very preliminary reference moon model abstract the deep structure of the moon is a missing piece to understand the formation and evolution of the earth moon system despite the great amount of information brought by the apollo passive seismic experiment alsep the lunar structure below deep moonquakes which occur around 900 km depth remains largely unknown we construct a reference moon model which incorporates physical constraints and fits both geodesic lunar mass and polar moment of inertia and love numbers and seismological body wave arrivals measured by apollo network data in this model the core radius is constrained by the detection of s waves reflected from the core in a first step for each core radius a radial model of the lunar interior including p and s wave velocities and density is inverted from seismic and geodesic data in a second step the core radius is determined from the detection of shear waves reflected on the lunar core by waveform stacking of deep moonquake apollo records this detection has been made possible by careful data selection and processing including a correction of the gain of horizontal sensors based on the principle of energy equipartition inside the coda of lunar seismic records and a precise alignment of sh waveforms by a non linear inversion method the very preliminary reference moon model vpremoon obtained here has a core radius of 380 40 km and an average core mass density of 5200 1000 kg m 3 the large error bars on these estimates are due to the poorly constrained s wave velocity profile at the base of the mantle and to mislocation errors of deep moonquakes the detection of horizontally polarized s waves reflected from the core and the absence of detection of vertically polarized s waves favour a liquid state in the outermost part of the core all these results are consistent within their error bars with previous estimates based on lunar rotation dissipation williams et al 2001 and on lunar induced magnetic moment hood et al 1999

seismic detection of the lunar core despite recent insight regarding the history and current state of the moon from satellite sensing and analyses of limited apollo era seismic data deficiencies remain in our understanding of the deep lunar interior we reanalyzed apollo lunar seismograms using array processing methods to search for the presence of reflected and converted seismic energy from the core our results suggest the presence of a solid inner and fluid outer core overlain by a partially molten boundary layer the relative sizes of the inner and outer core suggest that the core is 60 liquid by volume based on phase diagrams of iron alloys and the presence of partial melt the core probably contains less than 6 weight of lighter alloying components which is consistent with a volatile depleted interior

metamorphic evolution of the attic cycladic metamorphic belt on naxos cyclades greece utilizing 40ar 39ar age spectrum measurements 40ar 39ar age spectrum analysis of phengite separates from naxos part of the attic cycladic metamorphic belt in greece indicates that cooling following high pressure low to medium temperature metamorphism m1 occurred about 50 ma ago phengite has 40ar gradients that suggest that part of the scatter observed in conventional k ar ages was caused by diffusion of radiogenic argon from the minerals during a younger metamorphism m2 in central naxos this metamorphism m2 has overprinted the original mineral assemblages completely and is associated with development of a thermal dome excellent 40ar 39ar plateaus at 15 0 0 1 ma 11 8 0 1 ma and 11 4 0 1 ma obtained on hornblende muscovite and biotite respectively from the migmatite zone indicate that relatively rapid cooling followed the m2 event and that no significant thermal overprinting occurred subsequent to m2 toward lower m2 metamorphic grade 40ar 39ar plateau ages of hornblendes increase to 19 8 0 1 ma concomitantly the proportion of excess 40ar in the spectra increases as well we propose that the peak of m2 metamorphism occurred beween 15 0 and 19 8 ma ago k ar ages of biotites from a granodiorite on the west coast are indistinguishable from those found in the metamorphic complex and hornblende k ar ages from the same samples are in the range 12 1 13 6 ma as the latter ages are somewhat younger than most ages obtained from the metamorphic complex intrusion of the granodiorite most likely followed the peak of the m2 metamorphism the metamorphic evolution of naxos is consistent with rapid crustal thickening during the cretaceous or early tertiary causing conditions at which supracrustal rocks experienced pressures in the range 900 1500 mpa transition to normal crustal thicknesses ended the m1 metamorphism about 50 ma ago the m2 metamorphism and granodiorite intrusion occurred during a period of heat input into the crust possibly related to the migration of the hellenic volcanic ar c in a southerly direction through the area

on the hellenic subduction zone and the geodynamic evolution of crete since the late middle miocene abstract in recent syntheses of the geodynamic evolution of the aegean area the hellenic subduction zone and in particular its initiation plays a central role two basic aspects of the recent comprehensive model put forward by le pichon angelier and co workers are a initiation of subduction along the hellenic arc is inferred to have taken place approximately 13 ma ago whereas several others have suggested approximately 5 ma and b migration of the trench system to the south southwest giving rise to an extensional regime in the back arc region which led to general subsidence and formation of the present day aegean sea new data on the structure of the upper mantle underneath the aegean area indicate that the former aspect requires modification the seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 ma ago estimates of about 5 ma for the time of initiation of the present subduction zone are even more difficult to reconcile assuming 400 km as an upper bound for the effect of stretching of the aegean sea and of other processes contributing to the separation of crete from the eurasian mainland we arrive at an age for the hellenic subduction zone of at least 26 ma as to aspect b geological data of crete lend strong support to the idea that on crete compressional tectonics is of much greater importance than current models imply combining geophysical and geological data we propose a modification of the tectonic evolution for the cretan segment of the hellenic arc whereas the basic process of extension caused by a migrating trench system roll back in a land locked basin remains a very useful and sound concept the tectonics of the margins of a region subject to stretching in this case crete may be more complicated than hitherto thought in our model the documented fragmentation of crete into several basins which started about 12 ma ago is not attributed to initiation of subduction but to inception of the roll back process compressional tectonics on crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime

episodic and short lived granitic pulses in a post collisional setting evidence from precise u pb zircon dating through a crustal cross section in corsica abstract in western corsica a large granitoid batholith was emplaced during carboniferous and permian times these rocks display an evolution through time from high mg k calc alkaline to calc alkaline then alkaline affinities moreover the magmatic processes can be observed at different crustal levels new and precise isotope dilution and thermo ionisation mass spectrometry id tims u pb dating suggests that granite magmatism in corsica did not simply reflect the continuous thermal evolution of a thickened crust a precise timing for the post collisional magmatism is documented with four distinct short lived episodes respectively at 345 338 305 and 280 ma separated by periods of inactivity these four magma pulses display variable nd isotopic signatures related to mantle crust interactions granite magma generation and emplacement is strongly connected to the thermal and tectonic activity of the lithosphere an increasing contribution of a depleted mantle to the magmatic processes is documented for the last igneous event this is interpreted to reflect the emplacement of depleted mantle materials in the lower crust which enhanced heat flow and triggered partial melting of previously underplated mafic rocks this increasing contribution of mantle materials marks the onset of a new geodynamic cycle characterised by an extensional tectonic regime preluding to the opening of the alpine orogenic tract

intrusive rocks in the ophiolitic melange of crete witnesses to a late cretaceous thermal event of enigmatic geological position the ophiolitic melange in the uppermost tectonic unit of the cretan nappe pile contains crystalline slices which consist of a low pressure high temperature metamorphic sequence and synmetamorphic intrusions ranging in composition from diorite to granite the plutonic rocks conform to two different igneous suites dominated by diorites in eastern and granites in central crete displaying i type and a type characters respectively some of the granites from central crete are classified as transitional i s type they are closely associated with migmatitic paragneisses based on major and trace element ree sr and nd isotope geochemistry the mafic members of both suites are derived from a depleted mantle source the higher concentrations of p and ti in the mafic members of the igneous suite in central crete and the deviant trend of the whole suite may be explained by a different mantle source or a lower degree of partial melting in both suites magmatic evolution was governed by fractional crystallization of amphibole clinopyroxene plagioclase and minor phases in addition mixing or mingling of compositionally different magmas is indicated for the intrusive suite of eastern crete whereas in central crete the magma composition was at least partially modified through assimilation of meta pelites the geochemical results suggest that the plutonic rocks formed in a supra subduction zone setting however a formation during continental lithospheric extension cannot be ruled out published and new rb sr and k ar dates on amphiboles and biotites from intrusive rocks and their metamorphic country rocks show that the peak of the low p high t metamorphism and the intrusion of the two igneous suites testify to the same thermal event of late cretaceous age a similar late cretaceous association of metamorphic and plutonic rocks has been described from the uppermost tectonic unit in the attic cycladic crystalline complex together with the cretan occurrences they form a small sector radiating ssw along a distance of 300 km across the general trend of the tectonic zones in the hellenic orogen this n s alignment is regarded as a primary feature which may delineate the frontier zone between the hellenides and the taurides the real paleogeographic position and geodynamic significance of the late cretaceous low pressure high temperature belt however remains enigmatic

linking granulites silicic magmatism and crustal growth in arcs ion microprobe zircon u pb ages from the hidaka metamorphic belt japan there is no consensus as to how the extreme metamorphic conditions required to form granulites are attained or how these rocks relate to crustal growth and differentiation processes studying young granulites offers two advantages the tectonic setting is likely to be well constrained and the ambiguities that result from overprinting by younger metamorphic events are potentially avoided we report the first ion microprobe u pb zircon ages for orthopyroxene bearing granulites tonalites and gabbros of the cenozoic hidaka metamorphic belt hokkaido japan to clarify the magmatic metamorphic connection in this area the data support a two stage evolution for this terrane which is attributed to episodes of supra subduction zone magmatism late eocene and back arc extension early miocene we relate granulite facies metamorphism and garnet orthopyroxene tonalite generation to mafic magma under accretion and lithosphere thinning due to the opening of the japan sea at 19 ma the hidaka granulites are thus among the youngest exposed granulites on earth and manifest the thermal response to continental growth

a seismic model of the lunar mantle and constraints on temperature and mineralogy abstract we determine seismic profiles of the moon s interior using travel times obtained from a re analysis of the apollo data due to the limited number of quakes and stations travel times errors were determined and used in the inversions our model has a mean crustal thickness of about 30 km in the region of the apollo network with a 10 km zone of brecciation below the crust mean values of seismic velocities in the upper mantle are rather well constrained and are in the range 7 6 7 8 and 4 35 4 45 km s 1 for p and s waves respectively velocity variations in the middle mantle are less well defined in the zone of deep moonquakes below 740 km depth velocities increase slightly to 8 15 0 23 and 4 5 0 10 km s 1 for p and s waves respectively we analyse the seismic profile in term of mineralogy and temperature constraints our preferred models are a pyroxenite model for the upper mantle and a magnesian rich model for the lower mantle with increasing mg with depth we find temperatures of about 1100 k elastic lithosphere limit and 1500 k thermal lithosphere limit for radii of about 1400 and 1000 km respectively and show that the lunar mantle is probably depleted in th and u by at least 70 compared to an earth reference value of 25 7 ppb u for a crustal thickness of 40 km with a mean 1010 ppb th concentration we then find bulk th and u abundances comparable to and possibly lower than currently accepted terrestrial values

depositional features and stratigraphic sections in granitic plutons implications for the emplacement and crystallization of granitic magma abstract many granitic plutons contain sheet like masses of dioritic to gabbroic rocks or swarms of mafic to intermediate enclaves which represent the input of higher temperature more mafic magma during crystallization of the granitic plutons small scale structures associated with these bodies e g load cast and compaction features silicic pipes extending from granitic layers into adjacent gabbroic sheets indicate that the sheets and enclave swarms were deposited on a floor of the magma chamber on granitic crystal mush and beneath crystal poor magma while the mafic magma was incompletely crystallized these structures indicate way up typically toward the interior of the intrusions and appear to indicate that packages of mafic sheets and enclave concentrations in these plutons are a record of sequential deposition hence these plutons preserve a stratigraphic history of events involved in the construction filling replenishment and crystallization of the magma chamber the distinctive features of these depositional portions of plutons allow them to be distinguished from sheeted intrusions which usually preserve mutual intrusive contacts and dike sill relations of different magma types the considerable thickness of material that can be interpreted as depositional and the evidence for replenishment suggest that magma chamber volumes at any one time were probably much less than the final size of the pluton thus magma chambers may be constructed much more slowly than presently envisaged the present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber along with the underlying solidified granite and country rock sank during continuing episodes of magma chamber replenishment these internal magmatic structures support recent suggestions that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber

late pleistocene granodiorite source for recycled zircon and phenocrysts in rhyodacite lava at crater lake oregon abstract rhyodacite tephra and three lavas erupted 27 ka interpreted to be early leaks from the climactic magma chamber of mount mazama contain ubiquitous resorbed crystals antecrysts that were recycled from young granodiorite and related plutonic rocks of the same magmatic system the shallow composite pluton is represented by blocks ejected in the 7 7 ka climactic eruption that formed crater lake caldera plagioclase crystals in both rhyodacite and granodiorites commonly have cores with crystallographically oriented fe oxide needles exsolved at subsolidus conditions at least 80 of plagioclase crystals in the rhyodacite are antecrysts derived from plutonic rocks other crystals in the rhyodacite notably zircon also were recycled sims 238 u 230 th dating indicates that zircons in 4 granodiorite blocks crystallized at various times between 20 ka and 300 ka with concentrations of analyses near 50 70 110 and 200 ka that correspond to periods of dacitic volcanism dated by k ar u th ages of zircon from a rhyodacite sample yield similar results no analyzed zircons from the granodiorite or rhyodacite are pre quaternary zircon minimum ages in blocks from different locations around the caldera reflect ages of nearby volcanic vents and may map the distribution of intrusions within a composite pluton survival of zircon in zircon undersaturated hydrous magma and of fe oxide needles in plagioclase suggests that little time elapsed from entrainment of antecrysts to the 27 ka eruption of the rhyodacite the 27 ka rhyodacite is an example of young silicic magma that preserved unstable antecrysts from a known source early during growth of a large high level magma chamber in contrast the voluminous 7 7 ka climactic rhyodacite pumice is virtually lacking in zircon indicating dissolution of any granodioritic debris in the intervening period mineralogical evidence of assimilation may be destroyed in hot vigorously growing silicic magma bodies such as ultimately produced the climactic eruption of mount mazama

exhumation of high pressure rocks driven by slab rollback rocks metamorphosed under high pressure hp and ultra high pressure uhp conditions in subduction zones come back to the surface relatively soon after their burial and at rates comparable to plate boundary velocities in the mediterranean realm their occurrence in several belts related to a single subduction event shows that the burial exhumation cycle is a recurrent transient process using the calabria apennine and aegean belts as examples we show that the exhumation of hp rocks is associated in time and space with the subduction of small continental lithosphere blocks that triggers slab rollback creating the necessary space for the exhumation of the buoyant continental crust that was deeply buried just before the buoyancy force of the subducted crust increases until this crust detaches from the downgoing slab it then exhumes at a rate that depends directly on the velocity of trench retreat to become part of the overriding plate heated from below by the asthenosphere that flows into the opening mantle wedge the exhumed crust weakens and undergoes core complex type extension responsible for a second stage of exhumation at a lower rate the full sequence of events that characterizes this model crust mantle delamination slab rollback and trench retreat hp rock exhumation asthenosphere heating and core complex formation arises entirely from the initial condition imposed by the subduction of a small continental block no specific condition is required regarding the rheology and erosion rate of hp rocks the burial exhumation cycle is transient and can recur every time a small continental block is subducted

nappe stacking resulting from subduction of oceanic and continental lithosphere below greece we quantitatively investigate the relation between nappe stacking and subduction in the aegean region if nappe stacking is the result of the decoupling of upper crustal parts 5 10 km thick from subducting lithosphere then the amount of convergence estimated from balancing the nappe stack provides a lower limit to the amount of convergence accommodated by subduction the balanced nappe stack combined with the estimated amount of completely subducted lithosphere indicates 700 km of jurassic and 2400 km of post jurassic convergence from seismic tomographic images of the underlying mantle we estimate 2100 2500 km of post jurassic convergence we conclude that 1 the imaged slab represents the subducted lithosphere that originally underlay the nappes 2 since the early cretaceous subduction in the aegean has occurred in one single subduction zone and 3 the composition of the original basement of the nappes indicates that at least 900 km of sub upper crust continental lithosphere subducted in the aegean

moon meteoritic seismic hum steady state prediction 1 we use three different statistical models describing the frequency of meteoroid impacts on earth to estimate the seismic background noise due to impacts on the lunar surface because of diffraction seismic events on the moon are typically characterized by long codas lasting 1 h or more we find that the small but frequent impacts generate seismic signals whose codas overlap in time resulting in a permanent seismic noise that we term the lunar hum by analogy with the earth s continuous seismic background seismic hum we find that the apollo era impact detection rates and amplitudes are well explained by a model that parameterizes 1 the net seismic impulse due to the impactor and resulting ejecta and 2 the effects of diffraction and attenuation the formulation permits the calculation of a composite waveform at any point on the moon due to simulated impacts at any epicentral distance the root mean square amplitude of this waveform yields a background noise level that is about 100 times lower than the resolution of the apollo long period seismometers at 2 s periods this noise level is more than 1000 times lower than the low noise model prediction for earth s microseismic noise sufficiently sensitive seismometers will allow the future detection of several impacts per day at body wave frequencies

i type plutonism in a continental back arc setting miocene granitoids and monzonites from the central aegean sea greece miocene extension in the aegean sea was accompanied by the intrusion of granitoid and monzonitic magmas at upper crustal levels with increasing distance from the trench the metaluminous to slightly peraluminous i type intrusives show a systematic regional variation in their compositions medium to high k granodiorites in the wsw high k low silica granites in the central region and high k high silica granites monzonites monzogranites and composite lamprophyric monzonitic dikes in the ene the granodioritic and low silica granitic plutons comprise similar ranges of sio2 63 5 71 6 wt and initial nd sr and o isotopic values end i 7 0 to 9 8 87sr 86sr i 0 7092 0 7115 18o 9 7 11 5 but display significant differences in their chemical compositions compared with the granodiorites the low silica granites have higher abundances of large ion lithophile light rare earth and some high field strength elements initial isotopic signatures of the high silica granites in the ene end i 9 0 to 9 6 87sr 86sr i 0 7128 0 7144 18o 10 8 12 0 are slightly more crust like than those of the low silica granites in chemical variation diagrams samples from the high silica granites continue the trends defined by those from the low silica granites it is suggested that all granitoid magmas originated by dehydration melting of metaluminous older crustal sources most probably metagreywackes u pb systematics of zircon populations in conjunction with zr sio2 systematics and zircon saturation temperatures suggest a high proportion of restitic or assimilated crustal material in these magmas monzonitic to monzogranitic rocks show chemical and isotopic characteristics end i 0 8 to 3 6 87sr 86sr i 0 7059 0 7071 18o 9 4 10 6 that are significantly different from those of the granitoids a small portion of an older crustal component in these magmas is indicated by u pb systematics of zircon populations lamprophyric dikes display chemical and isotopic signatures end i 0 5 87sr 86sr i 0 7044 18o 8 9 that are compatible with an origin from either a mantle source previously enriched by slab derived hydrous fluids melts as suggested by negative nb ta anomalies or a new k rich basaltic underplate abundant composite dikes indicate the coexistence of and mingling mixing between lamprophyric melts and monzonitic magmas

relative oxidation states of magmas inferred from ce iv ce iii in zircon application to porphyry copper deposits of northern chile major and trace element compositions of zircons and whole rocks from 14 barren and seven ore bearing calc alkaline intrusions from the chuquicamata el abra porphyry copper belt of northern chile have been measured in situ by excimer laser ablation ela icp ms these data permit the ce iv ce iii ratio within zircon to be calculated using a lattice strain model for mineral melt partitioning of ce iv and ce iii zircon ce iv ce iii and eun eun ratios and by inference magmatic oxidation states generally increase from older mafic to younger felsic units within this sequence porphyry copper mineralization is directly associated only with intrusions with zircon ce iv ce iii 300 and eun eun 0 4 such trends can be understood in terms of interdependent relations between oxygen fugacity sulfur speciation and solubility and chalcophile element partitioning in silicate magmas because zircon occurs in most calc alkaline intrusions and is resistant to subsolidus alteration zircon ce iv ce iii ratios provide a useful tool for evaluating the economic potential of such rocks for magmatic hydrothermal cu au mineralization the approach is general and may provide a means to infer relative oxidation state in a wide range of intermediate to felsic igneous rocks

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

the late alpine evolution of an extensional shear zone naxos greece the mid miocene structural evolution of the metamorphic complex on naxos involved deformation in a kilometre scale low angle ductile shear zone the structures described are consistent with exhumation of the metamorphic complex during crustal extension after and possibly during localized high temperature barrovian style metamorphism non coaxial fabrics developed throughout the structural history indicate that upper levels were transported to the north during ductile extension this shear sense is opposite that inferred previously for the development cordilleran style metamophic core complexes in the cvclades ductile deformation was accompanied during its later stages by e w directed compression

low angle faults above and below a blueschist belt tinos island cyclades greece new observations from the island of tinos greece allow a better definition of the structural position of the alpine eocene blueschist belt exposed in the islands of the aegean sea these blueschists over a significant part of the aegean sea are delimited from below by a low angle thrust fault while from above they are delimited by a low angle normal type fault which omits a substantial crustal interval both underlying and overlying rocks were not affected by the high metamorphism the rapid uplift and exhumation of the high rocks was therefore mainly the result of fault movements rather than erosion and whole crust uplifting the low angle normal fault apparently had a major role in the uplift of the blueschists

the menderes massif of western turkey and the cycladic massif in the aegean do they really correlate based on lithostratigraphic comparisons the menderes massif has been correlated with the cycladic massif thereby implying that the eastern mediterranean consists of a narrow pre alpine basement belt which is laterally continuous over a long distance and which experienced a similar alpine orogenic history our work indicates that the architecture the age of basement and the pre alpine and alpine tectonometamorphic history of both massifs differ fundamentally from each other the menderes massif consists of remnants of the cycladic massif which overly an exotic unit the menderes nappes both massifs do not represent lateral continuations which has implications for palaeogeographic reconstructions

zircon growth and recycling during the assembly of large composite arc plutons abstract concordant u pb zircon dates have been interpreted traditionally to date the crystallization ages of plutons because until recently analytical uncertainties have generally been large enough to encompass the anticipated duration of pluton growth advances in zircon tims analysis and geochronological studies by sims on zircon from young volcanic rocks along with evolving views of the evolution of magmatic systems makes it necessary to revaluate this interpretation assignment of unique pluton crystallization ages based on zircon dating is complicated by the propensity of zircon to survive multiple intrusive events that culminate in a large pluton distinctions must be made between true inherited zircon xenocrystic zircon derived from host rocks during magma ascent and or emplacement and multi stage growth of zircon during waxing and waning of magma reservoirs that solidify to form large plutons these complications are exemplified by recent high precision u pb zircon age dating from the cretaceous tuolumne and mt stuart batholiths which clearly show that the timeframe of pluton assembly was long 5 ma for mt stuart and 8 ma for tuolumne zircon crystals from samples from both batholiths exhibit appreciable concordant age dispersion for zircon several 10 5 yr up to 2 10 6 yr and assignment of statistically valid rock solidification ages is not possible from these data low zr in the rocks of each batholith indicates that magmas were initially strongly undersaturated in zircon when emplaced and inherited zircon is rare or absent recycling of zircon antecrysts during successive magmatic injections is the primary cause of the modest age dispersion of concordant zircon ages and is compatible with progressive growth of a large long lived crystal mush body because eruption of magma requires low to moderate crystal fraction and high temperatures relative to stored crystal mushes zircon crystals are more likely to be eradicated during thermal rejuvenation preceding major eruptions

single grain argon laser probe dating of phengites from the blueschist to greenschist transition on sifnos cyclades greece measurements of 40ar 39ar age spectra on single white mica crystals of tertiary age is a new means of obtaining detailed geochronological information of alpine blueschists internal consistency of the data set as well as excellent agreement with previous conventional k ar results demonstrates that this new technique can be used with confidence to obtain information on the thermal evolution of young metamorphic belts

reflection imaging of the moon s interior using deep moonquake seismic interferometry the internal structure of the moon has been investigated over many years using a variety of seismic methods such as travel time analysis receiver functions and tomography here we propose to apply body wave seismic interferometry to deep moonquakes in order to retrieve zero offset reflection responses and thus images beneath the apollo stations on the nearside of the moon from virtual sources colocated with the stations this method is called deep moonquake seismic interferometry dmsi our results show a laterally coherent acoustic boundary around 50 km depth beneath all four apollo stations we interpret this boundary as the lunar seismic moho this depth agrees with japan aerospace exploration agency s jaxa selenological and engineering explorer selene result and previous travel time analysis at the apollo 12 14 sites the deeper part of the image we obtain from dmsi shows laterally incoherent structures such lateral inhomogeneity we interpret as representing a zone characterized by strong scattering and constant apparent seismic velocity at our resolution scale 0 2 2 0 hz

regional implications of geochemistry and style of emplacement of miocene i type diorite and granite delos cyclades greece abstract the miocene plutons of the cyclades were emplaced in a subduction setting during regional back arc extension of continental crust that led to flat lying mid crustal detachment faulting mapping of the island of delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction mafic magmas were followed by numerous small batches of felsic magma with magmatic and ductile deformation synchronous with magma emplacement late granite dykes occupy brittle fractures in the more deformed rocks mafic and intermediate rocks show a bimodal distribution of incompatible trace elements with one group of broadly tholeiitic character and the other with substantial enrichment in sr nb and hfse but low th and ba these differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the eastern cyclades voluminous granodiorite results from these mafic magmas fractionating and or mixing with felsic crustal material some of which was derived by anatexis of a sedimentary protolith indicated by high b and mn some late granites appear derived from partial melting of hercynian paragneiss regionally the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones the shear zones parallel the mid cycladic lineament a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the hellenic subduction zone distinctive geochemical features in miocene igneous rocks suggests that these two blocks had quite different geological histories the localisation of plutonism and core complexes near the mid cycladic lineament suggests that this crustal scale shear played a role in bringing subduction derived magmas to mid crustal levels the heat supplied by the mafic magmas promoted ductile deformation high in the crust where extension was concentrated leading to the formation of core complexes the regional extension resulted in progressive shallowing of the position of the granite solidus within the crust leading to welding of the mid cycladic lineament which is no longer seismically active

constraints on the shallow elastic and anelastic structure of mars from insight seismic data mars s seismic activity and noise have been monitored since january 2019 by the seismometer of the insight interior exploration using seismic investigations geodesy and heat transport lander at night mars is extremely quiet seismic noise is about 500 times lower than earth s microseismic noise at periods between 4 s and 30 s the recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground transferred wind generated lander noise here we constrain properties of the crust beneath insight using signals from atmospheric vortices and from the hammering of insight s heat flow and physical properties hp3 instrument as well as the three largest marsquakes detected as of september 2019 from receiver function analysis we infer that the uppermost 8 11 km of the crust is highly altered and or fractured we measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the moon which suggests that the crust contains small amounts of volatiles the crust beneath the insight lander on mars is altered or fractured to 8 11 km depth and may bear volatiles according to an analysis of seismic noise and wave scattering recorded by insight s seismometer

the extensional messaria shear zone and associated brittle detachment faults aegean sea greece structural thermochronological and metamorphic data are used to elucidate the tectonic nature and evolution of the ductile extensional messaria shear zone and the associated brittle messaria and fanari detachment faults which exhumed their footwall from mid crustal depths on the island of ikaria in the aegean thermobarometric data indicate that the messaria shear zone formed at 350 400 c and 3 4 kbar i e at a depth of c 15 km normal faulting was accompanied by the intrusion of two granites which together with the thermobarometric data indicate a relatively high thermal field gradient of 25 35 c km 1 zircon and apatite fission track and apatite u th he ages demonstrate rapid cooling in the footwall of the messaria detachment from c 400 c to c 40 c between 11 and 3 ma age distance relationships of the data suggest that the messaria shear zone and the messaria detachment slipped at apparent rates of c 6 9 km ma 1 kinematic indicators show a consistent top to the nne shear sense for the extensional faults however at the southern part of the messaria detachment some late stage shear sense indicators are top to the ssw and are assumed to be associated with updoming of the footwall numerous deformed pegmatite veins in the messaria shear zone allow the reconstruction of deformation and flow parameters the mean kinematic vorticity number ranges from 0 13 to 0 80 indicating that shearing deviated significantly from simple shear that is extensional shearing was associated with vertical ductile thinning which contributed to tectonic exhumation finite strain shows oblate geometries and axial ratios of the finite strain ellipse in sections parallel to tectonic transport and normal to the mylonitic foliation range from 1 8 to 19 9 we calculate using a 1d numerical model that vertical ductile thinning contributed c 20 to exhumation during extensional shearing normal faulting was the major agent exhuming the footwall from c 15 km depth

constraining the long term evolution of the slip rate for a major extensional fault system in the central aegean greece using thermochronology the brittle ductile transition is a major rheologic boundary in the crust yet little is known about how or if rates of tectonic processes are influenced by this boundary in this study we examine the slip history of the large scale naxos paros extensional fault system npefs cyclades greece by comparing published slip rates for the ductile crust with new thermochronological constraints on slip rates in the brittle regime based on apatite and zircon fission track aft and zft and u th he dating we observe variable slip rates across the brittle ductile transition on naxos zft and aft ages range from 11 8 0 8 to 9 7 0 8 ma and 11 2 1 6 to 8 2 1 2 ma and u th he zircon and apatite ages are between 10 4 0 4 to 9 2 0 3 ma and 10 7 1 0 to 8 9 0 6 ma respectively on paros zft and aft ages range from 13 1 1 4 ma to 11 1 1 0 ma and 12 7 2 8 ma to 10 5 2 0 ma while the u th he zircon ages are slightly younger between 8 3 0 4 ma and 9 8 0 3 ma all ages consistently decrease northwards in the direction of hanging wall transport most of our new thermochronological results and associated thermal modeling more strongly support the scenario of an identical fault dip and a constant or slightly accelerating slip rate of 6 8 km myr 1 on the npefs across the brittle ductile transition even the intrusion of a large granodiorite body into the narrowing fault zone at 12 ma on naxos does not seem to have affected the thermal structure of the area in a way that would significantly disturb the slip rate the data also show that the npefs accomplished a minimum total offset of 50 km between 16 and 8 ma

timing problem with the lunar module impact data as recorded by the lspe and corrected near surface structure at the apollo 17 landing site 1 it has recently been discovered that the apollo 17 lunar module lm impact data from the lunar seismic profiling experiment lspe had a serious timing problem correcting this problem changes the lunar near surface seismic velocity structure significantly from the structural models reported in the earlier publications extending a low velocity vp 1 km s layer down to a 3 km depth or deeper

open system magma chamber evolution an energy constrained geochemical model incorporating the effects of concurrent eruption recharge variable assimilation and fractional crystallization ec e raχfc significant petrogenetic processes governing the geochemical evolution of magma bodies include magma recharge including formation of quenched inclusions or enclaves heating and concomitant partial melting of country rock with possible contamination of the evolving magma body assimilation and formation and separation of cumulates by f ractional crystallization rafc although the importance of modeling such open system magma chambers subject to energy conservation has been demonstrated the effects of concurrent removal of magma by eruption and or variable assimilation involving imperfect extraction of anatectic melt from wall rock have not been considered in this study we extend the ec rafc model to include the effects of eruption and variable amounts of assimilation ax this model called ec e 0racfc tracks the compositions trace elements and isotopes temperatures and masses of magma body liquid melt eruptive magma cumulates and enclaves within a composite magmatic system undergoing simultaneous eruption recharge assimilation and fractional crystallization the model is formulated as a set of 4 t i s coupled nonlinear differential equations where the number of trace elements radiogenic and stable isotope ratios modeled are t i and s respectively solution of the ece 0racfc equations provides values for the average temperature of wall rock ta mass of melt within the magma body mm masses of cumulates mct enclaves men and wall rock m o a and the masses of anatectic melt generated m a and assimilated cm a in addition t trace element concentrations and i s isotopic ratios in melt and eruptive magma cm em dm cumulates cct em dm enclaves cen er d o r and anatectic melt ca ea d o a as a function of magma temperature tm are also computed input parameters include the user defined equilibration temperature teq a factor describing the efficiency of addition of anatectic melt c from country rock to host magma the initial temperature and composition of pristine host melt tom c o m em d o m recharge melt t o r c o r er dor and wall rock t o a c o a ea d o a distribution coefficients dm dr da and their temperature dependences dhm dhr dha latent heats of transition melting or crystallization for wall rock dha pristine magma dhm and recharge magma dhr as well as the isobaric specific heat capacity of assimilant cp a pristine cp m and recharge cp r melts the magma recharge mass and eruptive magma mass functions mr tm andme tm respectively are specified a priori mr tm and me tm are modeled as either continuous or episodic step like processes melt productivity functions which prescribe the relationship between melt mass fraction and temperature are defined for end member bulk compositions characterizing the local geologic site ec e 0racfc has potential for addressing fundamental questions in igneous petrology such as what are intrusive to extrusive ratios i e for particular magmatic systems and how does this factor relate to rates of crustal growth how does i e vary temporally at single long lived magmatic centers what system characteristics are most profoundly influenced by eruption what is the quantitative relationship between recharge and assimilation in cases where the extraction efficiency can be shown to be less than unity what geologic criteria are important and

styles and rates of long term denudation in carbonate terrains under a mediterranean to hyper arid climatic gradient abstract carbonate minerals unlike silicates have the potential to dissolve almost completely and with high efficiency thus in carbonate terrains denudation rate and style the governing process of denudation mechanical or chemical should be more sensitive to climatic forcing using 36 cl measurements in 39 carbonate bedrock and sediment samples we calculate long term denudation rates across a sharp climatic gradient from mediterranean to hyper arid conditions our samples were collected along the arugot watershed which drains the eastern flank of the judea range central israel to the dead sea and is characterized by a pronounced rain shadow denudation rates of flat lying bedrock outcrops sampled along interfluves differ by an order of magnitude from 20 mm ka 1 in the mediterranean zone to 1 3 mm ka 1 in the hyper arid zone these rates are strongly correlated with precipitation and thus reflect the importance of carbonate mineral dissolution in the overall denudation process in contrast denudation rates of steep bedrock surfaces depend on the hillslope gradient but only in the hyper arid climate zone indicating that mechanical processes dominate the overall hillslope denudation within this zone the dominance of slope dependent mechanical erosion in the hyper arid zone is also reflected by an increase in spatially average denudation rates from 17 19 mm ka 1 in the mediterranean semi arid zones to 21 25 mm ka 1 in the hyper arid zone these higher rates are attributed to clast contribution from steep slopes under arid climate this suggests an increased importance of mechanical processes to the overall denudation in the hyper arid zone we demonstrate that the transition between chemically dominated denudation to mechanically dominated denudation occurs between 100 and 200 mm of mean annual precipitation long term denudation rates across the judea range indicate that between mediterranean and hyper arid climates chemical weathering rates are limited by precipitation nevertheless in more humid climates chemical weathering rates are apparently limited by the rates of carbonate mineral dissolution this study demonstrates that carbonate terrains have the capacity to shift between mechanically and chemically dominated denudation in response to changes in precipitation similar transitions in response to changes in temperature or the level of tectonic activity have been previously reported we suggest that the abrupt nature of such transitions can be primarily attributed to the efficiency of carbonate dissolution processes and the competition between surface and subsurface drainage systems in carbonate terrains

spatial and temporal variation in late cenozoic back arc volcanic rocks aegean sea region abstract the aegean sea and adjacent areas comprise thinned continental crust forming an extensional back arc basin behind the south aegean arc in this back arc region are many small volcanic centres with a wide range of volcanic products this late miocene to quaternary volcanism is volumetrically minor in contrast to the voluminous igneous activity of the south aegean arc the age and major and trace element geochemistry of these back arc volcanic rocks are reviewed from the literature where necessary new geochemical analysis have been made five magma types are recognised continental alkaline basalts sodic basalts with incompatible element enrichment and nb depletion trachytes shoshonites and calc alkaline andesites all but the continental alkaline basalts appear geochemically related to subduction processes there is a regular distribution of rock types in time and space the subduction related rocks occur in a broad arc between the modern south aegean arc and the early to middle miocene volcanicity of the central aegean region sodic basalts occur in the most inboard regions and are later than the trachytes shoshonites and calc alkaline magmas occur in the most outboard regions this back arc volcanism occurs only in areas of abundant shallow seismicity however areas of extension and seismicity in the northeast aegean distant from the subducting slab lack volcanoes with the exception of the continental alkaline basalts the magmas are derived only from mantle influenced by the aseismic part of the hellenic subduction slab between 200 and 400 km depth back arc extension associated with rotation of the aegean microplate and strike slip motion on the north anatolian fault system has created a fault system allowing these magmas to reach the surface analogous processes may be common in the final stages of closure of ancient orogens

thermochronometric constraints on the tectonic evolution of the serifos detachment aegean sea greece we constrain the timing and kinematics of the serifos detachment in the southwestern cyclades greece using low temperature thermochronometry fission track dating shows that the serifos detachment was active between 13 and 6 ma and that the serifos granodiorite in its footwall intruded at or before 12 11 ma into the extensional shear zone and initially cooled very rapidly at rates 180 c per million year the mylonite zone at the top of the granodiorite and mylonitic structures in its country rocks record a consistent top ssw shear sense in the ductile crust in the brittle regime top nne shear sense indicators occur as well conjugate top ssw and top nne high angle normal faults are the youngest deformational features and cut across the detachment age distance relationships for the fission track data display a relatively flat pattern we discuss a model advocating initial top ssw movement on the serifos detachment before and during emplacement of the granodiorite updoming of the detachment during exhumation and cooling caused subsequent bivergent extension in the brittle crust

residence resorption and recycling of zircons in devils kitchen rhyolite coso volcanic field california zircons from the devils kitchen rhyolite in the pleistocene coso volcanic field california have been analyzed by in situ pb u ion microprobe shrimp rg and by detailed cathodoluminescence imaging the zircons yield common pb corrected and disequilibrium corrected pb u ages that predate a previously reported k ar sanidine age by up to 200 kyr and the range of ages exhibited by the zircons is also approximately 200 kyr cathodoluminescence imaging indicates that zircons formed in contrasting environments most zircons are euhedral and a majority of the zircons are weakly zoned but many also have anhedral embayed cores with euhedral overgrowths and multiple internal surfaces that are truncated by later crystal zones concentrations of u and th vary by two orders of magnitude within the zircon population and by 10 20 times between zones within some zircon crystals indicating that zircons were transferred between contrasting chemical environments a zircon saturation temperature of 750 c overlaps within error a previously reported phenocryst equilibration temperature of 740 25 c textures in zircons indicative of repeated dissolution and subsequent regrowth are probably caused by punctuated heating by mafic magma input into rhyolite the overall span of ages and large variation in u and th concentrations combined with calculated zircon saturation temperatures and resorption times are most compatible with crystallization in magma bodies that were emplaced piecemeal in the crust at coso over 200 kyr prior to eruption and that were periodically rejuvenated or melted by subsequent basaltic injections

field and geochemical constraints on mafic felsic interactions and processes in high level arc magma chambers an example from the halfmoon pluton new zealand the 140 ma halfmoon pluton of stewart island new zealand provides direct evidence for a number of physico chemical processes that operate at depth within active arc settings it is characterized by a sequence of mingled mafic sheets and enclaves that are preserved within intermediate felsic host rocks way up structures and textures are consistent with a younging direction to the south and allow a south dipping magma chamber stratigraphy to be constructed the similarity in modal mineralogy geochemistry and isotopic signature between the various components and their proximity in space and time indicates that the system can be considered as a single composite pluton with discrete portions active at different times interpretation of mingling structures and textures in the field combined with detailed geochemical and geochronological analyses has allowed the identification of several physical and chemical processes operating within the chamber including 1 multiple mafic magma pulses that were extensively mingled and sometimes physically mixed at the exposed level and at depth 2 the development of mineral fabrics e g aligned plagioclase and hornblende crystals and alignment of mafic enclaves caused by processes of crystal accumulation magmatic flow and compaction 3 shortening of the chamber during crystallization as a result of magmatic loading 4 fractional crystallization of the intermediate felsic host magma that was interrupted periodically by mafic magma intrusion 5 incremental assembly of the pluton from the base up 6 limited chemical transfer between the mingled mafic sheets and enclaves and the surrounding intermediate felsic host rocks variations in morphology chemistry and texture of the mingled mafic rocks relative to their position within the magmatic stratigraphy indicate that processes operating within the chamber varied in both space and time mineral assemblages chemical characteristics primitive isotopic signatures and a lack of zircon inheritance indicate that the amphibole rich calc alkaline halfmoon pluton was emplaced into a juvenile arc setting and experienced no contamination with ancient crustal materials a model of pluton construction and evolution is presented that shows that the halfmoon pluton consisted of at least two adjacent magma pods that grew incrementally by episodic replenishments of mafic magma into a magma chamber of evolving intermediate felsic composition data are consistent with a model whereby hydrous amphibole rich basaltic magmas ponded at the crust mantle interface and episodically rose injected and mingled

the timing of partial melting barrovian metamorphism and granite intrusion in the naxos metamorphic core complex cyclades aegean sea greece abstract the relationship between partial melting and granite intrusion in a classic barrovian metamorphic terrane has been assessed thirteen samples were dated by shrimp u pb zircon geochronology from the island of naxos greece one of the aegean metamorphic core complexes the effect of partial melting during peak barrovian metamorphism on naxos is recorded by fine

lateral variations of lunar crustal thickness from the apollo seismic data set seismic waves generated by meteoroid impacts have been detected by the apollo lunar seismic network these waves are sensitive to the crustal structure beneath both the seismic stations and the impact sites we use a markov chain monte carlo algorithm in order to invert for lateral variations of crustal thickness on the moon the inversion uses travel times of seismic waves originating from multiple meteoroid impact locations previous seismic investigations constrained the crustal thickness solely for apollo stations 12 14 and 16 whereas our approach enables to estimate the crustal thickness at locations far from the apollo network and to build a first crustal thickness map based on seismic data here we compare our crustal thickness estimates based on seismic travel times to those based on inversions of the topography and gravity field both methods turn out to be coherent in the sense that highland sites possess a thicker crust than mare sites

the hellenic subduction system high pressure metamorphism exhumation normal faulting and large scale extension the cenozoic history of the retreating hellenic subduction system in the eastern mediterranean involves subduction accretion arc magmatism exhumation normal faulting and large scale continental extension from 60 mya until the recent ages for high pressure metamorphism in the central aegean sea region range from 53 ma in the north the cyclades islands to 25 20 ma in the south crete younging of high pressure metamorphism reflects the southward retreat of the hellenic subduction zone the shape of pressure temperature time paths of high pressure rocks is remarkably similar across all tectonic units suggesting a steady state thermal profile of the subduction system and persistence of deformation and exhumation styles the high pressure metamorphic events were caused by the underthrusting of fragments of continental crust that were superimposed on slab retreat most of the exhumation of high pressure units occurred in extrusion wedges during ongoing lithospheric convergence at 23 19 mya large s

two ages of porphyry intrusion resolved for the super giant chuquicamata copper deposit of northern chile by ela icp ms and shrimp zircon u pb ages measured in situ by excimer laser ablation inductively coupled plasma mass spectrometry ela icp ms and verified by sensitive high resolution ion microprobe shrimp on ore bearing felsic porphyries from the chuquicamata porphyry copper molybdenum deposit northern chile identify two discrete igneous events the volumetrically dominant east porphyry has an age of 34 6 0 2 ma whereas the bench and west porphyries yield ages of 33 3 0 3 ma and 33 5 0 2 ma respectively the age of the east porphyry is indistinguishable from a re os age for early molybdenite mineralization 35 ma and the oldest reported 40 ar 39 ar ages for hydrothermal alteration confirming a genetic link with mineralization previous geological studies and 40 ar 39 ar and re os geochronology identify two main hydrothermal events high temperature potassic alteration with chalcopyrite at 33 4 0 3 ma followed by lower temperature quartz sericite alteration with pyrite at 31 1 0 3 ma the ages of the west and bench porphyries match the ages for potassic alteration younger quartz sericite alteration may reflect an additional fourth intrusion concealed at depth the anomalously large size of chuquicamata appears to be due to a protracted igneous history resulting in the superposition of at least two temporally distinct magmatic hydrothermal systems

rb sr isotope studies on tinos island cyclades greece additional time constraints for metamorphism extent of infiltration controlled overprinting and deformational activity this study presents new rb sr age data concerning the metamorphic evolution of the attic cycladic crystalline belt which represents a complex polymetamorphic terrane within the alpidic orogenic belt of the hellenides two major groups of tectonic units can be distinguished metamorphism in parts of the upper units is commonly considered as a cretaceous event in contrast the group of lower units experi enced tertiary high pressure metamorphism which was followed by a medium pressure overprint we focus on the island of tinos where a representative spectrum of the rock units found in the cyclades is exposed in three tectonic units the upper unit the intermediate unit and the basal unit the complete range of tectono metamorphic and magmatic events affecting the attic cycladic crystalline belt is documented by numerous petrological and tectonic studies phyllites and phyllonites from the ophiolitic upper unit yielded rb sr apparent ages phengite whole rock between c 92 and 21 ma the older age differs from the cretaceous dates reported for upper unit rocks elsewhere in the cyclades it is suggested that the sequence studied belongs to the jurassic ophiolites of the hellenides rather than to cretaceous occurrences the spread to younger ages is related to non pervasive rejuvenation and resetting of the rb sr system during tectonic juxtaposition of the upper unit over the intermediate unit the youngest age obtained so far for a sample from the upper unit 21 ma is believed to approximate the timing of tectonic juxtaposition which probably occurred during a regional greenschist facies episode producing a pervasive overprint in the struc turally lower tectonic unit the major phyllite meta gabbro serpentinite sequence of the upper unit is inter preted as an emplacement related ductile shear zone which experienced reworking under brittle conditions in the intermediate unit a gradient in rb sr ages from top c 40 ma to the bottom c 22 ma was recog nized which is interpreted to represent greater effects of fluid infiltration and overprinting in the lower parts of this unit possibly controlled by variable intensity of deformation which might be related to tectonic jux taposition onto the basal unit we suggest that synmetamorphic stacking of all three tectonic units took place during an oligocene miocene greenschist event extensional deformation continued after tectonic stacking and after intrusion of the main granite as is indicated by a rb sr whole rock isochron 15 1 0 6 ma for a ductilely deformed garnet bearing leucogranite from the marginal parts of the main undeformed pluton application of the rb sr dating technique provided no unequivocal evidence that previously pub lished eocene k ar and 40 ar 39 ar dates for high pressure phengites from the lower units are significantly contaminated with excess argon

alpine high pressure metamorphism at the almyropotamos window southern evia greece the alpine orogenic belt of the hellenides has been strongly reworked by ductile and brittle extensional tectonics extensional structures have affected the central aegean region and obliterated much of the original orogenic architecture since at least early miocene times in the area of almyropotamos on the island of evia flanking the western part of the aegean a unique remnant compressional nappe stack involving tertiary metamorphic rocks has been preserved this nappe sequence comprises a high pressure rock unit on top of a lower grade unit the upper unit south evia blueschist belt is thought to be the westward continuation of the cycladic blueschist belt metamor phosed at high pressure conditions during late cretaceous eocene times the underlying unit the almyropotamos unit is a continental margin sequence covered by a flysch and containing lutetian nummulites indicating that this unit accumulated sediments until at least late eocene times in the present study we analyse the petrology of the almyropotamos nappe stack and define the p t conditions of each of the different rock units exposed there the presence of glaucophane law sonite rimmed by epidote and jadeite 70 mol suggest that peak p t conditions in the south evia blueschist belt reached approximately 10 12 kbar and 350 450 c unlike previous studies which estimated that the underlying almyropotamos unit reached only greenschist facies conditions glau cophane relics and si rich phengites were found by us in this unit these indicate that high pressure metamorphism and crustal thickening in this part of the aegean lasted until at least the late eocene or early oligocene we note that in this respect the architecture of southern evia resembles that of north ern greece olympos ossa our structural data indicate that rock units in the almyropotamos area record different folding phases with the south evia blueschist belt having a more complex fold his tory than the underlying almyropotamos unit the entire nappe stack shares large scale folds which are e w trending and locally overturned to the south and which may represent at present coordi nates n s contraction and nappe transport

farside deep moonquakes and deep interior of the moon 1 an effort to find farside deep moonquakes among the recently discovered nests of deep moonquakes has identified about 30 nests that are likely to be on the farside although only a few of them are locatable with currently available data and those few provide little new information about the deep interior of the moon the inferred distribution of the rest of these nests indicates that either the region of the moon s deep interior within about 40 degrees from the antipode of the moon is nearly aseismic or alternatively the very deep interior of the moon severely attenuates or deflects seismic waves since this has important bearing on the origin and evolution of the moon future missions to the moon need to be oriented toward resolving this uncertainty some limited data favor the attenuation deflection hypotheses

receiver function tomography of the central tien shan abstract to obtain an image of the deep structure of the tien shan in central asia we invert p and s receiver functions jointly for almost 40 local broad band seismograph stations the inversion is performed using a simulated annealing technique the combined inversion is an improvement on earlier studies where p and s receiver functions were inverted separately using this approach we deal with structural imaging problems that are usually investigated with teleseismic body wave and surface wave tomography techniques we demonstrate that the uppermost mantle in the north of the central tien shan is composed of a high velocity lid a few tens of kilometers thick above a pronounced low velocity zone the crustal structure in this region provides evidence of magmatic underplating these features are likely related to a small plume that is manifested by basaltic eruptions of cretaceous paleogene age the low velocity layer is also found in a southeast trending corridor which may correspond to the bachu uplift in the tarim basin crustal thickness beneath the orogen varies from about 45 to about 70 km the smallest values most likely inherited from the pre orogenic era are found in a neighborhood of the talas fergana fault similar values are characteristic of the kazakh shield in the north and the tarim basin in the south the largest values are found beneath the bounding ranges we infer that uplift of the central tien shan is unlikely to be caused by crustal shortening alone

several distinct tectono metamorphic slices in the cycladic eclogite blueschist belt greece several relatively thin tectono metamorphic slices have been recognized in the cycladic eclogite blueschist belt through detailed studies on ios sifnos syros and tinos a sequence of distinct metamorphic mineral growth events has been documented these re cur in each tectonic slice although individual slices are dominated by different events to constrain the timing of these processes the method of asymptotes and limits has been used to reanalyze published 40 ar 39 ar apparent age spectra this reanalysis supports the concept that there were separate and quite distinct high pressure metamorphic mineral growth events and allows poten tial constraints as to the timing of some of these events to be developed m1b eclogite facies metamorphism is estimated to have occurred at some time in the period 53 49 ma the m1c blueschist facies metamorphic event at some time in the period 44 38 ma and the m1d transitional blueschist facies metamorphic event is esti mated to have occurred at some time in the period 35 30 ma a kinematic model is proposed to explain the geometry of a thinly sliced tectono metamorphic stra tigraphy as observed and the reason as to why indi vidual tectonic slices in this tectono metamorphic stratigraphy should display distinctive patterns of fab rics and micro structures as well as characteristic tem perature time curves as inferred by 40 ar 39 ar geochronology

middle miocene graben development in crete and its possible relation to large scale detachment faults in the southern aegean the linkage between the development of south facing cretan graben and large scale detachment faulting in the southern aegean is unknown widespread serravallian deposits in the ierapetra graben of crete supply constraints to middle miocene graben development in the southern aegean the ierapetra graben and by inference the cretan graben in general were hitherto believed to have formed as a result of sinistral transpression during n s shortening we argue that the formation of the cretan graben is due to n s extension the south dipping n s extending kritsa normal fault served as the master fault controlling graben development in the ierapetra graben the kritsa normal fault is either an antithetic fault related to the top n cretan detachment or a synthetic fault associated with the top s ios detachment the overall geometry and timing relationships lead us to favour a connection with the ios detachment which in turn implies a large scale displacement on the ios detachment

interior structure of terrestrial planets modeling mars mantle and its electromagnetic geodetic and seismic properties 1 we present a new procedure to describe the one dimensional thermodynamical state and mineralogy of any earth like planetary mantle with mars as an example the model parameters are directly related to expected results from a geophysical network mission in this case electromagnetic geodetic and seismological processed observations supplemented with laboratory measurements we describe the internal structure of the planet in terms of a one dimensional model depending on a set of eight parameters for the crust the thickness and the mean density for the mantle the bulk volume fraction of iron the olivine volume fraction the pressure gradient and the temperature profile and for the core its mass and radius currently available geophysical and geochemical knowledge constrains the range of the parameter values in the present paper we develop the forward problem and present the governing equations from which synthetic data are computed using a set of parameter values among all martian models fitting the currently available knowledge we select eight candidate models for which we compute synthetic network science data sets the synergy between the three geophysical experiments of electromagnetic sounding geodesy and seismology is emphasized the stochastic inversion of the synthetic data sets will be presented in a companion paper

first seismic receiver functions on the moon we applied the s receiver function technique farra and vinnik 2000 to the recordings of deep moon quakes at seismograph station apollo 12 in order to detect phases converted sp and reflected beneath the station we detected sp phases from the base of the surficial low velocity zone and from the mantle crust boundary the average p velocity in the surficial layer 1 km thick should be a few times higher than in reference model toksoz et al 1974 the observed time amplitude and waveform of sp phase from the mantle crust boundary are close to those predicted by the reference model but with a modified surficial layer the s wavetrains within the first 10 s may contain waves scattered in the mantle this scattering is stronger than in the earth at comparable depths the polarized component in the coda waves that we observe is another previously unknown phenomenon

lunar surface gravimeter as a lunar seismometer investigation of a new source of seismic information on the moon lunar seismology has always suffered from the limited number of seismic stations and limited coverage of the seismic network additional seismic data are necessary to probe the lunar interior in depth instead of a costly new deployment of seismometers the aim of this study is to investigate the possibility of using the apollo 17 lunar surface gravimeter lsg as a lunar seismometer the lsg was designed to detect gravitational waves associated to change in the curvature of spacetime and tidal ground motion on the moon but the data were not investigated for seismic use partially because of a malfunction of the instrument we first evaluated the influence of the malfunction through comparison with other apollo seismic data and found that the effect of the malfunction is small and the lsg detected seismic signals in a manner that was consistent with those of the other apollo seismometers then we carried out source location with the additional station of the lsg we relocated previously located deep moonquake nests to evaluate the influence of the lsg data which are generally noisier than other apollo seismic data then we located deep moonquake nests that were previously unlocatable forty deep moonquake nests were examined and we located five new nests one newly located nest a284 was most likely to be located on the farside this series of analyses indicates that the lsg functioned as a lunar seismometer and that its data are useful for improving seismic analyses with the previous seismic data set of the moon

high precision lu hf geochronology of eocene eclogite facies rocks from syros cyclades greece abstract garnet bearing high pressure low temperature hp lt metamorphic rocks of the cycladic blueschist unit have been investigated by lu hf geochronology eclogites from syros island yield precise ages of 52 2 0 3 ma 51 4 0 4 ma and 50 2 ma preserved major and trace element growth zoning in garnet suggests that the closure temperature of the lu hf system in garnet was higher than the estimated peak metamorphic temperature of 500 c hence lu hf ages most likely reflect garnet growth in the studied samples our new lu hf grt ages are in excellent agreement with previously published u pb shrimp ages of metamorphic zircon and the maximum reported white mica rb sr and ar ar ages from syros garnet growth in all samples apparently took place over a narrow time interval because the lu hf ages cluster tightly even though the distribution of lu between cores and rims varies among samples we find no evidence for garnet generations that are significantly older or younger than the given isochron ages this in conjunction with the agreement among the ages of metamorphic zircon the maximum white mica ages and the lu hf ages strongly suggests that the 52 ma age dates a single hp event that affected these rocks

verifying single station seismic approaches using earth based data preparation for data return from the insight mission to mars abstract the planned insight mission will deliver a single seismic station containing 3 component broadband and short period sensors to the surface of mars in 2016 while much of the progress in understanding the earth and moon s interior has relied on the use of seismic networks for accurate location of sources single station approaches can be applied to data returned from mars in order to locate events and determine interior structure in preparation for the data return from insight we use a terrestrial dataset recorded at the global seismic network station bfo located at the black forest observatory in germany to verify an approach for event location and structure determination based on recordings of multiple orbit surface waves which will be more favorable to record on mars than earth due to smaller planetary radius and potentially lower background noise with this approach applied to events near the threshold of observability on earth we are able to determine epicentral distance within approximately 1 corresponding to 60 km on mars and origin time within 30 s with back azimuth determined from rayleigh wave polarization absolute locations are determined generally within an aperture of 10 allowing for localization within large tectonic regions on mars with these locations we are able to recover earth mantle structure within 5 the insight mission requirements for martian mantle structure using 1d travel time inversions of p and s travel times for datasets of only 7 events the location algorithm also allows for the measurement of great circle averaged group velocity dispersion which we measure between 40 and 200 s to scale the expected reliable frequency range of the insight data from earth to mars data using the terrestrial data we are able to resolve structure down to 200 km but synthetic tests demonstrate we should be able to resolve martian structure to 400 km with the same frequency content given the smaller planetary size

high pressure metamorphism in the aegean eastern mediterranean underplating and exhumation from the late cretaceous until the miocene to recent above the retreating hellenic subduction zone 1 we report 40ar 39ar ages from various tectonic units in the aegean and westernmost turkey on the basis of published geochronologic data and our 40ar 39ar ages we propose that the aegean is made up of several high pressure units which were successively underplated from the late cretaceous until the miocene ages for high pressure metamorphism range from 80 83 ma in parts of the vardar izmir ankara suture zone in the north to 21 24 ma for the basal unit in the cyclades and the external high pressure belt on crete in the south published seismic data suggest that high pressure metamorphism is currently occurring underneath crete younging of high pressure metamorphism in a southerly direction mimics the southward retreat of the hellenic subduction zone we propose that distinct stages of high pressure metamorphism were controlled by the underthrusting of fragments of mainly thinned continental crust and that these punctuated events were superposed on progressive slab retreat by far most of the exhumation of the high pressure units occurred early during the orogenic history in a forearc position

i and s type plutonism on serifos w cyclades greece abstract tertiary i and s type plutonism is widespread in the aegean region and frequently associated with extensional tectonic structures this investigation presents the first evidence of protracted magmatism on the island of serifos in the western cyclades and at least two discrete generations of plutonism and coeval dyke generations can be distinguished 1 an older granitoid with s type characteristics intruded the attic cycladic crystalline rocks the granitoid and its host rocks were mylonitized by an earlier phase of deformation at temperature conditions 450 c and wsw directed shear this crustal scale ductile shear zone has been reactivated during the initial stage of a metamorphic core complex formation recording top ssw sense of shear rb sr muscovite data from the orthogneiss yield cooling respectively deformation ages of 15 11 3 ma 2 an i type hornblende biotite granodiorite pluton with dacitic to andesitic dyke generations intruded syn to post kinematically during ongoing extensional deformation at shallow crustal levels single grain zircon tims u pb ages of the main granodiorite body and its associated dykes are 11 6 9 5 ma cooling ages of these samples scatter between 8 5 and 7 7 ma rb sr on biotite

an integrated zircon geochronological and geochemical investigation into the miocene plutonic evolution of the cyclades aegean sea greece part 1 geochronology we use 369 individual u pb zircon ages from 14 granitoid samples collected on five islands in the cyclades in the aegean sea greece for constraining the crystallisation history of i and s type plutons above the retreating hellenic subduction zone miocene magmatism in the cyclades extended over a time span from 17 to 11 ma the ages for s type granites are systematically 2 million years older than those for i type granites considering plutons individually the zircon data define age spectra ranging from simple and unimodal to complex and multimodal seven of the 14 investigated samples yield more than one distinct zircon crystallisation age with one i type granodiorite sample from mykonos island representing the most complex case with three resolvable age peaks two samples from s type granites on ikaria appear to have crystallised zircon over 2 3 million years whereas for the majority of individual samples with multiple zircon age populations the calculated ages deviate by 1 1 5 million years we interpret our age data to reflect a protracted history involving initial partial melting at deeper lithospheric levels followed by crystallisation and cooling at shallower crustal levels our study corroborates published research arguing that pluton construction is due to incremental emplacement of multiple magma pulses over a few million years assuming that multiple age peaks of our 14 samples can indeed serve to quantify time spans for magmatic emplacement our data suggest that aegean plutons were constructed over a few million years our tectonic interpretation of the u pb ages is that the s type granites resulted from partial melting and migmatisation of the lower crust possibly starting at 23 ma the i type granites and associated mafic melts are interpreted to reflect the magmatic arc stage in the cyclades starting at 15 ma

investigation of scattering in lunar seismic coda 1 we investigate the intrinsic attenuation and scattering properties of the moon by parameterizing the coda decay of 369 higher quality lunar seismograms from 72 events via their characteristic rise and decay times we investigate any dependence of the decay times on source type frequency and epicentral distance intrinsic attenuation scattering and possible focusing of energy in a near surface low velocity layer all contribute to the coda decay although it is not possible to quantify the exact contribution of each of these effects in the seismograms results suggest that scattering in a near surface global layer dominates the records of shallow events 0 200 km depth particularly at frequencies above 2 hz and for increasing epicentral distance we propose that the scattering layer is the megaregolith and that energy from shallow sources encounters more scatterers as it travels longer distances in the layer increasing the coda decay times a size distribution of ejecta blocks that has more small scale than large scale scatterers intensifies this effect for increasing frequencies deep moonquakes 700 1100 km depth exhibit no dependence of the decay time on epicentral distance we suggest that because of their large depths and small amplitudes deep moonquakes from any distance sample a similar region near a given receiver near station structure and geology may also control the decay times of local events as evidenced by two natural impact records this study provides constraints and testable hypotheses for waveform modeling of the lunar interior that includes the effects of intense scattering and shallow low velocity layers

sources and evolution of arc magmas inferred from coupled o and hf isotope systematics of plutonic zircons from the cretaceous separation point suite new zealand abstract coupled o and hf isotopic compositions of zircons from early cretaceous 113 124 ma granitoids of the separation point suite sps new zealand obtained by cathodoluminescence imaging guided micro beam methods sims la icpms are used as a record of evolving magma compositions in a prominent mesozoic arc system eight representative sps samples from individual plutons in the nelson and fiordland regions yield magmatic zircons with initial hf isotope ratios expressed in e hf ranging from 4 to 11 nelson and 5 to 12 fiordland respectively initial hf isotope ratios of zircons are extremely heterogeneous within individual samples with the vast majority of values distinctly less radiogenic than depleted mantle at 120 ma e hf 16 o isotope ratios are likewise variable with 18 o zircon smow values of 2 8 nelson and 0 7 fiordland the within rock variability in both zircon hf and o isotope ratios is testimony to open system processes that operated during magma evolution and zircon crystallisation average 18 o zircon for cores and rims allow constraints to be placed on the o isotopic composition of magmas from which zircon precipitated 18 o magma 4 8 elevated 18 o magma 6 5 require involvement of 18 o enriched supracrustal material weathered continental crust or low t seawater hydrothermally altered oceanic crust while 18 o magma 18 o depleted crustal component whole rock sr isotope nb ta and nd pb systematics are inconsistent with 18 o depleted slab melts 18 o 0 6 as a source component for sps magmas instead low 18 o values suggest incorporation of high t meteoric hydrothermally altered country rocks similar to those of the largs terrane presently exposed in northern fiordland in diagrams of sio 2 versus inferred 18 o magma the most primitive sps samples from the nelson and fiordland regions plot close to the expected composition for primitive arc magmas more evolved granitoids however show strongly divergent trends of o isotope composition as a function of sio 2 suggestive of assimilation coupled to fractional crystallisation afc in contrasting crustal environments emplacement level contamination by local crust is supported by age distributions of inherited zircons which indicate a predominance of palaeozoic and mesozoic zircons in nelson and fiordland granitoids respectively

episodic growth of the gondwana supercontinent from hafnium and oxygen isotopes in zircon it is thought that continental crust existed as early as 150 million years after planetary accretion but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records for example the striking global peaks in juvenile igneous activity 2 7 1 9 and 1 2 gyr ago imply rapid crustal generation in response to the emplacement of mantle super plumes rather than by the continuous process of subduction yet uncertainties persist over whether these age peaks are artefacts of selective preservation and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle these model ages are only meaningful if the host magma lacked a mixed or sedimentary source component but the latter can be diagnosed by oxygen isotopes which are strongly fractionated by rock hydrosphere interactions here we report the first study that integrates hafnium and oxygen isotopes all measured in situ on the same precisely dated detrital zircon grains the data reveal that crust generation in part of gondwana was limited to major pulses at 1 9 and 3 3 gyr ago and that the zircons crystallized during repeated reworking of crust formed at these times the implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts

incremental growth of the patagonian torres del paine laccolith over 90 k y the miocene paine granite in the torres del paine intrusive complex southern chile is an extraordinary example of an upper crustal mafic and granitic intrusion the granite intruded as a series of three sheets each one underplating the previous sheet along the top of the basal paine mafic complex high precision u pb geochronology on single zircons using isotope dilution thermal ionization mass spectrometry yields distinct ages of 12 59 0 02 ma and 12 50 0 02 ma respectively for the first and last sheet of the laccolith this age relationship is consistent with field observations the zircon ages define a time frame of 90 40 k y for the emplacement of a 2000 m thick granite laccolith these precise u pb zircon ages permit identification of the pulses in a 20 k y range the data obtained for the paine granite fill the gap between 100 k y and 100 1000 yr pulses described in the literature for crustal magma chambers

extensional faulting on tinos island aegean sea greece how many detachments zircon and apatite fission track zft and aft and u th he 40ar 39ar hornblende and u pb zircon ages from the granites of tinos island in the aegean sea greece suggest together with published zft data that there are three extensional detachments on tinos the tinos granites crosscut the tinos detachment cooling of the granites was controlled by the livadi detachment which occurs structurally above the tinos detachment our u pb zircon age is 14 6 0 2 ma and two 40ar 39ar hornblende ages are 14 4 0 4 and 13 7 0 4 ma zft and aft ages go from 14 4 1 2 to 12 2 1 0 ma and 12 8 2 4 to 11 9 2 0 ma u th he ages are from 10 4 0 2 to 9 9 0 2 ma zircon and 11 9 0 5 to 10 0 0 3 ma apatite all ages decrease northeastward in the direction of hanging wall transport on the livadi detachment and age distance relationships yield a slip rate of 2 6 3 3 1 0 km ma 1 this rate is smaller than a published slip rate of 6 5 km ma 1 for the vari detachment which is another detachment structurally above the tinos detachment because of the different rates and because published zft ages from the footwall of the vari detachment are 10 ma we propose that the vari detachment has to be distinguished from the older livadi detachment we discuss various models of how the extensional detachments may have evolved and prefer a scenario in which the vari detachment cut down into the footwall of the livadi detachment successively exhuming deeper structural units the thermochronologic ages demonstrate the importance of quantitative data for constraining localization processes during extensional deformation

zircons from syros cyclades greece recrystallization and mobilization of zircon during high pressure metamorphism zircons were studied from high pressure low temperature metamorphosed meta igneous lithologies from syros these rocks carry several zircon generations related to each other by dissolution reprecipitation processes one generation is pristine zircon that shows growth zoning relatively elevated contents of trivalent cations and high th u ratios the other end member is a skeletal zircon generation with negligible trivalent cation contents and low th u ratios 0 1 texturally between these two there is a range of zircon crystals with complex inclusion populations of y hree th phases and fluid inclusions showing variable progress of replacement recrystallization both end members yield distinct sensitive high resolution ion microprobe shrimp u pb ages the pristine generation has an age of 80 2 1 6ma from a metagabbro and 76 4 2 1ma from a meta plagiogranite dyke the skeletal low th u zircon generation yields an age of 52 4 0 8ma the older late cretaceous zircons are interpreted to date emplacement of the magmatic protoliths in a small segment of oceanic crust the younger eocene age however dates a zircon recrystallization event which possibly coincides with high solubility and mobility of high field strength elements in a high pressure aqueous fluid phase intergrowth relations between zircon and peak metamorphic garnet and excellent agreement of the u pb ages with white mica ar ar ages for the same samples support the conclusion that eocene is the true age of high pressure metamorphism on syros

prograde mica 40ar 39ar growth ages recorded in high pressure rocks syros cyclades greece abstract phengites from the eclogite and blueschist facies sequences of the cycladic island of syros greece have been dated by the in situ uv laser ablation 40 ar 39 ar method a massive phengite rich eclogite and an omphacite rich metagabbro were investigated the phengites are euhedral and coarse grained several 100 m strain free and exhibit no evidence for late brittle deformation or recrystallization apparent ages in these samples range from 43 to 50 ma for the phengite rich eclogite and 42 to 52 ma for the omphacitic metagabbro this large spread of ages is visible at all scales within individual grains as well as in domains of several 100 m and across the entire sample ca 2 cm such variations have been traditionally attributed to metamorphic cooling or the incorporation of excess argon however the textural equilibrium between the phengites and other high pressure phases and the subtle compositional variations within the phengites especially the preservation of growth textures alternatively suggest that the observed range in ages may reflect variations of radiogenic argon acquired during phengite formation and subsequent growth thus dating a discrete event on the prograde path this implies that the oldest phengite 40 ar 39 ar ages provide the best estimate of a minimum crystallization age which is in agreement with recently reported u pb and lu hf geochronological data our results are consistent with available stable isotope data and further suggest that under fluid restricted conditions both stable and radiogenic isotopic systems can survive without significant isotopic exchange during subduction and exhumation from eclogite facies p t conditions

uplift and exhumation of high pressure metamorphic terrains the example of the cycladic blueschist belt aegean sea the cycladic blueschists emerged from a depth of more than 50 km during the tertiary these rocks are now covered only by a thin fraction of the synmetamorphic overburden upper plate remnants of the upper plate include low p crystalline rocks and sediments which have been juxtaposed onto the lower plate blueschists in several stages since the early miocene the low angle contacts operated as normal faults which removed the overburden from above the cycladic blueschists detailed investigations on tinos island indicate that the fractured blocks of the upper plate lying above a low angle normal fault did not rotate this shows that the faults initiated as rather gently dipping fractures similar structures were also reported from other blueschist terrains kinematic analysis of such flat lying faults implies that the synmetamorphic overburden should be mostly located several hundred kilometers away from the present exposure of the blueschists considering that the cycladic blueschist belt exposes successively shallower units in the west and that rocks of the upper plate have an anatolian nature we suggest that these blueschists were dragged from beneath turkey we recognize that the blueschist unit has undergone further thrusting in the final stage of the exhumation as have its counterparts elsewhere in the hellenides the emergence of the blueschists in the tertiary was concomitant with continental collision and thrusting in the hellenides the operation of low angle normal faults with large extensional displacements occurred within this context of collision tectonics this extension occurred parallel to the strike of the convergent orogen

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin

systematics of zircon crystallisation in the cretaceous separation point suite new zealand using u pb isotopes ree and ti geothermometry plutonic zircons from the cretaceous separation point suite sps were analysed by la icpms for u pb isotope ratios and trace element concentrations pooled 206pb 238u ages range from 112 to 124 ma cathodoluminescence imaging reveals minor inheritence and textural evidence of repeated dissolution and re precipitation of zircon core and rim spot analyses however document zircon growth during extended periods of time 2 myr protracted crystallisation histories for simple plutonic systems are inconsistent with generalised thermal constraints which predict cooling below the solidus within 1 myr consequently we conclude that the sps granitoids sampled in this study were not emplaced rapidly but incrementally over extended time periods zircon th u and zr hf ratios are positively correlated with crystallisation temperatures consistent with crystallisation from evolving melts however highly variable trace element concentrations along with temperature reversals are indicative of complex crystallisation histories involving continuous fractional crystallisation repeatedly punctuated by hotter more mafic magma recharge normalised abundances of the redox sensitive elements eu and ce in zircon vary systematically with degrees of whole rock differentiation pointing to evolutionary trends in magmatic oxidation states coupled with feldspar crystallisation

raman micro spectroscopy on diamond graphite and other carbon polymorphs from the ultrahigh pressure metamorphic kimi complex of the rhodope metamorphic province ne greece raman micro spectroscopy was applied on carbon inclusions in garnet porphyroblasts from kyanite biotite garnet schists of the rhodope metamorphic province rmp ne greece diamond and cuboids of poorly to highly ordered graphite were identified either as single phase inclusions or as polyphase inclusions along with co2 and or carbonates calcite magnesian calcite questionable raman bands that may be assigned to other c phases nanodiamond lonsdaleite a different c polymorph have been observed the presence of diamond confirms beyond any doubt the ultrahigh pressure uhp metamorphism reported by mposkos and kostopoulos 1 e mposkos d kostopoulos diamond former coesite and supersilisic garnet in metasedimentary rocks from the greek rhodope a new ultrahigh pressure metamorphic province established earth planet sci lett 192 2001 497 506 in the rmp cuboid graphite showing variable degree of disordering most probably formed after diamond the possible involvement of co2 and or c o h fluids in the formation of diamond is discussed

o sr isotopic variations in miocene granitoids from the aegean evidence for an origin by combined assimilation and fractional crystallization sr o and d h isotopic compositions have been analyzed in miocene metaluminous to slightly peraluminous i type granitoids of the central aegean individual plutonic complexes display significant variations in their 18o and initial87sr 86sr compositions d and 18o compositions of minerals and whole rocks are mostly in the magmatic range some samples from naxos and mykonos delos show low d and 18o values characteristic of meteoric water hydrothermal interaction but as a whole the changes in 18o and sr isotopic compositions as a result of hydrothermal alteration were slight even in instances where marked alteration is petrographically observable consequently the bulk rock variations of 18o from 8 1 to 12 0 and of87sr 86sr from 0 70438 to 0 71450 may be regarded as primary and indicative of the conditions of their evolution heterogeneous isotopic compositions observed in the individual plutons of serifos ikaria samos and kos may be caused by the multiple intrusion of chemically and isotopically distinct magma pulses with high viscosities and relatively rapid consolidation in most cases preventing complete homogenization the granitoids of serifos ikaria and kos display weak correlations between the initial87sr 86sr and 18o and 1 sr the granitoid province shows a positive correlation between87sr 86sr and 18o and a non linear relationship between87sr 86sr and 1 sr whereby 1 sr increases more rapidly than the isotopic ratio as the degree of fractionation of the rocks increases it is argued that assimilation of older continental material by mantle derived arc magmas with combined fractionation afc is the most plausible model to explain the chemical and isotopic characteristics of the granitoids and the geological situation in which rock types trend from granodiorites in the south west near the inferred oligocene miocene suture to granites in the center and monzonites in the north east of the province

time scales of pluton construction at differing crustal levels examples from the mount stuart and tenpeak intrusions north cascades washington deciphering the magmatic history of continental magmatic arcs in general and the growth history of individual intrusions in particular is key to understanding the complex history of magma generation segregation and transport that define the dynamics of crustal growth we utilize high precision u pb geochronology to resolve a detailed magmatic history from two composite intrusions the 2 4 kbar mount stuart batholith and the 7 10 kbar tenpeak pluton emplaced in the cretaceous north cascades arc this temporal framework provides a way to evaluate models of pluton growth that explain common features of intrusions such as concentric compositional zoning and internal magmatic contacts u pb zircon crystallization ages were obtained from 12 samples of the mount stuart batholith and 8 samples of the tenpeak intrusion representing the range of compositional diversity and geographical extent these dates indicate that the mount stuart batholith was constructed over a 5 5 m y time period that was punctuated by four intervals of high magma flux the durations of the high flux periods are short a few hundred thousand years relative to the duration of the batholith the consistent pattern of magmatic fabrics and the lack of distinct contacts in the batholith may be explained by the juxtaposition of melt rich and mush zones with subtle contacts between mineralogically and texturally similar tonalite and time transgressive magma fabrics in contrast the tenpeak intrusion was constructed over a 2 6 m y time period with magma influx distributed throughout the intrusive history and texturally distinct magma bodies the tenpeak intrusion lacks distinct age domains which suggests that any magma reservoir was smaller in size and potentially more ephemeral although the distinct age domains and discrete compositional and textural phases indicate that pluton growth occurred incrementally neither pluton bears resemblance to a purely end member incremental growth model whereby a pluton is constructed from hundreds to thousands of discrete magma pulses that have little if any interaction in particular ages from the youngest domain of the mount stuart batholith indicate that a melt rich magma reservoir of 520 km 3 existed over a 170 90 k y time span

impact cutoff frequency momentum scaling law inverted from apollo seismic data abstract we perform the analysis of both long and short period data for 40 large meteoroid impacts event gathered by the apollo lunar seismic network we extract the linear momentum released by the impact and the cutoff frequency of the recorded seismic spectrum related to the radiation process of the shock wave generated by the impact by using a proxy to the local porosity based on the density of surface craters and well correlated to the most recent grail observations we demonstrate that the seismic cutoff frequencies for 40 selected impacts correlate with this proxy and therefore likely with the porosity at the impacted areas our finding shows that lunar seismic records of meteoroid impacts represent unique geophysical data documenting medium to high energy 0 1 1 kt tnt yield impact processes including the interaction of shock waves with porous media this work can be applied to the analysis of the seismic data to be obtained by the insight mission in 2016 and the investigation of the lateral variations in the martian regolith

back arc extension and denudation of mediterranean eclogites eclogite facies rocks exposed in mediterranean back arcs are delimited from above by low angle normal faults and detachments nevertheless our work demonstrates that these extensional structures associated with back arc extension played only a limited role in removing the overburden from above the eclogites extension in mediterranean back arcs began in the late oligocene or early miocene but the pressure temperature time p t t paths of eclogite facies rocks exposed in these areas indicate that a major part of the overburden several tens of kilometers has been removed from above these rocks prior to the oligo miocene we show that the time period bracketed between the peak of eclogite metamorphism eocene in the central aegean probably upper cretaceous in corsica and the betics and the onset of back arc extension in the oligo miocene was characterized by thrust faulting in the central aegean corsica and the betics eclogite bearing units were partly unroofed and then overthrusted lower pressure units we emphasize that with one exception tinos island greece the entire inventory of extensional contacts operated subsequently to the overthrusting of the eclogites above the lower grade sequences thus mediterranean back arc extension lags behind a major part of the denudation process and is superposed on orogenic wedges that contain eclogite facies rocks at relatively shallow structural levels we emphasize that the mode of occurrence of eclogites in mediterranean back arc regions involves a continuum of in situ crustal accretion below the eclogites widespread p t paths that show cooling or isothermal decompression and lower grade rocks at the bottom of the structural pile thus instead of reflecting whole crust back arc extension the tectonic style associated with the denudation of mediterranean eclogites better fits an active accretionary wedge setting this is similar to the mode of occurrence of eclogite facies rocks in mountain belts such as the western alps where decompression was synorogenic and back arc extension played no role

ela icp ms u pb zircon geochronology of regional volcanism hosting the bajo de la alumbrera cu au deposit implications for porphyry related mineralization ela icp ms u pb zircon geochronology has been used to show that the porphyritic intrusions related to the formation of the bajo de la alumbrera porphyry cu au deposit nw argentina are cogenetic with stratigraphically well constrained volcanic and volcaniclastic rocks of the late miocene farallon negro volcanic complex zircon geochronology for intrusions in this deposit and the host volcanic sequence show that multiple mineralized porphyries were emplaced in a volcanic complex that developed over 1 5 million years volcanism occurred in a multi vent volcanic complex in a siliciclastic intermontane basin the complex evolved from early mafic intermediate effusive phases to a later silicic explosive phase associated with mafic intrusions zircons from the basal mafic intermediate lavas have ages that range from 8 46 0 14 to 7 94 0 27 ma regionally extensive silicic explosive volcanism occurred at 8 0 ma 8 05 0 13 and 7 96 0 11 ma which is co temporal with intrusion of the earliest mineralized porphyries at bajo de la alumbrera 8 02 0 14 and 7 98 0 14 ma regional uplift and erosion followed during which the magmatic hydrothermal system was probably unroofed shortly thereafter dacitic lava domes were extruded 7 95 0 17 ma and rhyolitic diatremes 7 79 0 13 ma deposited thick tuff blankets across the region emplacement of large intermediate composition stocks occurred at 7 37 0 22 ma shortly before renewed magmatism occurred at bajo de la alumbrera 7 10 0 07 ma the latest porphyry intrusive event is temporally associated with new ore bearing magmatic hydrothermal fluids other dacitic intrusions are associated with subeconomic deposits that formed synchronously with the mineralized porphyries at bajo de la alumbrera however their emplacement continued from 7 10 0 06 to 6 93 0 07 ma after the final intrusion at bajo de al alumbrera regional volcanism had ceased by 6 8 ma 6 92 0 07 ma

late miocene ductile extension and detachment faulting mykonos greece the geometry and style of structural relations at map to microscopic scale on mykonos cyclades aegean sea greece suggests ductile extension and detachment faulting during the late miocene this island is dominated by granitic rocks that have a well developed shallowly dipping mylonitic foliation and a northeast southwest trending mineral elongation lineation kinematic indicators in these rocks exhibit a top to the northeast down dip sense of shear textural relations suggest that conditions during mylonitic deformation were greenschist to amphibolite facies and published k ar geochronology suggests a late miocene age for this deformation event mylonitic rocks lie in the footwall of a low angle fault and fault striae parallel to the elongation lineation suggest kinematic coordination between mylonitic deformation and movement along the fault translation along the fault juxtaposes younger tilted sedimentary rocks of low metamorphic grade upon the once deeper mylonitic rocks the style and geometry of deformational fabrics and map relations on this island are strikingly similar to those observed in metamorphic core complexes of the western united states

upper mantle stratification by p and s receiver functions summary seismic stratification of the upper mantle is investigated by applying two complementary techniques to the records of the graefenberg array in southern germany the anisotropic p receiver function technique kosarev et al 1984 vinnik montagner 1996 is modified by using summary seismic events instead of individual events and different weighting functions instead of the same function for the harmonic angular analysis of the sv and t components of the pds phases the summary events provide better separation of the second azimuthal harmonic than the individual events the parameters of the second harmonics of sv and t thus evaluated should be similar if they reflect the effects of azimuthal anisotropy this can be used as a criterion to identify the anisotropy to detect the sdp phases and their azimuthal variations caused by azimuthal anisotropy we have developed a stacking technique which can be termed the s receiver function technique it includes axis rotation to separate interfering p and s arrivals determination of the principal m component of the s wave motion deconvolution of the p components of many recordings by their respective m components and stacking of the deconvolved p components with weights depending on the level of noise and the angle between the m direction and the backazimuth of the event both techniques yield consistent results for the graefenberg array as indicated by the p receiver functions the upper layer of the mantle between the moho and 80 km depth is anisotropic with dvs vs around 0 03 and the fast direction close to 20 clockwise from north the fast direction of anisotropy below this layer is around 110 the boundary between the upper and the lower anisotropic layers is manifested by the detectable pds and sdp converted phases shear wave splitting in sks is strongly dominated by azimuthal anisotropy in the lower layer asthenosphere

seismic velocity structure of the lunar mantle i have inverted the recently completed set of seismic arrival times from the apollo lunar seismic network to estimate the average seismic velocities in three sections of the lunar mantle two for the upper mantle and one for the middle mantle the method used is a variation of the linearized least squares inversion where the inversion is accomplished in steps the estimated average velocities in the upper mantle decrease from vp 7 74 km s and vs 4 49 km s in the section above 270 km depth to vp 7 46 km s and vs 4 25 km s in the section between 270 and 500 km depth confirming the earlier finding of negative gradients based on seismic amplitude variations the average velocities in the middle mantle between the depths of 500 km and 1000 km of vp 8 26 km s and vs 4 65 km s are significantly higher than those in the upper mantle contradicting earlier estimates based on more limited data the higher velocities may suggest initial melting of the moon down to at least 1000 km depth

rethinking the emplacement and evolution of zoned plutons geochronologic evidence for incremental assembly of the tuolumne intrusive suite california new u pb geochronologic data indicate that the tuolumne intrusive suite california was assembled over a period of at least 10 m y between 95 and 85 ma and that the half dome granodiorite intruded over a period approaching 4 m y simple thermal considerations preclude the possibility that a magma chamber the size of the half dome pluton could have existed as a liquid at shallow crustal depths for that long rather field evidence for sheeting along the margins of the suite the range of ages and the regular decrease of ages toward the center of the suite and within individual plutons suggest incremental assembly geochronologic evidence for incremental assembly is consistent with the failure of geophysical methods to detect large magma chambers with more than 20 melt even in active volcanic areas because it is unlikely that the individual plutons composing the tuolumne ever coexisted as liquid rich magmas the chemical evolution of the suite cannot be the result of simple fractionation and or mixing between exposed units but instead must reflect processes occurring during magma generation

isotopic evidence for rapid continental growth in an extensional accretionary orogen the tasmanides eastern australia the trace element signature of earth s continental crust resembles that of arc lavas but the continents may have formed during ancient igneous pulses that are hard to reconcile with supra subduction zone magmatism we explore the role of coupled arc back arc accretionary processes in crust generation by considering the tectonic context of whole rock nd isotope and zircon hf o isotope data from igneous rocks of the australian tasmanides 515 230 ma which is thought to have evolved by the repeated opening and closure of sediment filled back arc basins behind a long lived subduction zone the significance of this process for continental crust formation has yet to be evaluated from an isotopic perspective granitic rocks in this area define striking secular end ehf 18o trends that correlate with the pattern of deformational events and register changes in magma source during tectonic activity these trends reveal that juvenile magmatic input was enhanced during extensional back arc rifting episodes that immediately followed crustal thickening suggesting a relationship between slab rollback and continental growth interaction between juvenile magma and sedimentary units deposited during a preceding back arc rifting cycle was integral to the formation of stable continental material this highlights the importance of back arc environments for both the generation and differentiation of continental crust the juvenile component within the tasmanide igneous rocks increased from the cambrian to the triassic consistent with a diminished input from cratonderived metasedimentary material as the subduction zone migrated outboard of the gondwana margin subduction zone retreat formed large tracts of new crust in eastern australia at comparable rates to crust generation at modern island arcs providing a mechanism for rapid continental growth at convergent margins using isotopic tracers to link tectonic evolution and crust generation in modern and ancient orogens can lead to a better understanding of the geodynamic controls on planetary differentiation

integrated pb and s isotope investigation of sulphide minerals from the early archaean of southwest greenland we present high spatial resolution secondary ion mass spectrometry sims measurements of pb and s isotopes in sulphides from early archaean samples at two localities in southwest greenland secondary pyrite from a 3 71 ga sample of magnetite quartz banded iron formation in the isua greenstone belt which has previously yielded unradiogenic pb consistent with its ancient origin contains sulphur with a mass independently fractionated mif isotope signature delta 33 s 3 3 parts per thousand this reflects the secondary mineralization of remobilized sedimentary s carrying a component modified by photochemical reactions in the early archaean atmosphere it further represents one of the most extreme positive excursions so far known from the early archaean rock record sulphides from a quartz pyroxene rock and an ultramafic boudin from the island of akilia in the godth a over circle bsfjord have heterogeneous and generally radiogenic pb isotopic compositions that we interpret to represent partial re equilibration of pb between the sulphides and whole rocks during tectonothermal events at 3 6 2 7 and 1 6 ga both these samples have delta 33 s 0 within analytical error and therefore show no evidence for mif sulphur these data are consistent with previous interpretations that the rock cannot be proven to have a sedimentary origin our study illustrates that sims s isotope measurements in ancient rocks can be used to elucidate early atmospheric parameters because of the ability to obtain combined s and pb isotope data but caution must be applied when using such data to infer protolith when information from geological context petrography and chronology i e by pb isotopes is combined and fully evaluated delta 33 s signatures from sulphides and their geological significance can be interpreted with a higher degree of confidence c 2005 elsevier b v all rights reserved