sphalerite pyrite and enargite has not been found in most cases the cyclic rise of metal rich moderately saline fluids that issued from dilution of hypersaline fluids stored at depth by low salinity magmatic fluids is a major process in the formation of stages a b1 b2 and c1 of the giant epithermal polymetallic deposit of cerro de pasco such a mechanism may also explain moderate salinity fluids 20 wt nacl equiv recorded in other magmatic related polymetallic epithermal deposits worldwide

hydrocarbon generation from deltaic and intermontane fluviodeltaic coal and coaly shale from the tertiary of texas and carboniferous of nova scotia abstract selected samples of coal and coaly shale from southeastern texas depositional environment deltaic age paleocene eocene ro 0 25 0 75 and nova scotia depositional environment intermontane swamp delta and lacustrine age carboniferous westphalian a d ro 0 67 0 70 were analyzed by fluorescence microscopy rock eval pyrolysis nmr anhydrous pyrolysis temperature programed and flash and hydrous pyrolysis to evaluate the hydrocarbon potential and hydrocarbon types based on maceral assemblages palynofacies and hydrocarbon potential these coal and coaly shale samples are classified as humic mixinitic mixed and sapropelic compared to humic and sapropelic as defined by stach et al coal petrology gebruder borntraeger berlin 1982 mixinitic or mixed coal and coaly shale containing mainly humodetrinite and lipodetrinite generated more than 10 pyrolysate expelled oil oil in wash fraction remaining coal extract and show a bimodal n alkane distribution derived from cutinite suberinite and alginite pyrolysis of humotelinite humocollinite rich and liptinite poor humic coals generated low amounts

la icp ms trace element analysis of arsenopyrite from the samgwang gold deposit south korea and its genetic implications abstract the samgwang deposit previously classified as an orogenic gold deposit consists of several structurally controlled auriferous quartz veins hosted by metasedimentary rocks of the precambrian gyeonggi massif south korea the gold at samgwang occurs as electrum commonly associated with arsenopyrite laser ablation inductively coupled plasma mass spectrometry la icp ms coupled with ore microscopy was conducted on au and trace elements distributed in arsenopyrite grains contained in quartz vein and wall rock samples resulting profiles for au co ni and sb were relatively flat and showed little variability indicating that the elements were relatively homogeneously distributed and exchanged via substitution in arsenopyrite while variability and noisy depth profiles inferred that pb was present as tiny inclusions or discrete particles furthermore measured gold concentrations were typically higher in arsenopyrite grains from laminated quartz veins avg 2 07 ppm than in grains from massive quartz veins avg 0 26 ppm and wall rock samples avg 0 33 ppm in the case of wall rock and massive quartz vein samples arsenopyrite grains of euhedral shape illustrate an element distribution pattern whereby au concentrations tend to decrease towards the rims of the analyzed grains in contrast the rims of arsenopyrite grains in laminated quartz vein samples recorded much higher au concentrations of up to 20 1 ppm with increasing pb bi and ag particularly within domains of fractured or recrystallized arsenopyrite grains the newly acquired la icp ms data along with textural evidence may be interpreted in terms of the release and remobilization of invisible gold that was originally locked up in the arsenopyrite this release is linked to late deformation and hydrothermal event during which the remobilized invisible gold was redeposited as electrum in addition there is evidence for the introduction of additional gold and other precious and base metals by the late stage hydrothermal fluids based on the above and in contrast to previous genetic models we propose a more complex metallogenic concept for samgwang in which the economically important gold enrichment process was genetically related to intrusive activity during the waning stages of jurassic to early cretaceous daebo orogenesis

fluid evolution in zoned cordilleran polymetallic veins insights from microthermometry and la icp ms of fluid inclusions abstract fluid inclusion analysis through the paragenetic sequence of one symmetrically zoned vein sample is used to reconstruct the p t x fluid evolution of a porphyry intrusion related cordilleran polymetallic vein from morococha central peru results record an evolution from initial deep seated precipitation of quartz pyrite and base metal sulphides to final near surface deposition of carbonates demonstrating progressive mineralisation during uplift and erosion this is the first detailed study addressing meso to epithermal zn pb ag cu rich ore in a magmatic hydrothermal system by combination of fluid inclusion microthermometry with laser ablation inductively coupled plasma mass spectrometry la icp ms quantifying metal as well as sulphur concentrations in the evolving hydrothermal fluid scanning electron microscopy cathodoluminescence sem cl imaging of quartz and detailed transmitted and reflected light petrography provide textural evidence that early moderately saline 4 5 wt nacl eq and co 2 bearing fluids with homogenisation temperatures of 340 380 c precipitate cu bearing minerals in this open hydrothermal system the fluids record decreasing salinities co 2 contents and temperatures while zn pb and ag sulphides precipitate fluids related to early precipitation in the vein have metal contents of several 1000 g g s and fe over 1000 g g cu 100 g g pb 10 g g ag and several 100 g g zn sulphur concentrations in the fluid are sufficiently high to precipitate all metals in solution as sulphides the latest generation of fluid inclusions associated with abundant carbonate precipitation in the centre of the vein has homogenisation temperatures ranging from 260 to 220 c low metal concentrations and no measurable co 2 during vein formation cooling and several kilometres of erosion resulted in telescoping of consecutively precipitated mineral assemblages the deep input fluid dominating in the early vein stage is interpreted to be of magmatic origin most likely a single phase magmatic fluid of intermediate salinity and density it cooled to an aqueous liquid separated minor co 2 rich vapour and was eventually diluted by meteoric water in the late stages of vein formation when the progressively eroded land surface was only several hundred meters above the vein location

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

petroleum source rock assessment in non marine sequences pyrolysis and petrographic analysis of australian coals and carbonaceous shales a series of australian coals and terrestrial sediments ranging in age from permian through tertiary have been analyzed to assess their petroleum source character and the suitability of various techniques for assessment of source rock potential in non marine sequences the procedures used include organic petrography rock eval pyrolysis elemental analysis and quantitative pyrolysis gas chromatography the latter procedure was used to assess the potential yield of paraffins which is critical to the assessment of most non marine source rocks principal components analysis was used to assist in the analysis of the data although the petroleum potential of the samples follows the broad trends in petrographic composition established for australian coals i e relative proportions of vitrinite inertinite and liptinite there is much variation which cannot be explained petrographically at the maceral group level further pyrolytic hydrocarbon yield is not related to overall elemental composition below an atomic h c ratio of 1 0 the yield of phenols in flash pyrolysis is related to depositional setting as well as degree of maturation the yield and carbon number distribution of normal hydrocarbons in flash pyrolysis varied widely depending on the age nature and amount of liptinite macerals particularly in samples with hydrogen indices below 300 liptinite poor 10 samples may yield significant amounts of hydrocarbons but typically they have a low wax content sporinite rich and liptodetrinite rich samples give lower yields of normal hydrocarbons these are predominantly of lower molecular weight suberinite and to a lesser extent cutinite are associated with high yields of waxy normal hydrocarbons but some samples with high yields did not contain large amounts of these maceral the correlation of tmax to vitrinite reflectance varies with petrographic composition the results have implications for the way source rock analyses are conducted and interpreted in non marine sequences

hydrocarbon genesis of jurassic coal measures in the turpan basin china abstract a typical case of coal derived oils in china i e the crude oils from the middle lower jurassic coal measure strata in the turpan basin is presented by means of oil source correlation it is confirmed that low maturity crude oil in the shengjinkou oil field is derived from the coal bearing qiketai formation of middle jurassic age a brackish lacustrine sediment mature crude oils in the qiketai oil field and in well taican 1 are sourced from the badaowan formation of lower jurassic age which contains coal seams as thick as 100 m results show that commercial accumulations of liquid crude oils can be generated from coals and coal measure strata containing high volatile coal of bituminous rank despite unfavourable types of source material the total hydrocarbon generating potential can be great due to the unusual abundance of organic matter

a carbonaceous sedimentary source rock model for carlin type and orogenic gold deposits this paper presents evidence and arguments that carbonaceous sedimentary rocks were a source for au and as in sediment hosted orogenic and carlin type gold deposits and develops a corresponding genetic model in this two stage basin scale model gold and arsenic are introduced early into black shale and turbidite basins during sedimentation and diagenesis stage 1 and concentrated to ore grades by later hydrothermal structural or magmatic processes stage 2 in reduced continental margin basin settings organic matter sedimented under anoxic to euxinic conditions immobilizes and concentrates gold arsenic and a range of trace elements particularly v ni se ag zn mo cu u present in marine bottom waters into fine grained black mudstone and siltstone of slope and basin facies during early diagenesis gold and certain other trace elements ni se te ag mo cu pge are preferentially partitioned into arsenian pyrite that grows in the muds these processes produce regionally extensive black shale and turbidite sequences enriched in syngenetic gold and arsenic commonly from 5 to 100 ppb au and 10 to 200 ppm as rare organic and sulfide rich metalliferous black shales may contain up to 1 to 2 ppm au and over 1 000 ppm as present as refractory gold in arsenian pyrite and nanoparticles of free gold during late diagenesis and early metamorphism stage 2 the diagenetic arsenian pyrite is recrystallized to form coarser grained pyrite generations and the organic matter is cooked to bitumen under higher grade metamorphism lower greenschist facies and above arsenian pyrite in carbonaceous shales is converted to pyrrhotite these processes release gold arsenic sulfur and other elements sb te cu zn mo bi tl and pb from the source rocks to become concentrated by hydrothermal processes locally to produce gold ores in structural sites such as fold hinge zones shear or breccia zones within or above the black shale sequence la icp ms analyses of diagenetic pyrite in carbonaceous sediments both associated and not associated with gold deposits suggests that invisible gold contents of greater than 250 ppb in diagenetic pyrite are indicative of carbonaceous shale source rocks with the potential to produce economic gold deposits application of this sedimentary source rock model enables a systematic exploration approach for sediment hosted gold deposits based on the distribution composition and structure of carbonaceous shale sequences and their contained diagenetic pyrite

scaling relations of source parameters of earthquakes occurring on inland crustal mega fault systems we examined a new scaling relation between source area s and seismic moment m 0 for large crustal earthquakes on mega fault systems including earthquakes with magnitudes larger than m w7 4 we focused on earthquakes that occurred on inland crustal mega fault systems such as the 2008 wenchuan and 2002 denali earthquakes and compiled the source parameters using 11 inland crustal earthquakes which analyses of source rupture processes by waveform inversion as well as investigation of surface ruptures via geomorphological surveys we found that the maximum surface rupture displacement is two to three times larger than the average slip on the source fault and the length of the surface rupture is equivalent to the length of the source fault furthermore our compiled data shows the displacement of the surface rupture d saturates around 10 m when the length of the surface rupture l reaches 100 km assuming that the average width of the source fault w 18 km for japanese inland crustal earthquakes and the saturated surface displacement d 10 m we found that the scaling relations between rupture area s and seismic moment m 0 have three stages for the first stage s is proportional to m 0 2 3 for earthquakes smaller than m 0 7 5 1018 nm for the second stage s ranges from m 0 1 2 to m 0 2 3 depending on the thickness of the seismogenic zone for the third stage s is proportional to m 0 because of the saturation of the slip on the fault from our compiled data we derived the third scaling relation between source area s and seismic moment m 0 for inland crustal mega fault systems to be s km2 1 0 10 17 m 0 nm where m 0 1 8 1020 nm

the petroleum generation potential and effective oil window of humic coals related to coal composition and age abstract a worldwide data set of more than 500 humic coals from the major coal forming geological periods has been used to analyse the evolution in the remaining hydrogen index hi and total quality index qi generation potentials with increasing thermal maturity and the effective oil window oil expulsion window all samples describe hi and qi bands that are broad at low maturities and that gradually narrow with increasing maturity the oil generation potential is completely exhausted at a vitrinite reflectance of 2 0 2 2 ro or tmax of 500 510 c the initial large variation in the generation potential is related to the original depositional conditions particularly the degree of marine influence and the formation of hydrogen enriched vitrinite as suggested by increased sulphur and hydrogen contents during initial thermal maturation the hi increases to a maximum value himax similarly qi increases to a maximum value qimax this increase in hi and qi is related to the formation of an additional generation potential in the coal structure the decline in qi with further maturation is indicating onset of initial oil expulsion which precedes efficient expulsion liquid petroleum generation from humic coals is thus a complex three phase process i onset of petroleum generation ii petroleum build up in the coal and iii initial oil expulsion followed by efficient oil expulsion corresponding to the effective oil window efficient oil expulsion is indicated by a decline in the bitumen index bi when plotted against vitrinite reflectance or tmax this means that in humic coals the vitrinite reflectance or tmax values at which onset of petroleum generation occurs cannot be used to establish the start of the effective oil window the start of the effective oil window occurs within the vitrinite reflectance range 0 85 1 05 ro or tmax range 440 455 c and the oil window extends to 1 5 2 0 ro or 470 510 c for general use an effective oil window is proposed to occur from 0 85 to 1 7 ro or from 440 to 490 c specific ranges for himax and the effective oil window can be defined for cenozoic jurassic permian and carboniferous coals cenozoic coals reach the highest himax values 220 370 mg hc g toc and for the most oil prone cenozoic coals the effective oil window may possibly range from 0 65 to 2 0 ro or 430 to 510 c in contrast the most oil prone jurassic permian and carboniferous coals reach the expulsion threshold at a vitrinite reflectance of 0 85 0 9 ro or tmax of 440 445 c

replacement of pyrrhotite by pyrite and marcasite under hydrothermal conditions up to 220 c an experimental study of reaction textures and mechanisms the transformation of pyrrhotite to fe disulfide pyrite and or marcasite under hydrothermal conditions was studied experimentally by probing the effects of temperature up to 220 c vapor saturated pressures s ii concentrations ph and availability of oxygen on reaction progress and on the resulting textures the pyrrhotite to fe disulfide reaction proceeded by a dissolution reprecipitation mechanism under all conditions marcasite and pyrite formed under both oxic and anaerobic conditions which is inconsistent with the traditionally assumed polysulfide route for fes2 formation oxidants required for polysulfide formation the nature of the products was controlled by the level of supersaturation of the solution with respect to fe disulfide minerals marcasite formed preferentially at low ph or s ii deficient solutions saturation index 1000 different textures were obtained for the replacement of pyrrhotite by either pyrite or marcasite pyrite formation proceeded by direct replacement of pyrrhotite and simultaneously by overgrowth from solution the pyrite crystals were 10 m in size and randomly oriented in comparison marcasite crystals were 1 m in size and no significant overgrowth was observed at ph21 c 3 the marcasite nanocrystals showed the well known crystallographic relationship with pyrrhotite but at ph21 c 3 96 the marcasite crystallites were randomly oriented these experimental results confirm that the preservation of the crystallographic orientation is not a distinguishing feature between dissolution reprecipitation and solid state reactions the different textures among pyrite and marcasite reflect the dominance of crystal growth pyrite vs nucleation marcasite as a precipitation mechanism

sulfide replacement processes revealed by textural and la icp ms trace element analyses example from the early mineralization stages at cerro de pasco peru the large cerro de pasco cordilleran base metal deposit in central peru is the result of three successive mineralizing stages comprising both low and high sulfidation mineral associations a several pyrrhotite pipes grading outward to sphalerite and galena replacement bodies b a massive funnel shaped pyrite quartz replacement orebody and c e w trending cu ag au zn pb enargite pyrite veins and well zoned zn pb bi ag cu carbonate replacement orebodies this superposition of hydrothermal events leads to complex replacement textures and crosscutting relationships a detailed study of the textures and mineral composition of the up to 15 m wide replacement front existing between the pyrrhotite pipes and the pyrite quartz body allows for clarification of the relative chronology of the hydrothermal events the results show that in contrast to previous interpretations the emplacement of the pyrrhotite pipes and their zn pb mineralized rims precedes that of the pyrite quartz body the replacement textures affecting pyrrhotite and arsenopyrite and the nature of the newly formed minerals have been used as a qualitative way to track the evolution of fs2 fo2 and ph of the mineralizing fluids two steps of pyrrhotite replacement have been recorded the first one takes place under moderate acidity and relatively reduced to moderately oxidized conditions and is marked by replacement of pyrrhotite by euhedral nonporous pyrite the second step occurs under more acidic and oxidized conditions and is characterized by replacement of pyrrhotite by porous marcasite and replacement of arsenopyrite by pyrite subsequently marcasite is partly replaced by fine grained euhedral nonporous pyrite la icp ms trace element analyses of the replaced pyrrhotite and arsenopyrite and of the newly formed marcasite and pyrite support dissolution reprecipitation as the main mechanism for replacement positive correlations between some of the elements e g pb sb pb ag are indicative of the possible presence of nanoscale solid inclusions as main carriers for those elements however coupled substitutions and incorporation of some of the elements at a ppm level into the pyrite and marcasite structures cannot be excluded the obtained as sb pb and bi values in pyrite are systematically higher than published data of pyrite in epithermal and porphyry systems nature and trace element content of the newly formed minerals yield information on the physicochemical conditions during their precipitation the initial trace element content of replaced minerals and the subsequently dissolved neighboring phases the results show that the metal concentration of the fluid is locally influenced by the composition of the dissolved minerals this study leads to a simpler interpretation of the fluid evolution than previously proposed with a progressive increase of fs2 fo2 and ph as a result of decreasing wall rock buffering during the three successive mineralizing stages at cerro de pasco

sphalerite geochemistry of the zn pb orebodies in the taebaeksan metallogenic province korea abstract the taebaeksan region located in the northeastern part of south korea is an important metallogenic province which hosts numerous zn pb w mo fe cu au ag mineral systems the zn pb orebodies in the region inclusive of skarn carbonate replacement and vein breccia ore types are hosted on the early paleozoic carbonate sequences and they are associated with late cretaceous to early paleogene magmatic hydrothermal activities we collected zn pb orebodies from 15 areas including non metal deposits such as high ca calcite marble as well as exploration sites in the taebaeksan metallogenic province thereafter we studied the geochemistry of the sphalerite present in them to understand the regional zn pb mineralization process and to establish an exploration strategy the sphalerites collected from the region contained detectable amounts of fe mn cd co cu ga ge mo ag in sn sb w tl pb and bi which were identified using microbeam techniques like epma and la icp ms sphalerites from economically significant zn pb deposits characteristically have high mn and low cd content while w mo bearing deposits have remarkably high cd content correlation trends between trace elements demonstrate the coupled substitution mechanisms such as 3 zn2 2 cu or ag sn4 and 2 zn2 cu in3 occurring in the sphalerite high temperature ores such as skarn and vein breccia are relatively enriched with co and in while ga ag and sn tend to be concentrated in the relatively low temperature ores such as carbonate replacement type ores lead isotope compositions of the sphalerites show a well defined positive linear trend with those of the local cretaceous intrusions and the sedimentary sequence of the taebaeksan region major economic zn pb deposits show relatively more signatures of non radiogenic pb isotope closer to the intrusions as compared to the minor and sub economic zn pb orebodies the pb isotope signature suggests that cretaceous magmatic hydrothermal fluids with a minimal degree of fluid rock interactions are required for economic zn pb mineralization in the taebaeksan metallogenic province

petrogenetic and metallogenetic relationships in the eastern cordillera occidental of central peru abstract ore deposits spatially and temporally related to high k calc alkaline intrusions or domes are widespread in the central peruvian cordillera occidental geochronology and petrochemistry of intrusive rocks associated with mineralization reveal that most ore deposits 1 were emplaced in the late middle to early late miocene and 2 are related to calc alkaline igneous rocks of granodioritic composition with documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm sm mathrm yb 3 end document documentclass aas

possible chemical structures and biological precursors of different vitrinites in coal measure in northwest china abstract chemical structure of jurassic vitrinites isolated from the coals in basins in nw china have been checked using solid state 13c nmr and flash pyrolysis gc ms study shows some jurassic collodetrinites are rich in aliphatic products in pyrolysates consisting with the high amount of methylene carbon in 13c nmr spectra in contrast pyrolysates of jurassic collotelinites are rich in phenols and alkylbenzenes also one pennsylvanian and one permian vitrinite selected from the ordos basin nw china have been checked for comparison the proportion of aliphatics is low in pyrolysates and aliphatic carbon peak in 13c nmr spectrum of permian vitrinite is mostly composed of gas prone carbons compared with collodetrinites in those jurassic basins but both pyrolysis and 13c nmr data shows the pennsylvanian vitrinite is not only gas prone but also oil prone relatively high proportion of long chain aliphatic structure of some jurassic vitrinite in junggar turpan hami basins may be due to the contribution of liptodetrinites which may be included during the formation of vitrinites and it seems that suberinite is the most possible precursor of long chain aliphatics in the structure of jurassic collodetrinite

zoned base metal mineralization in a porphyry system origin and evolution of mineralizing fluids in the morococha district peru porphyry related base metal vein and replacement mineralization i e cordilleran polymetallic mineralization in the morococha district central peru is part of a large magmatic hydrothermal system associated with the emplacement of several late miocene porphyry intrusions and formation of important cu mo mineralization zn pb ag cu veins overprint the giant toromocho porphyry cu mo deposit in the center of the district and display a typical concentric base metal zonation cu zn pb ag covering an area of approximately 50km2 a detailed fluid inclusion study supports the hypothesis that base metal mineralization precipitated from cooled and evolved metal rich intermediate density porphyry type fluids in early stages of cordilleran base metal vein formation fluid inclusions have low salinities of 2 to 5 wt nacl equiv co2 contents of 3 to 10mol and homogenization temperatures th of 380 to 340 c they are similar to intermediate density fluid inclusions trapped in a milky quartz vein predating cordilleran polymetallic mineralization with similar low salinities 3 0 3 8 wt nacl equiv and low co2 contents 6 5 8 mol but higher th of 420 to 410 c during cooling of the intermediate density fluids from 400 to 300 c the lithostatic pressure regime changed to a hydrostatic one the fluids underwent pressure drop as well as phase separation i e unmixing and lost most of their co2 they acquired moderate salinities in some cases intermediate up to 16 wt nacl to brine compositions however the bulk of the magmatic fluid retained low salinity while it continued to cool under open system conditions and precipitated tennantite tetrahedrite chalcopyrite enargite sphalerite and galena upon cooling below 270 c the fluids deposited abundant rhodochrosite and quartz while following the boiling curve toward lower p t conditions these data record an evolution of mineral precipitation from deep minimum depth of 2 1 5 km to shallow environments 300 800 m oxygen hydrogen and carbon stable isotope data indicate that the hydrothermal fluids have a dominantly magmatic signature and were diluted by meteoric waters during the carbonate stage copper 5 000 18 000 g g sulfur up to 12 000 g g and iron 2 100 6 000 g g concentrations in the intermediate density fluid inclusions in the milky quartz veins are approximately 5 to 10 times higher than in intermediate density inclusions of the early cordilleran base metal veins the base metals zn pb and mn have comparable concentrations between 100 and 1 000 g g for both types of fluid these findings suggest that the fluids identified in cordilleran polymetallic veins are compositionally similar to the porphyry type fluids and could have derived from the latter after precipitation of cu and fe bearing sulfides in a deeper porphyry environment the new data explain the commonly observed base and precious metal zonation patterns encountered in porphyry centered districts e g bingham butte and show that both porphyry and polymetallic mineralization can precipitate from similar magmatic hydrothermal fluid pulses

application of an iterative least squares waveform inversion of strong motion and teleseismic records to the 1978 tabas iran earthquake an iterative least squares technique is used to simultaneously invert the strong motion records and teleseismic p waveforms for the 1978 tabas iran earthquake to deduce the rupture history the method solves for both slip amplitudes and rupture times on a finite fault several inversions of the data are done to determine the best fitting hypocenter average rupture velocity and source time function within the range of our parameter search the effects of using different data sets and different parametrizations of the problem linear versus nonlinear are also considered teleseismic body waves are shown to be essential to obtain a reliable solution due to the sparse coverage of the fault plane by strong motion stations a simple triangular source time function is compared with a modified kostrov source time function for a circular rupture and a constant propagating stress drop although the waveforms used in the inversions can not resolve between these two time functions the kostrov source time function gives a moment estimate and maximum fault displacement more consistent with long period surface waves and field observations the results of the iterative inversion for slip amplitudes and rupture times are compared with the results of a linear inversion for slip amplitudes in which the rupture velocity is fixed flexibility in the sequence of faulting for the linear inversion is obtained by allowing multiple rupture intervals a consensus of all the inversion runs indicates a complex multiple source for the tabas earthquake with four main source regions over a fault length of 90 km and an average rupture velocity of 2 5 km sec

self consistent earthquake fault scaling relations update and extension to stable continental strike slip faults using seismic moment m length l data for stable continental region scr faults augmented by data not included in previous studies this article reassesses and confirms the bilinear scaling relation for the dip slip faults of leonard 2010 furthermore using the new data i propose a separate bilinear relation for estimating magnitude from surface rupture length there are now a small number of scr strike slip earthquakes for which the fault dimensions have been estimated i use these to constrain a trilinear scaling relation for this class of fault for the four fault types interplate dip slip interplate strike slip scr intraplate dip slip and scr intraplate strike slip the scaling relations for the 10 permutations of m d l w and a are given

scaling differences between large interplate and intraplate earthquakes a study of large intraplate earthquakes with well determined source parameters shows that these earthquakes obey a scaling law similar to large interplate earthquakes in which m 0 l 2 or u l where l is rupture length and u is slip in contrast to interplate earthquakes for which 1 10 5 for for the intraplate events 6 10 5 which implies that these earthquakes have stress drops about 6 times higher than interplate events this result is independent of focal mechanism type this implies that intraplate faults have a higher frictional strength than do plate boundaries and hence that faults are velocity or slip weakening in their behavior this factor may be important in producing the concentrated deformation that creates and maintains plate boundaries

pyrite as a record of hydrothermal fluid evolution in a porphyry copper system a sims empa trace element study porphyry copper deposits are currently the world s largest source of copper and molybdenum and are also among the largest reservoirs of gold in the upper crust despite the fact that pyrite is a ubiquitous mineral phase in these deposits and secondary cu enrichment processes are commonly controlled by the abundance of this sulfide the major and trace element chemistry of pyrite from porphyry systems remains unconstrained in this study we report the first comprehensive trace element database of pyrite from the dexing deposit china s largest porphyry cu deposit by combining high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capabilities of secondary ion mass spectrometry sims in a suite of samples from the dexing deposit we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and heavy metals e g cu co ni zn hg in pyrite from porphyry systems are more significant than previously thought among the elements analyzed cu as au and ni are the most abundant with concentrations that vary from sub ppm levels to a few wt i e 6 wt cu 3 wt as 0 25 wt au and 0 2 wt ni detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrite from the dexing deposit is characterized by complex chemical zoning where the studied elements occur in different mineralogical forms while as occurs as a structurally bound element in pyrite cu and au can occur as both solid solution and micro to nano sized particles of chalcopyrite and native au or au tellurides respectively indicating that pyrite can control metal speciation and partitioning during porphyry cu mineralization the well developed oscillatory zoning detected in pyrite where cu rich as depleted growth zones alternate with cu depleted as rich layers indicates that cu is geochemically decoupled from as suggesting that this selective partitioning of metals into pyrite is most likely the result of changes in hydrothermal fluid composition

mineralized breccia clasts a window into hidden porphyry type mineralization underlying the epithermal polymetallic deposit of cerro de pasco peru cerro de pasco peru is known for its large epithermal polymetallic zn pb ag cu bi mineralization emplaced at shallow level a few hundred meters below the paleo surface at the border of a large diatreme dome complex porphyry style veins crosscutting hornfels and magmatic rock clasts are found in the diatreme breccia and in quartz monzonite porphyry dikes such mineralized veins in clasts allow investigation of high temperature porphyry style mineralization developed in the deep portions of magmatic hydrothermal systems quartz in porphyry style veins contains silicate melt inclusions as well as fluid and solid mineral inclusions two types of high temperature 600 c quartz molybdenite chalcopyrite pyrite veins are found in the clasts early thin 1 2 mm and sinuous ht1 veins are crosscut by slightly thicker up to 2 cm and more regular ht2 veins the ht1 vein quartz hosts co2 and sulfur rich high density vapor inclusions two subtypes of the ht1 veins have been defined based on the nature of mineral inclusions hosted in quartz i ht1bt veins with inclusions of k feldspar biotite rutile and minor titanite and ii ht1px veins with inclusions of actinolite augite titanite apatite and minor rutile using an emplacement depth of the veins of between 2 and 3 km 500 to 800 bar derived from the diatreme breccia architecture and the supposed erosion preceding the diatreme formation multiple mineral thermobarometers are applied the data indicate that ht1 veins were formed at temperatures 700 c ht2 veins host assemblages of polyphase brine inclusions generally coexisting with low density vapor rich inclusions trapped at temperatures around 600 c rhyolitic silicate melt inclusions found in both ht1 and ht2 veins represent melt droplets transported by the ascending hydrothermal fluids la icp ms analyses reveal a chemical evolution coherent with the crystallization of an evolved rhyolitic melt quartz from both ht1 and ht2 veins also contains secondary low temperature 300 c brine and aqueous fluid inclusions that record the cooling of the system both vein types are locally crosscut and or reopened by a pre diatreme polymetallic event consisting of pyrite sphalerite with chalcopyrite disease galena chalcopyrite tetrahedrite tennantite and minor quartz la icp ms analyses of mineral and high temperature fluid inclusions hosted in ht1 and ht2 veins and in situ secondary ion mass spectrometry oxygen isotope analyses of vein quartz indicate a magmatic signature for the mineralizing fluids with no major meteoric water input and allow reconstruction of the source and chemical evolution of fluids that formed these porphyry style veins as snapshots of the early and deep mineralizations at cerro de pasco this detailed study of the porphyry type mineralization hosted in clasts offers a unique opportunity to reconstruct the late magmatic and early hydrothermal evolutions of porphyry mineralization underlying the world class cerro de pasco epithermal polymetallic zn pb ag cu bi deposit

genesis of the bangbu gold deposit in the southern tibet evidenced from in situ sulfur isotopes and trace element compositions of pyrite abstract the bangbu orogenic gold deposit in the north himalaya of the southern tibet contains more than 40 t au at an average grade of 7 0 g t in this deposits gold bearing quartz veins were controlled by nearly e trending qusong cuogu zhemulang shear zone and occurred within the secondary faults which crosscut late triassic greenschist facies rocks to further understand the sulfur source and ore forming process we have conducted a compressive study of in situ sims sulfur isotopes and la icp ms trace element compositions of two stages of pyrite at bangbu early stage pyrite py1 is coarse grained mostly 0 2 2 mm and euhedral and has gold concentrations of less than 0 3 54 ppm mean of 20 ppm and 34s values of 1 6 5 1 mean of 3 2 late stage pyrite py2 is generally fine grained mostly

multiple rejuvenation episodes of a silicic magma reservoir at the origin of the large diatreme dome complex and porphyry type mineralization events at cerro de pasco peru abstract the cerro de pasco district in central peru hosts one of the world largest porphyry related epithermal polymetallic deposits the district is centered onto a large diatreme dome complex crosscut by numerous dacite to rhyodacite bodies showing domal structures and quartz monzonite dykes three temporally distinct high temperature porphyry type mineralization events have been recognized pm1 pm2 and pm3 dating of the latter by molybdenite re os and by zircon u pb la icp ms and ca id tims geochronology complements the already available dataset of zircon u pb ages of the subvolcanic and volcanic rocks mostly dacitic in composition occurring in the district and shows the existence of successive short lived episodes 50 at pressures between 0 9 and 3 4 kbar and at temperatures between 680 c and 725 c at such conditions magma is beyond the point of rheological lock up and is not eruptible the emplacement of the mostly dacitic subvolcanic and volcanic rocks has required a series of rejuvenation events of the upper crustal high crystallinity silicic magma reservoir field relationships and geochronology indicate that emplacement of the subvolcanic and volcanic rocks is preceded each time by high temperature 600 c quartz pyrite magnetite chalcopyrite and quartz molybdenite veining forming the three recognized porphyry type mineralization events hydrothermal quartz of these veins host silicate melt inclusions a rare feature in hydrothermal veins their composition determined by la icp ms analysis indicates that the mineralizing fluids potentially sourced from intermediate magma recharges have circulated in a magma reservoir in which the residual interstitial melt was more evolved than the melt trapped as inclusions in the magmatic quartz the combined geochemical and geochronological data obtained show that several episodes of rejuvenation of a highly crystallized upper crustal silicic magma reservoir probably triggered by intermediate magma recharges and by circulation of co2 and s rich fluids exsolved from them are at the origin of the large diatreme dome complex and porphyry type mineralization events at cerro de pasco

rupture complexity of a moderate sized mb 6 0 earthquake broadband body wave analysis of the north yemen earthquake of 13 december 1982 abstract the occurrence of the north yemen earthquake of 13 december 1982 provides an important opportunity to study source properties of earthquakes in the southern arabian peninsula although moderate in size m b 6 0 this earthquake is the largest to have occurred in the region since the deployment of the global digital seismograph network p waves recorded at teleseismic distances can be obtained from stations of this network and of the graefenberg array that are flat to displacement and velocity in the frequency range from 0 01 to 5 0 hz the broad bandwidth of the data is necessary for deriving a dynamic description of the earthquake as well as the static properties of the source in contrast inversions using only long period data provide much less insight into the complexity of rupture by fitting the displacement pulse shapes with synthetics we find that the yemen earthquake was a complex rupture consisting of two events that occurred about 3 0 sec apart the depth of both hypocenters is estimated to be 7 km the focal mechanisms of the events each have a nodal plane that strikes 340 and dips 60 to the east however the slip directions of the focal mechanisms are in slightly different directions 230 and 300 respectively the total moment of the earthquake is 3 0 10 25 dyne cm with the second event having three times the moment of the initial event by inverting p wave arrival time differences at each station we find the second hypocenter is located 7 5 km from the initial hypocenter in a direction that is nearly colinear with the nnw striking nodal plane of the focal mechanisms of each event the trend of extensional ground cracks in the epicentral region and the predominant strike of composite focal mechanisms of locally recorded aftershocks are also in a nnw direction from the consistency of these observations we infer that the east dipping nnw striking nodal planes are the fault planes the static stress drop of the first and second events are 44 and 31 bars respectively inverting the energy flux in the velocity waveforms we find the energy radiated by the earthquake is 4 8 10 20 dyne cm this implies an average apparent stress of 4 bars at different times during the aftershock sequence seismicity tended to cluster about one or another of two different planes which although having roughly the same strike had conjugate dips one of these planes delineated late in the aftershock sequence coincides with the inferred fault plane for the main shock the complexity of the main shock and of the aftershock sequence suggests that strain accumulated on a system of strongly interdependent faults as the region became critically loaded the effect of a major rupture was to critically stress faults adjacent to the initial nucleation the second event of the main shock represents the rapid release of stress from the fault system while the ensuing aftershock sequence represents the gradual release of stress

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

characterisation of triassic rifting in peru and implications for the early disassembly of western pangaea abstract triassic igneous and sedimentary rocks exposed within the basement of the andes were deposited in a series of rifts and may record the early disassembly of western pangaea these rocks are sporadically exposed along almost the entire length of western south america although reliable geochronological and isotopic data are sparse we combine new geochronological zircon u pb isotopic hf nd and geochemical data with stratigraphic observations to constrain the age and tectonic setting of the mitu rift of southern peru the peruvian mitu rift is compared with other triassic rifts in colombia and ecuador palanda rift 240 225 ma bolivia mitu rift triassic bolivia chile and argentina e g cuyo basin 246 230 ma and conclusions are reached regarding the relationship between triassic extension along the western margin of pangaea and the eventual formation of the proto caribbean and central atlantic oceans the mitu rift peru was active during 245 240 to 220 ma and was synchronous with rifting along the pacific margin of colombia and ecuador along the chilean margin and western argentina and probably rifting within bolivia rifting north of the huancabamba deflection was accompanied by subduction and led to seafloor spreading whereas rifting along the peruvian and chilean margins mainly occurred in the absence of subduction and terminated prior to the formation of extensive transitional crust extension within peru and chile probably occurred via a combination of transtension steepening and detachment of an arrested slab we propose that plate tectonic forces initiated the early break up of pangaea by attenuating its margins and enhancing mantle upwelling prolonged extension may have propagated along pre existing weak zones that extended into the continental interior captured melts derived from the upwelled mantle forming a lip e g central atlantic magmatic province became hot and weak and eventually lead to the formation of a juvenile ocean e g central atlantic

multi stage hydrothermal processes at the laozuoshan gold deposit in ne china insights from textures and compositions of sulfide assemblages abstract the laozuoshan gold deposit is a large gold deposit which experienced the early hydrothermal mineralization and the late hydrothermal mineralization in jiamusi massif northeast china the jiamusi massif hosts numerous gold deposits that are commonly considered as products of the metamorphic hydrothermal process during two oceanic subductions episodes in this study we report detailed textures observations identify the sulfides phases by the laser raman spectroscopy and obtain in situ composition data with electron probe micro analysis to further understand the formation and metasomatism of multi stage sulfides deposition in the laozuoshan gold deposit the paragenetic relationship between pyrite and marcasite at the nanoscale was also clarified by focused ion beam scanning electron microscopy and transmission electron microscopy according to the observed textural relationships among ore and gangue minerals the early hydrothermal mineralization period can be divided into three stages stage i to stage iii and the late hydrothermal mineralization period into four stages stage iv to stage vii the sulfides are mainly pyrrhotite po 1 in stage i with minor chalcopyrite arsenopyrite and pyrite the ag rich averaging 15 44 wt electrum au 1 is hosted in arsenopyrite which is also rich in cobalt averaging 2 69 wt pyrite py 2 is the main sulfide in stage ii with minor chalcedony and calcite the mineral stability relationships in both stage i and stage ii confirm that there was an increase in sulfur and oxygen fugacities and a decrease in temperature the sulfides are mainly arsenopyrite apy 2 in stage iii with minor native golds and tellurbismuth the native golds au 2 average 8 02 wt silver arsenopyrite geothermometers indicate precipitation temperatures between 420 and 390 c for stage iii the sulfur and oxygen fugacities of the ore related fluids were below the pyrite pyrrhotite buffer during stage iii revealing a reduced fluids system in the late hydrothermal mineralization period multiple magmatic activities caused multi stage hydrothermal fluids events in stage vi the pyrrhotite replaced by marcasite and pyrite through the dissolution reprecipitation mechanism indicating the increase in ph and oxygen fugacity of the fluids and alteration from weakly acidic and weakly reduced conditions to neutral and weakly oxidizing conditions the mineralogical and compositional evolution of the sulfides in the laozuoshan gold deposit constrain the physicochemical conditions of multi stage ore forming fluids which is of considerable significance in understanding the metamorphic hydrothermal superimposed gold bearing fluids evolved in the jiamusi massif

sedimentology organic geochemistry and petroleum potential of jurassic coal measures tarim junggar and turpan basins northwest china lower and middle jurassic coal bearing strata occur widely throughout central asia and are well developed in northwestern china where their thicknesses in the southern junggar northern tarim and turpan basins exceed 2500 2300 and 1500 m respectively examination of these strata along 13 transects across basin margin outcrop belts indicates that they are entirely nonmarine meandering fluvial deposits with local development of braided fluvial and lacustrine deltaic facies chinese subsurface data suggest that regional jurassic lacustrine facies are present down depositional dip consistent with predictions from global circulation modeling of early and middle jurassic monsoonal precipitation laboratory analyses of coals and organic rich shales show a dominance of terrestrial higher plant components visual kerogen analysis indicates that vitrinite inertinite and exinite are the dominant macerals and elemental analysis characterizes most kerogens as type iii rock eval analyses yield moderate hydrogen index values 50 300 and very low oxygen index values 20 jurassic source rock extracts are characterized by odd over even normal alkane distributions high pristane phytane and high hopane sterane ratios dominance of c29 sterane homologs local abundance of diterpenoid compounds and low abundance of tricyclic terpanes geochemical correlation with four petroleums from the junggar tarim and turpan basins strongly suggests that the jurassic coaly deposits and their lacustrine equivalents downdip are petroleum source rocks sterane and hopane distributions of petroleums and extracts of their putative jurassic source rock are similar and can be easily distinguished from published distributions of these compounds in other source rock layers additional correlation parameters include high pristane phytane low abundance or lack of tricyclic terpanes but similar distributions where present and lack of gammacerane with one exception and carotanes compounds that characterize permian and ordovician source rocks and their respective petroleums pyrolysis gas chromatography of selected jurassic samples s ggests that they possess potential for liquid hydrocarbon generation expulsion of c15 hydrocarbons from jurassic source rocks appears likely despite the traditional view that bituminous coals are incapable of expelling long chain hydrocarbons end page 929

element migration of pyrites during ductile deformation of the yuleken porphyry cu deposit nw china abstract the strongly deformed yuleken porphyry cu deposit ypcd occurs in the kalaxiangar porphyry cu belt kpcb which occupies the central area of the central asian orogenic belt caob between the sawu er island arc and the altay terrane in northern xinjiang the ypcd is one of several typical subduction related deposits in the kpcb which has undergone syn collisional and post collisional metallogenic overprinting the ypcd is characterized by three pyrite forming stages namely a hydrothermal stage a py i a syn ductile deformation stage b py ii characterized by cu au enrichment and a fracture filling stage c py iii in this study we conducted systematic petrographic and geochemical studies of pyrites and coexist biotite which formed during different stages in order to constrain the physicochemical conditions of the ore formation euhedral fragmented py i has low pb and high te and se concentration and ni contents are low with co ni ratios mostly between 1 and 10 average 9 00 py i is further characterized by enrichments of bi as ni cu te and se in the core relative to the rim domains anhedral round py ii has moderate co and ni contents with high co ni ratios 10 average 95 2 and average contents of 46 5 ppm pb and 5 80 ppm te py ii is further characterized by decreasing bi cu pb zn ag te mo sb and au contents from the rim to the core domains annealed py iii has the lowest co content of all pyrite types with co ni ratios mostly

trace element diffusion and incorporation in quartz during heating experiments heating of quartz crystals in order to study melt and high temperature fluid inclusions is a common practice to constrain major physical and chemical parameters of magmatic and hydrothermal processes diffusion and modification of trace element content in quartz and its hosted melt inclusions have been investigated through step heating experiments of both matrix free quartz crystals and quartz crystals associated with sulfides and other minerals using a linkam ts1500 stage magmatic and hydrothermal quartz were successively analyzed after each heating step for cu al and ti using electron probe micro analyzer after the last heating step quartz crystals and their hosted melt inclusions were analyzed by laser ablation inductively coupled plasma mass spectrometry and compared to unheated samples heated samples reveal modification of cu li na and b contents in quartz and modification of cu li ag and k concentrations in melt inclusions our results show that different mechanisms of cu li and na incorporation occur in magmatic and hydrothermal quartz heated magmatic quartz records only small up to a few ppm enrichment in cu and na mostly substituting for li by contrast heated hydrothermal quartz shows enrichment up to several hundreds of ppm in cu li and na which substitute for originally present h this study reveals that the composition of both quartz and its hosted melt inclusions may be significantly modified upon heating experiments leading to erroneous quantification of elemental concentrations in addition each quartz crystal also becomes significantly enriched in cu in the sub surface layer during heating we propose that sub surface cu enrichment is a direct indication of cu diffusion in quartz externally sourced from both the surrounding sulfides as well as the copper pins belonging to the heating device our study shows that the chemical compositions of both heated quartz and its hosted inclusions must be interpreted with great caution to avoid misleading geological interpretations

fluid evolution in the w cu zn pb san cristobal vein peru fluid inclusion and stable isotope evidence abstract the zn pb ag cu san cristobal district is located 100 km east of lima in the western cordillera of peru it is centred around the chumpe intrusion and is composed of vein and carbonate replacement ore types the main san cristobal vein presents a paragenesis that can be divided into three stages a an early wolframite quartz pyrite stage b a quartz base metal stage and c a late quartz carbonate barite stage fluid inclusions in quartz from the tungsten stage are biphase lv at room temperature and homogenise to the liquid phase between 146 and 257 c their salinities range between 2 1 and 5 1 wt nacl equiv rare inclusions contain an additional crystal of halite and have salinities of 46 54 wt nacl equiv data of the first two stages show a decrease in homogenisation temperatures concomitant with a salinity decline fluid inclusions in quartz from the late stage homogenise at higher temperatures between 252 and 323 c with salinities ranging between 4 6 and 6 7 wt nacl equiv hydrogen and oxygen isotope data indicate a two stage evolution isotopic compositions of the fluid associated with the first two stages define a trend with constant 18 o values and decreasing d values 18 o 3 2 to 5 0 v smow and d 60 to 112 v smow which is interpreted as mixing of a dominantly magmatic component with minor meteoric water that had equilibrated with the host rocks this interpretation is supported by sulphur and lead isotopic data from previous studies by contrast the quartz carbonate barite stage bears isotopic characteristics defining a trend with a coupled decrease of 18 o and d 18 o 8 1 to 2 5 v smow and d 57 to 91 v smow and is explained by addition of meteoric water to the system and subsequent mixing with a less important magmatic component different fluid origins are confirmed by laser ablation icp ms analyses of the triphase lvh and biphase lv primary inclusions the concentrations of the major ore elements i e w cu zn and pb decrease throughout the paragenesis w and to a lesser extent cu show significant variations associated with a steep decrease in their concentration the decreasing concentrations can be explained by mineral deposition and dilution by the meteoric fluid differences in the rate of decrease indicate selective precipitation of w fluid inclusions of the quartz carbonate stages show an abrupt increase in ba and sr concentrations this is interpreted to reflect a higher volume of host rock silicate alteration probably due to the increasing size of the fluid flow cell and is explained by the input of a third fluid of unknown origin la icp ms analyses show that the fluids were already depleted in w and cu before reaching the emplacement of carbonate replacement ore type whereas zn and pb were still present in considerable amounts this is again due to selective precipitation and is consistent with the interpretation that the economically interesting metals were dominantly introduced by magmatic fluids

comparison of earthquake scaling relations derived from data of the instrumental and preinstrumental era estimates of surface rupture displacement and magnitude for crustal earthquakes from the preinstrumental era pre 1900 tend to be greater than the corresponding estimates derived from modern scaling relations we investigate this tendency using an expanded and updated version of the earthquake dataset of wells and coppersmith 1994 to fit regression relations of moment magnitude on surface rupture length and rupture area and average surface displacement on surface rupture length separate relations are fitted to preinstrumental and instrumental data and the results compared to the equivalent relations of wells and coppersmith we find that our relations for instrumental data remove some but not all of the differences between the preinstrumental data and the relations of wells and coppersmith we attribute the remaining differences largely to natural censoring of surface displacements less than about 1 m and surface rupture lengths less than about 5 km from the dataset for the preinstrumental era because regressions constructed from similarly censored instrumental data are indistinguishable from the preinstrumental regressions since the regressions for our censored instrumental data i e restricted to moderate to large earthquakes are different from regressions for our complete dataset of instrumental earthquakes and from the regressions of wells and coppersmith both with a larger proportion of small to moderate earthquakes the results may indicate that large earthquakes have different scaling relationships from those of smaller earthquakes

rupture patterns and preshocks of large earthquakes in the southern san jacinto fault zone we relocated the large 1937 1942 and 1954 earthquakes in the san jacinto fault zone the epicenters of the main shocks aftershocks and some preshocks were determined using empirical station corrections from recent small events in the study areas the 1937 ml 5 9 earthquake has an epicenter between the surface traces of the san jacinto and buck ridge faults and aftershocks suggest about 7 km of rupture predominantly to the northwest a significant increase in small earthquake activity occurred about formula yr before this event the 1954 m l 6 2 earthquake is located at the southeast end of the mapped trace of the san jacinto fault and aftershocks suggest about 15 km of rupture further southeast into an area of folded young sediments with no surface fault trace this event was preceded by a cluster of small earthquakes which occurred within an 8 hr period 10 weeks before the main event and in the eventual rupture zone the 1942 m l 6 3 earthquake is located southwest of the southeast end of the coyote creek fault large aftershocks of this event are spread over a 15 by 18 km area southwest of the coyote creek fault and are not associated with any one fault the relation of the 1942 event to the san jacinto fault zone is not simple

marcasite inversion and the petrographic determination of pyrite ancestry pyrite formed by the inversion of marcasite or by oxidative leaching of pyrrhotite can be recognized in polished sections by the following characteristics compiled from synthetic pyrite after marcasite and natural samples of pyrite after marcasite and after pyrrhotite pyrite formed by inversion from marcasite is characterized by approximately 2 modal percent pore space no by products filling the pores optical anisotropy dark green to dark red anhedral shape and polycrystalline daughter pyrite domains in two orientations relative to the marcasite parent crystal pyrite or marcasite formed by oxidative dissolution as opposed to leaching of pyrrhotite exhibits up to 32 modal percent pore space gaps between the pyrite and parent pyrrhotite pores and gaps filled with by product siderite magnetite hisingerite or other fe bearing phase optically isotropic character for pyrite development of crystal faces and random orientation relative to the parent pyrrhotite marcasite formed by oxidative leaching of fe as opposed to complete dissolution from pyrrhotite also exhibits a large amount of pore space but has preferred orientation relative to the parent pyrrhotite pyrite after marcasite may be used as an indicator of ph 5 and t ca 240 degrees c during deposition of the parent marcasite marcasite precipitated following dissolution of pyrrhotite is also indicative of those conditions during alteration marcasite formed by oxidative leaching of pyrrhotite cannot be used as evidence of those conditions however

direct analysis of ore precipitating fluids combined ir microscopy and la icp ms study of fluid inclusions in opaque ore minerals laser ablation inductively coupled plasma mass spectrometry la icp ms in combination with near infrared microscopy of fluid inclusions hosted by ore minerals that are opaque to visible light can provide the composition of ore precipitating fluids we applied the two techniques to well constrained fluid inclusion assemblages hosted by pyrite enargite and quartz to trace the source and evolution of the fluids in high sulfidation epithermal veins overprinting a porphyry copper deposit at rosia poieni romania despite some analytical limitations caused by the sulfide host minerals the data demonstrate that fluids trapped in apparently cogenetic quartz and ore minerals are chemically different systematic changes in major and trace element ratios between liquid vapor vapor rich and brine fluid inclusion assemblages in the three minerals record an evolving fluid source at the porphyry to epithermal transition regarding their cs na k ratios most of epithermal quartz hosted fluid inclusion assemblages form a well defined cluster which coincides with the narrow range of the porphyry stage fluids trapped in early quartz of the porphyry stockwork veins their cu na k ratios are 10 to 100 times lower compared to the pyrite hosted inclusions and correspond to the lowest cu na k ratios recorded for the porphyry stage fluids by contrast pyrite hosted vapor rich fluid inclusions have the highest cu na k similar to the highest cu na k ratios measured in the porphyry stage fluid inclusions the results led to the conclusion that the gangue and ore minerals in the high sulfidation epithermal veins at rosia poieni formed by successive pulses of chemically distinct hydrothermal fluids that were successively exsolved from residual melt batches of a progressively crystallizing magma at greater depth these results are consistent with detailed textural observations but petrography alone could not have led to this unambiguous conclusion