the dinar earthquake mw 6 2 october 1 1995 afyon turkey and earthquake hazard of the dinar civril fault a moderately strong earthquake mw 6 2 occurred in the town of dinar at 17 57 ut on october 1 1995 taking the lives of 90 people and damaging about 4500 buildings its epicenter is located near the dinar civril fault and its focal mechanism is linked to a northeast southwesterly tensional stress field arising from the interaction between the subducting african plate and the overriding aegean anatolian plate in the eastern mediterranean surface cracks of the october 1 earthquake have been observed 10 km continuously along the dinar civril fault the cracks have displayed a mode of dip slip however some have also indicated lateral slip the different modes of slip are generally in agreement with the fault plane solution and are indicators of the complex nature of the rupture process in investigating the earthquake hazard of the dinar civril fault and proximity the maximum likelihood method was used to estimate seismic hazard parameters of b value seismicity activity rate m and the expected maximum magnitude mmax the data consisted of the historical data covering the period between 1800 1900 and instrumental data between 1900 and 1992 this method allowing use of the mixed earthquake catalogue containing both historical and instrumental earthquake data yielded values of 0 70 1 92 and 7 14 for b m and mmax respectively the recurrence time estimated for an earthquake of a magnitude of mw 6 2 is 123 years the non occurrence probabilities of such an earthquake in 1 and 50 years are 0 21 and 0 04 respectively

u pb geochronology of vms mineralization in the iberian pyrite belt a geochronology study using u pb isotope dilution tims analyses of zircon has been conducted to determine the ages of volcanic associated massive sulfide vms deposits in the iberian pyrite belt ipb the world s most prolific vms province ages have been determined for host rocks to four vms systems that span the ipb the giant rio tinto and aljustrel districts in the central region lagoa salgada to the west and las cruces to the east a sample of chloritized quartz porphyritic dacite rhyolite in the footwall of the san dionisio massive sulfide deposit of the rio tinto district is 349 76 0 90 ma this is taken as the best age estimate of the mineralization in the rio tinto district probably the world s largest volcanogenic massive sulfide system two xenocrystic zircons from the same sample yielded 207pb 206pb ages of 414 and 416 ma which provide a minimum estimate for the age of the inherited component a biotite tonalite from the campofrio area 3 5 km north of the center of the rio tinto district is chemically similar to the felsic host rock protolith at rio tinto the campofrio sample has an age of 346 26 0 81 ma slightly younger and outside of the 2 error for the rio tinto age therefore this phase of this intrusion was not a heat source for the hydrothermal system that formed the deposits of the rio tinto district the campofrio sample also has three zircon analyses with 207pb 206pb minimum ages of 534 536 and 985 ma indicating inheritance from ordovician and neoproterozoic sources in the aljustrel vms district a u pb zircon age of 352 9 1 9 ma characterizes the altered green tuff host rock of the algares deposit which is slightly older than the rio tinto age two zircons with 207pb 206pb ages of 531 and 571 ma from this sample indicate inheritance from a cambrian or older source the age of mineralization at lagoa salgada is given by essentially identical ages of 356 21 0 73 and 356 4 0 8 ma for footwall and hanging wall samples respectively the hanging wall sample has two zircon analyses with 207pb 206pb ages of 464 and 466 ma indicating inheritance from an ordovician or older source the age for an altered dacite tuff sample from the hanging wall of the las cruces deposit is 353 97 0 69 ma one zircon analysis from the las cruces sample has a 207pb 206pb age of 1048 ma indicating inheritance from a neoproterozoic source these u pb ages refine the ipb geochronology provided by previous studies and they suggest that either volcanism progressed toward the center of the ipb or that volcanism was broadly static and the strata were progressively rifted to the margins during transtensional basin formation the zircon inheritance provides direct evidence for proterozoic to ordovician sources reflecting either basement rocks beneath the phyllite quartzite group during vms formation in late tournaisian times or a proterozoic to ordovician detrital component in phyllite quartzite group source rocks the presence of an older crustal component is consistent with vms formation during rift development at a continental margin

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

late quaternary sea levels and crustal movements coastal british columbia late quaternary sea level fluctuations on the british columbia coast have been established from studies of terrestrial and marine sediments and landforms these studies indicate that the sea level history of mainland british columbia and eastern vancouver island is very different from that of the queen charlotte islands and western vancouver island specifically in the former areas there was a rapid rise of submerged coastal lowlands between about 13 000 and 10 000 years ago emergence culminated about 6000 9000 years ago depending on the locality when the sea relative to the land was 12 m or more lower than at present in some areas during middle and late holocene time relative sea level rose on the mainland coast and at least locally on eastern vancouver island resulting in inundation of coastal archaeological sites and low lying terrestrial vegetation tidal records and precise levelling suggest ongoing submergence of at least part of this region in contrast shorelines on the queen charlotte i

stratigraphy of the tectonically imbricated lithological succession of the neves corvo mine area iberian pyrite belt portugal biostratigraphic research based on palynomorphs and ammonoids of the tectonically imbricated lithological succession of the neves corvo mine in the portuguese part of the iberian pyrite belt has yielded ages for all formerly recognised lithostratigraphic units these can be assembled in three main lithological sequences 1 detrital sandy shale substrate phyllite quartzite formation of late famennian age 2 volcano sedimentary complex divided into a lower and an upper suite in which one basic three dolerite sills and four felsic volcanic units and a mineralised package of massive sulphides are identified with ages which range from the late famennian to the late visean 3 flysch succession mertola formation composed of shale and greywacke dated as late visean to early serpukhovian precise biostratigraphic dating of the sedimentrary host rocks of massive sulphide mineralisation constrains the age of the latter to the late strunian 354 8 354 0 ma three stratigraphic hiatuses corresponding to early middle strunian tournaisian and early visean respectively and a south westward progressive unconformity were also recognised sequences 1 and 2 are related to extensional episodes while sequence 3 marks the beginning of compressive tectonic inversion which gave rise to south westward flysch progradation in close relation to a foreland basin development our results lead to the reinterpretation of the tectonic structure of the neves corvo mine with implications for the interpretation of the regional basin dynamics and metal exploration

finite fault analysis of the 1979 march 14 petatlan mexico earthquake using teleseismic p waveforms summary vertical teleseismic p waves recorded for the 1979 march 14 petatlan mexico earthquake were used to derive the distribution of coseismic slip using a linear finite fault inversion scheme that solves for the amount of slip in each of a series of consecutive time windows data recorded by six stations of the global digital seismograph network were inverted in addition to digitized analogue long period recordings available from nine worldwide standardized seismograph network stations the digital data include four broad band and short period velocity waveforms reconstructed from the short and long period components the time window approach allows for a variable rise time on the fault and accounts for the source multiplicity evident in the recorded p waveforms synthetic tests conducted using the inversion method on the limited data set however reveal that the data are insufficient to identify the exact dislocation duration on the fault the method is thus implemented by prescribing the fault rise time using five consecutive 1 s time windows the coseismic slip inferred from the p waves shows a small 70 cm peak near the earthquake hypocentre and a large zone of dislocation 1 2 m maximum further south east the slip pattern covers depths from 3 to 25 km and is located south east of other recent large interplate ruptures on the michoacan segment of the mexican subduction zone this result indicates that the 1979 petatlan earthquake broke an independent adjacent portion of the cocos north america plate boundary the seismic moment of 1 5 1027 dyn cm inferred from the p waves is approximately one half the long period moment estimated by other investigators from the observed surface waves although the discrepancy is within the uncertainty of the seismic moment estimates it may suggest the presence of a component of slow interplate motion that did not radiate significant p wave energy

the 1 october 1995 dinar earthquake sw turkey the dinar earthquake ms 6 1 usgs pde of 1 october 1995 occurred on the nwse trending dinar fault the earthquake is associated with a 10 km long surface rupture with predominantly normal faulting the mainshock was preceded by a series of foreshocks that started 6 days before the mainshock and included two md 4 5 events the mainshock source mechanism derived from the inversion of broad band p waves revealed that two sub events occurred on a nw se trending normal fault with a small strike slip component according to the source model estimated in this study the first rupture started at a depth of about 8 km and reached to a depth of about 12 km propagating north west the total seismic moment found from the inversion of p waveforms is 2 0 times 10 18 nm the seismic moment of the second sub event was about four times larger than the first one field observations gps measurements and slip vector obtained from the inversion of broad band p waveforms suggest that the nw se trending dinar fault is due to the internal deformation of sw anatolia moving south westwards

facies analyses and volcanic setting of the giant neves corvo massive sulfide deposit iberian pyrite belt portugal in the iberian pyrite belt volcanic rocks are relatively scarce accounting for approximately only 25 of the geologic record with the remaining 75 consisting of sedimentary units this association is very clear in the host succession to the neves corvo massive sulfide deposit in portugal the neves corvo host succession comprises the products of explosive and effusive rhyolitic eruptions intercalated with mudstone that records a submarine below wave base environment and provides precise biostratigraphic age constraints the first and second volcanic events involved eruptions at local intrabasinal vents the first event generated thick beds of fiamme breccia that are late famennian in age the fiamme were originally pumice clasts produced by explosive eruptions and were subsequently compacted the second event was the late strunian latest famennian effusion of rhyolitic lava that was pervasively quench fragmented the third and final event is younger than the massive sulfide deposits poorly represented in the mine area and minor compared with the two other events the integration of biostratigraphic data with the volcanic facies architecture indicates that the neves corvo ore deposits are similar in age to the late strunian rhyolitic lava although regionally the iberian pyrite belt is essentially a sedimentary succession ore formation at neves corvo can be closely linked to discrete volcanic events that produced a relatively narrow range of volcanic facies

high pressure metamorphism in the early variscan subduction complex of the sw iberian massif abstract several units exposed in the boundary area of the ossa morena zone omz and the south portuguese zone spz preserve petrographic and thermobarometric evidence for an early metamorphic episode m1 developed under a high p low to intermediate t gradient related to early variscan subduction in the sw iberian massif in the omz these are the cubito moura unit p min 9 2 kbar and t 395 45 c blueschists from its basal melange p min 12 4 kbar and t 310 11 c and the underlying fuenteheridos group p 10 9 0 4 kbar and t 449 31 c the equivalent units in the spz are the la minilla formation p 8 7 0 4 kbar and t 388 16 c and the lawsonite pseudomorphs bearing pulo do lobo formation all these units formed part of an approximately ne verging orogenic wedge present coordinates developed by the accretion of subducted slabs of the outermost margin of gondwana and other elements of the rheic ocean realm from at least the middle devonian to the lowermost tournaisian high pressure rocks were subsequently emplaced on more internal zones of the omz that only experienced a younger high t low to intermediate p metamorphism m2 this high t event was coeval with magmatic activity from the uppermost devonian to the middle mississippian probably as a consequence of transtensional lithospheric thinning and or delamination of the lower crust and mantle lithosphere of the gondwana margin pre late devonian synorogenic sedimentation in forearc and back arc basins of the subduction complex evolved to a late devonian middle mississippian foreland basin system in early collisional stages finally a new middle late mississippian fold and thrust belt with opposite sw vergence and new foreland basins developed during late collisional stages

trondhjemites tonalites and diorites in the south portuguese zone and their relations to the vulcanites and mineral deposits of the iberian pyrite belt in the south portuguese zone close associations of diorites tonalites and trondhjemites occur north of the pyrite belt the period of their emplacement is pre carboniferous and not as has generally been assumed variscanpostorogen the trondhjemitic intrusive suite and the lower carboniferous spilite keratophyre association are related through their comagmatic derivation both series share sodium dominance low concentrations of large ion lithophile elements indicators of a water rich original magma and a deficient scorification of the element potential which was acummulated in the sulphide and manganese deposits of the pyrite belt through post volcanic hydrothermal processes the mineralogically and geochemically primitive composition of both plutomtes and vulcanites their mode of eruption from acid to basic facies as well as their position in the orogenic process indicate that they represent products of a successively proceeding partial melting of subducting oceanic crust the trondhjemitic intrusives are the initialites in the magmatic orogenic development

rapid creation and destruction of sedimentary basins on mature strike slip faults an example from the offshore alpine fault new zealand abstract seismic reflection profiles and multibeam bathymetric data are integrated to analyse the structure of the 25 km long strike slip dagg basin associated with the marine section of the alpine fault fiordland new zealand the basin is developing in almost 3000 m water depth at a releasing bend whilst contemporaneous transpression results in inversion of its southern end fiord derived glacio marine sediments flooded the basin during the last glaciation and provide a stratigraphic framework for structural analysis geometrical analysis enables an estimation of 450 1650 m of dextral displacement on the alpine fault at the releasing bend since the development of an unconformity estimated to have formed at between 30 and 110 ka this implies a dextral slip rate ranging from a possible minimum of 4 mm yr to the maximum of 35 mm yr constrained by the pacific australian plate motion rate despite total dextral displacement of 480 km on the alpine fault zone and a growth history spanning 15 20 myr this geomorphically well expressed and structurally complex strike slip basin developed and evolved rapidly during the late pleistocene and thus represents only the latest phase in the evolution of the alpine fault upward splaying structures within the fault zone exhibit a rapid spatial evolution in pleistocene strata which may reflect the interactions between high fault slip rate voluminous sedimentation supply inherited structural complexities in the basement rocks and deeper cover sequence and interactions between adjacent faults the present through going releasing bend at the northern end of the basin may have evolved from a more complex pull apart basin that developed between separate segments of the alpine fault the results from dagg basin illustrate the rates at which structural complexities and sedimentary basins can develop within highly active very mature through going continental wrench faults strike slip basins on the scale of 40 80 km 2 on such faults may be ephemeral features that can be developed and destroyed on a time scale of 10 5 10 6 years

strike slip orogens an explanation for the hercynides the nature of oblique plate interactions is not yet well understood the oblique interaction of pacific and n american plates has resulted in large scale migration rotation and accretion of microplates intervening basins are ephemeral individually filled and deformed oblique motion results in zones of both compression and extension the latter may be sufficient to generate new oceanic crust and the former to obduct it both subduction and collision are restricted in time and space the resulting orogen is extraordinarily complex in detail the far more complicated hercynides are the result of dextral interaction between continental plates europe and africa the lateral variability of the orogen the major and long lived strike slip faults the bimodal volcanism and related ore deposits of the european trough the lizard ophiolite and its melanges the nw spanish ophiolites and the iberian pyrite belt are all explained using an oblique collision model in particular the generation deformation and obduction of ophiolites in oblique slip mobile zones is discussed

rupture process of the 1987 superstition hills earthquake from the inversion of strong motion data a pair of significant earthquakes occurred on conjugate faults in the western imperial valley involving the through going superstition hills fault and the elmore ranch cross fault the first event was located on the elmore ranch fault m s 6 2 and the larger event on the superstition hills fault m s 6 6 the latter event is seen as a doublet teleseismically with the amplitudes in the ratio of 1 2 and delayed by about 8 sec this 8 sec delay is also seen in about a dozen strong motion records these strong motion records are used in a constrained least squares inversion scheme to determine the distribution of slip on a 2 d fault upon closer examination the first of the doublets was found to be itself complex requiring two episodes of slip thus the rupture model was allowed to have three separate subevents treated as separate ruptures with independent locations and start times the best fits were obtained when all three events initiated at the northwestern end of the fault near the intersection of the cross fault their respective delays are 2 1 and 8 6 sec relative to the first subevent and their moments are 0 4 0 9 and 3 5 10 25 dyne cm which is about half of that seen teleseismically this slip distribution suggests multi rupturing of a single asperity with stress drops of 60 200 and 15 bars respectively the first two subevents were confined to a small area around the epicenter while the third propagated 18 km southwestward compatible with the teleseismic and afterslip observations

inversion for slip distribution using teleseismic p waveforms north palm springs borah peak and michoacan earthquakes we have inverted the teleseismic p waveforms recorded by stations of the global digital seismograph network for the 8 july 1986 north palm springs california the 28 october 1983 borah peak idaho and the 19 september 1985 michoacan mexico earthquakes to recover the distribution of slip on each of the faults using a point by point inversion method with smoothing and positivity constraints in the inversion procedure a fault plane with fixed strike and dip is placed in the region of the earthquake hypocenter and divided into a large number of subfaults rupture is assumed to propagate at a constant velocity away from the hypocenter and synthetic ground motions for pure strike slip and dip slip dislocations are calculated at the teleseismic stations for each subfault the observed seismograms are then inverted to obtain the distribution of strike slip and dip slip displacement for the earthquake results of the inversion indicate that the global digital seismograph network data are useful for deriving fault dislocation models for moderate to large events however a wide range of frequencies which includes periods shorter than those within the passband of the long period global digital seismograph network instruments is necessary to infer the distribution of slip on the earthquake fault although the long period waveforms define the size dimensions and seismic moment of the earthquake data at shorter periods provide additional constraints on the variation of slip on the fault dislocation models obtained for all three earthquakes are consistent with a heterogeneous rupture process where failure is controlled largely by the size and location of high strength asperity regions

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

geology and geophysics as successful tools in the discovery of the lagoa salgada orebody sado tertiary basin iberian pyrite belt grândola portugal gravimetry was the main exploration method used in this high risk area to the north of the gr ndola fault in the iberian pyrite belt ipb it showed several targets among which the valverde lagoa salgada area stood out here in august 1992 a polymetallic massive sulphide orebody was found named lagoa salgada according to the geological characteristics of the area and to the nature of the surveyed targets other exploration techniques were used namely geology magnetometry resistivity electrical sounding magneto telluric seismic and mechanical drilling the deposit was found under a tertiary cover 128 m in depth complete with a 15 m thick gossan caused by paleoalteration with a supergene enrichment zone this gossan gave way to massive sulphides with intersections at times exceeding 60 m they are limited towards the footwall by an important fault with strong associated kaolinization which is interpreted as a reverse fault placed on the inverse limb of an anticlinal structure throughout the deposit the chemical composition of the mineralization showed great variation reaching significant values of zn pb sn cu as hg sb cd au and ag in the initial phase the deposit has an estimated tonnage of 5 mt it is related to a large gravity anomaly with the general orientation nw se which was investigated by 15 boreholes made by the instituto geologico e mineiro the drilling cut an important volcanic centre of an acid to intermediate nature around which intense hydrothermal activity was associated with contemporaneous sulphide mineralization the gravity anomaly has two nuclei a nw and a central one about 450 m apart where a pyrite orebody with polymetallic sulphides and stockwork sulphide mineralization are developed this discovery led to an extensive exploration project that confirmed the mining potentialities of the nw sector of the ipb to the north of gr ndola fault where previously no polymetallic sulphide occurrences were known

geochronological constraints on the emplacement history of an anorthosite rapakivi granite suite u pb zircon and baddeleyite study of the korosten complex ukraine u pb zircon baddeleyite ages obtained for the korosten anorthosite rapakivi granite complex ukrainian shield suggest that different magmatic phases were emplaced during a period of ca 30 million years as a series of distinct igneous episodes the earliest 1789 1 2 0 ma anorthosites were followed by 1781 3 3 2 ma dykes of plagiogranite porphyries the emplacement of a major rapakivi granite phase took place at 1767 4 2 2 ma and was followed by emplacement of layered intrusions of anorthosites gabbronorites diabases and ultrabasic rocks between 1761 and 1758 ma the minimum duration of magmatism of about 30 million years the 6 15 million years interval between igneous pulses and alternation of discrete episodes of basic and felsie magmatism are common features of major anorthositemangerite charnockite rapakivi granite complexes temporal distribution of igneous activity in the korosten complex shows that the gabbro anorthosites and the granites are not comagmatic although they are possibly cogenetic and that at least four portions of granitic and basic magmas were generated during a relatively long period of at least 30 million years the time gap of about 20 25 million years between early basic and later and more voluminous granitic magmatism characteristic of the korosten pluton wiborg and salmi batholiths probably reflects the duration of extensional processes before the generation of large volumes of magma in the lower crust

the ca 350 ma beja igneous complex a record of transcurrent slab break off in the southern iberia variscan belt abstract we report the results of an isotopic study of the large gabbro dioritic beja igneous complex bic in the boundary between the highly contrasting ossa morena om and south portuguese sp zones of the southern iberian variscan orogen this boundary is interpreted as a major suture zone materialized by discontinuous scattered strips of mafic ultramafic rocks the so called beja acebuches ophiolite complex baoc and by melange deposits of middle to late devonian age in the pulo do lobo accretionary prism plap the beja gabbro was interpreted either as part of the ophiolite like units or as a broadly arc related massif reflecting the northward subduction of oceanic lithosphere u pb zircon id tims dating of two diorites and a granodiorite points to igneous emplacement ages of 350 2 ma serpa 352 2 ma torrao and 353 4 ma sao pedro respectively whereas a felsic dyke yields a slightly younger age of 345 2 ma these results show that published ar ar dates do not represent igneous crystallization ages but merely reflect regional cooling below ca 500 c at least 10 ma after the major intrusive event probably as a result of uplift of the omz side of the suture zone relative to the subsiding spz 87sr 86sr350 and end350 display a large range of values from 0 7041 to 0 7093 and from 4 0 to 6 1 respectively which documents a rather complex petrogenetic history with an important role played by crustal contamination processes the more primitive sr and nd isotope signatures are measured in the mafic cumulates while radiogenic sr and unradiogenic nd isotope compositions occur in the more evolved rock types the broad trend of decreasing end350 with decreasing sm nd and increasing sio2 concentration is reminiscent of crustal assimilation combined with fractional assimilation afc end values of flasergabbros and associated cumulates ascribed to the ophiolite like unit in the guadiana valley are close to zero or even slightly negative irrespective of the age chosen for the correction for in situ radioactive decay of 147sm in the range 350 500 ma assumed to encompass the true geological age this observation conflicts with a truly oceanic derivation of these rocks which could rather represent early stage deformed and metamorphosed equivalents of the beja gabbro most metabasalts of the same area have positive albeit variable end consistent with mildly depleted mantle sources and or significant crustal assimilation only a few samples reach highly positive values end350 500 ca 8 similar to those typical for n morbs as do the acebuches amphibolites near aracena end350 500 ca 9 these data suggest that the baoc is not only disrupted but also composite since the gabbroic rocks are not cogenetic with the basalts based on the late devonian age of the collision between the omz and spz the emplacement of the beja gabbro cannot be related to an active subduction of oceanic lithosphere instead the generation in the mantle and emplacement in the overlying continental crust of copious volumes of mafic magmas with concomitant lp ht metamorphism is tentatively ascribed to a process of transcurrent slab break off that followed oblique subduction and collision

late quaternary evolution of a fjord environment in preservation inlet new zealand abstract high resolution seismic profiles as well as sedimentological and micropaleontological analyses of three cores are used to reconstruct the environmental and sedimentological evolution of preservation inlet the southernmost new zealand fjord toward the end of the last glaciation a series of deep oligotrophic lakes impounded by shallow sills occupied preservation inlet glaciers filled the headwater valleys and the vegetation consisted of a sparse cover of grass scrub and shrubs the principal rivers discharged into the head of these lakes forming large sandy deltas while finely laminated clays were deposited in the distal basins as the climate started warming ca 18 000 yr b p the snowline rose and glaciers retreated developing forests were dominated by metrosideros and cyathea fringed by coastal shrubland in the now more productive lakes a rich freshwater fauna developed sedimentation rates increased and organic mud accumulated under rapidly rising sea level between 9500 and ca 8000 yr b p the sills enclosing the lakes were successively overtopped marine water intruded into the fjord basins and flooded the deltas at the head of the lakes by 6500 yr b p sea level had stabilized and the fjord assumed its present condition shrubs decreased in abundance and forests dominated by weinmannia and dacrydium cupressinum then developed a forest dominated by nothofagus fusca spread between 2000 and 1500 yr b p indicating a cooler climate in preservation inlet and other new zealand fjords eustatic sea level rise has been greater than isostatic rebound or tectonic uplift coastal inundation has resulted in a transgressional sequence from a limnic to marine environment this contrasts with fjord coasts of the northern hemisphere where isostatic rebound has produced coastal emergence or coastal emergence followed by submergence

comparison of rio tinto spain and guaymas basin gulf of california an explanation of a supergiant massive sulfide deposit in an ancient sill sediment complex the volcano sedimentary unit that hosts the stratiform massive sulfide mineralization at rio tinto is reinterpreted as a sill sediment complex that in many respects is analogous to the example that is currently forming in the guaymas basin gulf of california however rio tinto is distinctive because 1 it is a product of bimodal magmatism 2 it has a much higher sill sediment ratio 4 1 lessening the extent of ore forming metal depletion during interaction between hydrothermal fluid and wet sediment and 3 most of the sills were emplaced penecontemporaneously as shown by the ubiquitous development of peperitic sill margins despite the narrowness of the sedimentary screens these data together with evidence for local extrusive behavior imply rapid formation of the complex at exceptionally high levels of emplacement it follows that in the complex variations in thickness of 400 m were directly expressed as basin floor deformation and that troughs in the resultant topography were able to trap exhalative hydrothermal plumes thus preserving the sulfides from dispersion also crucial to the mineralization process was the sheetlike form of the sill complex which by acting as a cap prevented regular convective cell patterns from forming and focused considerable discharge at areas of weakness the intense magmatic pulse the creation of pronounced topography and the capping of the hydrothermal system combined to make a 500 mt supergiant deposit

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

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

petrology and u pb geochronology of footwall porphyritic rhyolites from the wolverine volcanogenic massive sulfide deposit yukon canada implications for the genesis of massive sulfide deposits in continental margin environments porphyritic rhyolite sills form an important component of the footwall of the wolverine volcanogenic massive sulfide vms deposit yukon canada and occur proximal to mineralization in the immediate deposit area wolverine lynx zone and at similar stratigraphic levels along strike fisher puck and sable zones porphyritic rhyolites are of two types an older quartz feldspar porphyritic qfp rhyolite suite and a younger feldspar porphyritic fp suite both the qfp and fp suites of intrusions are semiconcordant suggesting a silllike morphology and are altered and crosscut by veinlet mineralization suggesting that they are pre to synmineralization the margins of qfp suite of intrusions contain minor xenoliths of surrounding shales and poorly developed chilled margins suggesting emplacement into partially consolidated sedimentary rocks whereas the fp suite of intrusions shows well developed chilled margins indicative of emplacement into fully solidified sedimentary rock these features suggest that the qfp suite of intrusions represents an older phase of rhyolitic magmatism whereas the fp suite represents a younger event this is supported by u pb zircon ages which indicate a 352 4 1 5 ma emplacement age for the fp suite and a 347 to 346 ma emplacement for the fp suite two ages at 347 8 1 3 and 346 0 2 2 ma both suites of porphyries have inherited proterozoic zircon and have ratios of la smucn 1 and nb thucn 1 ucn upper continental crust normalized indicating derivation from and or extensive interaction with ancient upper continental crustal materials the fp suite however has elevated high field strength element hfse and rare earth element ree contents high zircon saturation temperatures and higher nb ta ratios and lower ti sc ratios than the qfp suite these features are interpreted to reflect that the fp suite of magmas was hotter 900 c melts with a greater mantle component in their genesis both suites however are interpreted to have formed due to basaltic upwelling crustal melting and crust mantle mixing during ensialic back arc basin activity the presence of mantle heat within the wolverine basin from 352 to 347 to 346 ma a minimum of 5 m y suggests that sustained mantle heat flow was critical to the genesis of the wolverine porphyries it is also suggested that this sustained mantle heat was responsible for the wolverine hydrothermal system and that upwelling mantle may be essential in providing the heat to drive hydrothermal systems even in continental margin type vms environments e g bathurst iberian pyrite belt the wolverine porphyries are among the most hfse and ree enriched felsic rocks associated with vms mineralization globally the high hfse and ree concentrations in these rocks are interpreted to be due to

the las cruces deposit iberian pyrite belt spain abstract the las cruces deposit is located at the eastern margin of the iberian pyrite belt ipb beneath the neogene quaternary deposits of the guadalquivir basin these sediments covered and preserved the supergene profile somewhat after its generation until its recent discovering for this reason the las cruces ore deposits together with lagoa salgada in portugal are the only known deposits in the ipb that preserve the entire weathering profile including both the gossan and the enrichment zone in that sense the present study provides new data on the ipb ore deposits and their post palaeozoic evolution the primary mineralization consists of massive and semi massive polymetallic sulfides overlaying a cupriferous and pyritic stockwork the supergene enrichment extends from the primary zone to gossan and consists of a thick cementation zone characterized by intense replacement of part of the primary sulfides by cu rich supergene sulfides at present the only economic resource of las cruces is the cementation zone with initial reserves of 17 6 mt 6 2 cu but the orebody also includes significant contents of cu and zn within the primary mineralization and au ag and pb in the gossan mineralogical and geochemical data confirm that the primary mineralization at las cruces resembles other ipb deposits in terms of distribution and evolution however the gossan and cementation zone show an uncommon evolution for this kind of supergene profile the major singularity that makes the las cruces supergene mineralisation noticeably different from others in the ipb or elsewhere resides in its unusual mineralogical composition mostly comprised of newly formed siderite calcite fe sulfides and galena the genetic model proposed for the las cruces deposit includes three main stages 1 ore genesis and evolution of primary mineralization which seems to be comparable to other ipb deposits 2 genesis of cu rich secondary mineralization and gossan by weathering after miocene exhumation of the upper part of the massive sulfide deposit under oxidizing and acidic conditions and 3 late evolution of supergene profile below the carbonated rich sediments of the guadalquivir basin with the subsequent change in the redox conditions due to water rock interaction between the supergene profile and basinal fluids

u pb geochronology and petrology of the late paleozoic gil marquez pluton magmatism in the variscan suture zone southern iberia during continental collision and the amalgamation of pangea the origin of plutonic complexes that stitch suture zones developed during collision is not well understood in southern iberia the pulo du lobo suture zone pdlz is intruded by the syn to postcollisional gil marquez pluton gmp thought to be part of the sierra norte batholith u pb la icpms zircon data on various phases of the gmp yield from oldest to youngest 1 a 354 4 7 6 ma unfoliated gabbro 2 a 345 6 2 5 ma foliated intermediate phase 3 a 346 5 5 4 ma unfoliated porphyritic granite 4 a 335 1 2 8 ma unfoliated biotite granite this sequence is consistent with cross cutting relationships observed in the field the range in ages is consistent with interpretations that the gmp is part of the composite ca 350 308 ma snb inherited ages preserved in the gmp intermediate and felsic phases indicate that its magmas traversed through south portuguese zone and pdlz crust during emplacement the ca 345 ma emplacement of the late kinematic foliated intermediate phase constrains the age of late stage strike slip deformation within the pdlz and the lack of a foliation in the older gabbro indicates that is was not proximal to a shear zone neither at the time of emplacement nor during its subsequent history the unfoliated porphyritic granite and unfoliated biotite granite cut the foliation of the intermediate phase indicating emplacement during the waning stages of collision while the ca 335 ma biotite granite intrudes the santa ira flysch thereby providing a tight constraint for the latest stage of deformation in the pdlz

orbital forcing of mid latitude southern hemisphere glaciation since 100 ka inferred from cosmogenic nuclide ages of moraine boulders from the cascade plateau southwest new zealand cosmogenic nuclide be 10 exposure dating of moraine boulders in the cascade valley southwest new zealand reveals three phases of glaciation with similar maximum magnitude since 100 ka in this area 8 10 lateral moraines were deposited during the last glacial maximum lgm at 22 19 ka and 15 lateral moraines and three end moraines were deposited during recession after the lgm also three exposure ages of 29 33 ka from pre lgm deposits may indicate increased weathering and erosion at the onset of the lgm in new zealand as has been suggested by other studies an exposure age of 57 8 2 7 ka from one of the highest moraines combined with previous studies of cave speleothems glacial features offset by the alpine fault the vostok dust record and sediment cores supports the inference that a significant glacial phase culminated at 66 58 ka a cluster of five exposure ages from older moraines reveals a glacial phase with at least three advance retreat cycles at 79 0 3 9 ka correlation between the ages of glacial periods and the timing of southern hemisphere summer insolation minima suggests that orbital forcing has played a first order role in regulating glacial extent in new zealand

the lagoa salgada orebody iberian pyrite belt portugal the iberian pyrite belt is one of the most outstanding european ore provinces and hosts one of the largest concentrations of massive sulfide deposits today totaling 1 850 million metric tons mt in more than 90 deposits lagoa salgada is a small orebody estimated to have at least 4 mt and as yet an unexploited orebody found within this ore province it is located 80 km northwest of neves corvo and occurs 130 m beneath sediments of the sado tertiary basin limiting interpretation to drill hole data lagoa salgada is folded faulted and interpreted to occur mostly on the subvertical overturned and intensely faulted limb of a southwest verging anticline it is represented by a central stockwork zone and a massive sulfide lens zone in the northwestern part of the orebody mineralization is mainly composed of pyrite with minor sphalerite tetrahedrite tennantite arsenopyrite chalcopyrite galena stannite and supergene minerals the orebody is hosted by a volcanic succession of rhyodacitic composition these small orebodies and some of the other abandoned mines within the iberian pyrite belt may represent interesting and feasible mining projects as a result of the added value generated by the presence of trace metals such as in serving a significant future demand for the high tech industry lagoa salgada is one such case indium is a significant trace metal in the ores of lagoa salgada as indicated by whole rock analyses this element is preferentially contained by sphalerite electron probe microanalyses epma of in contents within sphalerite show a large variability ranging from below detection limits to an obtained maximum of 0 8 percent in discrete inclusions of in bearing minerals have not been observed thus favoring the idea that in occurs either dispersed or in nanodomains within the host mineral

modern deposition rates and patterns of organic carbon burial in fiordland new zealand fjords are disproportionately important for global organic carbon oc burial relative to their spatial extent and may be important in sequestering atmospheric co2 providing a negative climate feedback within fjords multiple locally variable delivery mechanisms control mineral sediment deposition which in turn modulates oc burial sediment and oc sources in fiordland new zealand include terrigenous input at fjord heads sediment reworking over fjord mouth sills and landslide events from steep fjord walls box cores were analyzed for sedimentary texture sediment accumulation rate and oc content to evaluate the relative importance of each delivery mechanism sediment accumulation was up to 3 4 mm yr in proximal and distal fjord areas with lower rates in medial reaches x radiograph and 210pb stratigraphy indicate mass wasting and surface sediment bioturbation throughout the fjords sediment accumulation rates are inversely correlated with oc spatial heterogeneity in sediment depositional processes and rates is important when evaluating oc burial within fjords

revealing hidden structures the application of cathodoluminescence and back scattered electron imaging to dating zircons from lower crustal xenoliths abstract the use of cathodoluminescence cl and or back scattered electron bse imaging techniques with in situ ion probe analyses of zircons can help unravel complex crustal histories of metamorphic rocks that otherwise might remain elusive using these techniques we have imaged zircons from three lower crustal xenolith suites that have previously been dated by shrimp sensitive high resolution ion microprobe in all three cases the zircons are featureless in transmitted light but cl and bse reveal internal structures that correlate with distinct growth events generally cl and bse images reveal similar structures with cl showing finer detail neither imaging technique is capable of delineating all growth features in every sample and the best results are obtained using a combination of the two techniques igneous cores in zircons commonly emit a different color cl emission in many cases zoning in the cores is truncated indicating that the zircons either spent time in the supracrustal environment after their initial crystallization and prior to the granulite facies event s or that part of the core zircon was resorbed during the subsequent metamorphic event metamorphic rims when present are commonly 10 to 30 m thick and are nearly always unzoned and featureless igneous cores and metamorphic overgrowths commonly have distinctive cl emission spectra and trace element concentrations however the cl spectra can only be used to qualify chemical differences as a linear relationship has not been shown to exist between cl intensity and trace element concentration in natural zircons in many cases the hf y p u and the heavy rare earth elements hrees concentrations can be correlated to igneous and metamorphic growth using a combination of cl and bse imaging techniques and in situ trace element analyses with either the electron microprobe or pixe particle induced x ray emission

a detailed slip model for the 1995 october 1 dinar turkey earthquake ms 6 1 determined from inversion of teleseismic p and sh waveforms summary teleseismically recorded p and sh waveforms of the 1995 october 1 dinar turkey earthquake are inverted to find detailed coseismic slip distribution on the ruptured part of the dinar civril fault for this purpose a linear finite fault inversion procedure with time window approach is used to allow variable rise time and rupture velocity on the model fault the source is represented by a 24 21 km rectangle fault plane which is divided into 56 equal size subfaults the strike and the dip of the fault plane are assumed as determined by a previous study the amount of slip and the rake angle on each subfault is retrieved through fitting the observed and synthetic seismograms in a least squares sense the previous inversion studies indicated that the earthquake was associated with two subevents with a 6 s time lag of the nw subevent therefore the model fault plane is also divided into two separate equal area segments the se and the nw segments to delay the rupture propagation over the nw segment we tried several models to fix the delay time and hypocentral depth and to explain the waveforms the smallest misfit error resulted from a model with 5 s delay time and 7 5 km hypocentral depth the preferred solution suggests that the earthquake is associated with breaking of two asperities and the coseismic slip occurred mostly above the depth of 10 km the smaller asperity is located to the se just beneath dinar town with peak slip of 26 cm while the larger one is located to the nw with peak slip of 41 cm the observed surface rupture coincides with the location of the smaller asperity the seismic moment for our slip model is 2 8 1018 n m the modelling yields an average rake angle of 102 and almost no difference between the average rake angles of the two asperities

tectonic evolution of variscan iberia gondwana laurussia collision revisited an integrated interpretation of the late paleozoic structural and geochronological record of the iberian massif is presented and discussed under the perspective of a gondwana laurussia collision giving way to the variscan orogen compressional and extensional structures developed during the building of the variscan orogenic crust of iberia are linked together into major tectonic events operating at lithosphere scale a review of the tectonometamorphic and magmatic evolution of the iberian massif reveals backs and forths in the overall convergence between gondwana and laurussia during the amalgamation of pangea in late paleozoic times stages dominated by lithosphere compression are characterized by subduction both oceanic and continental development of magmatic arcs over and under thrusting of continental lithosphere and folding variscan convergence resulted in the eventual transference of a large allochthonous set of peri gondwanan terranes the iberian allochthon onto the gondwana mainland the iberian allochthon bears the imprint of previous interaction between gondwana and laurussia including their juxtaposition after the closure of the rheic ocean in lower devonian times stages governed by lithosphere extension are featured by the opening of two short lived oceanic basins that dissected previous variscan orogenic crust first in the lower middle devonian following the closure of the rheic ocean and then in the early carboniferous following the emplacement of the peri gondwanan allochthon an additional major intra orogenic extensional event in the early middle carboniferous dismembered the iberian allochthon into individual thrust stacks separated by extensional faults and domes lateral tectonics played an important role through the variscan orogenesis especially during the creation of new tectonic blocks separated by intracontinental strike slip shear zones in the late stages of continental convergence

active fault segmentation of the civril graben system and surface rupture of the 1 october 1995 dinar earthquake mw 6 2 southwestern anatolia turkey abstract the civril graben system cgs is one of the important tectonic structures developed within the western anatolia extensional tectonic regime the cgs has an arcuate geometry looking south and comprises two main geometric sections of the nw striking dinar graben and the ne striking baklan graben with a total length of 100 km the main faults limit the north edge of the cgs while the south edge is bounded by their antithetic structures the northern boundary structures of the graben comprise two main fault segments of dinar and civril graben fill is plio quaternary lacustrine fluvial sediments with late pleistocene holocene flood plain lacustrine marsh and alluvial fan sediments historical records and destructive earthquakes occurred in the last century indicate the region is one of the significant seismogenic zones the last destructive earthquake in the graben was the 1995 dinar earthquake mw 6 2 which caused approximately 10 km long surface rupture on the kizilli segment of the dinar fault field based geological mapping and structural geology in this study and available seismic and paleoseismological data reveal that the other sub segments of the dinar and civril faults which have not ruptured in the last 150 years have the potential to produce earthquakes with mw 6 0 and larger the paleoseismic rate is assessed to be 1 mm year for the kizilli segment while the geologically long term slip rate range is calculated to be 0 27 0 05 mm year

supergene enrichment of precious metals by natural amalgamation in the las cruces weathering profile iberian pyrite belt sw spain abstract natural au ag hg alloys occur in the las cruces ore deposit in the eastern part of the iberian pyrite belt they are mainly concentrated in the lower part of the gossan profile including a sheared black shale level where the gossan makes contact with a barren pyrite zone within the supergene cu rich mineralization drill core analyses show a heterogeneous distribution of au ag and hg within the weathering profile with mean values of 5 1 ppm 155 ppm and 52 ppm respectively in general the absolute tenures increase towards the bottom of the weathered profile mineralogical studies conducted on samples from the active mine workings indicate that hg and precious metals occur mainly as au ag hg alloys these associations constitute the best potential resource for precious metals at the las cruces deposit this paper describes how this unusual precious metal enrichment is produced along the weathering profile by supergene processes combining paragenetic information mineral chemistry and the data pertaining to the solubilities of au ag and hg in a weathering profile we suggest a two stage genetic model for the formation of the las cruces au ag hg mineralization 1 release of au ag and hg from the massive sulfide deposit by weathering processes during the gossan formation at ph 0 9 v conditions au ag and hg are mobilized downward through the weathering profile as chloride complexes and fixed as elemental au halides oxides and sulfates and 2 remobilization of hg ag and au in the gossan after the deposit was buried beneath the neogene carbonate rich sedimentary cover the buffering capacity of the percolating fluids due to their interaction with the carbonate rich sedimentary pile leads to significant mineralogical and geochemical changes at near neutral conditions ph 6 7 eh 0 v hg ag and au are newly remobilized as thiosulfate sulfate and hydroxide complexes and newly fixed by sorption during ferric hydroxide formation and as sulfates several cycles of dissolution precipitation of au ag and hg near the redox front occur by oscillations in the water table and changes in the ph eh conditions the interaction of downward migrating fluids with high reductant lithologies black shales and massive sulfides seems to be responsible for the reduction of different complexes and for the precipitation of cinnabar ag sulfides and sulfosalts as well as the precipitation of au ag hg amalgams

ore deposit types and tectonic evolution of the iberian pyrite belt from transtensional basins and magmatism to transpression and inversion tectonics abstract a new interpretation of the structural evolution of the iberian pyrite belt ipb and volcanogenic massive sulfide mineralization vms is presented in this work based on a review of the ore deposit types the analysis of the hosting volcanic sequences and the tectonic evolution the vms deposits of the ipb are hosted by volcanic and siliciclastic rocks four main volcano sedimentary sequences vsc from vsc0 to vsc3 have been assumed the main deposits being located in the vsc0 and at the top of the vsc2 we have defined three main sectors oriented approximately e w and hosting the vms deposits in the northern sector which is mostly located in spain graben basins and local pull aparts are the main structures in this sector two belts can be distinguished the deposits being located at the top of the vsc2 felsic volcanism rio tinto type ipb deposits in the central sector both in spain and portugal half graben basins are the most common structures and the deposits are mostly located in the vsc0 andesitic volcanic sedimentary sequence tharsis type ipb deposits in the southern sector which is only located in portugal a graben basin with a pull apart is again the main structure and the deposits are located in black slates and at the top of a felsic volcanism strunian in age vsc0 the deposits located in graben basin with a pull apart are essentially felsic volcanic hosted with some siliciclastic material mostly black shales by contrast those located in half graben basins are mainly hosted by black shales with minor amounts of andesitic rocks the tectonic evolution shows that as a result of a counterclockwise rotation of the stress axes the formation of the ipb and the associated ore deposits took place during several episodes from transtension with the development of both graben with pull aparts and half graben basins through left lateral e w shearing to transpression at the beginning of the transtensional process several extensional roughly e w trending faults that developed graben and half graben basins were generated and the first volcanic andesite rhyolite rocks vsc0 formed the tharsis type deposits mainly hosted by black slates with some volcanic rocks were formed in the central sector while the neves corvo type deposit hosted by black slates and felsic volcanism formed in the southern one after a period characterized by barren mafic volcanism vsc1 a sinistral shear affected the previous fractures due to the stress axis rotation and felsic crustal volcanism started vsc2 rhyolites and dacites were particularly abundant in two graben basins which developed rollovers in pull apart zones forming the rio tinto type deposits in the northern sector the thermal increase associated with vsc0 and vsc2 gave rise to the development of crustal scale hydrothermal convective cells which generated both types of deposits after a barren vsc3 felsic volcanism subsequently during the variscan transpressional phase the e w extensional faults were reactivated as reverse faults affecting the volcanic sequence vsc0 to vsc3 as well as the interbedded sedimentary rocks mostly black shales as has been recognized at the rio tinto deposit buttressing must have played a significant role in the geometry of inverted structures and the vms ores were intensely recrystallized it should be emphasized that this new regional geological model for the ipb is an approach to provide a better insight into vms deposits and could be a key point for further studies providing a new tool to improve knowledge of the vms mineralizations and exploration guidelines elsewhere in the ipb

chert in the iberian pyrite belt since lenses of chert are common within the volcano sedimentary succession hosting the massive sulphide deposits of the iberian pyrite belt spain and portugal we examined numerous chert occurrences both petrographically and geochemically to test their possible value for massive sulphide exploration the chert is found at two main lithostratigraphic levels upper and lower that are also interpreted as massive sulphide bearing in both cases the chert is located at the top of acidic volcanic sequences or in the associated sediments we have not been able to observe the relationships between massive sulphides and chert but some of the large orebodies of the province lousal la zarza tharsis planes san antonio body of rio tinto neves are described as being locally capped by chert facies four main types are recognized among the chert and associated facies 1 red hematitic chert magnetite 2 radiolarian and or sedimentary textured conglomeratic chert with hematite and or mn oxides 3 pale sulphidic chert 4 rhodonite and or mn carbonate magnetite facies in the spanish part of the province the radiolarian chert is confined to the upper level the distribution of the other types appears to be haphazard the hydrothermal origin of the south iberian chert is shown by its high fe mn and low co ni cu contents the presence of small positive ce anomalies indicates a shallow marine environment shelf or epicontinental sea which is consistent with the volcanological and sedimentological data the chert was emplaced below the sea floor through chemical precipitation and or through alteration and replacement of the country rock residual traces of which are ghost phenocrysts and high al ti and rare earth contents macro and microscopic relationships indicate that the oxide facies hematite magnetite formed first probably providing a protective insulating cover against the marine environment and enabling an evolution towards sulphide facies a phase of mn carbonate and silicate quartz chlorite sulphides appears to be even later it was not possible through discrimination to isolate a chert that could be considered as representing a lateral marker of massive sulphides moreover both field observations and geochemical data seem to indicate a relative independence of this siliceous sulphide hydrothermal activity from the hydrothermal activity giving rise to the massive sulphides such is also indicated by the lead isotopic signature of the chert which is appreciably more radiogenic than that of the massive sulphides the lead enrichment in the sulphidic chert facies indicates the participation of a different source sediments sea water from that of the massive sulphides the hypothesis of an independent hydrothermal chert event can thus be envisaged wherein the chert reflects submarine low temperature hydrothermal activity that is most apparent during a break within the volcano sedimentary succession and which may locally have competed with the high temperature hydrothermal activity giving rise to the massive sulphides the interest of the chert thus rests in its palaeodynamic significance as a marker of periods of volcanic quiescence and in its possible role as a protective insulating cap favourable to the deposition of massive sulphides

carbon cycling and burial in new zealand s fjords understanding carbon cycling in continental margin settings is critical for constraining the global carbon cycle here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six new zealand fjords using carbon and nitrogen concentrations and isotopes lipid biomarkers and redox sensitive element concentrations we show that the new zealand fjords have carbon rich surface sediments in basins that promote long term storage i e semirestricted basins with sediment accumulation rates of up to 4 mm yr 1 using 13c distributions to develop a mixing model we find that organic carbon in fjord sediments is well mixed from marine and terrestrial sources in down fjord gradients this is driven by high regional precipitation rates of 6 m yr 1 which promote carbon accumulation in fjord basins through terrestrial runoff in addition we have identified at least two euxinic subbasins based on uranium molybdenum iron and cadmium enrichment that contain 7 organic carbon because the strength and position of the southern hemisphere westerly winds control precipitation and fjord circulation carbon delivery and storage in the region are intimately linked to westerly wind variability we estimate that the fjord region 759 km2 may be exporting up to 1 4 107 kgc yr 1 outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude

circulation and sedimentation in a tidal influenced fjord lake lake mckerrow new zealand lake mckerrow is a tide influenced fjord lake separated from the open sea by a holocene barrier spit fresh oxygenated waters of the epilimnion overlie saline deoxygenated waters of the hypolimnion during winter water from the upper hollyford river interflows along the pycnocline depositing coarse silt on the steep delta and transporting finer sediment down lake an extensive sub lacustrine channel system on the foreset delta slope is possibly maintained by turbidity currents saline waters of the hypolimnion are periodically replenished during high tides and low lake levels saline water flows into the lake and downslope into the lake basin as a density current in a well defined channel

late glacial and early holocene glacier activity in the southern alps new zealand abstract in the southern alps of new zealand glaciers advanced to their last glacial maximum limits between 22 3 and 18 ka bp and there is evidence for at least four more advances between 18 and 8 ka bp a widespread glacier advance possibly with two maxima occurred between 16 and 14 ka bp during which glaciers reached positions close to those attained at the last glacial maximum after 14 ka bp there was a significant and sustained retreat of glaciers that marks the beginning of the post glacial interval in new zealand locally known as the aranui interglacial during the aranui there is evidence for a much smaller glacier advance around 11 ka bp that may have been coeval with the younger dryas stade but opinions on this are still controversial two younger ice advances may have occurred close to 10 25 and 8 6 ka bp although regional patterns of late glacial advances are reasonably well established the post glacial advances are known only from single sites and require closer investigation

how long can a hydrothermal system be sustained by a single intrusive event published numerical calculations show that the convective systems which produce near surface geothermal systems or ore deposits are likely to cool their intrusion heat source in at most a few tens of thousands of years even if the intrusion is large generally hydrothermal circulation near surface geothermal activity and magmatic intrusion should be closely tied in time and space long lived approximately 1 m y hydrothermal activity normally suggests multiple pulses of intrusion with associated pulses of hydrothermal circulation however if the permeability of the intruded environment is just above that which allows convection and the volume of the intrusion is very large calculations presented here show that a single episode of intrusion can sustain hydrothermal circulation and near surface geothermal activity for approximately 800 000 yr for a deep sill heat source these unusually long lived hydrothermal systems can vent through a few very widely separated discharge sites and have the potential to produce isolated massive sulfide deposits of unusually large size

metamorphosed pb zn ag ores of the keketale vms deposit nw china evidence from ore textures fluid inclusions geochronology and pyrite compositions abstract the keketale pb zn deposit is located in the devonian volcanic sedimentary maizi basin of the altay orogenic belt the mineralization at keketale is hosted in marbles and deformed volcanic tuffs and biotite garnet chlorite schists folded into a series of overturned synclines formed in multiple deformation events keketale contains economic amounts of pb 0 89 mt 1 51 wt zn 1 94 mt 3 16 wt and ag 650 t 40 g t detailed petrographic studies have defined two main generations of sulfide development the banded pyrite of the early stage a is commonly stratiform with minor galena sphalerite and chalcopyrite stage b is characterized by a large amount of polymetallic sulfides including pyrrhotite chalcopyrite sphalerite and galena with minor pyrite hosted in quartz veins three types of fluid inclusions fis including mixed carbonic aqueous c type pure carbonic pc type and aqueous w type have been recognized in quartz of stage b the c type fis have homogenization temperatures of 150 326 c and salinities of 0 2 16 6 wt nacl equivalent the pc type fis are dominated by co2 with minor ch4 and n2 and have initial ice melting temperatures of 57 5 to 56 7 c co2 homogenization temperatures of 11 14 1 c the w type primary fis were completely homogenized at temperatures of 124 359 c with salinities of 5 0 14 6 wt nacl equivalent such co2 rich fluid inclusions are consistent with those discovered in orogenic type deposits in the altay area and elsewhere muscovite separates from the polymetallic quartz veinlets of stage b yield a well defined 40ar 39ar isotopic plateau age of 259 33 2 56 ma with an isochron age of 259 62 2 65 ma this age is coeval with the closure of the paleo asia ocean and reactivation of the ertix fault system la icp ms analyses of two generations of pyrite indicate that the banded pyrite of stage a is relatively depleted in metallic elements and contains low contents of cu 0 39 ppm ag 0 20 ppm au below the detection limits pb 17 43 ppm and zn 14 38 ppm whereas the pyrite in quartz polymetallic sulfide veinlets of the stage b is relatively rich in metallic elements e g cu 2 56 ppm ag 3 07 ppm au 0 01 ppm pb 1047 ppm and zn 1136 ppm the trace amounts of cu pb zn au and ag are interpreted to have been initially locked in the lattice of type a pyrite and then liberated and precipitated as micromineral inclusions with type b pyrite during subsequent metamorphism and deformation two key factors are considered vital to the formation of economic ores of the keketale pb zn deposit namely the original devonian banded pyrite formed in a vms system and subsequent permian deformation and metamorphic processes that liberated cu pb zn au and ag from the lattice of type a pyrite to form galena sphalerite and chalcopyrite with minor muscovite in quartz veinlets the model provides a new interpretation of vms pb zn deposit occurring in back arc basin environments followed by collision and new insights into the unique regional fe cu pb zn au mineralization in the altay orogenic belt

postvolcanic paleozoic of the iberian pyrite belt an example of basin morphologic control on sediment distribution in a turbidite basin abstract the iberian pyrite belt south portuguese zone hercynian chain an important metallogenic province has a volcanic sedimentary origin overlying this volcanic succession is a thick sedimentary unit the culm group which represents postvolcanic paleozoic sediments of the iberian pyrite belt it consists of three stratigraphic units the basal shaly formation bsf the culm facies turbiditic formation cftf and the shallow platform sandy unit spsu the bsf is represented by finegrained sediments of volcanic to nonvolcanic origin that mark the end of volcanism in the region the reworking of volcanic products in a shallow marine basin and the beginning of autochthonous sedimentation of pelagic clay it constitutes a depositional sequence sensu mitchum et al 1977 the d stribution facies and facies associations of the turbidites of the cftf are related to the configuration of the basin which controlled the mechanisms of deposition and distribution of the detritus from different source areas the spsu represents sediments eroded from the volcanic upland and redistributed over the shelf detailed study of these three units and their relationships provides the means to define the geometry and evolution of the postvolcanic carboniferous basin of the iberian pyrite belt the basin was roughly subdivided by the paymogo and the puebla de guzman paleoridges together with the allochthonous ossa morena zone north of the study area they formed three topographic barriers that delineated two interconnected subbasins sedimentation in the postvolcanic basin of the iberian pyrite belt can be related to a model of oscillating sea level synorogenic characteristics of the culm group sediments support a tectonic origin for the sea level oscillations particularly since the sediments had already been affected by the first pulses of the hercynian orogeny

stress coupling between earthquakes in northwest turkey and the north aegean sea we have investigated the coulomb stress interactions of 29 earthquakes m s greater than or equal to 6 0 that have occurred in the region of northwest turkey and north aegean sea since 1912 of these events 23 may be related to earlier events and 16 are clearly related to earlier events all events after 1967 are related to previous events events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified in some cases faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local coulomb stress rise thus regions of coulomb stress shadow can become regions where a damaging earthquake may occur the relation between smaller events and the coulomb stress distribution is less clear but may be related to poor data quality and practical limitations of our modeling technique nonetheless there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced we discuss the contemporary distribution of coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults

recognizing metasedimentary sequences potentially hosting concealed massive sulfide accumulations in the iberian pyrite belt using geochemical fingerprints abstract promising advances in the development of new greenfield and brownfield exploration methods and methodologies for massive sulfide ore systems in the iberian pyrite belt ipb have been made over the last two decades however the effects of lateral and vertical facies variations in metasedimentary piles forming the two main lithostratigraphic units that potentially host massive sulfide deposits the phyllite quartzite group pqg and the volcanic sedimentary complex vsc on mineral exploration remain unknown herein we report on results of a multi element geochemical study of 133 samples representing pqg and vsc metasedimentary rocks from the albernoa area 713 km2 this dataset is complemented by whole rock sr nd and pb isotopic data for a subset of 12 vsc metasedimentary rock samples the prevalent siliciclastic component in the analyzed rocks derives from an evolved felsic source as suggested by the zr sc th sc eu eu relationships that according to cia values should have been affected by significant weathering before they were deposited in the basin from middle devonian to visean time the siliciclastic component comprises clay and fine grained sand whose relative abundance can be distinguished on the basis of al2o3 tio2 sc tio2 ga tio2 zr tio2 and sio2 al2o3 ratios these terrigenous components are in places variably mixed with volcanic derived fractions leading to the formation of tuffaceous metapelites typical of the vsc sequences but also present in the upper stratigraphic sections of the pqg in general vsc samples display the following parameters 2 5 sio2 al2o3 6 5 0 02 tio2 al2o3 0 06 and 0 2 cao na2o k2o al2o3 0 25 whereas pqg samples display 2 5 sio2 al2o3 12 0 08 tio2 al2o3 0 58 and cao na2o k2o al2o3 0 3 fe2o3 tio2 ratios 10 and al2o3 al2o3 fe2o3 mno ratios 0 6 indicate the strong influence of an early developed prior to variscan metamorphism and deformation hydrothermal component on the prevalent siliciclastic component sometimes mixed with a variable volcanic derived fraction moreover values of as sb sc cu zn pb sc and 5 fe2o3 mgo mno al2o3 ratios between 1 and 10 indicate the influence of seafloor metasomatism processes and ratios 10 indicate close proximity to hydrothermal discharge potentially associated with massive sulfide mineralization the sr nd pb isotopic data show that vsc metasedimentary rocks are mostly derived from old reworked upper continental crust isotope ratios characterizing the main siliciclastic component are somewhat disturbed by the significant presence of volcanic derived components and or mineral changes due to early hydrothermal alteration mineralization processes which should have involved isotopically distinct fluids

circulation and sedimentation of suspended particulate matter in new zealand fjords abstract circulation in the new zealand fjords is estuarine with a seaward flowing brackish layer overflowing saline water despite an extremely high rainfall 6000 mm yr 1 terrestrial dediment input is low and concentrations of suspended particulate matter spm rarely exceed 1 mg 1 1 the terrestrial influence is barely detectable anywhere in the fjords spm in near surface waters is dominated by phytoplankton in surface waters spm components remain separate as they settle they are clustered into larger groups by agglomeration faecal pelletization and flocculation phytoplankton produce a secondary spm maximum at the top of the deep zone deep waters are barren of living plankton with clustered spm and broken phytoplankton settling from above the low terrestrial spm input and high organic biogenic concentrations are reflected in low sedimentation rates and high organic carbon content of bottom sediments the estuarine stratification is broken up in the fjord entrances by ocean waves which also resuspend sediment off the entrance sills thereby increasing spm concentrations in bottom waters high spm concentrations are found in basins cut off from the main fjord by shallow sills which inhibit deep water renewal

a review of new zealand palaeoclimate from the last interglacial to the global last glacial maximum abstract results from terrestrial and marine palaeoclimate proxies are integrated to reconstruct palaeoclimate variations in new zealand from the last interglacial to the global last glacial maximum glgm by combining data from 21 speleothems we have constructed composite o c stable isotope sequences from 0 to 88 5 ka bp and from 107 8 to 128 2 ka bp the gaps in the sequence a 19 3 ka break in coverage in mis 5b c and a 2 97 ka gap in mis 5a preclude the construct of a continuous record so data were referenced to a common scale by normalising individual records subtracting means and dividing by standard deviation overlapping records were then merged chronologically these records were compared to integrated summer insolation for 45 s and to terrestrial and marine environmental proxies available for the new zealand region the mis 5e thermal maximum in new zealand was around 128 122 kiloyears bp ka bp and therefore similar in timing to the last interglacial in australia southern europe and greenland temperatures in parts of the north island may have been 2 3 c warmer than present and the sea rose 3 6 m above modern level in mis 5d and 5b cool conditions with glacial advances occurred in the south island but from about 87 to 73 ka in mis 5a warmth within 2 c of present characterised most of the interstadial locally termed the otamangakau interstadial conditions then cooled rapidly and culminated in a mis 4 glacial advance that was the greatest of the new zealand last glacial cycle nzlgm the climate was cool to cold and while wet in westerly windward locations may have been dry in the east combined australian and new zealand evidence suggests glacial culmination around 67 62 ka this regional lgm coincided with severe cooling in europe during mis 3 conditions were very variable the climate in eastern north island hawke bay and the bay of plenty at the start of mis 3 was similar to the holocene and the period 61 43 ka was relatively mild overall and is termed the aurora interstadial although it contained a short interval of mountain glacier expansion around 49 47 ka after 43 ka conditions cooled again with a glacial advance from 42 to 38 ka before a return to milder but still cool conditions during the moerangi interstadial from 37 to 31 ka after this conditions deteriorated at the lead in to the glgm the maximum glacial advance occurred in late mis 3 between 31 and 29 ka the glacial onset was abrupt with te anau glacier in fiordland one of the largest in the southern alps taking only about 2000 years to achieve its maximum glgm depth probably because conditions were wet as well as cold but stable isotope data suggest that the climate then became drier while remaining cold and the glacier progressively ablated such that its surface had lowered 390 m by the start of mis 2 and by 600 m by ca 18 ka the glgm maximum in new zealand may have led the terrestrial ice sheet lgm in the northern hemisphere by a few thousand years possibly because alpine glaciers respond more rapidly to climate change than continental ice sheets the culmination of the glgm in nz occurred in mis 3 about 12 000 years before global ice volume reached its peak as determined by the marine stable isotope record the marine glgm by the time global ice volume was at a maximum 19 ka glaciers had almost disappeared from major fiordland valleys in new zealand whereas polar ice sheet records have revealed a bi polar see saw this is not so evident in the mid latitudes because some temperate zone inter hemispheric climate events coincide closely in time perhaps the see saw effect diminishes with distance from the poles

brine pool deposition for the zn pb cu massive sulphide deposits of the bathurst mining camp new brunswick canada i comparisons with the iberian pyrite belt abstract the ordovician zn pb cu massive sulphide ore deposits of the bathurst mining camp share many features with those of the devonian carboniferous iberian pyrite belt particularly the tendency to large size tonnage and metal content shape as far as can be determined after allowing for deformation metal content particularly fe cu pb zn and sn mineral assemblages pyrite arsenopyrite pyrrhotite and lack or rarity of sulphates sulphide textures particularly framboidal pyrite lack of chimney structures and rubble mounds irregular metal or mineral zoning and the low degree of zone refining compared to hokuroku ores the major differences between the provinces are the lack of vent complexes and the presence of sn cu ores in the iberian pyrite belt there are also similarities in the geological setting of the two camps both lie within continental terranes undergoing arc continent and continent continent collision and in each case massive sulphide mineralisation followed ophiolite obduction the ore deposits are associated with bimodal volcanic rocks derived from morb and continental crust and marine shales and mineralisation was locally accompanied or followed by deposition of iron formations fluid inclusion data from veins in stockworks from at least six of the iberian massive sulphide deposits point to sulphide deposition having taken place in basins containing mostly spent saline ore forming fluids brine pools and it is suggested that most of the major features of the bathurst deposits can be explained by similar processes the proposed model is largely independent of ocean sulphate and o 2 content whereas low values of each are requisites for the current spreading plume model of sulphide deposition in the bathurst camp

type of volcanoes hosting the massive sulfide deposits of the iberian pyrite belt the volcanic sedimentary complex vsc of the iberian pyrite belt ipb in southern portugal and spain comprises an upper devonian to lower carboniferous submarine succession with a variety of felsic volcanic lithofacies the architecture of the felsic volcanic centres includes felsic lavas domes pyroclastic units intrusions and minor mafic units that define lava cryptodome pumice cone volcanoes the diversity of volcanic lithofacies recognized in different areas of the ipb mainly reflects variations in proximity to source but also differences in the eruption style the ipb volcanoes are intrabasinal range in length from 2 km to 8 km and their thickest sections vary from 400 m to 800 m these volcanoes are dominated by felsic lavas domes that occur at several stratigraphic positions within the volcanic centre however the pyroclastic units are also abundant and are spatially related to the lavas domes the intrusions are minor and define cryptodomes and partly extrusive cryptodomes the hydrothermal systems that formed the neves corvo and lousal massive sulfide ore deposits are associated with effusive units of felsic volcanic centres at neves corvo the massive sulfide orebodies are associated to rhyolitic lavas that overlie relatively thick fiamme rich pyroclastic unit in several other locations within the belt pyroclastic units contain sulfide clasts that may have been derived from yet to be discovered coeval massive sulfide deposits at or below the sea floor which enhances the exploration potential of these pyroclastic units and demonstrates the need for volcanic facies analysis in exploration

syn to late tectonic stockwork emplacement within the spanish section of the iberian pyrite belt structural textural and mineralogical constraints in the tharsis and la zarza areas in deformed massive sulfide deposits it is commonly difficult to distinguish between primary stockwork mineralization and remobilized sulfides that occupy late cleavages and deformation structures and the mechanism of formation of the deformation veins is not always clear an analysis of sulfide vein networks associated with two massive sulfide deposits of the iberian pyrite belt is presented as an example of this complexity variscan deformation has affected the massive sulfide related stockworks at la zarza and tharsis and led to the formation of sulfide bearing deformation veins the primary feeder stockwork has a complex mineralogical composition with pyrite rich veins rimmed by narrow co as assemblages e g cobaltite and arsenopyrite interstitial galena chalcopyrite and sphalerite minerals are also observed the vein set developed during deformation was emplaced within cleavage and shear planes characteristic of the regional south verging tectonics away from massive sulfides the characteristic minerals of the syntectonic veins are pyrite and quartz however deformation veins developed in contact with primary feeder veins and massive sulfide have co as rich rims and base metal sulfides similar to the primary feeder veins the development of the complex vein paragenesis within the stockwork zones is explained in terms of regional scale deformation models

a new 3d geological model and interpretation of structural evolution of the world class rio tinto vms deposit iberian pyrite belt spain abstract a new 3d geological model and interpretation of structural evolution of the rio tinto world class vms deposit are presented in this work the rio tinto volcanogenic massive sulfide vms deposit is located in the spanish segment of the iberian pyrite belt and is hosted by felsic porphyritic volcanic rocks and tuffs computer generated 3d modeling of the different orebodies and host rocks has been carried out using data from around 3000 drill core logs allowing us to build 93 cross sections and 6 plants both 50 m spacing this has enabled us to recognize the geometry and relationships between the mineralization and the earliest carboniferous transtensional tectonics through the development of an extensional pull apart basin with two sub basins separated by the nw se trending eduardo fault the sub basins cerro colorado and san dionisio were limited by two e w strike slip faults the northern and southern faults and bounded in the east and west by the nw se trending nerva and western faults respectively the generated pull apart basin was first filled by a basaltic magmatism of mantle origin and later following the deposition of the intermediate complex sedimentary unit by rhyodacitic volcanic rocks of crustal origin the evolution of the subsiding basins caused the development of an e w oriented rollover anticline that affected these filling rocks as a result of a counterclockwise rotation of the stress axes the primitive pull apart basin evolved into a basin affected by e w transtensional sinistral shearing its northern and southern limits were favorable areas for increased hydrothermal fluid flow which gave way to the huge concentration of vms mineralization located near the limits the northern and to a lesser degree the southern extensional faults thus become channel areas for feeding and discharging of the vms and stockwork ores the main mineralizing period was related to this stage subsequently during the variscan transpressional phase the e w extensional faults were reactivated as inverse faults affecting the volcanic sequence of mafic to felsic composition and the intermediate complex sedimentary unit fault propagation folds developed above these faults affecting the massive sulfides the transition series and the culm flysch sediments with buttressing playing a significant role in the geometry of tectonically inverted structures the vms mineralization and cupriferous stockworks were folded and dismembered from the original conduits in the volcanic series and a dextral reactivation of the nw se trending faults also developed finally it should be emphasized that this new 3d geological model is an approach to provide a better insight into the 3d structure of the world class vms rio tinto deposit and could be a key point for further studies providing a new tool to increase knowledge of the vms mineralizations and exploration guidelines elsewhere in the ipb

geological constraints on the paleozoic tectonic evolution of tectonostratigraphic terranes in the iberian massif abstract the presence of oceanic paleozoic sequences in the iberian variscan fold belt is used to identify and separate suspected exotic terranes from a reference iberian autochthon terrane which constitutes the greater part of it in this paper the relevant data characterizing the pre accretionary evolution of the paleozoic iberian terranes are presented as well as the available evidence concerning the accretionary process itself emphasis is placed on the analysis of the sedimentary igneous and structural expression of the major events which affected the iberian terranes before during and after their amalgamation the main conclusions of such an analysis may be summarized as follows 1 a recognition of rift and passive margin stages in all the iberian massif terranes during the early paleozoic 2 b late paleozoic accretion of the exotic terranes to the iberian autochthon via a long and complex process variscan orogeny which involved initial subduction underneath the latter and eventual obduction followed by oblique collision of a promontory the iberian autochthon northwestern margin with a northwestern continental block this latter process could account for the large scale crustal imbrication shown by the northern branch of the orogen coeval with predominant strike slip faulting in the southern branch as well as with the formation of the typical arcuate shape of this orogenic belt major present uncertainties relate to the palinspastic provenance of continental suspect terranes and their correlation with similar units in other circum atlantic paleozoic orogens a discussion and speculations on this subject are dealt with in the final section of this paper

reconstructing atmospheric circulation over southern new zealand establishment of modern westerly airflow 5500 years ago and implications for southern hemisphere holocene climate change abstract late twentieth century changes in the intensity and migration of southern hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation and ice sheet dynamics across the mid to high latitudes a major uncertainty however is whether present day hemispheric wide symmetrical airflow is representative of past behaviour here we report a multi proxy study from stewart island and southern fiordland new zealand 46 47 s reconstructing holocene changes at the northern limit of westerly airflow increased minerogenic input and a pronounced shift in cool loving vegetation around 5500 years ago is consistent with the establishment of westerly airflow at this latitude in the southwest pacific in marked contrast stronger winds are reported further south over the subantarctic auckland 50 s and campbell 52 s islands from 8000 years ago intriguingly reconstructions from the east pacific suggest a weakening of core westerly airflow after 8500 years ago but an expansion along the northern limits sometime after 5500 years ago our results suggest similar atmospheric circulation changes have been experienced in the pacific since 5500 years ago but indicate an expanded network of sites is needed to comprehensively test the driver s and impact s of holocene mid latitude westerly winds across the southern hemisphere

volcanism mineralization and metamorphism at the xitieshan pb zn deposit nw china insights from zircon geochronology and geochemistry abstract the footwall volcanic rocks of the ordovician tanjianshan group in the world class xitieshan pb zn deposit have experienced prolonged arc volcanism followed by strong metamorphism and deformation this has resulted in a complex thermal history and led to ambiguity in interpretation of zircon geochronological results an integrated study involving textural characterization cl imaging trace element analysis ti in zircon thermometry and la icpms u pb dating has provided tight constraints on the age and genesis of the zircon groups in the volcanic rocks the temperature of metamorphism and deformation indicated by metacryst minerals and micro structures in the volcanic rocks ranges from 550 to 650 c which partially overlaps with the lower temperature range of zircon crystallization 600 750 c calculated using the ti in zircon thermometer cathodoluminescence images and trace element compositions confirm a magmatic origin for the zircons which have also been variably altered by metamorphic fluids two ranges of u pb ages 475 470 ma and 460 450 ma have been obtained on typical magmatic zircons and are interpreted to represent pre mineralization arc volcanism in the xitieshan deposit a younger age group of 440 430 ma for the fluid modified zircons is considered to record post ore metamorphism during the north qadaim orogeny thus we propose that the original exhalative ores at the xitieshan pb zn deposit formed at 450 440 ma

source complexity of the 1987 whittier narrows california earthquake from the inversion of strong motion records strong motion records for the whittier narrows earthquake are inverted to obtain the history of slip both constant rupture velocity models and variable rupture velocity models are considered the results show a complex rupture process within a relatively small source volume with at least four separate concentrations of slip two sources are associated with the hypocenter the larger having a slip of 55 90 cm depending on the rupture model these sources have a radius of approximately 2 3 km and are ringed by a region of reduced slip the aftershocks fall within this low slip annulus other sources with slips from 40 to 70 cm each ring the central source region and the aftershock pattern all the sources are predominantly thrust although some minor right lateral strike slip motion is seen the overall dimensions of the whittier earthquake from the strong notion inversions is 10 km long along the strike and 6 km wide down the dip the preferred dip is 30 degree and the preferred average rupture velocity is 2 5 km s moment estimates range from 7 4 to 10 0 times 10 sup 24 dyn cm depending on the rupture model

geochemical and nd isotopic signature of felsic volcanic rocks as a proxy of volcanic hosted massive sulphide deposits in the iberian pyrite belt sw spain the paymogo volcano sedimentary alignment abstract the iberian pyrite belt ipb located in the south portuguese zone of the iberian massif spain is a world class vhms province containing numerous huge mineral deposits hosted by bimodal volcanic sequences the province can be subdivided in several domains which differ from each other both in the nature and relative abundance of their volcanic sequences and in the distribution of associated vhms deposits in spite of its geological and economic interest information available for the northern part of the province is still relatively scarce we present a new dataset of geochemical and nd isotopic analyses on the paymogo volcano sedimentary alignment pvsa an area that is considered to be representative of this northern segment of the ipb volcanic sequences in the pvsa contain very scarce mafic rocks in contrast felsic rocks are abundant and have been classified in two groups i the paymogo rhyolitic sequence hosting most of the vhms deposits and ii a dacitic sequence although approximately coeval these groups of felsic rocks clearly differ in geochemical features and nd signature in view of these differences it is suggested that felsic rocks were produced from different mid crustal domains during a major event of partial melting related to a regional late devonian early carboniferous transtensional event it is further suggested that some volcanic rocks previously described as andesites are better interpreted as dacites the age 347 3 0 8 ma geochemical features zr

source inversion of the october 1 1995 dinar earthquake ms 6 1 a rupture model with implications for seismotectonics in sw turkey abstract an earthquake of ms 6 1 devastated the town of dinar sw turkey population 35 000 on october 1 1995 killing 90 people and destroying 30 of the town the earthquake generated complex body waveforms varying with azimuth at teleseismic distances the method of complex body waveform inversion developed by kikuchi and kanamori 1991 was used to infer a source process for the earthquake two subevents were necessary to explain the observed seismic records the inversion result suggests that the dinar earthquake initiated at the se end of the dinar fault with a subevent of seismic moment mo 0 5 1018 n m six seconds later the second subevent took place about 10 km to the northwest of the first subevent with a seismic moment a few times larger than the first the cmt depths of the first and second subevents were found to be 10 and 15 km respectively both subevents had a predominantly normal faulting mechanism with slip vectors oriented ne sw showing good agreement with the velocity vectors obtained from the recent slr and gps studies as well as with the regional stress orientation obtained from geological data the main shock was preceded by foreshock activity concentrated at the se end of the dinar fault where the first subevent took place while the aftershock activity was concentrated in the vicinity of the second subevent the spatial distribution of the foreshock and the aftershock activities and the locations of the subevents suggest that the first subevent broke an asperity and the second subevent broke a barrier on the fault following the definition by aki 1984 of an asperity and barrier earthquake model about 10 km of surface ruptures were associated with the earthquake while the estimates yield a rupture length of 25 km the calculated source parameters of the subevents and their locations suggest that the surface ruptures were probably associated with the first subevent the estimates also show that the rupture zones of the two subevents overlapped where the maximum vertical displacement was observed

mineralogical evolution of the las cruces gossan cap iberian pyrite belt from subaerial to underground conditions abstract the las cruces vms deposit is located at the eastern corner of the iberian pyrite belt sw spain and is overlain by the neogene quaternary sediments of the guadalquivir foreland basin the deposit is currently exploited from an open pit by cobre las cruces s a being the supergene cu enriched zone the present mined resource the las cruces orebody is composed of a polymetallic massive sulfide orebody a cu rich stockwork and an overlying supergene profile that includes a cu rich secondary ore initial reserves of 17 6 mt 6 2 cu and a gossan cap initial reserves of 3 6 mt 3 3 pb 2 5 g t au and 56 3 g t ag the mineralogy of the las cruces weathering profile has been studied in this work textural relationships mineral chemistry deposition order of the minerals and genesis of the las cruces gossan are described and discussed in detail a complex mineral assemblage composed by the following minerals has been determined carbonates such as siderite calcite and cerussite fe sulfides including pyrite marcasite greigite and pyrrhotite pb sb sulfides and sulfosalts like galena stibnite fuloppite plagionite boulangerite plumosite and the jordanite geocronite series ag hg sb sulfides and sulfosalts including miargyrite pyrargyrite sternbergite acanthite freibergite cinnabar ag au hg amalgams and bi pb bi sulfides and sulfosalts such as bismuthinite galenobismutite others unidentified bi pb sulfosalts native bi and unidentified fe pb sb sulfosalts remains of the former oxidized assemblage appear as relicts comprised of hematite and goethite combining paragenetic information textures and mineral chemistry it has been possible to derive a sequence of events for the las cruces gossan generation and subsequent evolution in that sense the small amount of fe oxyhydroxides and their relict textures replaced by carbonates and sulfides suggest that the gossan was generated under changing physico chemical conditions it is proposed that the las cruces current gossan represents the modified residue of a former gossan mineralization where prolonged weathering led to dissolution and leaching out of highly mobile elements and oxidation of the primary sulfides later the gossan was subject to seawater gossan interaction and then buried beneath a carbonated rich cover the basinal fluids gossan interaction and the equilibration of fluids with the carbonated sediments brought to the carbonatization and sulfidation of the gossan and thus to the generation of fe carbonates and pb sb sulfides the las cruces mineral system likely represents a new category within the weathering class of ore deposits

coseismic slip of two large mexican earthquakes from teleseismic body waveforms implications for asperity interaction in the michoacan plate boundary segment teleseismic body waves recorded for the october 25 1981 playa azul and september 21 1985 zihuatanejo earthquakes in western mexico were inverted to derive the distributions and depths of coseismic slip broadband p wave displacements and intermediate period records were included to incorporate a wide frequency band in the analysis for the zihuatanejo earthquake digital sh records located away from the nodal directions were used in the inversion process nonnodal sh waveforms were not available for the playa azul earthquake but additional azimuthal coverage was obtained by including selected worldwide analog p wave records the results for the playa azul earthquake indicate that rupture occurred in two separate zones both updip and downdip of the point of initial nucleation with the majority of the slip concentrated in a circular region 15 km radius downdip from the hypocenter the maximum slip in this downdip region exceeds 3 6 m and is at a depth of about 16 km the computed seismic moment is 7 14 1026 dyn cm coseismic slip is observed to occur entirely within the area of reduced slip separating the two main shallow sources of the michoacan earthquake that occurred almost 4 years later on september 19 1985 for the zihuatanejo earthquake the p and sh data suggest rupture over a larger area 30 km radius with a lower peak slip 2 m and encompassing depths between 12 and 26 km slip is concentrated in an area adjacent to one of the major sources of the michoacan earthquake and represents the southeastern continuation of rupture along the cocos north america plate boundary the corresponding seismic moment is 1 35 1027 dyn cm the zones of peak slip observed for the playa azul zihuatanejo and michoacan earthquakes are interpreted as asperity regions that control the cessation and generation of large earthquakes within the michoacan segment of the plate boundary the stress drops within each of these asperities are observed to be very similar and may reflect a characteristic asperity strength for this portion of the subduction zone

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

strong motion and broadband teleseismic analysis of the 1991 sierra madre california earthquake short period and broadband teleseismic waveform data and three component strong motion records were analyzed to obtain the source parameters of the 1991 sierra madre earthquake close in strong motion velocity records analyzed from 5 s to 5 hz show two distinct pulses about 0 35 s apart requiring some rupture complexity the near field shear wave displacement pulse from this event has a relatively short duration about 1 s for the magnitude of the event requiring a particularly high average stress drop to further constrain the rupture process the data were used in a finite fault source inversion to determine the temporal and spatial distribution of slip we chose a fault plane orientation striking s 62 w and dipping 50 toward the northwest as required by the distribution of aftershocks the first motion mechanism and the teleseismic bodywave point source inversion in addition to the aftershock locations depth constraints are provided by teleseismic short period and broadband recordings which require a centroid depth of 10 11 km our inverse modeling results indicate that both the teleseismic and strong motion data sets can be fit with a compact rupture area about 12 km2 southwest and up dip from the hypocenter the average slip is approximately 50 cm and the maximum slip is 120 cm the seismic moment obtained from either of the separate data sets or both sets combined is about 2 8 0 3 1024 dyn cm and the potency is 0 01 km3 using the area of significant slip estimated from the finite fault inversion the resulting stress drop is on the order of 150 200 bars

association between catastrophic paleovegetation changes during devonian carboniferous boundary and the formation of giant massive sulfide deposits abstract the iberian pyrite belt sw iberia is one of the largest sulfur anomalies in the earth s crust in the southern iberian pyrite belt more than 820 mt of exhalative massive sulfides were deposited in less than one million years at the devonian carboniferous boundary the shale of the ore bearing horizon contains biomarkers indicating major biogenic activity in a methanogenic setting including a five fold increase in typical vascular plant biomarkers and a significant anomaly in those probably indicating the presence of thermophilic archaea this contrasts with signatures in the average sedimentary rocks of the basin that indicate the sediments settled in oxic to sub oxic environments and that they have only minor biomarkers derived from continental paleoflora these data show that the formation of the mineralization was not only related to major hydrothermal activity synchronous with volcanism but may also have been controlled by the input of large amounts of organic matter mostly derived from the degradation of woodland detritus sourced in the nearby continent this massive influx of organic matter could have accelerated extremophilic microbial activity that used short chain hydrocarbons as electron donors for seawater sulfate reduction resulting in concomitant massive sulfide precipitation we propose that the giant massive sulfide deposits resulted from overlapping of geological and biological processes that occurred at the devonian to carboniferous transition including 1 continent collision during the onset of the variscan orogeny leading to major paleogeographic changes and volcanism 2 dramatic stress of continental ecosystems due to the combination of climatic change volcanism variations in the sea level and erosion on a regional scale 3 major biomass destruction and increase of organic supply to marine environments and 4 generation of anoxic conditions and the thriving of sulfate reducing microorganisms under these conditions massive sulfide deposits formed where venting sulfur poor but metal rich hydrothermal brines flowed into a hydrogen sulfide rich anoxic water column the data presented strongly suggest that there was a temporal and causal relationship between the devonian carboniferous geotectonic climatic and biological crises and the formation of the giant volcano sedimentary massive sulfide deposits of the southern iberian pyrite belt

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

a non linear geodetic data inversion using abic for slip distribution on a fault with an unknown dip angle summary we have developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle a common strategy for obtaining slip distribution in previous studies is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault it is not guaranteed however that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution the inverse problem is non linear for cases with unknown fault geometries but the non linearity of the problems is actually weak when we can assume the fault surface to be a flat plane in particular when a clear trace of coseismic faults is observed on the earth s surface only the dip angle is an unknown parameter to determine the fault geometry then we regarded the dip angle as an hyperparameter that prescribed the structure of parametric models and obtained the best estimate of the dip angle using akaike s bayesian information criterion abic with the best estimate of the dip angle we can obtain the slip distribution on the fault based on the maximum likelihood principle we applied the method to the insar data of the 1995 dinar turkey earthquake and obtained a much lower dip angle than the previous analyses

the salton sea scientific drilling project in march 1986 a research borehole called the state 2 14 reached a depth of 3 22 km in the salton sea geothermal system of southern california this was part of the salton sea scientific drilling project sssdp the first major i e multimillion dollar research drilling project in the u s continental scientific drilling program the principal goals of the project were to investigate the physical and chemical processes of a high temperature high salinity magmatically driven hydrothermal system the borehole encountered temperatures of up to 355 c and produced metal rich alkali chloride brines containing 25 wt of total dissolved solids the rocks penetrated exhibit metamorphism and ore genesis in action they show a progressive transition from unconsolidated lacustrine and deltaic sediments to hornfelses with lower amphibolite facies mineralogy accompanied by pervasive veins containing iron copper lead and zinc ore minerals the sssdp included an intensive program of rock and fluid sampling flow testing and downhole logging and scientific measurement the purpose of this paper is to introduce this special section of the journal of geophysical research on the sssdp to describe briefly the background of the project and the drilling and testing of the borehole to summarize the initial scientific results and to discuss how the lessons learned are applicable to future scientific drilling projects

lateglacial landscape and vegetation change and the younger dryas climatic oscillation in new zealand abstract lateglacial sequences in new zealand show progressive afforestation and landscape stabilization reflecting a warming climate between 14 500 bp and 11 500 bp afforestation and landscape stability was achieved throughout most of the north island and the northwest sector of the south island in the south island scrub and tree ferns were replacing previous grasslands in the east by 11 000 bp and broadleaved forest was spreading in the west no significant reversals of these trends occurred and afforestation was complete by 9500 bp glaciers of the high central part of the southern alps made a series of advances between 14 000 and 9000 bp most of these advances are poorly dated but two moraines are of younger dryas age glacial advances in the face of the general lateglacial warming trend may have been driven by stronger westerly winds increasing snowfall on high altitude neves and by reduced ablation as a consequence of moist cloudy low insolation summers the cause of the northern hemisphere younger dryas cooling is still uncertain and expected southern hemisphere responses may differ according to the mechanism proposed for the cooling poor chronological resolution and apparent conflict between the various types of evidence for climatic change make detection of an unambiguous younger dryas in new zealand problematical

zn pb cu massive sulfide deposits brine pool types occur in collisional orogens black smoker types occur in backarc and or arc basins volcanic hosted massive sulfide deposits of zn pb cu type were derived either from seawater dominated buoyant fluids that built mounds on the seafloor e g the ores of the hokuroku basin japan or from saline fluids that reversed buoyancy on mixing with seawater and filled basins on the seafloor e g several ores of the iberian pyrite belt and the mount read province in tasmania the hokuroku ores formed above subduction zones during protracted periods of regional extension but both the iberian pyrite belt and the mount read province formed under extensional stress during continent continent iberia or arc continent mount read collision and orogenesis in the iberian pyrite belt oblique convergence resulted in transcurrent faulting and this may also be the case for the mount read province transcurrent faulting may have allowed easy vertical access for the ore related magmas some of which were sourced in the asthenosphere as well as the blueschist and eclogitic facies emplaced in adjacent terrains and possibly also saline fluids exsolved from the magmas

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

late glacial and holocene vegetation and environment of campbell island far southern new zealand campbell island lies 600 km southeast of the new zealand mainland scrub grassland rushes and large leaved forb vegetation grow on the deep peats that cover nearly the entire island campbell isl

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

rupture history of the 1984 morgan hill california earthquake from the inversion of strong motion records near source strong motion velocity records and teleseismic short period p waveforms are modeled to obtain the spatial and temporal distribution of slip for the 1984 morgan hill earthquake both forward modeling and constrained least squares inversion techniques are used to interpret the strong motion velocity waveforms in the frequency range of approximately 0 2 to 2 0 hz these data support a nearly unilateral rupture to the southeast with a rupture propagation velocity of nine tenths of the local s wave velocity the majority of the slip occurs over a fault length of 25 km and to a first approximation can be interpreted as two main source regions each with an extent of about 5 km with their centers separated by about 12 km however each of the sources has detailed structure of its own and a simple two point source model is not an accurate representation of the morgan hill earthquake the second source occurs about 4 5 sec after the first and is approximately 3 times larger the maximum dislocation on the fault plane is about 1 m the total moment of the earthquake is estimated to be 2 1 10 25 dyne cm the morgan hill earthquake offers convincing evidence for very inhomogeneous slip and stress distributions on shallow strike slip faults

3 d electromagnetic imaging of a palaeozoic plate tectonic boundary segment in sw iberian variscides s alentejo portugal abstract in sw iberian variscides the boundary between the south portuguese zone spz and the ossa morena zone omz corresponds to a major tectonic suture that includes the beja acebuches ophiolite complex baoc and the pulo do lobo antiform terrane plat three sub parallel and approximately equidistant mt profiles were performed covering a critical area of this palaeozoic plate tectonic boundary in portugal the profiles running roughly along an ne sw direction are sub perpendicular to the main variscan tectonic features results of the three dimensional 3 d modelling of mt data allow to generate for the first time a 3 d electromagnetic imaging of the omz spz boundary which reveals different conductive and resistive domains that display morphological variations in depth and are intersected by two major sub vertical corridors these corridors coincide roughly with the ne sw messejana strike slip fault zone and with the wnw ese ferreira ficalho thrust fault zone the distribution of the shallow resistive domains is consistent with the lithological and structural features observed and mapped integrating the expected electrical features produced by igneous intrusions and metamorphic sequences of variable nature and age the development in depth of these resistive domains suggests that 1 a significant vertical displacement along an early tectonic structure subsequently re taken by the messejana fault zone in late variscan times has to be considered to explain differences in deepness of the base of the precambrian cambrian metamorphic pile 2 hidden syn to late collision igneous bodies intrude the meta sedimentary sequences of plat 3 the roots of baoc are inferred from 12 km depth onwards forming a moderate resistive band located between two middle crust conductive layers extended to the north in omz and to the south in spz these conductive layers overlap the iberian reflective body evidenced by the available seismic reflection data and are interpreted as part of an important middle crust decollement developed immediately above or coinciding with the top of a graphite bearing granulitic basement

comparison of l1 and l2 norms in a teleseismic waveform inversion for the slip history of the loma prieta california earthquake abstract broadband digital teleseismic body waves p and sh are inverted to obtain the history of slip for the 17 october 1989 loma prieta earthquake comparison of finite fault waveform inversion results using an l 1 norm and an l 2 norm reveal some basic uncertainties in the rupture history that are not usually appreciated in earthquake source studies however the more robust features of the source can be identified that are less dependent on the choice of minimization norm from a consideration of first motion data and forward modeling of body waves the strike and dip of our model fault plane are set at 126 and 67 respectively the waveform inversion results indicate that the majority of the moment release occurs over a fault length of 35 to 40 km and a depth range of 2 to 18 km the hypocenter 18 km depth experienced a relatively small amount of slip the rupture propagated upward and bilaterally with a peak slip of about 3 m occurring at a depth of 10 km the average velocity of the rupture propagation is 2 5 km sec the details of the slip distribution depend on the minimization norm but two main sources can be identified with the larger source above and to the southeast of the hypocenter the rake vector varies considerably over the fault the southern source is mostly strike slip while the northern source is approximately equally partitioned between dip slip and strike slip there is also a trend for more strike slip motion at shallower depths the majority of the moment release occurs in the first 7 5 sec with an integrated moment of 2 6 10 26 dyne cm including smaller peripheral sources that are less well resolved raises the moment estimate to 3 0 10 26 dyne cm

magmatic evolution and tectonic setting of the iberian pyrite belt volcanism rocks has been carried out to determine the primary magmatic aynity tectonics iberian pyrite belt and tectonic setting of the iberian pyrite belt volcanism most of the basaltic rocks are continental tholeiites but a few samples show an alkaline aynity the origin of the basaltic rocks and their diversity of compositions are explained by a single mixing model between e and n morb mid ocean ridge basalt and as introduction similation of crustal material calc alkaline intermediate and silicic volcanic hosted massive sulphide deposits are mainly rocks include basaltic andesites andesites dacites and rhyolites associated world wide with calc alkaline submarine volvolumetrically dacites and rhyolites are the most abundant inter canism petrological and geochemical data together with mediate and silicic rocks are not related by fractional crystallization stratigraphic and structural studies have been of major nor is there a relationship between the basaltic and calc alkaline importance in constraining geological models of the volrocks by the same process we suggest that in the iberian pyrite canism associated with massive sulphide deposits inbelt silicic calc alkaline magmas were generated on a large scale tegrated studies in areas such as the kuroko province in by the invasion of continental crust by mafic magmas generated in japan ohmoto 1983 the mount read volcanics in the underlying upper mantle the diversity of compositions shown tasmania crawford et al 1992 and the mount windsor by dacites and rhyolites can mainly be explained either by diverences volcanics in northwestern australia stolz 1995 have in the composition of the source rocks or by diverent degrees of revealed that this volcanism may be developed during partial melting of upper crust rocks andesites however formed by diverent stages of the subduction process always being mixing between basaltic magmas and upper crust material the new located on the overriding plate geochemical data agree with previously published tectonostratigraphic this paper documents the petrology and geochemistry data which suggest that the iberian pyrite belt volcanism formed of the volcanism of the iberian pyrite belt an early on the south portuguese plate owing to strike slip tectonics this carboniferous metallogenic province that extends from portugal to spain in southwest iberia and constitutes local extensional tectonic setting was related to transtension as a