translation and docking of an arc terrane geological and geochemical evidence from the southern zambales ophiolite complex philippines abstract the zambales ophiolite complex is made up of three massifs the masinloc cabangan and san antonio massifs field petrographic and geochemical analyses show that the cabangan and san antonio massifs are genetically related to the coto transitional mid ocean ridge island arc and acoje island arc blocks of the masinloc massif respectively the subic bay fault zone a left lateral fault zone separates the san antonio massif island arc terrane from the transitional mid ocean ridge island arc like sheeted diabase dikes pillow basalts of the cabangan massif the san antonio massif is a rifted terrane from the acoje block which was translated southward to its present position through the west luzon shear subic bay fault zone tectonized clinopyroxenite and gabbronorite hills which mimic the physical and geochemical characteristics of the acoje block and the san antonio massif ultramafic mafic cumulate rocks were left behind along the western side of the cabangan massif during the translation of the arc massif southward this scenario can account for the present day configuration of the zambales ophiolite complex

crystal poor rhyolites and rhyodacites from volcan tepetiltic mexico evidence for melt formation crystallization and eruption over short timescales abstract a detailed petrologic study is presented for six rhyolite and rhyodacite pumices that erupted from volcan tepetiltic in western mexico to determine the pre eruptive conditions of the magma reservoir as the volcano exited a 180 kya hiatus of activity rhyolite pumices are crystal poor 6 7 and minimally saturated in seven mineral phases plagioclase titanomagnetite ilmenite apatite quartz orthopyroxene clinopyroxene hornblende zircon in all samples plagioclase is the most abundant phenocryst phase and spans a range of composition of 20 30 mol an in each sample pre eruptive temperatures determined from two fe ti oxide geo thermometry range from 703 to 857 c maximum pre eruptive h2o contents determined from plagioclase hygrometry range from 5 0 8 9 wt where the most calcic plagioclase compositions correspond to the highest water contents comparison of compositions textures and sr and ba concentrations in plagioclase are used to determine phenocrysts from xenocrysts through comparison with experiments xenocrysts are identified in one sample comp 48 comparison of plagioclase abundances textures and sizes with those grown in the run products of experiments from the literature reveals that 1 the pumices were all likely super heated prior to crystallization 2 they experienced a low degree of undercooling induced by either degassing or cooling and 3 four of the pumices those with

simulation of igneous differentiation processes one of the primary goals of igneous petrology is the definition and evaluation of the roles of the processes responsible for chemical differentiation quantitative simulation of these processes not only requires an understanding of the systematics of mineral liquid equilibria in natural systems but also some understanding of how different processes interact the programs presented here consist of empirically calibrated expressions of mineral melt equilibria that are built around a thermodynamic framework the framework of the programs which are designed to model phase equilibria based igneous differentiation have been published in earlier works nielsen and dungan 1983 nielsen 1985 nielsen 1988 a b nielsen et al 1988 this presentation is to show how modeling can be used to gain otherwise unobtainable insights into the mechanics of igneous differentiation in particular for processes that are difficult to simulate in the laboratory in this chapter we will simulate the major differentiation processes that are characteristic of shallow igneous magma chambers these processes include crystallization recharge assimilation and eruption in each example we will examine how observations of natural systems can be converted into the mathematical constraints necessary for the construction of computer based models since our primary goal is to model natural igneous systems the examples show how phase equilibria modeling can be used to help solve problems related to interpretation of the chemical and mineralogic diversity of suites of natural lavas

seismic structure of the northeastern japan convergent margin a synthesis many studies recently made on the basis of seismic observations have revealed a detailed structure of the crust and the upper mantle beneath the northeastern japan arc and its relationship to seismic and volcanic activity spatial distributions of the depths to the conrad and the moho discontinuities estimated from shallow earthquake data and seismic explosion data show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines of the japan sea and the pacific ocean the pn velocity has a lateral variation it is as low as 7 5 km s beneath the land area while that beneath the japan sea and the pacific ocean is 8 0 8 2 km s it changes abruptly at the transition zones which are located along the coastlines precise structure and location of the subducted pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate the pacific plate is composed of a thin 5 km low velocity upper layer and a thick high velocity lower layer its total thickness being 80 90 km the upper plane seismicity of the double seismic zone is confined to the thin low velocity upper layer which probably corresponds to the subducted former oceanic crust the lower plane seismicity lies at the middle of the high velocity lower layer and the lower half of the plate below it is incapable of generating earthquakes the shallower portion of the upper surface of the plate beneath the pacific ocean along which major seismicity with low angle thrust faultings is actually occurring is also located by seismic observations on land and in the sea the pacific plate subducts at an extremely low angle of 5 for the first 25 km depth and then the dip steepens rather abruptly to 30 normal fault type events at the top of the plate have not been detected in the portion where the downward bending is the largest but have been ditected near the trench axis where it is rather small tomographic inversions for seismic velocity structure clearly delineate the inclined high velocity pacific plate with a thickness of 80 90 km and low velocity zones in the crust and the mantle wedge beneath active volcanoes seismic attenuation tomography also shows similar zones of low q value beneath active volcanoes although its spatial resolution is much lower the low velocity zones with 2 6 velocity lows are continuously distributed from the upper crust just beneath active volcanoes to a depth of 100 150 km in the mantle wedge and are approximately parallel to the dip of the underlying pacific plate these low velocity zones probably reflect the pathway of magma ascent from a depth in the mantle wedge to the earth s surface corresponding to a portion of the subduction induced secondary mantle wedge flow

laser ablation icpms study of trace element partitioning between plagioclase and basaltic melts an experimental approach plagioclase melt partition coefficients d for 34 trace elements at natural concentration levels were determined experimentally in a natural morb composition at atmospheric pressure using thin pt wire loops experiments were carried out at three tempera tures 1 220 1 200 and 1 180 c and at three different oxygen fugacities fo2 iw qfm air in order to assess the effect of fo2 on the partitioning of elements with multiple valence fe eu cr run products were analyzed by laser ablation icp ms most trace element ds increase slightly as temperature decreases except for dzr dfe deu and dcr that vary systematically with fo2 applying the lattice strain model to our data suggests the presence of fe 2 entirely in the octahedral

on the elusive isotopic composition of lunar pb highly radiogenic pb isotope compositions determined for volcanic glass beads from the apollo 14 soil sample 14163 are similar to those commonly determined for mare basalts and are correlated with chemical variations observed in the beads this indicates that pb unsupported by in situ u decay has a similar origin in both glass beads and mare basalt samples and is likely to reflect variations of 238u 204pb in the lunar mantle an alternative explanation that this pb is a result of late equilibration with the radiogenic pb present in soil is less likely as it would imply that all other characteristics of glass beads such as their chemistry must also be a consequence of equilibration near the lunar surface regardless of the origin of unsupported pb observed variations of pb isotope compositions in the glass beads and mare basalts appear to be a result of two component mixing between a primitive reservoir with a value similar to the earth s mantle and kreep with a value in excess of several thousand this range cannot be explained by the fractionation of major rock forming minerals from the crystallising lunar magma ocean and instead requires substantial extraction of sulphide late in the crystallisation sequence the proportion of sulphide required to produce the inferred range places limits on the starting of the moon prior to differentiation demanding a relatively high value of about 100 200 low indicated by several basalt samples and previously analysed volcanic glass beads can be explained by the preservation of an early but post ferroan anorthosite sulphide rich reservoir in the lunar mantle while a complete range of pb isotope compositions observed in the glass beads and mare basalts can be interpreted as mixing between this sulphide rich reservoir and kreep

ree patterns nd sm and u pb ages of the metamorphic rocks of the diagorou darbani greenstone belt liptako sw niger implication for birimian palaeoproterozoic crustal genesis

element partitioning between minerals and melt melt composition and melt structure abstract mineral melt trace element partition coefficients d i mineral melt concentration ratio mineral melt can vary by up to two orders of magnitude in the melt composition range of natural magmatic liquids as most geochemically interesting minor and trace elements are network modifiers in silicate melts one would expect as observed positive correlation between mineral melt partition coefficients d i mineral melt and the degree of polymerization of the silicate melt nbo t linear relationships between d i mineral melt and nbo t sometimes exist over restricted nbo t ranges where the type of q n species in the melt does not change and their abundance does not vary greatly other experimental d i mineral melt vs nbo t data suggest log linear or log log relations in some cases whereas in other studies there are no simple relationships between d i mineral melt and nbo t of the melt when relating mineral melt partition coefficients to degree of melt polymerization nbo t it is assumed that a principal melt structural control on d i mineral melt is the activity of nonbridging oxygen in the melt a nbo the a nbo is related to nbo t the nbo t is not however a quantitative measure of a nbo because the nonbridging oxygens in coexisting q n species in melts are energetically non equivalent this is evident in relationships between activity coefficient ratios of melt network modifying cations i j where the ionization potentials of i and j differ and nbo t of the melt such relationships are parabolic with minima or maxima at nbo t near 1 and resemble the relations of abundance ratio x q3 x q2 vs nbo t of the melt interestingly this nbo t value is near that of natural basalt melt these observations suggest that i nbo q 3 and j nbo q 2 bond characteristics differ from one another govern trace element solution behavior in silicate melts and therefore control the effect of melt composition on mineral melt partitioning in silicate systems

basement character and basin formation in gorontalo bay sulawesi indonesia new observations from the togian islands we present a new stratigraphy for the togian islands sulawesi and interpret the age character and evolution of gorontalo bay at its western end the bay is underlain by continental crust the central part is underlain by eocene to miocene oceanic and arc rocks although the area south of the togian islands could have continental crust of the banggai sula microcontinent thrust beneath this and the east arm ophiolite gorontalo bay was not a significant deep bathymetric feature before the miocene field relationships indicate a latest miocene to pliocene age for inception of the basin medium k to shoshonitic volcanism in the togian islands is not due to subduction but reflects crustal thinning and extension in the pliocene and pleistocene causing the underlying mantle to rise decompress and melt extension is continuing today and is probably the cause of volcanism at una una volcanic activity migrated west with time and volcanic products have been offset by dextral strike slip displacement along the balantak fault extension and subsidence was driven by rollback of the subduction hinge at the north sulawesi trench with a possible contribution due to flow of the lower crust 2011 the geological society of london

using ambient noise seismic interferometry and local and teleseismic earthquakes to determine crustal thickness and moho structure of the northwestern gulf of mexico margin

dolerites of the woodlark basin papuan peninsula new guinea a geochemical record of the influence of a neighbouring subduction zone abstract the moresby seamount located in the woodlark basin is a fragment of oceanic crust dolerites and gabbros generated 66 4 1 5 my ago before being obducted during the eocene on the australian margin since 8 my the motion of a normal fault related to the opening of the woodlark basin is responsible for the unroofing of the moresby seamount the latter was sampled during the odp campaign leg 180 in 1998 geochemical compositions of dolerites can be explained by a process of fractional crystallization in which the magnesian spinel was involved therefore fractionation processes took place at relatively high pressure 1 gpa most likely during the upward migration of deep magmas throughout the mantle the fe rich gabbros more differentiated than the dolerites could have derived from an early differentiated magma evolving in the crust at relatively low pressures the trace element content of dolerites indicates that their source was a depleted oceanic mantle slightly influenced by arc related magmas this study suggests that the ophiolites fragment of the moresby seamount was created in the vicinity of a subduction zone this model being in agreement with the regional tectonic setting of se asian since the cainozoic

crustal strains in the japanese islands as deduced from dense gps array data from the nationwide continuous gps network operated by the geographical survey institute of japan were used to estimate crustal strains in the japanese islands we used horizontal velocity vectors at 610 sites for the period april 1996 to march 1997 and employed the least squares prediction method to interpolate the velocities to a uniform 7km 7km grid over japan the gridded velocities were then differentiated in space to calculate principal components of strains results clearly portray tectonic strainings of the japanese islands in one year 1 dilatational strains show that the japanese islands are under a compressive strain regime induced by the subducting oceanic plates 2 distribution of high maximum shear strains coincides with the regions of crustal activities and 3 principal axes of the strains indicate influences of e w and nw se compression due to the converging oceanic plates north south extension in kyushu is also visible

full interseismic locking of the nankai and japan west kurile subduction zones an analysis of uniform elastic strain accumulation in japan constrained by permanent gps we analyze permanent global positioning system gps data obtained over japan between 1995 and 1997 to estimate the instantaneous interseismic coupling ratio of the seismogenic zones due to the subduction of the pacific and philippine sea plates below the japanese islands we first derive the gps strain rate fields that characterize the crustal deformation of southern and northern japan and invert them to determine the effective subduction velocity along the central nankai trough on one side and the japan west kurile trench on the other these reference free velocities are close to those predicted by plate motion models with respect to eurasia we conclude that the eurasian reference frame gives a good approximation to the subduction motion and that to first order both subduction zones were fully locked during the period of measurements we then test whether the coupling ratio shows local variations within the seismogenic zones to do this we divide the subduction interface into 35 km 30 km elements that we model by point source groups and we invert the gps velocity field referenced to eurasia to derive the coupling ratio between 0 and 1 on each fault element the results are coherent over the 3 years and confirm that both the central nankai and the japan west kurile seismogenic zones are homogeneously fully locked most of the coupling ratios are close to 1 and a few are close to 0 intermediate values are rare the zones of decoupling correspond either to strong postseismic afterslip associated with the 1994 sanriku oki interplate earthquake japan trench or to a small overestimation of the actual lower limit of the locked zone we conclude that within the resolution of the gps data and the model 1 partial coupling did not exist during these 3 years along the nankai and japan west kurile trenches 2 the small seismic coupling ratio previously derived from earthquakes analysis for the japan and kurile trenches may indicate that a significant part of the elastic energy is dissipated silently through slow earthquakes and postseismic afterslip and 3 the heterogeneous coseismic slip pattern observed for the large and great earthquakes that rupture both subduction zones is in great contrast to the homogeneous loading finally we discuss the nonelastic residual deformation within the frame of the long term deformation of the japanese islands

slip history of the 1994 sanriku haruka oki japan earthquake deduced from strong motion data abstract we analyzed the seismic waves of the 1994 sanriku haruka oki earthquake m w 7 7 which occurred in the aftershock area of the 1968 tokachi oki earthquake m w 8 2 applying a multiple time window inversion scheme to near source strong motion data we obtained a detailed spatiotemporal rupture process and compared it with that of the tokachi oki earthquake the fault geometry is constructed based on the aftershock distribution the obtained rupture model is consistent with the cmt solution even for a non double couple component the total seismic moment is 4 0 10 20 n m large slips are concentrated in three asperities the first asperity centers about 40 km south and 50 km west from the hypocenter with a maximum slip of 4 4 m the second one centers about 60 km west from the hypocenter with a maximum slip of 2 2 m and the third one lies about 110 km west from the hypocenter with a maximum slip of 2 6 m the obtained moment rate and the duration on the first and second asperities are lower and much longer than those on the third asperity respectively the first asperity does not overlap with an area of large slip during the tokachi oki earthquake but the second or third seem to overlap with or be adjacent to the asperity of the tokachi oki earthquake our inversion result also shows an abrupt change of the rupture velocity from 1 8 to 3 0 km sec at the central part of the fault plane a difference of the seismic coupling between the oceanic and the continental lithospheres at the trenchward side and at the landward side of the 143 e meridian seems to affect the rupture process of this earthquake

cenozoic plate interaction of the australia and philippine sea plates hit and run tectonics abstract recent studies in northwest new guinea have shown the presence of at least two marginal basins of different age both of which formed in back arc settings the older basin opened between the middle jurassic and early cretaceous a remnant of which is now preserved as the new guinea ophiolite its obduction started at 40 ma and it was finally emplaced on the australian margin at 30 ma the younger basin was active during the oligocene to middle miocene and was obducted in the early pliocene studies of the western edge of the philippine sea also reveal an important deformation of the philippine arc in the oligocene which hitherto has remained unexplained using information from these systems paleomagnetic results kinematic reconstructions and geochemistry of the supra subduction ophiolite we present a plate model to explain the region s eo oligocene development we suggest that an extensive portion of oceanic crust extended the australian plate a considerable distance north of the australian craton as australia began its steady 7 8 cm year northward drift in the early eocene this lithosphere was subducted thus the portion of the philippine sea plate carrying the taiwan philippine arc to its present site may have actually been in contact with the ophiolite now in new guinea and obduction led to deformation of the philippine sea plate itself neogene plate kinematics transported the deformed belt in contact with the sunda block in the late miocene and pliocene this interpretation has implications for the origin for the philippine sea plate and the potential incorporation of continental fragments against its boundaries

back arc basin origin for the east sulawesi ophiolite eastern indonesia the east sulawesi ophiolite is one of the three largest ophiolites in the world it displays all the components of a typical sequence from residual mantle peridotites to cumulate gabbros sheeted dolerites and lavas of normal mid oceanic ridge basalt morb composition trace element data on the lavas and dolerites and particularly their depletion in nb compared to neighboring incompatible elements suggest a subduction zone environment for their origin the chemical similarity between the east sulawesi ophiolite lavas and those from the eocene celebes sea back arc basin crust together with their identical age strongly suggest a back arc tectonic environment for this ophiolite which represents a fragment of the eurasian plate obducted onto the east sulawesi basement of australian origin

plate kinematics origin and tectonic emplacement of supra subduction ophiolites in se asia abstract a unique feature of the circum pacific orogenic belts is the occurrence of ophiolitic bodies of various sizes most of which display petrological and geochemical characteristics typical of supra subduction zone oceanic crust in se asia a majority of the ophiolites appear to have originated at convergent margins and specifically in backarc or island arc settings which evolved either along the edge of the sunda eurasia and australian cratons or within the philippine sea plate these ophiolites were later accreted to continental margins during the tertiary because of fast relative plate velocities tectonic regimes at the active margins of these three plates also changed rapidly strain partitioning associated with oblique convergence caused arc trench systems to move further away from the locus of their accretion we distinguish relatively autochthonous ophiolites resulting from the shortening of marginal basins such as the present day south china sea or the coral sea and highly displaced ophiolites developed in oblique convergent margins where they were dismantled transported and locally severely sheared during final docking in peri cratonic mobile belts i e the philippine mobile belt we find a series of oceanic basins which have been slightly deformed and uplifted varying lithologies and geochemical compositions of tectonic units in these basins as well as their age discrepancies suggest important displacements along major wrench faults we have used plate tectonic reconstructions to restore the former backarc basins and island arcs characterized by known petro geochemical data to their original location and their former tectonic settings some of the ophiolites occurring in front of the sunda plate represent supra subduction zone basins formed along the australian craton margin during the mesozoic the philippine sea basin the huatung basin south of taiwan and composite ophiolitic basements of the philippines and halmahera may represent remnants of such marginal basins the portion of the philippine sea plate carrying the taiwan philippine arc and its composite ophiolitic continental crustal basement might have actually originated in a different setting closer to that of the papua new guinea ophiolite and then have been displaced rapidly as a result of shearing associated with fast oblique convergence

evidence of chemical heterogeneity within lunar anorthosite parental magmas abstract lunar anorthosites are known for displaying a limited range of plagioclase an content an 94 to 98 here we demonstrate that plagioclase trace element variations from apollo ferroan anorthosites fan samples collected by the apollo 15 and 16 missions display more significant chemical heterogeneity e g chondrite normalized la sm 0 33 5 42 than previously reported we report mineral plagioclase pyroxene and olivine major and trace element abundances for a suite of apollo fan samples in addition to anorthositic clasts within apollo 16 regolith breccias this suite of data extends the compositional range currently reported for apollo anorthosites and for anorthositic clasts previously found within lunar meteorites petrological classifications of the regolith breccia clasts e g anorthosite versus noritic anorthosites cannot always be accurately assessed due to the limited size

the earthquake deformation cycle at the nankai trough southwest japan geodetic measurements made landward of the nankai trough site of great subduction zone thrust earthquakes in 1854 and 1946 provide a uniquely detailed picture of the strain buildup process supply constraints on the mechanism of strain accumulation and allow for improved estimates of earthquake recurrence provided the two most recent movement cycles are similar the observations dating from about 1890 may be used to reconstruct a single complete deformation cycle coseismic strain release postseismic transients interseismic strain accumulation very complete leveling and tidal gage data indicate that postseismic deformation extends more than 300 km inland from the plate boundary persists for at least 30 years and shows a clear tendency to become longer wavelength with increasing time the transient movements have two timescales the first of about a year or less corresponds to deformation largely uplift concentrated close to the coseismic fault and is most easily explained by aseismic slip or very localized deformation downdip of the earthquake rupture plane the second longer timescale is associated with a diffusion like spread of the deformation further landward an effect qualitatively similar to that first predicted by elsasser to be an expected consequence of faulting in an elastic plate overlying a viscoelastic asthenosphere cumulative uplift since 1890 correlates well with the distribution of uplifted marine terraces although average post 1890 tilt rates exceed late quaternary and holocene averages by at least a factor of three because of the nonlinearity of strain buildup and the significant permanent deformation simple recurrence calculations typically overestimate the true interval between great earthquakes by a factor of 2 to a factor of 3 strict application of the time predictable model assumed correct overcomes these difficulties provided the cumulative transient deformation and the proportion of permanent deformation per cycle can be estimated

short wavelength high amplitude gravity anomalies around the banda sea and the collapse of the sulawesi orogen abstract in eastern indonesia high density ophiolitic rocks outcropping on islands surrounding the banda sea are in many cases associated with strong gravity anomalies and steep gravity gradients however the relationships are not always straightforward bouguer gravity levels and gradients over the extensive east sulawesi ophiolite are generally relatively low although short wavelength high amplitude anomalies indicate rapid changes in thickness of high density rocks in a few places in the banda arc most local positive anomalies due to ophiolites are superimposed on a steep regional gravity gradient but in one case in western seram there is a distinct and important spatial separation between the two on buru west of seram a gradient of more than 10 mgal km testifies to the presence of very dense rocks in the near subsurface despite the absence of ophiolites in the outcrop gravity variations and ophiolite distribution around the banda sea are compatible with extension having occurred in the sulawesi region following and as a result of oligo miocene collision with an australian derived microcontinent similar histories have been proposed for many mediterranean deep basins of similar size shape and character and emplacement of some of the high density masses in the banda arc has probably resembled at least the later stages in the emplacement of peridotite massifs in the rif betic belt in both areas the present close association of the ultramafic rocks and their associated local anomalies with a strong regional gravity gradient is largely coincidental

cenozoic palaeogeographic evolution of sulawesi and borneo abstract sulawesi and borneo are located in the middle of the indonesian archipelago an area which has been extremely tectonically active throughout the cenozoic this paper compiles current knowledge on the geology and palaeogeography of this complex region and includes the first attempt to synthesise palaeogeographic data onto plate tectonic reconstructions construction of palaeogeographic maps helped to identify some of the strengths and weaknesses of current plate tectonic models for the region thereby highlighting areas where further geological research is required palaeogeographic maps presented using plate tectonic reconstructions as a base illustrate the evolution of borneo and sulawesi and highlight important changes in the environment during the cenozoic the tertiary geological history of eastern borneo and sulawesi is inextricably linked to the progressive accretion of continental and oceanic material from the east onto the eastern margin of sundaland and to the resultant development of volcanic arcs large tracts of western sulawesi eastern borneo the east java sea and the makassar straits formed an extensive basinal area throughout much of the tertiary implications for plate tectonics exploration for natural resources and biogeography are discussed from the palaeogeographic reconstructions of sulawesi and borneo

a 40 000 yr record of clay mineralogy at lake towuti indonesia paleoclimate reconstruction from reflectance spectroscopy and perspectives on paleolakes on mars sediment deposited within lake basins can preserve detailed records of past environmental conditions on planetary surfaces including both earth and mars establishing how to best characterize these paleoclimate records is thus critical for understanding the evolution of past planetary climates here we present an 40 k y lake sediment record from lake towuti indonesia developed using visible to near infrared vnir reflectance spectroscopy source sediment from the main river input to lake towuti the mahalona river is spectrally dominated by mg rich serpentine however we also identify a distinct al phyllosilicate component which we interpret as kaolinite that increases in relative proportion to serpentine with decreasing grain size sink sediment from two cores collected at the distal margins of the mahalona river delta has similar spectral signatures to the input source sediment the cores capture systematic variations in the proportion of al phyllosilicate to serpentine over time which is also expressed in changes in bulk elemental chemistry of the sediment we show that the abundance of serpentine relative to al phyllosilicate increases dramatically during the globally cooler regionally drier climate of the last glacial maximum this change records the grain size dependent mineralogy of deltaic sediment which is ultimately driven by forced delta progradation and river incision during lake lowstands our analyses show that vnir reflectance spectroscopy offers a rapid nondestructive and effective method for developing paleoenvironmental records from sedimentary phyllosilicate mineralogy exposed paleolake deposits on mars should preserve similar paleoenvironmental information that can be accessed through detailed remote sensing observations of stratigraphy and vnir reflectance spectroscopy in a source to sink framework

trace element partitioning between ilmenite armalcolite and anhydrous silicate melt implications for the formation of lunar high ti mare basalts abstract we performed a series of experiments at high pressures and temperatures to determine the partitioning of a wide range of trace elements between ilmenite ilm armalcolite arm and anhydrous lunar silicate melt to constrain geochemical models of the formation of titanium rich melts in the moon experiments were performed in graphite lined platinum capsules at pressures and temperatures ranging from 1 1 to 2 3 gpa and 1300 1400 c using a synthetic ti enriched apollo black glass composition in the cao feo mgo al2o3 tio2 sio2 system ilmenite melt and armalcolite melt partition coefficients d show highly incompatible values for the rare earth elements ree with the light ree more incompatible compared to the heavy ree d la ilm melt 0 0020 0 0010 to d lu ilm melt 0 069 0 010 for ilmenite d la arm melt 0 0048 0 0023 to d lu arm melt 0 041 0 008 for armalcolite d values for the high field strength elements vary from highly incompatible for th u and to a lesser extent w for ilmenite d th ilm melt 0 0013 0 0008 d u ilm melt 0 0035 0 0015 and d w ilm melt 0 039 0 005 and for armalcolite d th arm melt 0 008 0 003 d u arm melt 0 0048 0 0022 and d w arm melt 0 062 0 03 to mildly incompatible for nb ta zr and hf e g d hf ilm melt 0 28 0 05 and d hf arm melt 0 76 0 07 both minerals fractionate the high field strength elements with dta dnb and dhf dzr between 1 3 and 1 6 for ilmenite and 1 3 and 1 4 for armalcolite armalcolite is slightly more efficient at fractionating hf from w during lunar magma ocean crystallisation with dhf dw 12 13 compared to 6 7 7 5 for ilmenite the transition metals vary from mildly incompatible to compatible with the highest compatibilities for cr in ilmenite d 7 5 and v in armalcolite d 8 1 d values show no clear variation with pressure in the small range covered crystal lattice strain modelling of d values for di tri and tetravalent trace elements shows that in ilmenite divalent elements prefer to substitute for fe while armalcolite data suggest ree replacing mg tetravalent cations appear to preferentially substitute for ti in both minerals with the exception of th and u that likely substitute for the larger fe or mg cations crystal lattice strain modelling is also used to identify and correct for very small 0 3 wt melt contamination of trace element concentration determinations in crystals our results are used to model the lu hf ti concentrations of lunar high ti mare basalts the combination of their subchondritic lu hf ratios and high tio2 contents requires preferential dissolution of ilmenite or armalcolite from late stage lunar magma ocean cumulates into low ti partial melts of deeper pyroxene rich cumulates

investigating the origin of anorthitic plagioclase through a combination of experiments and natural observations abstract the origin of anorthitic plagioclase in volcanic rocks worldwide remains an enigma arenal volcano costa rica provides a good example of the problem up to an 96 plagioclase are found within moderately evolved basaltic andesites we follow up a recent suggestion lundstrom c c boudreau a pertermann m 2005 diffusion reaction in a thermal gradient implications for the genesis of anorthitic plagioclase high alumina basalt and igneous mineral layering earth planet sci lett 237 829 854 that diffusion reaction processes occurring between ascending magmas and gabbroic wall rocks might provide a means of producing anorthitic plagioclase without requiring exotic ultra calcic melt compositions by integrating observations from three analytical methods 1 laboratory diffusion reaction experiments in the diopside albite anorthite daa system 2 transmission electron microscopy tem of plagioclase grains from both a diffusion reaction experiment and an arenal lava and 3 sr isotope microstratigraphy of phenocrysts and megacrysts from natural lavas from the current eruption at arenal two plagioclase saturated daa melts juxtaposed in experiments at either 1 bar pressure anhydrous or at 0 5 gpa pressure hydrous for 3 5 days at 1244 or 1125 c illustrate the dramatic effect of h 2 o on facilitating plagioclase reaction in the presence of wet melt enrichment in anorthitic plagioclase occurs at the material interface while in the presence of the dry 1 bar melt plagioclase shows no reaction tem analyses of a homogeneous anorthitic plagioclase from a diffusion reaction experiment indicates heterogeneous columns of more anorthite rich plagioclase at the 87 sr 86 sr occur within three plagioclase phenocrysts from both 1968 and 1999 arenal lavas although core compositions vary widely 0 7038 0 7052 all three phenocrysts have similar 87 sr 86 sr rim compositions 0 7043 the variability in 87 sr 86 sr at the phenocryst scale but homogeneity in 87 sr 86 sr at the bulk scale in arenal lavas ryder c h gill j b tepley iii f j ramos f reagan m this volume closed to open differentiation at arenal volcano 1968 2003 j volcanol geotherm res could be explained by erupted lavas representing a near steady state balance between ascending magmas and a flux derived from diffusion reaction processes occurring with surrounding crustal gabbros

magma ascent and crustal accretion at ultraslow spreading ridges constraints from plagioclase ultraphyric basalts from the arctic mid ocean ridge plagioclase ultraphyric basalts pubs with up to 54 plagioclase phenocrysts were dredged in the rift valley and adjacent flanks of the ultraslow spreading mohns and knipovich ridges the pubs show large variations in crystal morphologies and zoning the large variations suggest that single basalt samples contain a mixture of plagioclase crystals that aggregated at different levels in the magma conduits resorbed crystals and repeated reverse zones suggest that the magma reservoirs were replenished and heated several times thin concentric zones with melt inclusions and sharp reductions in the anorthite content of 3 7 are common between the reverse zones these zones and skeletal crystals with distinctly lower anorthite contents than massive crystals are interpreted to be the result of rapid crystalliztion during strong undercooling the changes between short periods of cooling and longer periods with reheating are explained by multiple advances of crystal rich magma into cool regions followed by longer periods of gradual magma inflow and temperature increase the porphyritic basalts are characterizd by more depleted and more fractionated compositions than the aphyric basalts with lower la sm n k 2 oa nd mg numbers this relationship and the observation that pubs are sampled only close to segment centres along these ridges suggests that the pubs formed by higher degrees of melting and evolved in more long lived magma reservoirs we propose that the zoning patterns of plagioclase crystals and crystal morphologies of these pubs reflect the development and flow of magma through a stacked sill complex like conduit system whereas the aphyric equivalents represent later flow of magma through the conduit the formation of voluminous higher degree melts may trigger the development of the magma conduits and explain the generally depleted compositions of pub magmas

geology of the southern zambales ophiolite complex philippines juxtaposed terranes of diverse origin abstract the zambales ophiolite complex which is made up of three massifs masinloc cabangan and san antonio was generated in a subduction related marginal basin combined field geological and geochemical evidences show that the cabangan and san antonio massifs are genetically related to the coto transitional mid ocean ridge island arc and acoje island arc blocks of the masinloc massif respectively a tectonic contact the subic bay fault zone is believed to separate the san antonio and cabangan massifs the san antonio massif is a displaced terrane rifted from the acoje block and translated southward to its present position through the west luzon shear subic bay fault zone the zambales ophiolite complex could have not formed through the rifting or folding of the arc related acoje block san antonio massif to generate the transitional mid ocean ridge island arc like coto block cabangan massif

three dimensional seismic structure beneath southwest japan the subducting philippine sea plate abstract a three dimensional seismic structure beneath southwest japan has been investigated in detail by applying an inversion method this analysis clearly reveals the present and possibly the past subduction of the philippine sea plate beneath southwest japan beneath the izu peninsula the philippine sea plate does not appear to subduct but collides against the continental asian plate here and its thickness appears thinnest at most about 30 km from the tokai to the shikoku regions the high velocity zone corresponds well to the zone of subcrustal earthquakes down to a depth of about 60 70 km indicating that the subduction of the present philippine sea plate does not reach below this depth here however a small high velocity portion appears at depths between 100 km and 150 km beneath a part of the kinki region and probably extends to the chugoku region where no corresponding seismic activities exist these high velocities might be an indication of the remnants of the past subduction of the philippine sea plate in the kyushu region the high velocity zone continues down to a depth of about 150 km or even to 200 km in the southern part corresponding to a steeply inclined seismic zone the philippine sea plate in this region appears to be thicker than in regions east of the kyushu palau ridge it was also found that there exist narrow low velocity zones intervening within the philippine sea plate where two aseismic ridges the kyushu palau and shichito iwojima ridges extend northwards and the nankai trough shows warping these low velocity zones give support to the buoyant subduction hypothesis it also appears that lateral heterogeneities existing within and around the subducting plate are closely related to the mode of rupture of large earthquakes occurring around there

magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase a new bulk silicate moon model with sub chondritic ti ba sr ba and sr al ratios abstract the compositions of host magmas of ferroan anorthosites fan host magmas were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks the evolution of the magmas was investigated by considering phase relations based on the melts algorithm and by re examining partition coefficients for trace elements between plagioclase and melts data little affected by post magmatic processes were selected by using plagioclase with relatively primitive sc and co contents the fan host magma contained 90 174 ppm sr 40 119 ppm ba and 0 5 1 3 tio2 and had sub chondritic sr ba and ti ba ratios it is difficult to account for the formation of fan host magma on the basis of magma evolution processes of previously proposed bulk silicate moon models with chondritic ratios for refractory elements at global scale therefore the source of the fan host magma must have had primordial sub chondritic sr ba and ti ba ratios the fan host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites and some very low ti mare rocks from lunar meteorites here we propose an alternative bulk silicate moon model the cbsm model which is enriched in crustal components of proto bodies relative to the present whole earth moon system

emplacement of the east sulawesi ophiolite evidence from subophiolite metamorphic rocks abstract a newly discovered high temperature metamorphic sole at the base of the extensive east sulawesi ophiolite in sulawesi indonesia yields new structural and petrological data with which to constrain the emplacement history the metamorphic sole is composed of a thin sequence of garnet and epidote amphibolite and basal greenschist metaclastics east dipping tectonite fabrics in the metamorphic sole amphibolite are coincident with those in subjacent basement mica schist and superjacent peridotite and indicate orthogonal east to west emplacement of the ophiolite in central sulawesi metabasite in the upper levels of the sole has morb geochemical characteristics was recrystallized at temperatures of about 700 c and yielded k ar radiometric ages of approximately 30 ma initial detachment of the ophiolite probably occurred at a ridge segment transform intersection in a back arc basin at the south east margin of sundaland detachment closely preceded nw directed overthrusting and orthogonal obduction on to the sundaland continental margin in the oligocene sinistral movement on a paleo transform boundary now the lawanopo fault may have facilitated obduction although the westernmost segments of ophiolite may represent younger more proximal slices of a marginal basin those further east probably represent successively older more distal slices of underthrust indian ocean back arc or forearc

the late quaternary tectonic biogeochemical and environmental evolution of ferruginous lake towuti indonesia abstract there is a paucity of long and continuous continental records from south east asia suitable to inform on past changes and underlying causes of the region s climate and associated diverse ecosystem evolution during the late quaternary in 2015 the towuti drilling project tdp collected a series of sedimentary drill cores from the tectonic ferruginous and highly biodiverse lake towuti sulawesi one of indonesia s oldest lakes the drill cores contain 1 myr of uninterrupted lacustrine sedimentation to document long term environmental and climatic change in the tropical western pacific the impacts of geological and environmental changes on the biological evolution of aquatic taxa and the geomicrobiology and biogeochemistry of metal rich ultramafic hosted lake sediment here we use lithostratigraphic mineralogical geochemical and geochronological datasets to elucidate lake towuti s tectonic emergence and its biogeochemical responses to climatic and volcanic forcings since lake formation our data document that lake towuti emerged during a phase of accelerated tectonic subsidence from a landscape characterized by active river channels shallow lakes and swamps into a permanent lake at 1 ma the lacustrine sediments feature quasi rhythmic alternations of green organic rich and red sideritic clay beds reflecting changes in lake mixing and biogeochemistry as a response to temperature and hydrological changes driven by orbital scale changes in insolation and continental ice volume through the mid to late pleistocene clay deposition is interrupted by two beds of diatomaceous oozes composed primarily of planktonic diatoms that reflect phases of substantially increased primary productivity the occurrence of these diatomaceous oozes in close association with multiple tephra beds suggests a trophic state change driven by the addition of volcanically sourced p possibly in combination with a lake mixing state that supports recycling of p data on lake age and ontogeny are also in agreement with molecular clock estimates of 0 7 ma 0 18 1 37 ma for the divergence of lake towuti s telmatherinid fishes from a riverine ancestor our data therefore are compatible with an evolutionary model in which lake towuti s endemic fauna is a result of geographic speciation in the malili lakes a set of large lakes in southeast sulawesi driven by physical or chemical dispersal limits imposed by the regional rivers and lakes more detailed chronological constraints and refined climate and environmental proxy datasets are currently in preparation and will help to paint a more detailed history of the region s climate and environmental history in future studies

coupled caal nasi diffusion in plagioclase feldspar experiments and applications to cooling rate speedometry abstract the rate of caal nasi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400 to 1000 c in calcic plagioclase an80 81 by homogenizing coherent exsolution lamellae the dependence of the average interdiffusion coefficient on temperature is given by the expression d 10 99 cm 2 sec exp 123 4 kcal mol rt t in k this value is for diffusion perpendicular to the 03 1 interface of the lamellae caal nasi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400 to 1200 c and possibly 10 orders of magnitude slower at subsolidus temperatures the large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions e g the skaergaard which retain delicate ca na compositional zoning profiles on the micron scale but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks caal nasi diffusion is slow the closure temperature is high within the solidus liquidus interval and ca na zoning is preserved oxygen diffusion is faster the closure temperature is lower 350 400 c and the feldspars exchange oxygen with the low temperature hydrothermal fluids the complex micron scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase cooling histories typical of large mafic intrusions e g the stillwater are slow begin at high initial temperatures 1200 c and result in homogenization of oscillatory zones on the scale of 10 microns the oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature 1000 c limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion

mesozoic porphyry cu au mineralization and associated adakite like magmatism in the philippines insights from the giant atlas deposit the atlas porphyry cu au deposit is located in central cebu island in the philippines with a proven mineral reserve of 1420 mt at 0 45 cu 0 24 g t au 0 018 g t mo and 1 8 g t ag it is associated with the lutopan quartz diorite porphyry stock that was emplaced into the cretaceous volcano sedimentary sequences of the cansi formation two stages of hypogene alteration have been identified at atlas stage i quartz magnetite chalcopyrite pyrite veins associated with potassic and propylitic alteration and stage ii anhydrite pyrite chalcopyrite specularite veins associated with phyllic alteration supergene gypsum veins are also present mineralization is mainly associated with the stage i and stage ii veins the lutopan quartz diorite porphyry yielded a zircon u pb age of 108 5 1 6 ma and is characterized by high sr y 54 69 with the corresponding magma having high oxygen fugacity avg fmq 2 7 avg ce4 ce3 of zircon 439 and h2o concentrations presence of amphibole and biotite phenocrysts and low magmatic temperatures avg ti in zircon thermometry 706 c the relatively low la yb ratios 9 11 listric shaped normalized ree patterns with weak or absent eu anomalies together with zircon ehf t values of 3 4 to 10 0 whole rock isr values of 0 70373 0 70382 end t values of 2 4 3 4 and mg numbers of 49 53 suggest that the lutopan quartz diorite porphyry was likely derived from partial melting of young lower continental crust or interaction between asthenospheric melts and lower crust melts that evolved to adakite like trace element compositions through amphibole fractionation stage i veins yielded a pyrite re os isochron age of 110 2 5 6 ma making atlas the only mesozoic porphyry deposit discovered in the philippines

tertiary evolution of the eastern indonesia collision complex abstract eastern indonesia is the zone of interaction between three converging megaplates eurasia the pacific and indo australia the geological basis for interpretations of the tertiary tectonic evolution of eastern indonesia is reviewed and a series of plate tectonic reconstructions for this region at 5 million year intervals covering the last 35 million years is presented the oldest reconstruction predates the onset of regional collisional deformation at this time a simple plate configuration is interpreted consisting of the northward moving australian continent approaching an approximately e w oriented southward facing subduction zone extending from the southern margin of the eurasian continent eastwards into the pacific oceanic domain beginning at about 30 ma the australian continental margin commenced collision with the subduction zone along its entire palinspastically restored northern margin from sulawesi in the west to papua new guinea in the east from this time until ca 24 ma the australian continent indented the former arc trend with the northward convergence of australia absorbed at the palaeo northern boundary of the philippine sea plate the present day palau kyushu ridge at ca 24 ma the present day pattern of oblique convergence between the northern margin of australia and the philippine sea plate began to develop at about this time a large portion of the palaeogene colliding volcanic arc the future eastern philippines began to detach from the northern continental margin by left lateral strike slip from ca 18 ma oblique southward directed subduction commenced at the maramuni arc in northern new guinea at ca 12 ma the sorong fault zone strike slip system developed effectively separating the philippines from the indonesian tectonic domain the sorong fault zone became inactive at ca 6 ma since which time the tectonics of eastern indonesia has been dominated by the anticlockwise rotation of the bird s head structural block by some 30 40 contemporaneously with post 18 ma tectonism the banda arc subduction collision system developed off the northwestern margin of the australian continent convergence between indo australia and eurasia was accommodated initially by northward subduction of the indian ocean and subsequently since ca 8 ma by the development of a second phase of arc continent collision around the former passive continental margin of nw australia

modern sedimentation processes in lake towuti indonesia revealed by the composition of surface sediments abstract lake towuti on sulawesi island indonesia is located within the heart of the indo pacific warm pool this tropical lake is surrounded by ultramafic ophiolitic rocks and lateritic soils that create a unique ferruginous depositional setting in order to understand modern sediment deposition in lake towuti a set of 84 lake surface sediment samples was collected from across the entirety of the lake and samples were analyzed for their physical chemical mineralogical and biological constituents end member analyses were carried out to elucidate modern sediment origin transport and depositional processes this study found that allochthonous sediment characterized by the concentrations of the elements mg fe si and al as well as the clay and serpentine minerals is dominated by fluvial supply from five distinct source areas granulometric data and the occurrence of organic matter of terrestrial origin suggest that in the southern and north eastern parts of the lake the near shore sediments may additionally be influenced by mass wasting this at least is partly due to the particularly steep slopes in these areas furthermore sediment composition suggests that sediment transport into deeper parts of the lake particularly in the northern basin is partly controlled by gravitational and density driven processes such as turbidity currents directional sediment transport by persistent lake currents in contrast appears less important organic matter deposition in the ultra oligotrophic lake albeit limited is dominated by autochthonous production but with some contribution of fluvial and gravitational supply biogenic silica deposition primarily from diatom frustules and sponge spicules is very limited and is concentrated in only a few areas close to the shoreline that are characterized by shallow waters but away from the areas of high suspension loads at the mouths of the major inlets the results of this study build upon current and published work on short piston cores from lake towuti conversely the results will support the interpretation of the depositional history and past climatic and environmental conditions derived from the composition of much longer records which were obtained by the towuti drilling project in may 2015 and are currently under investigation this article is protected by copyright all rights reserved

early eocene volcanic ashes on greifswalder oie and their depositional environment with an overview of coeval ash bearing deposits in northern germany and denmark unconsolidated bentonites and carbonate cemented volcanic ashes occur in northern germany within the clay sequence of the lamstedt and schlieven formations documented by several wells ash bearing carbonate concretions so called cementstones are also known from glacially transported rafts and erratic boulders on the baltic sea island greifswalder oie representing the easternmost exposures of early eocene sediments in the north sea basin the ashes can be correlated with water lain ashes of the danish fur and olst formations mo clay generated during the opening of the north atlantic ocean about 55 ma ago two types of cementstones can be distinguished on the basis of the mineralogical composition sedimentary features and fossil content greifswalder oie type i contains a black up to 12 cm thick ash deposit that follows above two distinct thin grey ash layers the major ash unit has a rather homogeneous lower part only a very weak normal grading and faint lamination are discernible in the upper part however intercalations with light mudstone in part intensively bioturbated together with parallel and cross lamination suggest reworking of the ash in a shallow marine environment major and trace element compositions are used to correlate type i ashes with those of the danish positive series which represent rather uniform ferrobasalts of the danish stage 4 probably related to the emergence of proto iceland in contrast type ii ash comprises a single normally graded about 5 cm thick layer of water lain air fall tuff which is embedded in fine grained sandstone to muddy siltstone type ii ash is characterised by very high tio2 but low mgo contents exceptional ree patterns with a pronounced positive eu anomaly suggest intense leaching of the glass that hampers exact correlation with pyroclastic deposits within the north atlantic igneous province

neogene sutures in eastern indonesia five suture zones are described from the zone of collision between the eurasian indian australian and pacific philippine sea plates within the eastern indonesia region these are the molucca sorong sulawesi banda and borneo sutures each of these sutures has a relatively short history compared to most pre neogene orogenic belts but each preserves a record of major changes in tectonics including subduction polarity reversals elimination of volcanic arcs changing plate boundaries and important extension within an overall contractional setting rapid tectonic changes have occurred within periods of less than 5 ma many of these events although important would be overlooked in older orogenic belts because the age resolution required to identify them even when the evidence is preserved is simply not possible q 2000 elsevier science ltd all rights reserved

investigation into the petrogenesis of apollo 14 high al basaltic melts through crystal stratigraphy of plagioclase abstract the petrogenesis of apollo 14 high al basaltic melts was studied using crystal stratigraphy which involves textural crystal size distributions csds and chemical analyses electron microprobe and laser ablation inductively coupled plasma mass spectrometry the samples studied here include pristine basalt 14072 and basaltic clasts from breccia 14321 and impact generated crystalline samples 14073 14276 and 14310 plagioclase was the focus of this study because of its relatively high modal abundances and because it was on the liquidus for much of the melt cooling histories plagioclase crystals were analyzed core to rim compositions where possible to test and refine petrogenetic models based upon whole rock compositions groups a b and c designations and to investigate basalt 14072 and impact melt crystallization textural studies have shown that each basalt group has distinctive plagioclase csds which are in turn distinctive from those of the impact melts evolution of the individual basaltic melts was studied by comparing the equilibrium melt compositions calculated from plagioclase compositions using relevant partition coefficients to fractional crystallization fc and assimilation and fractional crystallization afc models petrogenetic modeling of trace elements in group a basalts revealed that petrogenesis continued beyond 40 total crystallization required to model whole rock compositions and that there were open system processes that affected the magma during plagioclase crystallization petrogenetic modeling of pristine high al basalts 14072 and groups a b and c using trace elements shows that the equilibrium melt compositions do not fall on a single afc or fc trajectory this is consistent with fluctuating degrees of assimilation i e variable r values and or variable assimilant compositions during petrogenesis petrogenetic modeling reveals that the impact melts experienced only closed system fractional crystallization this work demonstrates the importance of crystal stratigraphy in revealing the intricacies of lunar basalt petrogenesis

redox controls on tungsten and uranium crystal silicate melt partitioning and implications for the u w and th w ratio of the lunar mantle the timing of core formation is essential for understanding the early differentiation history of the earth and the moon because hf is lithophile and w is siderophile during metal silicate segregation the decay of 182hf to 182w half life of 9 ma has proven to be a useful chronometer of core mantle differentiation events a key parameter for the interpretation of 182hf 182w data is the hf w ratio of the primitive i e undepleted mantle since w is incompatible during mantle melting its ratio relative to u and other similarly incompatible elements in basalts e g th la may be used as proxies for their mantle sources however the assumption that w and u are equally incompatible may be flawed for petrological systems that equilibrated over a large range of oxygen fugacity fo2 although w is typically perceived as being homovalent evidence suggests that u is heterovalent over the range of fo2 inferred for the silicate mantles of the earth and the moon here we report new partitioning data for w u high field strength elements hfse and th between clinopyroxene orthopyroxene olivine plagioclase and silicate melt in agreement with previous studies we show that these elements behave as homovalent elements at fo2 characteristic of earth s upper mantle however both w and u become more compatible at low fo2 indicating a change in their redox state with w becoming more compatible at progressively lower fo2 this result for w is particularly unexpected because this element was thought to be hexavalent even at very low fo2 the much higher compatibility of w4 the species inferred here at low fo2 relative to w6 means that even a small fraction of w4 will have a significant effect on the overall compatibility of w our results imply that over the range of reducing conditions in which lunar differentiation is thought to have taken place i e iw 2 to iw 0 5 w is likely to become fractionated from u when our partitioning data are applied to model the fractional crystallization of a lunar magma ocean lunar trends for u w hf w and th w are well reproduced the result of this model carries with it the implication that the hf w of the bulk silicate fractions that comprise the earth and the moon are virtually identical

the interplate coupling and stress accumulation process of large earthquakes along the nankai trough southwest japan derived from geodetic and seismic data abstract the interplate coupling and stress accumulation process associated with the subduction of the philippine sea plate beneath the eurasian plate along the nankai trough where large earthquakes have occurred periodically have been investigated in detail taking into account the three dimensional complicated structure of the philippine sea plate and its motion relative to the eurasian plate for this purpose we mainly used extensive geodetic data in southwest japan such as levelling tide gauge and trilateration which presumably are effective means of revealing coupling properties and applied a three dimensional finite element method here two seismic periods associated with the 1944 tonankai and 1946 nankaido earthquakes were considered interseismic and pre seismic stages comparing the coupled regions obtained for the two cases a possible explanation of its temporal change was proposed it might gradually spread from a shallower to deeper portion with transition from the interseismic to pre seismic stage a comparison of the coupling properties between southwest japan and northeast japan reveals the following properties in southwest japan the coupling is generally strong and its region is limited in a relatively shallow portion the pre seismic coupled regions coincide with the co seismic and post seismic fault zone suggesting that the accumulated stress is released at the time of a large earthquake in northeast japan on the other hand the coupling is weak and its extent appears to reach a depth of about 100 km and the co seismic and post seismic regions are limited to the upper half of the coupled region the weakly coupled region in southwest japan seems to correspond well to the region with high seismic activity a high dip angle subducting slab and the possible existence of seamounts in contrast to the strongly coupled region correlated with low seismicity low dip angle subduction and no seamounts on the western coupled region off shikoku an anomalously strongly coupled region corresponding to a convergence rate of 7 8 cm year 1 was identified this may be caused by geomorphological properties such as the low dip angle of the subducting plate and smooth plate boundary resulting in a large amount of stress concentration there the stress field associated with the interplate coupling was also calculated there is fair agreement between the observations and calculations near the plate boundary beneath the southern kii peninsula and shikoku although the effects of the interplate coupling may have some influence on strike slip faulting with the n s compressive axes beneath shikoku other earthquake generating stress such as a two layered double buckling would be dominant there

coseismic slip resolution along a plate boundary megathrust the nankai trough southwest japan geodetic survey measurements are used to estimate the coseismic slip distribution in the 1944 tonankai mw 8 1 and 1946 nankaido mw 8 3 earthquakes and to assess quantitatively the degree to which this slip is resolved on the plate boundary megathrust data used include 798 angle changes from triangulation surveys 328 leveling section differences and 5 coseismic tidal gage offsets many of the nominally coseismic triangulation data span 50 years nearly half the earthquake cycle and correction for interseismic deformation using post 1950 observations is applied microseismicity is used to define the configuration of the plate boundary interface and approximate it with a continuous multisegment fault model because the onshore geodetic data have very limited resolving power for offshore fault segments offshore coseismic slip was constrained by satake s 1993 estimation based on tsunami data the majority of the coseismic slip occurs between 15 and 25 km depth although resolution declines toward the trench axis it is sufficiently good to define two distinct high slip regions one off southeastern shikoku island 11 m maximum and the other offshore of kii peninsula 3 m maximum the slip magnitude off southeastern shikoku coupled with the plate convergence rate would imply an recurrence interval of about 270 years much longer than the average repeat time of 120 years for historical great earthquakes on the nankai trough however the maximum coseismic slip is sensitive to the assumed fault geometry and slippage on trough parallel splay faults could significantly decrease the maximum slip to about 6 m

tectonostratigraphic evolution of cenozoic marginal basin and continental margin successions in the bone mountains southwest sulawesi indonesia abstract the bone mountains located in southwest sulawesi along the se margin of sundaland are composed of oligocene to possibly lower miocene marginal basin successions bone group that are juxtaposed against continental margin assemblages of eocene miocene age salokalupang group three distinct units make up the latter i middle upper eocene volcaniclastic sediments with volcanic and limestone intercalations in the upper part matajang formation reflecting a period of arc volcanism and carbonate development along the sundaland margin ii a well bedded series of oligocene calc arenites karopa formation deposited in a passive margin environment following cessation of volcanic activity and iii a series of lower middle miocene sedimentary rocks in part turbiditic which interfinger in the upper part with volcaniclastic and volcanic rocks of potassic affinity baco formation formed in an extensional regime without subduction the bone group consists of morb like volcanics showing weak to moderate subduction signatures kalamiseng formation and a series of interbedded hemipelagic mudstones and volcanics deko formation the deko volcanics are in part subduction related and in part formed from melting of a basaltic precursor in the overriding crust we postulate that the bone group rocks formed in a transtensional marginal basin bordered by a transform passive margin to the west sundaland and by a newly initiated westerly dipping subduction zone on its eastern side around 14 13 ma an extensional tectonic event began in sw sulawesi characterized by widespread block faulting and the onset of potassic volcanism it reached its peak about 1 ma year later with the juxtaposition of the bone group against the salokalupang group along a major strike slip fault walanae fault zone the latter group was sliced up in variously sized fragments tilted and locally folded potassic volcanism continued up to the end of the pliocene and locally into the quaternary

lithological structural and geochemical characteristics of the mesoarchean târtoq greenstone belt southern west greenland and the chugach prince william accretionary complex southern alaska evidence for uniformitarian plate tectonic processes the mesoarchean t rtoq greenstone belt southern west greenland consists of tectonically imbricated slices of metamorphosed basalt gabbro peridotite and sedimentary rocks and is intruded by fel

the july 12 1993 hokkaido nansei oki japan earthquake coseismic slip pattern from strong motion and teleseismic recordings we employ a finite fault inversion scheme to infer the distribution of coseismic slip for the july 12 1993 hokkaido nansei oki earthquake using strong ground motions recorded by the japan meteorological agency within 400 km of the epicenter and vertical p waveforms recorded by the global digital seismograph network at teleseismic distances the assumed fault geometry is based on the location of the aftershock zone and comprises two fault segments with different orientations a northern segment striking at n20 e with a 30 dip to the west and a southern segment with an n20 w strike for the southern segment we use both westerly and easterly dip directions to test thrust orientations previously proposed for this portion of the fault the variance reduction is greater using a shallow west dipping segment suggesting that the direction of dip did not change as the rupture propagated south from the hypocenter this indicates that the earthquake resulted from the shallow underthrusting of hokkaido beneath the sea of japan static vertical movements predicted by the corresponding distribution of fault slip are consistent with the general pattern of surface deformation observed following the earthquake fault rupture in the northern segment accounts for about 60 of the total p wave seismic moment of 3 4 1020 n m and includes a large circular slip zone 4 m peak near the earthquake hypocenter at depths between 10 and 25 km slip in the southern segment is also predominantly shallower than 25 km but the maximum coseismic displacements 2 0 2 5 m are observed at a depth of about 5 km this significant shallow slip in the southern portion of the rupture zone may have been responsible for the large tsunami that devastated the small offshore island of okushiri localized shallow faulting near the island however may require a steep westerly dip to reconcile the measured values of ground subsidence

magmatic evolution of sulawesi indonesia constraints on the cenozoic geodynamic history of the sundaland active margin abstract tertiary and quaternary magmatic rocks from west sulawesi record the complex history of part of the sundaland margin where subduction and collision have been and are still active the present study based on petrographic data major and trace element chemistry and 40 k 40 ar dating aims to document the age and chemical characteristics of the magmatic formations from west sulawesi and to determine the corresponding constraints on the geodynamic evolution of the sundaland border the west sulawesi magmatic province includes the south arm of sulawesi ujung pandang area the western part of central sulawesi with the toraja and palu areas and finally the north arm extending from palu to manado which includes the tolitoli and manado areas paleocene magmatic activity seems to be restricted to an episode of calc alkaline magmatism in the ujung pandang area 61 59 ma the major eocene 50 40 ma magmatic event is tholeiitic and is documented in all areas except in ujung pandang it led to the emplacement of tholeiitic pillow lavas and basaltic dykes of back arc basin bab affinity these rocks are potential equivalents to the celebes sea basaltic basement from oligocene to miocene magmatic eruptions produced successively island arc tholeiitic iat and calc alkaline ca rock series the youngest iat activity occurred around 18 ma in the central part palu area and around 14 ma in the north arm tolitoli area while ca magmas were emplaced in the north arm at ca 18 ma tolitoli and manado areas typical calc alkaline activity resumed only in the north arm tolitoli and manado areas during the late miocene 9 ma and is still active in the manado region in other areas palu toraja and ujung pandang areas an important and widespread magmatic event occurred between 13 and 10 ma and emplaced k rich magmas either silica undersaturated alkali potassic basalts ak ultrapotassic basanites uk or shoshonites sh k rich activity continued in the south until the pleistocene 0 77 ma with alkali potassic ultrapotassic and shoshonitic magmas in central sulawesi toraja and palu areas the most recent magmatic event occurred between 6 5 and 0 6 ma the corresponding products are granitic rocks and widely distributed rhyolitic pyroclastic flow deposits all these rocks are acidic in character sio 2 60 with trace element and isotopic signatures sr nd pb typical of a strong continental imprint the most striking tectonic implication of this magmatic evolution is that west sulawesi can no longer be considered as a typical magmatic arc as previously assumed with the exception of the manado area beneath which subduction is still active calc alkaline and island arc tholeiitic lavas and plutonics are volumetrically minor with respect to k rich magmas their occurrence through time is also fairly restricted mostly to the period between 30 and 15 ma another important feature is the occurrence of island arc tholeiitic and calc alkaline magmas crosscutting an older terrane of bab affinity the tinombo formation manado tolitoli and palu areas as this formation is being regarded as an equivalent to the celebes sea floor the most likely explanation for this feature is the hypothesis of tectonic erosion linked to the nw dipping subduction beneath the north arm the late miocene high k magmatic activity in central and south sulawesi reflects the prevalence of a post collisional tectonic regime following the docking of microcontinents of australian origin to central sulawesi during neogene times the incompatible element enriched character of these high k rocks might reflect their derivation from a mantle source enriched through metasomatism related to a previous subduction event such a model cannot account for the plio pleistocene cak magmatism of central sulawesi the acidic composition of which does not support a derivation from an ultrabasic source the trace element patterns of the cak rocks are very similar to those of the high grade metamorphics of central sulawesi suggesting that the latter might represent their possible source such an anatectic model implies a collisional to post collisional tectonic regime limited to central sulawesi while a post subduction regime prevailed in the south

the origin and significance of metamorphosed tectonic blocks in melanges evidence from sulawesi indonesia metamorphosed tectonic blocks or knockers are widespread but volumetrically minor constituents of many circum pacific melange belts due to the common lack of an exposed in situ provenance and to the seemingly chaotic field disposition of most block bearing melanges their origin and uplift history are problematic and controversial on the indonesian island of sulawesi a block bearing melange is overlain by an ophiolite nappe the base of which is characterized by a metamorphic sole sequence petrological geochemical and geochronological data indicate a direct genetic relationship between high grade tectonic blocks in the melange and amphibolites in the metamorphic sole amphibolite precursors to lower temperature blueschist assemblages are virtually ubiquitous in the tectonic blocks and subdivisions based on the nature of the overprinting relationships can be systematically correlated with block distribution patterns orientated subparallel to the strike of the melange belt it is suggested here that the high grade tectonic blocks originated in a thin thermally zoned metamorphic sheet welded to the oceanic hangingwall plate at the inception of subduction break up of this sequence at depth by tectonic erosion led to dispersal of fragments into a newly developed serpentinite melange wedge blocks experienced abrupt changes in p t x conditions due to a combination of hydration in the new fluid rich environment gradual cooling of the hangingwall over time and continuing underflow dragging sheared blocks deeper into the subduction zone prior to upflow blocks plucked from the hangingwall at different depths and at different times evidently experienced uplift in different flow channels resulting in block concentrations with p t t paths characteristic of their source and flow trajectory at systematically greater distances from the subduction zone hangingwall the elucidation of the origin and significance of tectonic blocks in sulawesi has important implications not only for the tectonometamorphic evolution of similar inclusions in other melange belts but also for models of the inception and early stages of subduction

interplate coupling along the nankai trough off southwest japan derived from gps measurements we investigate interplate coupling between the philippine sea and the eurasian plates at the nankai trough off southwest japan during the interseismic period plate coupling is modeled by imaginary backward normal slip superposed on the steady state subduction we divide the plate interface into several segments and estimate coupling on each segment from gps horizontal velocity data estimated coupling is in general agreement with the rate of steady state subduction predicted from a plate motion model this implies that current coupling at the nankai trough is so strong that much of the relative plate motion is taken up by shortening of the leading edge of the overriding plate it seems that stronger interseismic coupling is realized on the segment where larger coseismic dislocation occurred and vice versa time fluctuation of plate coupling from 1995 to 1996 is found on a small segment

geodynamic patterns of ophiolites and marginal basins in the indonesian and new guinea regions analysis of spatial temporal geological and geochemical patterns of ophiolites in the indonesian and new guinea region indicates a strong correlation with marginal basin development and closure the spatial distribution of ophiolites is mostly linked with marginal basin producing zones of oblique convergence and collision strain partitioning in these zones creates a series of ephemeral plate boundaries between several independently moving lithospheric blocks repeated disruption of the diffuse boundaries between the blocks by changes in plate motion and collision induced mantle extrusion creates space that is rapidly filled by new ocean basins in the upper plate of subduction zones suprasubduction zone ssz spreading of these basins is enhanced by episodic extrusion of asthenosphere escaping collisional suture zones various closure events and global plate motion changes are reflected in the temporal distribution of marginal basin and ophiolite ages most ophiolite slabs in the indonesian and new guinea region represent fragments of oceanic lithosphere with a subduction zone component as indicated by the common refractory petrochemistry of the mantle sequence and occurrence of boninite age and compositional heterogeneity may indicate that some ophiolite bodies are composite terranes collisions with buoyant lithosphere transfo parts of these ocean basins into ophiolites the connection between ophiolites and marginal basins is strongest where parts of actively spreading ssz basins are partially represented as ophiolites in collision zones many of the various tectonic models proposed for the origin and tectonic evolution of ophiolites are supported by plate interactions in the indonesian and new guinea region dewey bird 1970 silver smith 1983 moores et al 1984 searle stevens 1984 dilek moores 1990 harris 1992 dickinson et at 1996 however the geolo gical associations of these interactions remain poorly resolved allowing different parts of the region to be used as modern analogues for almost any tectonic scenario simple explanations based on plate kinematics alone fail to account for the increasing levels of complexity observed in the indonesian and new guinea region new ideas and supporting evidence for mantle extrusion mechanisms e g flower et at 2001 also rely heavily on descriptions of plate interactions in this region doglioni et at 1999 and raise new questions about how these processes may relate to the spatial and temporal pattern of ophiolites this paper provides a synthesis of the temporal and spatial patterns and tectonic associations of marginal basins and ophiolites throughout the indonesian and new guinea region it explores the relations between various plate boundary processes and ophiolite genesis and emplacement such as the role of strain partitioning trench rollback subduction polarity asymmetry astheno spheric flow and plate kinematics

minor element partitioning and sector zoning in synthetic and meteoritic anorthite regular geometric apparently crystallographically controlled sector zoning has been produced in synthetic anorthite crystallized from a liquid of type b ca al rich inclusion cai composition cathodoluminescence cl provides a rapid method for observing the sectors sharp discontinuities in mg concentration always accompany sharp changes in cl intensity at sector boundaries although cl intensity anti correlates with mg concentration there is not a well defined quantitative relationship and mg concentration steps range from as little as 5 to almost a factor of 2 for different cl boundaries when measurable na also tends to anti correlate with cl brightness in a given crystal and thus correlates with mg the partition coefficients for mg and na can vary by up to a factor of 2 depending on the particular sector and thus are not constant for cai anorthite which formed by fractional crystallization in contrast ti either ti 3 or ti 4 concentration is not a function of sector zoning and thus does not affect the cl intensity the sector zoning and correlated chemical variations for synthetic anorthite are similar to those in natural anorthite from type b cais the cl intensity boundary sharpness and minor element zoning in synthetic anorthite are not affected by annealing at 850 c for three weeks overall our observations suggest that the observed cl patterns and minor element zoning in type b anorthite are igneous in origin and have not been modified by subsolidus reequilibration or alteration this leads to the conclusion that the 26 mg 26 al systematics in cais based almost entirely on anorthite have not been modified by subsolidus reequilibration or alteration

crystal accumulation in a 4 2 ga lunar impact melt abstract the ages of lunar impact basins and the role of fractional crystallization in producing compositional heterogeneity of lunar melt sheets are long standing problems with significant implications for solar system dynamics and the petrologic evolution of the lunar crust here we document the formation of a basin scale impact on the moon at 4 20 0 07 ga based on the 147 sm 143 nd isochron age of a magnesian noritic anorthosite melt rock from lunar breccia 67955 major element compositions of plagioclase and mafic silicates in the melt rock imply a substantial component of primary mg suite cumulates or related lithologies in the pre impact crustal stratigraphy trace element compositions of the plagioclase including diagnostic ratios such as sr ba are also mostly similar to those in plagioclase from mg suite cumulates with a small number of grains trending toward compositions observed in ferroan anorthosites mineral melt distribution coefficients applied to trace element compositions of the 67955 plagioclase and pyroxene predict parental melt compositions that contrast strongly with the bulk rock compared to the whole rock parental melts calculated from the plagioclase are enriched in ree ree la yb 131 885 average 619 ppm vs 39 8 ppm and they have more fractionated ree patterns la yb n 1 2 9 8 average 4 9 vs 1 5 with deep negative eu anomalies eu eu 0 09 0 40 vs 1 36 trace element data for the pyroxenes also imply incompatible element enriched parental melts subsolidus equilibration between the plagioclase and the pyroxene apparently rotated the ree patterns but the conclusion that the parental melt was highly enriched in ree relative to the whole rock appears robust quantitative modeling shows that fractional crystallization of the 67955 whole rock composition cannot reproduce the range of ba sr ti and la concentrations measured in the 67955 plagioclase rather the models require an initial melt composition that was strongly enriched in these elements and they suggest that fractional crystallization became less efficient as crystallization proceeded the contrast between the inferred parental melt composition and the bulk rock implies formation of the 67955 noritic anorthosite as a crystal cumulate and that the cogenetic residual melt was strongly enriched in incompatible elements if so this would be the first documented example of fractional crystallization in a lunar impact melt sheet the petrological and geochemical characteristics of the 67955 noritic anorthosite suggest that it formed by an impact in the procellarum kreep terrane and was transported to the apollo 16 site as imbrium ejecta inheritance of ejecta related to this pre imbrium basin may contribute to the common occurrence of 4 2 ga 40 ar 39 ar plateau ages in breccia clasts and regolith fragments from the rim of north ray crater in that case those data may provide no constraints on the age of the nectaris basin despite its proximity to the apollo 16 site

a test of present day plate geometries for northeast asia and japan alternative geometries for the present day configuration of plate boundaries in northeast asia and japan are tested using nuvel 1 and 256 horizontal earthquake slip vectors from the japan and northern kuril trenches statistical analysis of the slip vectors is used to determine whether the north american eurasian or okhotsk plate overlies the trench along the northern kuril trench sup vectors are well fit by the nuvel 1 pacific north america euler pole but are poorly fit by the pacific eurasia euler pole results for the japan trench are less conclusive but suggest that much of honshu and hokkaido are also part of the north american plate the simplest geometry consistent with the trench slip vectors is a geometry in which the north american plate extends south to 41 n and possibly includes northern honshu and southern hokkaido although these results imply that the diffuse seismicity that connects the lena river delta to sakhalin island and the eastern sea of japan records motion between eurasia and north america onshore geologic and seismic data define an additional belt of seismicity in siberia that cannot be explained with this geometry assuming that these two seismic belts constitute evidence for an okhotsk block two published kinematic models for motion of the okhotsk block are tested the first model which predicts motion of up to 15 mm yr 1 relative to north america is rejected because kuril and japan trench slip vectors are fit more poorly than for the simpler geometry described above the second model gives a good fit to the trench slip vectors but only if okhotsk north america motion is slower than 5 mm yr 1

trace element partitioning between high an plagioclase and basaltic to basaltic andesite melt at 1 atmosphere pressure we determined plagioclase melt partition coefficients for 18 elements by performing controlled cooling rate 1 atmosphere experiments using both natural and synthetic basaltic 51 wt sio2 and basaltic andesite 56 wt sio2 powders in a vertical quench furnace the experiments produced an69 to an87 composition plagioclase three starting powders were gorda ridge basalt synthetic diopside 40 albite 28 anorthite 32 mixture and arenal volcano costa rica basaltic andesite the gorda and synthetic powders were doped at both low concentrations 20 200 ppm and high concentration 200 5000 ppm whereas the arenal powder was doped only at high concentrations resulting in two doped gorda powders low np and high sdp two doped diopside albite anorthite powders low dad high sdd and one doped arenal powder high ar99 2 trace elements concentrations in both glass and plagioclase were measured by secondary ion mass spectrometry sims and or by laser ablation inductively coupled plasma mass spectrometry la icp ms results for the partitioning of trace elements between plagioclase and melt at different doping levels demonstrate both adherence to henry s law and good agreement between the different analytical techniques in general plagioclase melt partition coefficients determined in the an69 73 range are similar to other published values however some of those occurring for plagioclase compositions an75 are distinctly lower than those predicted by current regression formulations we applied a two lattice melt model to these data to account for differences in melt composition and temperature and found that there were no aberrations associated with partition coefficients a new set of regression formulations is determined involving the newly determined dataset for plagioclase with an contents between 75 and 87

interseismic deformation at the nankai trough japan subduction zone uplift along the coast of southwestern japan following the 1944 tonankai ms 8 0 and 1946 nankaido ms 8 2 earthquakes has been inferred from the 1950 1985 tide gage records although uplift rates vary with geographic position the temporal dependence at each site can be described as the superposition of an exponentially decaying time constant 5 years transient significant only in the first decade postseismic and a steady interseismic rate the steady interseismic uplift rate is defined only over the 1956 1985 interval but the linearity in time ofthat uplift record is such that uplift over the remainder of the interseismic cycle 80 years might reasonably be expected to occur at the same rate moreover the spatial pattern and magnitude of the steady uplift rate are reasonably close to those predicted by a simple dislocation model of subduction however the currently observed steady uplift rate is not consistent with the uplift rate inferred from geodetic leveling for the final half of the previous earthquake cycle thus either the hypothesis of a steady interseismic uplift rate after the first decade postseismic is wrong or the strain accumulation pattern for one earthquake need not be the same as for the preceding earthquake on the same segment

spinel compositions of mantle hosted chromitite from the eastern anatolian ophiolite body turkey implications for deep and shallow magmatic processes abstract the eastern anatolian accretionary complex includes several ophiolitic megablocks and or tectonic slivers within a 150 180 km long east west trending complex formed during the late cretaceous tertiary in eastern turkey the alabayir mollatopuz yukaribalcikli and mehmetalan ophiolites are megablocks or tectonic slivers containing locally massive nodular or schlieren banded chromitite layers these podiform chromitites formed in mantle sequences and are classified as high cr chromitites cr 0 63 0 88 mg 0 50 0 64 0 01 0 5 wt tio 2 5 7 18 8 wt al 2 o 3 calculated parental melt compositions of these chromitites indicate boninite magma characteristics 8 2 13 4 wt al 2 o 3 0 64 1 50 feo mgo the pge patterns also support the view that they crystallized from a boninitic melt the total pge contents of chromitites vary between 79 and 390 ppb pd ir ratios of chromitites vary from 0 07 to 0 28 and are consistent with an ipge fractionated nature the examined chromitites were divided into two groups in terms of their mineral chemistry group i alabayir mollatopuz yukaribalcikli and mehmetalan i chromitites group ii mehmetalan ii chromitites mineral chemistry of these chromitites and their parental melt composition indicate that group i chromitites were probably formed at shallow mantle depths and that group ii chromitites formed in deeper parts of the mantle mineral chemistry of these eastern anatolia high cr chromitites indicate that they formed not only in the deeper mantle but also in shallower parts of the moho transition zone