texturing in earth s inner core due to preferential growth in its equatorial belt we propose an extension of the model by yoshida et al 1996 where deformation in the inner core is forced by preferential growth in the equatorial belt by taking into account the presence of a stable compositional stratification stratification inhibits vertical motion imposes a flow parallel to isodensity surfaces and concentrates most deformation in a shallow shear layer of thickness sim b 1 5 where b is the dimensionless buoyancy number the localization of the flow results in large strain rates and enables the development of a strong alignment of iron crystals in the upper inner core we couple our dynamical model with a numerical model of texture development and compute the time evolution of the lattice preferred orientation of different samples in the inner core with sufficient stratification texturing is significant in the uppermost inner core in contrast the deeper inner core is unaffected by any flow and may preserve a fossil texture we investigate the effect of an initial texture resulting from solidification texturing at the icb in the present inner core the deformation rate in the shallow shear layer is large and can significantly alter the solidification texturing but the solidification texture acquired early in the inner core history can be preserved in the deeper part using elastic constants from textit ab initio calculations we predict different maps of anisotropy in the modern inner core a model with both solidification texturing and subsequent deformation in a stratified inner core produces a global anisotropy in reasonable agreement with seismological observations

effects of regolith megaregolith insulation on the cooling histories of differentiated asteroids the cooling histories and in particular the core cooling rates of differentiated asteroids are calculated employing a variety of thermal conductivity structures in order to simulate the potential insulating effects of regolith and megaregolith brecciated impact rubble layers the regolith is assumed to have thermal conductivity 0 005 the unbrecciated mantle conductivity and its thickness in our most typical model is assumed to be 0 003 the parent body radius the megaregolith if present is assumed to have thermal conductivity 0 1 that of unbrecciated mantle we find that a combination of relatively thick megaregolith and regolith can potentially reduce the core cooling rate by more than a factor of 10 below the rate predicted by models with conventional thermal conductivity structure for any given measured cooling rate the radius implied for the parent asteroid can potentially be reduced by a factor of 5 from the radius predicted by models with conventional thermal conductivity structure realistically the regolith and megaregolith thicknesses required to engender these extreme effects were probably seldom generated except perhaps within the largest asteroids where even if generated they would quickly be reduced by compaction and sintering nonetheless our results for models with plausible regolith and megaregolith thicknesses indicate that most of the iron meteorites and the pallasites probably formed in relatively small r less than 50 km parent bodies we have parameterized our results so that effects of intermediate configurations can readily be calculated the parameterization also facilitates evaluation of additional variables e g the initial temperature the concentrations of long lived radioactive heat sources etc albeit these variables are far less crucial than the thermal conductivity structure our results indicate that the insulation of even a thin regolith causes metallalographic cooling rates to be relatively uniform and practically independent of depth within a given asteroid stochastic differences in cratering regolith production histories may have engendered radically different cooling rates from asteroids of similar radius or similar cooling rates from asteroids of different radius

seismic evidence for distinct anisotropy in the innermost inner core to understand the evolution of the inner core it is important to constrain the structure of its innermost part analysis of two types of seismic waves that traverse the inner core reveals seismic anisotropy of the innermost region and is consistent with the slowest direction of anisotropy being tilted away from the equatorial plane

depleted mantle source for the ulungur river a type granites from north xinjiang china geochemistry and nd sr isotopic evidence and implications for phanerozoic crustal growth abstract the ulungur river granites from north xinjiang china display two petrological trends 1 a peralkaline trend composed of alkali amphibole and alkali pyroxene bearing granites and dykes and 2 an aluminous trend represented by alkali granites monzogranites and aluminous granite dykes within the peralkaline granites rb sr whole rock isochron dating yielded an age of 300 ma for the emplacement of the peralkaline granites and 270 ma for the aluminous granites the ulungur river granites share all the geochemical features common to a type granites of the world the ulungur river granites are post orogenic and emplaced in a post collisional extensional environment the peralkaline and aluminous rocks have indistinguishable nd isotopic compositions they have unusually positive and relatively uniform nd t values ranging from 5 1 to 6 7 for the peralkaline rocks at 300 ma and from 5 5 to 5 9 for the aluminous rocks at 270 ma the initial 87sr 86sr ratios cannot be determined precisely by the whole rock isochron technique mainly because most samples are highly radiogenic and have high rb sr ratios in addition the large variation in sr isotopic compositions can partly be explained by crustal contamination during magma differentiation the nd isotopic data clearly indicate that both the peralkaline and aluminous rocks were derived from a long lived depleted mantle reservoir the formation of the ulungur river a type granites is hypothesized as follows 1 a depleted mantle was first metasomatised then subjected to partial melting leading to the generation of basic magmas now represented by the kalatongke mafic ultramafic complex in the ulungur river area 2 the basic magmas have undergone high degrees of fractional crystallisation with separation of biotite hornblende plagioclase potassium feldspar and other accessory phases such as apatite and ilmenite with the residual magmas forming the peralkaline granites during the magmatic differentiation the liquids were probably contaminated by crustal materials as evidenced by nb depletion and nd sr isotopic systematics on the other hand the formation of aluminous granites involved a replenishment of new mantle derived magmas into the differentiating magma chamber and followed by fractional crystallisation with retention of hydrous phases hornblende and biotite the petrological evolution of the ulungur river granites is thus from peralkaline to calc alkaline and not from calc alkaline to peralkaline as more often observed elsewhere the ulungur river granites in common with the voluminous granitoids occurring in the central asian orogenic belt represent a significant juvenile addition of the continental crust in the phanerozoic

highly fractionated i type granites in ne china ii isotopic geochemistry and implications for crustal growth in the phanerozoic ne china is the easternmost part of the central asian orogenic belt caob the area is distinguished by widespread occurrence of phanerozoic granitic rocks in the companion paper part i we established the jurassic ages 184 137 ma for three granitic plutons xinhuatun lamashan and yiershi we also used geochemical data to argue that these rocks are highly fractionated i type granites in this paper we present sr nd o isotope data of the three plutons and 32 additional samples to delineate the nature of their source to determine the proportion of mantle to crustal components in the generation of the voluminous granitoids and to discuss crustal growth in the phanerozoic despite their difference in emplacement age sr nd isotopic analyses reveal that these jurassic granites have common isotopic characteristics they all have low initial 87 sr 86 sr ratios 0 7045f0 0015 positive end t values 1 3 to 2 8 and young sm nd model ages 720 840 ma these characteristics are indicative of juvenile nature for these granites other late paleozoic to mesozoic granites in this region also show the same features sr nd and oxygen isotopic data suggest that the magmatic evolution of the granites can be explained in terms of two stage processes 1 formation of parental magmas by melting of a relatively juvenile crust which is probably a mixed lithology formed by pre existing lower crust intruded or underplated by mantle derived basaltic magma and 2 extensive magmatic differentiation of the parental magmas in a slow cooling environment the widespread distribution of juvenile granitoids in ne china indicates a massive transfer of mantle material to the crust in a post orogenic tectonic setting several recent studies have documented that juvenile granitoids of paleozoic to mesozoic ages are ubiquitous in the central asian orogenic belt hence suggesting a significant growth of the continental crust in the phanerozoic d 2003 elsevier science b v all rights reserved

chronology and petrogenesis of a 1 8 g lunar granitic clast 14321 1062 abstract a study was undertaken to determine the chronology of a pristine granite clast 1062 from apollo 14 breccia 14321 using rb sr sm nd and 39ar 40ar methods the genesis of the granite as constrained by the isotopic results and trace element characteristics is discussed chronology the rb sr internal isochron is slightly disturbed and yields an age of 4 09 0 11 ae 87 rb 0 0139 ae 1 and an imprecise initial i sr 0 702 008 if two data are excluded the age becomes 4 13 0 03 ae and i sr 0 698 003 the whole rock and mineral separates are extremely radiogenic they yield model ages which are relatively well defined the average model age is 4 12 0 03 ae relative to babi 0 69898 the sm nd internal isochron is also slightly disturbed and gives an age of 4 11 0 20 ae 147 sm 0 00654 ae 1 the 39ar 40ar average age of the non magnetic fraction of the sample yields a slightly younger age of 3 88 0 03 ae k ar constants from steiger and a 1977 the concordancy of rb sr and sm nd internal isochrons with the rb sr model age strongly suggests that the granitic clast formed at 4 1 ae ago in the shallow crust and was later excavated and brecciated about 3 88 ae ago petrogenesis isotopic and trace element data of the lunar granite show large k la and rb sr fractionations small sm nd fractionation and the distinct v shaped ree distribution pattern at the time of crystallization a two stage model involving crystal fractionation followed by silicate liquid immiscibility sli is proposed for lunar granite genesis we propose that the granite can be the immiscible acidic liquid produced by sli from a residual liquid which underwent fractionation of ca 3 of phases with ree distribution coefficients similar to those of phosphate minerals from a highly evolved parental magma with ree contents about twice those of the 15405 85 quartz monzodiorite qmd the extreme scarcity of lunar granitic samples and their young formation ages suggest that they are probably not directly crystallized from the differentiation of the primordial magma ocean our isotopic results and trace elements data from other workers suggest that granites qmd and probably mggabbronorites may be genetically related and may have formed in a plutonic environment similar to gabbro granophyre associations in terrestrial layered intrusions such as the skaergaard intrusions

antipodal focusing of seismic waves observed with the usarray we present an analysis of the mw 5 3 earthquake that occurred in the southeast indian ridge on 2010 february 11 using usarray data the epicentre of this event is antipodal to the usarray providing us with an opportunity to observe in details the antipodal focusing of seismic waves in space and time we compare the observed signals with synthetic seismograms computed for a spherically symmetric earth model prem a beamforming analysis is performed over the different seismic phases detected at antipodal distances direct spatial snapshots of the signals and the beamforming results show that the focusing is well predicted for the first p wave phases such as pkp or pp however converted phases sksp pps show a deviation of the energy focusing to the south likely caused by the earth s heterogeneity focusing of multiple s wave phases strongly deteriorates and is barely observable

high resolution probing of inner core structure with seismic interferometry increasing complexity of earth s inner core has been revealed in recent decades as the global distribution of seismic stations has improved the uneven distribution of earthquakes however still causes a biased geographical sampling of the inner core recent developments in seismic interferometry which allow for the retrieval of core sensitive body waves propagating between two receivers can significantly improve ray path coverage of the inner core in this study we apply such earthquake coda interferometry to 1846 usarray stations deployed across the u s from 2004 through 2013 clear inner core phases pkikp 2 and pkiikp 2 are observed across the entire array spatial analysis of the differential travel time residuals between the two phases reveals significant short wavelength variation and implies the existence of strong structural variability in the deep earth a linear n s trending anomaly across the middle of the u s may reflect an asymmetric quasi hemispherical structure deep within the inner core with boundaries of 99 w and 88 e

sm nd age of lherzolite 67667 implications for the processes involved in lunar crustal formation abstract pristine samples from the lunar highlands potentially offer important information bearing on the nature of early crustal development on all the terrestrial planets one apparently unique sample of this group of lunar crustal rocks the feldspathic lherzolite 67667 was studied utilizing the sm nd radiometric system in an attempt to define its age and the implications of that age for the evolution of the lunar highlands data for 67667 precisely define an isochron corresponding to an age of 4 18 0 07 ae the observed lack of disturbance of the sm nd system of this sample may suggest that this time marks its crystallization at shallow depth in the lunar crust however the possibility that this age as well as those of other highland rocks indicate the time of their impact induced excavation from regions deep enough in the lunar crust to allow subsolidus isotopic equilibrium to be produced or maintained between their constituent minerals is also considered taken together bulk rock sm nd data for four high mg rocks including 67667 indicate that the chemical characteristics of all their source materials were established 4 33 0 08 ae ago and were intimately associated with the parent materials of kreep this finding provides more support for the concept of a large scale differentiation episode early in lunar history the possible roles of the crystallization of a global magma ocean endogenous igneous activity and of planetesimal impact in producing the observed geochemical and chronological aspects of lunar highland rocks are discussed

ages and geodynamic settings of xilamulun mo cu metallogenic belt in the northern part of the north china craton abstract the xilamulun belt along the northern part of the north china craton is located in eastern segment of the central asian orogenic belt and has great economic potential for mo cu mineralization more than ten medium to large ore deposits have been discovered in this region in the recent years the major types of mineralization type include porphyry chehugou mo cu kulitou mo cu xiaodonggou mo and jiguanshan mo quartz vein nianzigou mo xinjing mo epithermal hongshanzi mo u and alteration assemblage liulingou mo the timing of mineralization was previously thought to be yanshanian 208 290 ma however indosinian 260 208 ma ages for intrusions and mineralization have been recognized in recent years based on geochronologic data and regional geological evidence it is suggested that the mineralization in the xilamulun belt was formed during multiple events the mineralization processes are related to a post collisional extension stage 258 210 ma with the generation of the porphyry molybdenum copper deposit a tectonic stress transformation from ns to ew 185 150 ma that gave rise to vein or porphyry molybdenum deposit and a lithospheric thinning stage 140 110 ma with porphyry molybdenum deposit

observations of exotic inner core waves the seismic structure of earth s inner core is highly complex displaying strong anisotropy and further regional variations however few seismic waves are sensitive to the inner core and fundamental questions regarding the origin of the observed seismic features remain unanswered thus new techniques to observe different types of inner core waves are imperative to improve data coverage here we detail our method for detecting exotic inner core phases such as pkjkp and pkiikp using inner core compressional waves as proof of concept we use phase weighted stacking on long period data from a global distribution of stations and employ several synthetic methods including normal mode summation and specfem to identify and confirm the inner core phases we present evidence for two observations of exotic inner core compressional waves and apply the technique to a previously detected inner core shear wave a possible new inner core shear wave remains unconfirmed additionally we show how our method is important for rejecting potential observations and distinguishing between waves with similar traveltime and slowness the method is most successful for detecting exotic inner core compressional waves and will provide a new approach for studying the compressional wave structures in the upper inner core

composite nature of the north china granulite facies belt tectonothermal and geochronological constraints granulite facies rocks are intermittently exposed in a roughly e w trending belt that extends for approximately 2000 km across the north china craton from the helanshan qianlishan wulashan daqingshan guyang and jining complexes in the western block through the huai an hengshan xuanhua and chengde complexes in the trans north china orogen to the jianping western liaoning eastern hebei northern liaoning and southern jilin complexes in the eastern block the belt is generally referred to as the north china granulite facies belt previously interpreted as the lowest part of an obliquely exposed crust of the north china craton recent data indicate that the north china granulite facies belt is not a single terrane instead it represents components of three separate terranes the eastern and western blocks and trans north china orogen each of these units records different metamorphic histories and reflect the complex tectonic evolution of the ncc during the late archean and paleoproterozoic mafic granulites in the eastern block and the yinshan terrane western block underwent medium pressure granulite facies metamorphism at about 2 5 ga with anticlockwise p t paths involving near isobaric cooling following peak metamorphism reflecting an origin related to intrusion and underplating of mantle derived magmas pelitic granulites in the khondalite belt western block underwent medium pressure granulite facies metamorphism at about 2 0 1 9 ga with clockwise p t paths which record the paleoproterozoic amalgamation of the yinshan and ordos terranes to form the western block mafic and pelitic granulites in the trans north china orogen experienced high to medium pressure granulite facies metamorphism at 1 85 ga with clockwise p t paths involving nearly isothermal decompression following peak metamorphism which are in accord with the final collision between the eastern and western blocks to form the north china craton at 1 8 ga the ncgb cannot therefore represent a separate unique terrane instead it reflects the amalgamation of three separate granulite terranes that evolved independently and at different times d 2005 international association for gondwana research published by elsevier b v all rights reserved

time and duration of lunar highlands crust formation abstract all radiometric systems indicate that crust mantle differentiation on the moon is dominated by events which occurred very early in lunar history however due to remaining uncertainties in model parameters and assumptions in the calculation of model ages it is not yet possible to resolve the precise times of occurrence of these events nor the duration of the formation of the highlands crust the strongest time constraints are offered by direct radiometric ages of samples formed during this earliest period two possible candidates for this material norites 78236 and 73255 27 45 were examined utilizing the sm nd radiometric system sm nd systematics of 78236 show post crystallization disturbance but indicate that this norite crystallized in the lunar crust about 4 34 ae ago data for 73255 27 45 define an isochron and yield a crystallization age of 4 23 0 05 ae the initial nd isotopic composition of both norites is within uncertainty of a chondritic reference reservoir at the time of their respective crystallizations the implications for lunar crustal formation persisting over a time span of close to 350 m y are discussed

equatorial anisotropy in the inner part of earth s inner core from autocorrelation of earthquake coda the speed of seismic waves passing through the earth s inner core varies with direction analysis of earthquake seismic data suggests that this directional dependence differs between innermost and outer inner core

isotope analysis of crystalline impact melt rocks from apollo 16 stations 11 and 13 north ray crater rubidium strontium and sm nd isotopic data were obtained for lunar impact melt rocks from apollo 16 stations 11 and 13 as part of the north ray crater target rock consortium study rubidium strontium whole rock data define an isochron age t 3 69 0 16 b y 0 0142 b y 1 and initial 87sr 86sr isr 0 69918 5 for feldspathic microporphyritic fm samples internal rb sr isochrons of t 3 86 0 05 b y isr 0 69952 10 and t 3 76 0 04 b y isr 0 69916 4 were determined for very high alumina vha melt rock 67747 and anorthositic noritic melt rock anmr 67559 respectively t isr for these and other lunar melt rocks were examined to infer the nature of the protolith for the rocks isr values for the an mr and fm rocks are consistent with an anorthositic protolith probably a mixture of nonpristine anorthositic gabbros and pristine anorthosites anorthositic norites norites troctolites and possibly dunites the source protolith of the vha rocks apparently had a significant kreep component and the protolith for apollo 16 kreep must have had nearly the same rb sr ratio as that of apollo 14 kreep two stage model calculations using the t isr parameters suggest that some of the melt rocks were open rb sr systems during impact melting rubidium strontium model ages for the fm and vha rocks show a smoothly monotonic decrease with increasing rb content model ages of the anmr are uniformly low relative to 4 56 b y it is suggested that these effects are due to formation of these rocks by impact partial melting rubidium strontium model ages of the kreep rocks do not vary with rb content suggesting that they were closed rb sr systems during impact melting samarium neodymium data for mineral separates of 67747 showed only a small variation in sm nd ratio and yield an imprecisely defined isochron of 3 6 0 4 b y plagioclase separates of 67559 appear not to have reached nd isotopic equilibrium during impact melting consequently the internal isochron age is also imprecisely defined at 4 0 0 4 b y nd values for the melt rocks are about 1 to 2 at their rb sr or 40ar 39ar ages are consistent with the protolith compositions inferred from the rb sr data and show that lunar crustal sm nd evolution departed from chondritic evolution early in lunar history the average chondritic uniform reservoir chur model age of those anmr and fm rocks that apparently remained closed rb sr and sm nd systems during impact melting is 4 37 0 10 b y consistent with earlier suggestions that the lunar crust formed at about that time the average chur model age of two vha rocks is 4 10 0 15 b y suggesting that these rocks were open sm nd systems as well as open rb sr systems during impact partial melting current hypotheses for the site geology stratigraphy and radiometric age data lead us to suggest that the nectaris basin and the descartes formation were formed about 4 1 b y ago and the imbrium basin and the cayley formation were formed about 3 81 3 86 b y ago the ages of some individual melt rocks probably date local cratering events however

thermochemical convection in earth s inner core summary the dynamics of earth s inner core depends critically on whether it is stably stratified or unstably stratified we propose here a general analysis of the thermal evolution of the inner core whether the geotherm in the inner core is superadiabatic or not depends on the inner core solidification rate on the thermal diffusivity of iron at inner core conditions and on the ratio of the clapeyron slope to the adiabatic gradient in the inner core the temperature field within the inner core can be destabilizing and could drive convection if the growth of the inner core is fast enough the effect of radiogenic heating is probably small and perhaps surprisingly can even stabilize the inner core against convection the uncertainties are such that it is not possible at present to conclude about the likelihood of thermal convection in the inner core but recent estimates of the core mantle boundary cmb heat flux and inner core conductivity favour convection thermal convection is more likely early in the inner core history a consequence of the secular decrease in cooling rate of the core in addition solidification induced partitioning of the light elements may induce a stable density stratification within the inner core we develop a numerical model of thermochemical convection in a growing inner core which couples the evolution and dynamics of the inner core with the thermal and compositional evolution of the outer core melting and crystallization associated with deformation of the inner core boundary icb would be of importance for the style of convection if the viscosity is large but we focus here on the case of low viscosity for which phase change associated with dynamic topography at the icb is expected to play a secondary role in this regime convection is typical of high rayleigh number internally heated convection with cold plumes falling from the icb several possible scenarios can lead to a layered inner core either because of cessation of thermal convection due to the decrease in cooling rate of the core or because of a compositional stratification which can confine convection in the deep inner core or stabilize the whole inner core for each of these scenarios it is possible to find plausible sets of parameters inner core age viscosity magnitude of the compositional stratification for which the radius at which convection stops corresponds to the radius of the seismically inferred innermost inner core

a new model for the dynamic evolution of chinese lithosphere continental roots plume tectonics abstract chinese continental lithosphere comprises three tectonic domains 1 eastern china a region characterized by rifting extensional basins and voluminous basaltic volcanism 2 central china a plexus of cratonic terrains with low heat flow 40 50 mw m2 including the tarim erdos and yangtze blocks welded by pre cenozoic orogenic belts and 3 western china a region comprising the qinghai tibet himalaya orogen the relatively thin crust 35 km and lithosphere 70 km of eastern china is believed to reflect mantle upwelling while near normal crust 45 km and thickened lithosphere 200 km in central china suggest a mantle lithosphere root resembling those inferred for the kaapvaal and siberian cratons thickened crust 70 km and lithosphere 150 km in western china reflect the advanced development of an orogen root the lower density and relative buoyancy of central cratonic mantle roots appear to have contributed to the long term tectonic stability of the central chinese lithospheric blocks in contrast gravitational instability produced by thickening of the denser western chinese lithosphere and the resulting subsidence and eventual delamination of orogenic roots are believed to have led to postorogenic extensional collapse although the geological relationships suggest compressional forces caused both mountain building and orogen root development extensional stress resulting from gravitational collapse is believed to have induced lithospheric and crustal thinning with concomitant reduction of topography the term continental roots plume tectonics has been adopted to describe the configuration and dynamic condition of subcontinental lithosphere and upper mantle beneath china accordingly it is proposed that supracrustal tectonic forms represent the surface expressions of and responses to deep continental roots plume tectonics while the prevailing view is that the western orogenic belt is not genetically related to eastern continental rifting such a relationship is inherent to the continental roots plume tectonics model it is further proposed that the formation of orogenic lithosphere roots triggered eastward extrusion of the asthenosphere along the 400 km depth mantle interface and in response to subduction at the eastern margin produces plume like upwelling beneath eastern china we suggest that processes involved in continental roots plume tectonics are directly responsible for the formation and evolution of the eurasian supercontinent

a young solidification age for the lunar magma ocean abstract the time at which the lunar magma ocean solidified can be determined from the lu hf isotope systematics of lunar rocks derived from magma sources that formed during crystallization of the lunar magma ocean the final magma ocean crystallization product termed urkreep is enriched in incompatible elements including k ree and p we have determined the initial hf isotopic compositions of four samples two kreep basalts and two mg suite norites the incompatible trace element compositions of these samples are controlled by an urkreep component and therefore the initial hf isotopic compositions of these samples represent the hf isotopic evolution of urkreep in order to correct the effects of neutron irradiation on the hf isotopic compositions of these samples we have developed a model that uses the stable hf and sm isotopic compositions measured on an irradiated sample to determine and correct for the thermal and epithermal neutron fluence that has modified the hf isotopic composition of the sample we use our corrected results to calculate a 176 lu 176 hf urkreep model age of 4353 37 ma and the 176 lu 177 hf of urkreep to be 0 0153 0 0033 the lu hf model age is concordant with the re calculated sm nd urkreep model age of 4389 45 ma and we take the average of these ages 4368 29 ma to represent the time at which urkreep formed this age is concordant with the age of the most reliably dated ferroan noritic anorthosite as well as 142 nd model ages for the formation or re equilibration of mare basalt sources taken together these ages indicate that the moon experienced a widespread large scale magmatic event around 4370 ma most plausibly attributed to solidification of the lunar magma ocean

seismic velocity and attenuation structures in the top of the earth s inner core 1 we collect a global data set of pkikp and pkikp phases recorded by the global seismic network and many regional seismic arrays to study seismic structure in the top of the earth s inner core the pkikp and pkikp observations show different characteristics between those sampling the eastern hemisphere 40 e 180 e of the inner core and those sampling the western hemisphere 180 w 40 e pkikp phases 1 arrive about 0 4 s earlier than the theoretical arrivals based on preliminary reference earth model prem for those sampling the eastern hemisphere of the inner core and about 0 3 s later for those sampling the western hemisphere 131 141 2 bifurcate at smaller epicentral distances for those sampling the eastern hemisphere compared to those sampling the western hemisphere and 3 have smaller amplitudes for those sampling the eastern hemisphere waveform modeling of these observations suggests two different types of models for the two hemispheres of the top of the inner core with a model in the eastern hemisphere having a p velocity increase of 0 765 km s across the inner core boundary a small radial velocity gradient of 0 000055 km s km and an average q value of 250 and a model in the western hemisphere with a p velocity increase of 0 633 km s across the inner core boundary a radial velocity gradient of 0 000533 km s km and an average q value of 600 the hemispherical difference of seismic structures may be explained by different geometric inclusions of melt and or different alignments of iron crystals with anisotropic properties in both velocity and attenuation we speculate that this large scale pattern of seismic heterogeneities may be caused by a large scale heat flow anomaly at the bottom of the outer core and or different vigorousness of convection in the top of the inner core between the two hemispheres

origin of the lunar highlands mg suite an integrated petrology geochemistry chronology and remote sensing perspective the mg suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation this review examines the mineralogy geochemistry petrology chronology and the planetary scale distribution of this suite of highlands plutonic rocks presents models for their origin examines petrogenetic relationships to other highlands rocks and explores the link between this style of magmatism and early stages of lunar differentiation of the models considered for the origin of the parent magmas for the mg suite the data best fit a process in which hot solidus temperature at 2 gpa 1600 to 1800 c and less dense 3100 kg m3 early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn some decompressional melting would occur but placing a hot cumulate horizon adjacent to the plagioclase rich primordial crust and kreep rich lithologies at temperatures of 1300 c would result in the hybridization of these divergent primordial lithologies producing mg suite parent magmas as urkreep primeval kreep is not the petrologic driver of this style of magmatism outside of the procellarum kreep terrane pkt mg suite magmas are not required to have a kreep signature evaluation of the chronology of this episode of highlands evolution indicates that mg suite magmatism was initiated soon after primordial differentiation 10 m y alternatively the thermal event associated with the mantle overturn may have disrupted the chronometers utilized to date the primordial crust petrogenetic relationships between the mg suite and other highlands suites e g alkali suite and magnesian anorthositic granulites are consistent with both fractional crystallization processes and melting of distinctly different hybrid sources

discovery of sapphirine bearing mg al granulites in the north china craton implications for paleoproterozoic ultrahigh temperature metamorphism abstract we report here for the first time the occurrence of mg al granulites within the khondalite belt of the north china craton and provide robust evidence for extreme crustal metamorphism at ultrahigh temperature uht conditions in this region the uht indicator assemblages in these rocks include equilibrium sapphirine quartz high alumina orthopyroxene sillimanite quartz and high temperature perthites the surrounding khondalites also carry spinel quartz equilibrium assemblage the sapphirines occurring in various microstructural associations are markedly magnesian x mg 0 69 0 77 with a composition varying from 7 9 3 to 2 2 1 end members spinel is a solid solution of mg spinel and hercynite x mg 0 41 0 54 with zno content varying from 0 48 to 1 79 wt garnet shows a compositional range between pyrope and almandine x mg 0 39 0 48 with minor grossular 2 6 3 8 mol and spessartine 0 5 1 8 mol the orthopyroxenes display marked compositional variations in terms of al 2 o 3 content with the core of the medium grained orthopyroxene adjacent to sillimanite in the matrix showing the highest al 2 o 3 content 8 4 wt the history of prograde to peak metamorphism of these rocks is indicated by inclusions of sapphirine spinel quartz and sillimanite within garnet sapphirine formed during the peak stage through the reaction spl qtz sil spr occurrence of sapphirine and quartz inclusions trapped in sillimanite suggests the reaction spr qtz grt opx sil a series of retrograde reactions are observed in these rocks as corona and symplectite textures around early coarse grained minerals such as opx sil qtz crd grt sil qtz crd grt qtz crd opx grt o 2 crd qtz fe 2 o 3 in mag or ilm and finally opx kfs h 2 o bt qtz whereas the stability of sapphirine quartz and orthopyroxene sillimanite quartz in the matrix assemblage suggests t 1000 c and p 10 kbar peak metamorphism conventional geothermobarometric estimates confirm the ultrahigh temperature nature and also trace the retrograde conditions 930 970 c at p 10 kbar al in opx 900 1000 c perthite 930 990 c grt opx and 910 940 c sapphirine spinel electron microprobe dating of monazites in textural association with the uht assemblages yield a sharply defined isochron age of 1917 48 ma which correlates with the 1927 11 ma obtained in a previous study from monazites in the surrounding khondalites carrying spinel quartz assemblage an evaluation of the assemblages and textures using appropriate petrogenetic grids indicate that following peak ultrahigh temperature conditions the rocks underwent initial isobaric cooling and subsequent isothermal decompression and we interpret these trajectories to be part of an overall anti clockwise p t evolution the study area located within the northern margin of the north china craton defines a collisional orogenic belt where continental collision and deep subduction was possibly followed by extensional collapse of the orogen evidence for the extensional phase is provided by the several mafic magmatic intrusives of paleoproterozoic age occurring in the region which suggest a possible link between the thermal anomaly associated with extreme crustal metamorphism in this region with mantle derived magmas the uht metamorphism in north china craton coincided with the assembly of the paleoproterozoic supercontinent columbia

onset and orientation of convection in the inner core summary thermal convection is an effective mechanism for producing seismic anisotropy in many regions of the earth however it is not known whether this mechanism is relevant for the anisotropy observed in the inner core here we establish the requirements for convection in the inner core by combining a simple model for inner core growth with a solution for conductive cooling thermal convection is likely during the early stages of inner core growth but becomes less probable as the volume of the inner core increases the transition to a non convecting state is driven by changes in both the thermal and compositional stratification a decrease in the vigour of convection near the transition to a non convecting state isolates the pattern of flow with the lowest critical rayleigh number rac we apply a perturbation method based on rayleigh s principle to calculate rac in a hydrostatically flattened inner core we find that the final pattern of flow is characterized by a degree l 1 mode in which the axis of upwelling aligns with the rotation axis this pattern of flow has the symmetry required to explain the distribution of anisotropy at the largest scales the extent of crystal alignment depends on the level of stress during this final convective state one possible interpretation of the observed anisotropy is that the final convective state establishes the large scale crystal alignment without completely erasing a more complicated texture that developed when convection was more vigorous

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

waveform search for the innermost inner core abstract waveforms of the pkikp seismic phase are inconsistent with the effects of a sharp boundary at 300 km radius of an inner most inner core seismograms synthesized for the distance range 150 to 180 in models having a discontinuity at 300 km radius in the inner core exhibit focused diffractions around the innermost sphere at antipodal range that are inconsistent with observed pkikp waveforms a few examples however can be found of pkikp complexity near 165 consistent with a triplication created by a 475 km radius discontinuity a rapid change in the magnitude and variance of seismic attenuation of pkikp whose rays turn between 400 and 600 km radius is also observed consistent with an innermost sphere of low regionally uniform seismic attenuation models predicting waveforms in agreement with observed waveforms have either a transition in elastic and anelastic properties spread over a depth interval greater than 100 km or an innermost sphere of differing elastic properties that exceeds 450 km radius the weak but suggestive evidence for an innermost inner core may simply represent a transition in fabric spread over 100 km or more centered near 500 km radius this change may signify the end stage of solidification flow and re crystallization resulting in the highest ordering and largest grain sizes of intrinsically anisotropic crystals

constraints on the timing of uplift of the yanshan fold and thrust belt north china this paper reports in situ u pb ages and hf isotopic data on detrital zircons from paleozoic to late mesozoic strata in the xishan area near beijing that provide important constraints on the evolution and paleogeography of the northern part of the north china craton ncc zircons from carboniferous to late mesozoic sandstones are characterized by three major groups of u pb ages 2 5 2 3 ga 1 9 1 7 ga and late phanerozoic ages the neoarchean and paleoproterozoic zircons and some phanerozoic zircons have negative ehf t values similar to igneous zircons from intrusive rocks known from the ncc indicating that the source of the sandstones was locally derived however late triassic to late jurassic 205 158 ma sandstones contain a group of phanerozoic zircons with positive ehf t values distinct from known igneous zircons in the ncc suggesting an exotic source the nearest potential source is the xing meng orogenic belt xmob to the north of the ncc where considerable amounts of juvenile crustal materials exist it is concluded that there are two sudden shifts in source provenances of the xishan sediments from the ncc before the late triassic to a mixed source from the ncc and xmob during the late triassic to late jurassic and then from the ncc again during the late jurassic 158 ma the first shift in source resulted from the exhumation and denudation of rocks due to uplift of the xmob which coincided with post collisional extension in the late triassic and intraplate extension of the ncc in the middle to late jurassic the second source shift resulted from the uplift of the yanshan fold and thrust belt thus constraining the timing of this to the late jurassic

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

antipodal seismic observations of temporal and global variation at earth s inner outer core boundary 1 we have found two pairs of earthquake doublets closely located antipodally on one diametral axis between tonga algeria and several other events on other axes these doublets show significant correlation and exhibit seismic phases traversing the core that cannot be explained by a standard radial earth model such as prem the antipodal waveform data are highly variable between axes the observed variability of the waveforms indicates global variations in the structure above and below the inner outer core boundary region we have found evidence for a regional low velocity zone at the base of the outer core corresponding with a decadal temporal variation 0 55 s in seismic energy traversing the top of the inner core we propose an antipodal seismic array to constrain and to provide further progress for the study of the inner and outer core

recognition of the latest permian to early triassic cu mo mineralization on the northern margin of the north china block and its geological significance abstract in this paper we present newly obtained molybdenite re os ages for the chehugou copper molybdenum deposit and the yuanbaoshan molybdenum mineral locality from the chifeng area on the northern margin of the north china block combined with u pb zircon ages of the host granites the re os isochron age of six molybdenite samples from the chehugou deposit is 257 5 2 5 ma and one molybdenite sample from the yuanbaoshan locality yields a re os model age of 248 0 2 7 ma these ages clearly indicate the signature latest permian to early triassic cu mo or mo mineralization that has not been previously recognized zircon la icp ms u pb dating shows that the host granites of the chehugou deposit and yuanbaoshan locality formed in the late devonian 376 3 ma and late permian 269 3 ma respectively and is not of jurassic age as previously thought the latest permian to early triassic cu mo mineralization is likely related to extension due to final closure of the paleo asian ocean and amalgamation of the mongolian arc terranes with the northern north china block the establishment of a latest permian to early triassic age for mineralization should encourage renewed exploration aimed at the discovery of new mo or cu mo resources along the northern margin of the north china block

subdivision of the mg suite noritic rocks into mg gabbronorites and mg norites mg suite noritic rocks can be divided into two groups the mg gabbronorites and the mg norites the rocks of these groups differ in ratios of high ca pyroxene to total pyroxene compositions of pyroxene and plagioclase assemblages of ti nb and zr bearing minerals compositions of chrome spinel bulk rock ti sm and sc sm and measured ages the two groups probably crystallized from different types of parent magmas two hypotheses are offered for the differences in composition of the parent magmas one hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas the other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation

ages of pristine noritic clasts from lunar breccias 15445 and 15455 abstract rb sr and sm nd isotopic studies were undertaken of two apollo 15 breccias 15445 and 15455 collected near spur crater on the apennine front seven pristine lithic clasts including four norites one anorthositic norite one troctolitic anorthosite and one spinel troctolite as well as a matrix sample of 15445 were analysed in addition a k ar age determination was also made for a plagioclase separate from a different anorthositic norite clast sm nd isotopic data of a pristine mg norite sample 15445 17 from the large white clast b of breccia 15445 yielded a precise internal isochron age of 4 46 0 07 ga for 147 sm 0 00654 ga 1 and an initial 143 nd 144 nd of 0 506058 0 000078 normalized to 148 nd 144 nd 0 24308 corresponding to an initial nd of 0 71 however sm nd isotopic results of another mg norite sample 15445 247 chipped from the same clast b about 1 cm away from 15445 17 yielded a significantly younger isochron age of 4 28 0 03 ga and a higher initial 143 nd 144 nd of 0 506246 0 000037 corresponding to an initial nd of 0 35 the sm nd data indicate that clast b is heterogeneous and contains at least two similar lithologies the rb sr isotopic systems were severely disturbed for both norites no useful isochron ages were observed the sm nd age and nd data for a 15 mg norites 15445 17 and 15445 247 a 17 mgnorite 78236 and two mg gabbronorites 73255 27 45 and 67667 are clearly resolved from each other four distinct parental magmas are required for derivation of these two major groups of mg suite noritic rocks the rb sr isotopic system of an anorthositic norite clast 15455 228 was slightly disturbed and isotopic data defined an isochron age of 4 59 0 13 ga for 87 rb 0 0139 ga 1 or 4 55 0 13 ga for 87 rb 0 01402 ga 1 the corresponding initial 87 sr 86 sr for the rock is 0 69899 0 00006 and is in satisfactory agreement with the luni value of nyquist et al 1974 the sm nd system is more disturbed than the rb sr system for this rock a tie line between whole rock samples and a pyroxene separate gives a sm nd age of 4 53 0 29 ga which is in nominal agreement with the rb sr isochron age the 39ar40ar age of a plagioclase separate of the rock has a weighted average value of 3 83 ga suggesting that the age was reset by the imbrium impact event probably the sm nd and rb sr systems of the clast were also partly reset by this event our age results indicate that some mg suite rocks are as old as ferroan anorthosite suite rocks furthermore age data of three major crustal rocks a mg suite a ferroan anorthosite suite and an evolved suite show that they all have variable ages these observations are difficult to explain by the magma ocean hypothesis alone petrogenetic processes such as production of mg suite rocks by serial magmatism walker 1983 of ferroan anorthosite suite rocks by multiple diapiric intrusions longhi and ashwal 1985 and evolved suite rocks by continuous magmatism meyer et al 1988 1989 probably all played a role these processes seem to be able to accommodate the wide ranges of ages and different origins observed for lunar crustal rocks

a review of lunar chronology revealing a preponderance of 4 34 4 37 ga ages in this study data obtained from sm nd and rb sr isotopic measurements of lunar highlands samples are renormalized to common standard values and then used to define ages with a common isochron regression algorithm the reliability of these ages is evaluated using five criteria that include whether 1 the ages are defined by multiple isotopic systems 2 the data demonstrate limited scatter outside uncertainty 3 initial isotopic compositions are consistent with the petrogenesis of the samples 4 the ages are defined by an isotopic system that is resistant to disturbance by impact metamorphism and 5 the rare earth element abundances determined by isotope dilution of bulk of mineral fractions match those measured by in situ analyses from this analysis it is apparent that the oldest highlands rock ages are some of the least reliable and that there is little support for crustal ages older than 4 40 ga a model age for ur kreep formation calculated using the most reliable mg suite sm nd isotopic systematics in conjunction with sm nd analyses of kreep basalts is 4389 45 ma this age is a good match to the lu hf model age of 4353 37 ma determined using a subset of this sample suite the average modelmore age of 4353 25 ma determined on mare basalts with the 146sm 142nd isotopic system with a peak in pb pb ages observed in lunar zircons of 4340 20 ma and the oldest terrestrial zircon age of 4374 6 ma the preponderance of ages between 4 34 and 4 37 ga reflect either primordial solidification of a lunar magma ocean or a widespread secondary magmatic event on the lunar nearside the first scenario is not consistent with the oldest ages reported for lunar zircons whereas the second scenario does not account for concordance between ages of crustal rocks and mantle reservoirs less

geochronology of high k aluminous mare basalt clasts from apollo 14 breccia 14304 abstract rb sr k ar and sm nd age determinations were undertaken for two aluminous mare basalt clasts 127 and 128 of high potassium abundances from apollo 14 breccia 14304 genesis of the basalts is discussed in the context of the ages and the rb sr and sm nd isotopic evidence the rb sr isochrons for these rocks are well defined and yield slightly different old ages of 3 95 0 04 ga and 3 99 0 02 ga relative to 87 rb 0 0139 ga 1 and identical low initial 87 sr 86 sr i sr of 0 69938 0 00011 and 0 69938 0 00007 respectively the age and i sr results suggest that these basalts probably represent two related flows derived from a common source the sm nd internal isochron for the basalt clast 14304 128 is also well defined but yields a less precise age of 4 04 0 11 ga and an initial nd of 0 27 2 61 the average 39 ar 40 ar plateau age of the whole rock sample of 14304 127 yields a slightly younger age of 3 85 0 04 ga the concordancy of rb sr and smnd isotopic ages for these rocks strongly suggest that they were crystallized at 3 95 3 99 ga ago the younger 39 ar 40 ar age was probably reset by the imbrium event 3 85 ga ago the rb sr and sm nd age data also show that these basalts are younger than most of the apollo 14 mare basalts but distinctly older than the very high potassium vhk mare basalts there seems to be an anti correlation between potassium abundances and ages of aluminous mare basalts at the apollo 14 site the age and the i sr value for these basalts show an approximately ten fold fractionation of rb sr for a two stage evolution model however the age and the nd values indicate no significant fractionation of sm nd the large rb sr enrichment but minimum sm nd fractionation relative to their source materials can be explained by the assimilation model proposed recently for vhk basalt genesis involving granitic material and aluminous basaltic magma aluminous mare basalt volcanism was probably derived from shallow mantle sources underlying thick highland crust and these magmas are more likely to be contaminated by crustal materials on ascent than are other types of mare magmas

petrological evolution of the crust and mantle in its simplest form crust mantle evolution can be thought of as a study of the processes by which material is lost from the mantle and forms new crust the overall goal is achievement of mass balance between the average composition of material known to have been added to the crust and the estimated average composition of the entire crust attainment of this goal for the earth has been elusive primarily because the materials available for study have generally been involved in several stages of evolution including fractionation within both the crust and mantle and recycling of material from crust to mantle thereby complicating the interpretation of available data although the overall composition of the continental crust generally has been modelled as andesitic taylor and mclennan 1981a the present upper continental crust is granodioritic and requires a more mafic lower crust it has been proposed taylor and mclennan 1981a that originally the archean crust had an andesitic composition throughout its volume and that partial melting in the lower crust developed more felsic melts that rose to enrich the upper crust leaving a more mafic residuum of lower crust this concept has been challenged by weaver and tarney 1981a who argue that the granulites of presumed lower crustal origin do not have the correct compositions for this model if one considers more recent additions to the crust from the mantle over the past several hundred million years it appears that these latest additions are basaltic with very little if any granitic additions in fact barker 1981 in his introduction to a special issue of jgr on granites and rhyolites states to date no one has demonstrated that such magmas may form in the mantle indeed much experimental and geochemical work indicates that such siliceous liquids cannot originate there therefore such magmas must be generated in the crust in island arc environments where the average composition of added material normally is thought to be andesitic a anderson 1982 has shown that the parent melt is basaltic not andesitic in addition kay 1980 has shown that the k content of the newly added material is less than the average k content of the previously existing crust in the oceanic crust the additions from the mantle are basaltic and according to o hara 1982 probably are derived from very mafic picritic melts as parents continental flood basalts which have also added material from mantle to crust also are clearly derived from basaltic parental melts basaltic volcanism study project 1981 thus the evidence for the nature of material subtracted from the mantle and added to the crust for the past several hundred million or perhaps a billion years points to very mafic melts this contrasts significantly with the overall andesitic composition of continental crust it implies furthermore that if the overall archean crustal composition was andesitic as estimated by taylor and mclennan 1981a then additions to the crust have become more mafic with time a concept in direct conflict with most models in which secular trends are from mafic to felsic with time veizer and jansen 1979 and mclennan et al 198o a question which is beginning to appear either explicitly or implicitly is whether crustal volcanic rocks or the crust as a whole really represents the parent melt that formed in the mantle a anderson 1982 o hara 1982 and nisbet and walker 1982

geochronology and petrogenesis of apollo 14 very high potassium mare basalts rb sr k ar and sm nd isotopic studies were undertaken for two apollo 14 very high potassium vhk mare basaltic clasts from breccias 14305 and 14168 the samples are distinctly more radiogenic than other lunar mare basalts rb sr data for the whole rock and mineral separates determine internal isochrons corresponding to essentially identical ages of 3 83 0 08 b y and 3 82 0 12 b y for samples 14305 and 14168 respectively for 87rb 0 0139 b y 1 their corresponding initial 87sr 86sr ratios are indistinguishable and are 0 6995 0 0005 and 0 6997 0 0004 respectively the 39ar 40ar age spectra for the two samples are very similar and give identical plateau ages of 3 85 0 02 b y for 14305 and 3 85 0 05 b y for 14168 the identical rb sr and k ar isotopic results for the two rocks indicate that they could be derived from the same flow the sm nd isotopic data of whole rock and mineral separates for the two vhk basalts define an internal isochron age of 3 94 0 16 b y for 147sm 0 00654 b y 1 and an initial 143nd 144nd of 0 50673 21 the averaged model age relative to the chondritic initial 143nd 144nd of 0 505893 for the basalts is 4 56 0 04 b y the concordance of rb sr k ar and sm nd ages strongly suggests that vhk basalts crystallized from a melt 3 85 b y ago the rb sr and sm nd isotopic data indicate that vhk basalts show very large rb sr fractionation but no significant sm nd fractionation at the time of crystallization the source material for these basalts had a rb sr ratio similar to those of apollo 14 high a1 mare basalts and a nearly chondritic sm nd ratio extreme enrichments of rb sr and k la during the formation of vhk basalts can be adequately explained by an assimilation model that involves basalt granite interaction k rb rich components of granitic wall rocks in highland crust were selectively introduced into ascending hot high a1 mare basaltic magma upon contact a similar crustal assimilation process has been frequently observed in terrestrial mantle derived magma that ascended through the continental crust

the innermost inner core of the earth evidence for a change in anisotropic behavior at the radius of about 300 km since the discovery of the inner core in 1936 no additional spherical subshell of the earth has been observed based on an extensive seismic data set we propose the existence of an innermost inner core with a radius of 300 km that exhibits a distinct transverse isotropy relative to the bulk inner core specifically within the innermost inner core the slowest direction of wave propagation is 45 from the east west direction in contrast the direction of the slowest wave propagation in the overlying inner core is east west the distinct anisotropy at the center of the earth may represent fossil evidence of a unique early history of inner core evolution

isotopic analysis of basaltic fragments from lunar breccia 14321 chronology and petrogenesis of pre imbrium mare volcanism fragments of aluminous mare basalts high potassium hk aluminous mare basalts and very high potassium vhk mare basalts from apollo 14 breccias have been studied extensively rb sr isochron ages of aluminous mare basalts reported herein range from 3 96 to 4 24 and possibly up to 4 33 ga 87rb 0 0139 ga 1 they include and extend the range for the oldest mare basalts reported clasts of aluminous basalts from breccia 14321 though similar to each other in petrography mineralogy and major element composition have widely differing trace element abundances and are separable into chemical subgroups dickinsonet al 1985 shervaiset al 1985a rb sr and sm nd isotopic analysis of the grouped rocks of dicktnsonet al 1985 grouped rocks hereinafter and hk and vhk basalts shihet al 1986a b 1987 indicates that they differ with respect to time of crystallization t vs initial isotopic composition i parameters t i plots in a systematic way data for this set of rocks suggests radiogenic growth of 87sr86sr in the basalt source region corresponding to 87rb86sr 0 06 similar to the whole moon value earlier proposed nyquistet al 1977 tridymite ferrobasalt and olivine basalt from 14321 display parent daughter evolution distinct from the grouped rocks of dickinsonet al 1985 and the hk and vhk rocks and do not appear to be isotopically related to these rocks assimilation of kreep dickinsonet al 1985 does not appear to be a reasonable mechanism for forming the grouped basalts but assimilation of urkreep residuals binder 1985 or a granitic component shihet al 1986a b 1987 by more primitive magma are alternative possibilities for explaining their trace elemental and isotopic characteristics nd values for the three whole rocks that were analyzed are near 0 the value for an undifferentiated moon these rocks may be linked to the mg suite of highland rocks

geochronology petrogenesis and tectonic implications of granites from the fuxin area western liaoning ne china article i nfo new geochemical and sr nd isotopic data from the ping andi granitic pluton in the fuxin area which straddles the north china craton ncc and the central asian orogenic belt caob border are presented here to discuss the geochronology petrogenesis and tectonic implications petrographically the ping andi granites contain monzogranites to minor granodiorites they are high k calc alkaline series silica rich sio2 66 78 wt peraluminous a cnk 0 98 1 10 with enrichment in lree lan ybn 6 51 8 53 moderately negative eu anomalies eu eu 0 33 0 90 with enrichment in lile rb and k and with depletion in hfse nb ti and p they also have slightly negative and positive end t 1 1 0 4 low initial isr 0 70587 0 70620 and young depleted mantle model ages tdm2 911 1027 ma the emplacement of the ping andi granites took place at 150 ma as revealed by whole rock rb sr isochron age the petrography geochemistry and isotopic compositions indicate that they are i type and were the result of partial melting of mixed sources composed of a juvenile component and a pre existing crust coupled with plagioclase dominated fractionation and that there was a significant crustal growth in the phanerozoic in the northern margin of the ncc the formation of the ping andi granites was related to the tectonic transformation from the convergent tectonic regime of paleo asian ocean to that of the paleo pacific ocean which also induced

detection of inner core solidification from observations of antipodal pkiikp pkiikp waves reflected from the underside of the inner core boundary are very sensitive to the s velocity in the uppermost 80 km of the inner core at antipodal distances undergoing a phase change and a factor of 4 amplification as the distance approaches 180 modeled pkiikp waveforms are consistent with a near zero shear modulus in the uppermost inner core in a 20 40 km thick patch beneath the eastern equatorial hemisphere this bright spot of pkiikp reflection correlates with a thin zone of low p velocity inferred from the complexity of pkikp waveforms sampling this patch estimates of grain sizes from seismic attenuation the absence of backscattered pkikp coda in this region and a prediction for enhanced heat flow through this patch suggest that it is a region of solidification rather than melting

formation and tectonic evolution of southeastern china and taiwan isotopic and geochemical constraints abstract the southern part of china consists of the proterozoic yangtze craton and the phanerozoic south china foldbelts including the himalayan foldbelt of taiwan models for continental growth have been many and controversial isotopic and geochemical data from mesozoic and younger granitoids and sediments are used here to place constraints on the tectonic evolution of southeastern china and to evaluate whether the young phanerozoic foldbelts are representative of old rejuvenated landmass whether they characterize crustal accretion through successive subduction processes hence suggesting a net growth of continental mass or whether they represent some intermediate situation available sm nd isotopic data for phanerozoic granitoids and metasediments from the south china foldbelts and taiwan invariably show proterozoic model ages t dm ranging from 1 to 2 5 ga with a mean of 1 54 0 30 1 ga all rocks have negative nd t values 2 to 15 suggesting variable but important contributions of old continental materials to the sources of the phanerozoic rocks obviously they do not represent wholesale growth of continental mass the granitoids of the south china foldbelts have multiple origins as viewed from their chemical and isotopic characteristics secular geochemical variation has been established for inland granitoids of proterozoic to mesozoic age their high i sr values 0 710 0 737 suggest that most granitoids are essentially anatectic products of ancient continental crust this is compatible with remelting via microcontinental collision or terrane accretion repeated intracrustal reprocessing by partial fusion and differentiation has undoutedly contributed to important mineralization mesozoic granitoids excluding a type alkaline granites in the coastal region and taiwan show relatively low i sr 0 705 0 710 and high nd values implying that greater amounts of mantle components have been added to ancient continental material in the generation of these rocks this means that mesozoic magmatism in the coastal region resulted from subduction of a paleo pacific plate kula beneath the asian continent the overall geochemical evidence seems to be consistent with a model of serial collisions between microcontinental blocks for the bulk of the south china foldbelts the latest arc continent collision began about 4 ma ago in eastern taiwan

chronologic implications for slow cooling of troctolite 76535 and temporal relationships between the mg suite and the ferroan anorthosite suite abstract ages have been obtained using the 87 rb 87 sr 147 sm 143 nd and 146 sm 142 nd isotopic systems for one of the most slowly cooled lunar rocks apollo 17 mg suite troctolite 76535 the 147 sm 143 nd 146 sm 142 nd and rb sr ages derived from plagioclase olivine and pyroxene mineral isochrons yield concordant ages of 4307 11 ma 4299 29 35 ma and 4279 52 ma respectively these ages are slightly younger than the age determined on ferroan anorthosite suite fas rock 60025 and are therefore consistent with the traditional magma ocean model of lunar differentiation in which the mg suite is intruded into the anorthositic crust however the sm nd ages record when the rock passed below the closing temperature of the sm nd system in this rock at 825 c whereas the rb sr age likely records the closure temperature of 650 c a cooling rate of 3 9 c ma is determined using the ages reported here and in the literature and calculated closure temperatures for the ar ar pb pb rb sr and sm nd systems this cooling rate is in good agreement with cooling rates estimated from petrographic observations slow cooling can lower apparent sm nd crystallization ages by up to 80 ma in the slowest cooled rocks like 76535 and likely accounts for some of the variation of ages reported for lunar crustal rocks nevertheless slow cooling cannot account for the overlap in fas and mg suite rock ages instead this overlap appears to reflect the concordance of mg suite and fas magmatism in the lunar crust as indicated by ages calculated for the solidus temperature of 76535 and 60025 of 4384 24 ma and 4383 17 respectively not only are the solidus ages of 76535 and 60025 nearly concordant but the sm nd isotopic systematics suggest they are derived from reservoirs that were minimally differentiated prior to 4 38 ga although the sr isotopic composition of 60025 indicates its source was minimally differentiated the sr isotopic composition of 76535 indicates it underwent fractionation just prior to solidification of the 76535 these observations are consistent with both a magma ocean or a serial magmatism model of lunar differentiation in either model differentiation of lunar source regions must occur near the solidification age of thee samples perhaps the best estimate for the formation age of lunar source regions is the rb sr model age of the 76535 source region age of 4401 32 ma this is in good agreement with sm nd model ages for the formation of ur kreep and suggests that differentiation of a least part of the moon could not have occurred prior to 4 43 ga

detecting seismic anisotropy above the 410 km discontinuity using reflection coefficients of underside reflections abstract we investigate the effect of various types of deformation mechanisms on the reflection coefficients of p and s waves underside reflections off the 410 km discontinuity to develop a diagnostic tool to detect the style of deformation at boundary layers we calculate the reflection coefficient for p and sh underside reflections using velocity perturbations resulting from aligned minerals above the 410 km discontinuity for different deformation scenarios the results show that in the case of an anisotropic olivine layer above an isotropic wadsleyite layer the p wave reflection coefficient amplitudes are only slightly influenced by the joint effect of angle of incidence and the strength of imposed deformation without any polarity reversal and for all deformation styles for the sh wave underside reflections the incidence angle for which a polarity reversal occurs changes with distance for all scenarios and in addition changes with azimuth for shear deformation scenarios these differences in amplitude and polarity patterns of reflection coefficients of different deformation geometries especially for s wave at shorter distances potentially provide a possibility to distinguish between different styles of deformation at a boundary layer we also show a first test using currently available elastic constants of anisotropic wadsleyite beneath anisotropic olivine

constraints on the formation age and evolution of the moon from 142 nd 143 nd systematics of apollo 12 basalts the moon likely formed as a result of a giant impact between proto earth and another large body the timing of this event and the subsequent lunar differentiation timescales are actively debated new high precision nd isotope data of apollo mare basalts are used to evaluate the low ti high ti and kreep mantle source reservoirs within the context of lunar formation and evolution the resulting models are assessed using both reported 146sm half lives 68 and 103 myr the linear relationship defined by 142nd 143nd systematics does not represent multi component mixing and is interpreted as an isochron recording a mantle closure age for the sm nd system in the moon using a chondritic source model with present day 142nd of 7 3 the mare basalt mantle source reservoirs closed at 4 45 09 10 ga t1 2sm146 68 myr or 4 39 14 16 ga t1 2sm146 103 myr in a superchondritic 2 stage evolution model with present day nd142 of 0 mantle source closure ages are constrained to 4 41 08 10 t1 2sm146 68 myr or 4 34 14 15 ga t1 2sm146 103 myr the lunar mantle source reservoir closure ages 4 5 ga may be reconciled by 3 potential scenarios first the moon formed later than currently favored models indicate such that the lunar mantle closure age is near or at the time of lunar formation second the moon formed ca 4 55 to 4 47 ga and small amounts of residual melts were sustained within a crystallizing lunar magma ocean lmo for up to ca 200 myr from tidal heating or asymmetric lmo evolution third the lmo crystallized rapidly after early moon formation thus the sm nd mantle closure age represents a later resetting of isotope systematics this may have resulted from a global wide remelting event while current earth moon formation constraints cannot exclusively advocate or dismiss any of these models the fact that u pb ages and hf isotopes for jack hills zircons from australia are best explained by an earth that re equilibrated at 4 4 ga or earlier following the moon forming impact does not favor a later forming moon if magma oceans crystallize in a few million years as currently advocated then a global resetting possibly by a large impact at 4 40 to 4 34 ga such as that which formed the south pole aitken basin best explains the late mantle closure age for the coupled sm nd isotope systematics presented here

structure and dynamics of earth s inner core abstract the seismological exploration of the earth s inner core has revealed unexpected and puzzling structural complexities its elastic anisotropy is now well established and has been shown to vary spatially there is a well defined hemispherical dichotomy in anisotropy and attenuation and significant variations in the radial direction with weaker anisotropy in the uppermost regions and possibly different properties in an innermost inner core of radius 300 600 km perhaps even more puzzling is the observation of a stably stratified layer at the base of the outer core which has recently been proposed to result from melting of inner core material if confirmed the presence of this layer has major implications for our understanding of convection in the outer core inner core differential rotation with respect to the mantle remains controversial we will review here recent progress in understanding the dynamics of the inner core a number of different models have been proposed for the development of the inner core s structure and formation of the stable layer at the base of the outer core and particular care will be taken to clarify under which conditions the proposed mechanisms can be active

rb sr and sm nd chronology of an apollo 17 kreep basalt sm nd and rb sr mineral isochrons were determined for an apollo 17 kreep pigeonite basalt clast 543 from breccia 72275 collected from boulder 1 station 2 in the valley of taurus littrow sm nd analyses of the basalt yield a precise mineral isochron age of 4 08 0 07 ga for 147sm 0 00654 ga 1 the rb sr mineral isochron age of 4 13 0 08 ga for 87rb 0 0139 ga 1 is concordant with the sm nd age however the rb sr isotopic system has been slightly disturbed probably by the serenitatis impact event 3 95 ga ago the sm nd age is interpreted as the crystallization age of this apollo 17 kreep basalt ages and initial 87sr 86sr and end values for this basalt and apollo 14 and 15 kreep basalts suggest that these two types of kreep basalts could be produced from sources having similar rb sr and sm nd ratios these new age data suggest that kreep basaltic volcanism started 200 ma earlier than the 3 85 ga age generally accepted from studies of apollo 15 pristine kreep basalts apollo 17 kreep basalts probably pre date the serenitatis impact strongly indicating that not all kreep basaltic volcanism was necessarily related to basin forming impacts the younger apollo 15 and 14 kreep basalts probably are related to the imbrium impact however the ages and end values for kreep basalts granites troctolites and norites from a variety of lunar sites form a linear array corresponding to source s with sm nd lower by 15 than the chondritic value slightly enriched in lree suggesting that these rocks could be genetically related formation of a common sm nd isotopic growth curve by these data is most easily explained by an early moon wide differentiation accompanying the formation and subsequent solidification of a global magma ocean

shear wave anisotropy of textured hcp fe in the earth s inner core abstract many seismological studies have confirmed that vp travels 3 4 faster along the rotation axis of the earth than along the equatorial plane in the inner core indicating that the inner core is elastically anisotropic however seismic and mineral physics observations of the polarized vs are still emerging thus far the vs anisotropy of the constitute iron crystals at relevant pressures of the earth s core has remained mostly theoretical mainly because of the technical difficulties involved in measuring reliable vs velocities of iron crystals here we have measured azimuthal vs anisotropy of highly textured hcp fe at high pressures using nuclear resonant inelastic x ray scattering a technique sensitive to vs in a diamond anvil cell our results show that the azimuthal vs is 2 4 faster along the crystallographic c axis than along the a axis at 158 gpa and 172 gpa if one describes the vp anisotropy of the inner core as a result of the textured hcp fe crystals it is conceivable that azimuthal and polarized vs anisotropies with a magnitude of a few percent also exist in the region since vp and vs of candidate iron phases behave quite differently in theoretical predictions our results here indicate that future seismic observations of the vs and vp anisotropies of the inner core thus hold the key to deciphering the causes for the seismic and dynamic signatures as well as constitute iron phase s of the region

paleozoic accretionary and collisional tectonics of the eastern tianshan china implications for the continental growth of central asia this paper deals with the various tectonic units in the chinese eastern tianshan orogenic collage in the central asian orogenic belt and discusses the paleozoic geological history of the several periods of accretion and collision of archipelago systems lying between the tarim and southern angaran continental margins the late ordovician silurian to early devonian eastern tianshan archipelago was characterized by a the harlik dananhu subduction system with a s dipping polarity in the north b a southerly n dipping subduction system beneath the central tianshan arc in the middle and c the south tianshan ocean against tarim in the south during the devonian to early carboniferous n dipping subduction led to the harlik dananhu arc and the kanggurtag forearc basin accretionary complex in the early to mid carboniferous the magmatic front associated with the n dipping subduction beneath the dananhu harlik arc migrated southwards forming the yamansu arc constructed upon the kanggurtag accretionary forearc by the late carboniferous the dananhu harlik arc was attached northwards to the angaran margin resulting in lateral enlargement of the angaran continent in the latest carboniferous to early permian a multiple soft collision left wide suture zones in the south that include the ophiolite strewn aqikkuduk shaquanzi and kumishi accretion collision complexes which were stitched by early permian post collisional plutons by re defining and re interpreting the various tectonic terranes this paper presents a new improved model for the paleozoic evolution of this part of central asia

a possible model for the lithospheric thinning of north china craton evidence from the yanshanian jura cretaceous magmatism and tectonism it is well known that the north china craton was largely formed in the archean and was reactivated and transformed during the jura cretaceous yanshanian time into an orogenic belt which is believed to be related to the lithospheric thinning recent debate is centered on the mechanisms and processes of the lithospheric thinning there are two prevailing models for the lithosphere thinning 1 thermal erosion or and chemical metasomatism allowed the lower part of the lithospheric mantle to be transformed into asthenosphere 2 delamination of the lithospheric mantle and perhaps also the lowermost crust in this paper we attempt to explain how the buoyant cratonic lithosphere may be transformed into a denser one allowing delamination to take place on the basis of field observation tectonic analysis and petrologic data on igneous rocks formed during the yanshanian we recognize four episodes of contractional deformation that resulted in significant crustal shortening and vertical thickening the counter clockwise pressure temperature time path of the tectonomagmatic events suggests that the underplating basaltic magma may have heated and weakened the existing cold and strong crust this crustal change in rheology may have facilitated the contractional deformation and crustal thickening petrologic data of the contemporary igneous rocks and the lower crustal xenoliths suggest that the crust had reached 50 65 km in thickness it suggests that input of large amount of asthenosphere derived mafic magmas is required to cause crustal melting thus a large amount of eclogite may be formed at the lowermost crust following the transient thickening events the dense eclogite may trigger the lithosphere delamination

metallogenesis and ore controls of cenozoic porphyry mo deposits in the gangdese belt of southern tibet abstract the gangdese is a newly explored porphyry copper ore belt in china except for the cu mo au porphyry deposits there are some mo cu w porphyry and skarn deposits in this belt two pulses of molybdenite mineralization are recognized in the central lhasa subterrane with ancient continent crust including the paleocene eocene 65 52 ma porphyry mo and skarn mo w deposits formed during the rollback of neo tethyan oceanic slab in collisional setting and miocene 21 15 ma porphyry mo cu deposits generated in the postcollisional setting the gangdese copper deposits also occur during these two periods but are distributed in the southern lhasa subterrane dominated by juvenile crust through mantle derived magmatism resulting from neo tethyan ocean lithosphere subduction the intrusions related to molybdenite mineralization have relatively lower bulk rock e nd t and higher 87 sr 86 sr i values lower zircon e hf t values and older hf model ages lower molybdenite re contents and more radiogenic pb isotopes than the coeval copper related porphyries in the gangdese belt in addition the miocene mo cu related intrusions generally have lower zircon ce 4 ce 3 ratios than the miocene cu mo related intrusions these data indicate that more contributions from mature continental crustal materials play crucial role in the generation of mo than cu porphyry mineralization in the gangdese belt the eocene mo related intrusions are characterized by high sio 2 68 76 and k 2 o 5 1 5 9 concentrations enrichment of large ion lithophile elements lile depletion of high field strength elements hfse and low sr y 7 5 23 8 ratios their sr nd isotope compositions e nd t 3 4 to 4 6 87 sr 86 sr i 0 70622 0 70679 indicate that they are associated with partial melting of mantle wedge mixing with significant amounts 55 65 of middle upper crustal materials the miocene mo cu related intrusions have relatively high sio 2 64 73 and k 2 o 1 9 4 8 contents and are characterized by enrichment of lile depletion of hfse and high sr y ratios 55 189 their sr nd isotope compositions e nd t 4 6 to 3 4 87 sr 86 sr i 0 70622 0 70679 are indicative of derivation from remelting of previously subduction modified tibetan lithosphere with significant amounts 50 70 of middle upper crustal materials for the gangdese mo cu porphyry mineralization mo metal was suggested to be derived from the middle upper crustal materials particularly the carbonaceous permian marine sedimentary whereas cu metal to be sourced from the gangdese miocene cu fertile magmas the exploration targeting of the gangdese molybdenite deposits should be focused on southern part of the central lhasa subterrane where the carbonaceous permian strata occur the occurrence of mo cu porphyry deposits could provide clue for targeting cu mo porphyry deposits in the gangdese belt the gangdese molybdenite deposits share many similarities with the east qinling molybdenite deposits such as type of ore deposits geodynamic setting of their formation variable mo grades and high f contents

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

geology distribution types and tectonic settings of mesozoic molybdenum deposits in east qinling area located on the southern margin of the north china craton the east qinling molybdenum metallogenic belt is one of several regions in china characterized by the distribution of some important large size molybdenum deposits molybdenum deposits generally occur in nearly e w direction along the tectonic lineament and are mostly concentrated in a zone stretching from jinduicheng area of shaanxi province in the west to nannihu sandaozhuang shangganggou area of luanchuan and leimenggou of songxian in western henan province they are genetically related to yanshanian intermediate acid granites distributed extensively in east qinling area and occur along the endo and exo contact zones of the porphyry the molybdenum deposits are mainly of porphyry and porphyry skarn type and subordinately of carbonatite vein type the ore forming ages of the molybdenum deposits in east qinling area are within 221 5 0 3 ma 132 4 2 0 ma and cluster mainly into two pulses of 221 5 0 3 ma and 144 8 2 1 132 4 2 0 ma the former pulse geodynamically correspond to the extensional period of post collision orogenic process between north china and yangtze cratons the latter pulse results from the transformation of the tectonic regime from ns to nearly ew directions in east china

core structure re examined using new teleseismic data recorded in antarctica evidence for at most weak cylindrical seismic anisotropy in the inner core we present a significant addition to the data set of traveltimes of seismic pkp waves that sample the earth s lowermost mantle and core along the earth s rotation axis recorded at permanent global seismic network gsn and temporary sscua deployment broad band seismographic stations in antarctica the new data improve the previously poor and biased coverage that underlies the seismic constraints on recent models of inner core structure and anisotropy on the one hand new differential pkp traveltime measurements improve the sampling of predominantly the eastern inner core hemisphere pkpab df and pkpbc df differential traveltime residuals with respect to the spherically symmetric model ak135 are consistently smaller than two seconds along the north south paths sampled axially symmetric models of inner core seismic anisotropy with fast axis parallel to the earth s rotation axis require a weak anisotropy of 0 7 0 1 per cent to be consistent with our pkpbc df observations pkpbc df residuals from the quasi eastern hemisphere indicate 0 4 0 1 per cent anisotropy if only pkpbc df observations from the top 200 km of this hemisphere are considered this is reduced to 0 1 0 2 per cent consistent with an isotropic layer on the other hand new absolute pkp traveltime measurements add to the sampling of both hemispheres of the inner core but it is difficult to use them with more confidence to assess structure of the core since they are affected by crustal and mantle structure and source uncertainties the newly collected data set also increases constraints on d structure beneath the south pole in contrast to previous inferences based on data from northern stations we find no evidence of a velocity heterogeneity in the outer core near the inner core boundary associated with the cylinder tangent to the inner core in the southern hemisphere

the formation and evolution of the moon s crust inferred from the sm nd isotopic systematics of highlands rocks abstract ages determined for magnesian and ferroan anorthosite crustal rock suites overlap suggesting they formed contemporaneously about 4 3 4 5 ga a notable exception is the sm nd age previously determined on mg suite gabbronorite 67667 which is at least 100 ma younger than the youngest ferroan anorthosite new chronologic measurements of 67667 presented here yield concordant sm nd and rb sr mineral isochron ages of 4349 31 ma and 4368 67 ma suggesting the sample is older than previous estimates furthermore a whole rock sm nd isochron of mg suite rocks from the apollo 14 15 16 and 17 landing sites yields an age of 4348 25 ma indicating that mg suite magmatism was widespread and roughly contemporaneous on the lunar nearside analysis of sm nd internal isochron ages confirms that mg suite magmatism was restricted to a period between about 4 33 and 4 35 ga at the apollo 14 15 16 and 17 landing sites and was synchronous with magmatism at the apollo 16 site associated with the ferroan anorthosite suite between 4 35 and 4 37 ga magnesian and ferroan anorthosite suite rocks with ages younger than 4 33 ga appear to have experienced slow cooling in the deep lunar interior so that the ages record when the samples cooled below the closure temperature of the sm nd isotopic system and not the time they crystallized the ages determined for mg suite and ferroan anorthosite suite rocks are concordant with the age determined for the formation of urkreep of 4350 34 ma using the sm nd isotopic systematics of 67667 and measurements completed on norite 78238 troctolite 76535 kreep basalt 15386 and gabbronorite nwa 773 crystallization ages of mg suite and fas are also concordant with the average of 146sm 142nd ages previously determined for the formation of the mare basalt source region of 4333 30 ma the similarity of ages for mg suite magmatism ferroan anorthosite suite magmatism urkreep formation and formation of the mare basalt source regions implies the processes that produced these rocks were petrogenetically linked it also implies that both early stage and late stage lunar magma ocean cumulates formed over a relatively short duration of

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

tectonic history of the earth s inner core preserved in its seismic structure seismic data show that the earth s inner core is structurally complex numerical simulations suggest that whereas the deeper structure may be inherited from past episodes of inner core growth the origin of the shallow structure is due to ongoing deformation

importance of the lu hf isotopic system in studies of planetary chronology and chemical evolution the 176lu 176hf isotope method and its applications in earth sciences are discussed greater fractionation of lu hf than sm nd in planetary magmatic processes makes 176hf177hf a powerful geochemical tracer in general proportional variations of 176hf177hf exceed those of 143ndl44nd by factors of 1 5 3 in terrestrial and lunar materials lu hf studies therefore have a major contribution to make in understanding of terrestrial and other planetary evolution through time and this is the principal importance of lu hf new data on basalts from oceanic islands show unequivocally that whereas considerable divergences occur in 176hf177hf 87sr86sr and 143ndl44nd 87sr86sr diagrams 176hf177hf and 143nd144nd display a single linear isotopic variation in the suboceanic mantle these discordant 87sr86sr relationships may allow with the acquisition of further hf nd sr isotopic data a distinction between processes such as mantle metasomatism influence of seawater altered material in the magma source or recycling of sediments into the mantle in order to evaluate the hf nd isotopic correlation in terms of mantle fractionation history there is a need for measurements of hf distribution coefficients between silicate minerals and liquids and specifically for a knowledge of hf behavior in relation to rareearth elements for studying ancient terrestrial hf isotopic variations the best quality hf isotope data are obtained from granitoid rocks or zircons new data show that very u pb discordant zircons may have upwardly biased 176hf177hf but that at least concordant to slightly discordant zircons appear to be reliable carriers of initial 176hf177hf until the controls on addition of radiogenic hf to zircon are understood combined zircon whole rock studies are recommended lu hf has been demonstrated as a viable tool for dating of ancient terrestrial and extraterrestrial samples but because it offers little advantage over existing methods is unlikely to find wide application in pure chronological studies

isotopic evidence for a young lunar magma ocean abstract mare basalt sources and ferroan anorthosite suite cumulates define a linear array on a 146sm 144nd versus 142nd 144nd isochron plot demonstrating these materials were derived from a common reservoir at 4336 31 32 ma the minimum proportion of the moon that was in isotopic equilibrium at this time is estimated to be 1 3 of its entire volume based on the geographic extent from which the analyzed samples were collected and the calculated depths from which the samples were derived scenarios in which large portions of the moon were molten to depths of many hundreds of kilometers are required to produce the observed sm nd isotopic equilibrium between the mantle and crustal rocks at 4 34 ga this is a consequence of the fact that limited heating of a solid moon above the blocking temperature of the sm nd isotopic system is insufficient to diffusively homogenize radiogenic nd throughout the mantle and crust there are three scenarios that might account for global scale isotopic equilibrium on the moon relatively late in solar system history including 1 sm nd re equilibration of a solid moon resulting from widespread melting in response to mantle overturn or a very large impact 2 early accretion of the moon followed by delayed cooling due to the presence of an additional heat source that kept a large portion of the moon molten until 4 34 ga or 3 late accretion of the moon followed by rapid cooling of the magma ocean late in solar system history neither density driven overturn of the mantle nor a large impact are likely to homogenize the mantle and crust to the extent required by the sm nd isochron likewise secondary heating mechanisms such as tidal heating or radioactive decay are not efficient enough to keep the moon molten to the depth of the mare basalt source regions for many tens to hundreds of millions of years instead the age of equilibrium between such a compositionally diverse set of rocks produced on a global scale likely records the time of primordial solidification of the moon from a magma ocean this scenario accounts for both the petrogenetic characteristics of lunar rock suites as well as their sm nd isotopic systematics it is supported by the preponderance of 4 35 ga ages obtained for other hypothetical magma ocean crystallization products such as ferroan anorthosite suite rocks and k ree and p enriched cumulates that are thought to represent flotation cumulates of the magma ocean and the last vestiges of magma ocean solidification respectively

hemispherical structure in inner core velocity anisotropy 1 we investigate the hemispherical pattern in inner core velocity anisotropy using a new and independent high quality data set of pkpbc pkpdf and pkpab pkpdf body wave observations our data show no evidence for a tilted anisotropy axis with respect to the earth s rotation axis and is significantly better fit by a model with 4 4 anisotropy in the western hemisphere and only 1 0 in the eastern hemisphere than by a model of uniform anisotropy we carry out variance minimization and find the boundaries between the hemispheres at lines of constant longitude at 14 e and 151 w variance minimization enables us to extract the imprint of hemispherical structure from all of the data and not just polar paths resulting in boundaries which are nearly 30 from the results of previous studies the high quality of the data allows us to provide robust evidence that the isotropic velocity in the eastern hemisphere is 0 2 lower than in the western hemisphere in the top 660 km of the inner core our data set also suggests an increase in inner core anisotropy in the eastern hemisphere from 1 to around 6 at depths deeper than 660 km indicating that the hemispherical pattern in anisotropy may disappear at greater depths the presence of hemispherical structure rules out mechanisms for creating anisotropy which are unable to sustain longitudinal variations in the inner core furthermore steady inner core superrotation of the order of 0 1 year would eradicate the hemispherical differences though inner core oscillation would still be permissible

the age of ferroan anorthosite 60025 oldest crust on a young moon abstract sm nd isotopic data for mineral separates from the ferroan anorthosite 60025 define a precise isochron of 4 44 0 02ga age this age is roughly 110 m y younger than the formation of the first large solid objects in the solar nebula as recorded by the radiometric ages of the differentiated meteorites in the magma ocean model for early lunar differentiation ferroan anorthosites are the first crustal rocks to form on the moon if the moon is as old as the oldest meteorites the relatively young age determined for 60025 implies either that the magma ocean did not form synchronously with lunar formation or that the magma ocean required over 100 m y before reaching the stage of ferroan anorthosite crystallization alternatively we propose that the accumulated body of radiogenic isotope data for lunar rocks permit the moon to be as young as 4 44 4 51 ga if so isotopic evidence for chemical differentiation on the earth at about this same time suggests that the formation of the moon is reflected in the chemical evolution of the earth this in turn is consistent with the idea that the materials that now make up the moon were derived from the earth perhaps ejected by collision between the earth and another very large planetesimal during the final stages of accumulation of the terrestrial planets terrestrial origin models for the moon lessen the requirement that the earth and moon each have near chondritic relative abundances of the refractory elements and could require that certain chemical and isotopic characteristics of both bodies be considered in the framework of the chemical mass balance of the combined earth moon system

inner core differential rotation inferred from antipodal seismic observations abstract the earth s inner core may rotate at a different speed than earth s crust mantle we use observations for antipodal earthquake and station pairs to examine the arrival time shift of the whispering gallery wave which propagates tangentially along the top of the inner core observations of these waves for earthquakes which occurred at the same location reveal that travel times vary by 0 2 s over the past 20 years we propose that these time shifts are caused by the interaction of a zero rigidity patch lateral heterogeneity at the inner core surface with the inner core differential rotation the simplest interpretation infers a rotation rate of 0 05 year which is one order of magnitude smaller than those reported by previous studies our result may also give constraint to the provenance of a zero rigidity patch at the inner core surface the fresnel zone coverage of whispering gallery pkiikp antipodal measurements beneath the inner core boundary extend over 60 of the boundary surface in contrast to pkikp pkp paths which individually measure specular reflections 1 hz from the top of the icb over fresnel zones each encompassing 0 002 of the inner outer core boundary

the effect of d on pkp ab df travel time residuals and possible implications for inner core structure abstract the hypothesis that the deep inner core is anisotropic is based on pkp travel time observations at large distances and relies on a small number of very anomalous measurements for paths quasi parallel to the earth s rotation axis here we analyze a global dataset of pkp ab df travel times residuals and discuss their significant dispersion 2 s and coherent large scale patterns we show that the trends observed for quasi equatorial paths are consistent with predictions from recent tomographic mantle models when the latter are modified to account for strong heterogeneity at the base of the mantle under the pacific ocean and africa as documented in several recent studies likewise for polar paths we show that a large part of the signal could be explained by deep mantle structure the effects of complex structure in the deep mantle on pkp ab df travel times should be carefully considered in order to reliably estimate the anisotropic structure of the central part of the inner core

a re os study of molybdenites from the lanjiagou mo deposit of north china craton and its geological significance article i nfo the lanjiagou mo deposit is located in the eastern part of the north china craton rhenium and osmium isotopes in molybdenites from the lanjiagou porphyry mo deposit have been used to determine the timing of mineralization molybdenite was analyzed mainly from granite porphyry which is characterized by moderate to strong silicification rhenium concentrations in molybdenite samples are between 33 and 48 g g analysis of eleven molybdenite samples yields an isochron age of 181 6 6 5 ma 2 based on the geological history and spatio temporal distribution of the granitoids it is proposed that the mo deposits in the eastern part of the north china craton were related to the subduction of the paleo pacific plate during jurassic time 2009 published by elsevier b v on behalf of international association for gondwana research

the timing of lunar solidification and mantle overturn recorded in ferroan anorthosite 62237 abstract ferroan anorthosite suite fas rocks are widely interpreted to represent primordial lunar crust despite their importance in pinpointing the timing of lunar crust formation robust chronological investigations for this rock type are scarce here we report the ar ar rb sr and sm nd isotopic systematics for the fas troctolitic anorthosite 62237 the ar ar isotopic system has been reset by a thermal event at 3710 48 ma and the rb sr isotopic systematics has been disturbed such that a rb sr isochron age cannot be determined however an internal isochron for the sm nd isotopic system has yielded an age of 4350 73 ma mswd 2 0 with an initial 143 ndchur of 0 53 0 26 the mineral and whole rock fractions of 62237 plot on the same internal isochron as fas sample 60025 the combined datasets define an age of 4372 35 ma mswd 4 0 with an initial 143 ndchur of 0 17 0 22 literature sm nd data for fas and mg suite whole rocks also plot on the 60025 62237 isochron the coherence of data from both fas and mg suite rocks examined thus far suggests that both rock suites formed contemporaneously from identical or nearly identical sources in addition the concordance of fas and mg suite ages suggests that primordial crust solidification either involved both magmatic suites or that mg suite magmatism was contemporaneous with fas magmatism within resolution of the sm nd chronometer the ages for fas and mg suite also coincide with the formation ages of the mare basalt source regions and urkreep ferroan anorthosite suite rocks and urkreep are thought to represent primordial lmo solidification products whereas mg suite and the mare basalt source regions are argued to represent mixtures of various lmo crystallization products that were formed during density driven overturn of the lmo the concordance of ages implies that the 4372 35 ma sm nd isochron records the age of mantle overturn and that overturn occurred during or shortly after solidification of the lmo

metallogenic epoch and geodynamic framework of cu au mo w deposits in southeastern hubei province constraints from re os molybdenite ages cu au mo w deposits in southeastern hubei province constitute one of the important areas in the middle lower yangtze river metallogenic belt re os ages for molybdenite provide constraints on the ore forming epoch of late mesozoic cu au mo w mineralization molybdenites from the fengshangdong cu mo au ag deposit the ruanjiawan w cu mo deposit the qianjiawan cu au deposit the tonglushan cu fe au mo deposit and the tongshanko cu mo deposit yield ages of 144 0 2 1 ma 143 6 1 7 ma 137 7 1 7 ma 137 8 1 7 138 1 1 8 ma and 143 5 1 7 142 3 1 8 ma respectively these data and other highly precise isotopic ages available for cu fe au polymetallic deposits in the middle lower yangtze river metallogenic belt such as molybdenite re os ages and mica 40 ar 39 ar ages in the literature demonstrate that cu au mo w deposits in tongling anqing jiurui and eastern hubei ore cluster areas were formed at ca 140 5 ma reflecting an important ore forming episode in this belt previous petrological and geophysical data as well as metallogenic ages and their relation to the magmatism and geodynamic framework indicate that largescale cu au mo w deposits were developed during the tectonic transformation from the ns trending compressional regime to ne trending extension which resulted from asthenospheric upwelling and basaltic magma underplating in the late jurassic early cretaceous period in east china

uranium lead ages for lunar zircons evidence for a prolonged period of granophyre formation from 4 32 to 3 88 ga the ages of a number of small fragments of lunar granophyre have been determined by the in situ u th pb isotopic analysis of zircon using a sensitive high mass resolution ion microprobe shrimp i the zircon from lunar granophyre is characterized by consistently high u and th contents most 200 500 ppm and 100 300 ppm respectively compared to zircon from mafic lunar rocks some fragments of lunar granophyre are found to be as old as 4 32 ga supporting other evidence that the original lunar magma ocean crystallized completely within 200 ma of the formation of the moon itself other fragments are as young as 3 88 ga which is much later than the time of formation of most of the lunar crust the older lunar granophyres have rare earth element ree patterns that are similar to lunar kreep whilst the younger granophyres have bow shaped ree patterns that feature a greater relative enrichment in the heavy ree the wide range of ages of numerous lunar zircons lunar granophyres and other rocks indicates that zircon forming magmatism in the lunar highlands was most active prior to 4 3 ga but continuous until at least 3 88 ga the u pb isotopic composition of much lunar zircon is near concordant but the effects of isotopic disturbance as late as 1 0 ga are observed in some zircon both within granophyre fragments recrystallized by reheating and within fragments in which the original delicate silica k feldspar granophyric intergrowth is well preserved it is therefore essential to make multiple analyses of individual zircon grains and preferably analyses of suites of zircons from lunar igneous rocks if they are to be dated reliably by the u pb method it is possible that some of the younger lunar granophyres are the product of large scale silicate liquid immiscibility within late stage differentiates but this remains unproven until remnants of demonstrably cogenetic fe rich immiscible liquid are positively identified

seismic anisotropy estimated from p wave arrival times in crosshole measurements summary seismic anisotropy is evidenced in the inner core upper mantle and the lower crust in large scale and the evidence is generally provided by shear wave splitting analysis here this paper searches for the evidence of anisotropy in the uppermost crust by using p wave arrival times from crosshole seismic measurement to directly estimate velocity anisotropy associated with the fine layering effect of multiple sedimentary beds conceptually fine layering causes the so called vti vertical transverse isotropy anisotropy with a vertical symmetry and the effect is parametrized by the horizontal and vertical velocity ratio it is found however that the vti anisotropic parameter does not have a simple vertical symmetry but is also azimuth dependent this azimuthal anisotropy may reflect the fracture orientation due to large scale tectonic movements and is very important in the production of oil reservoirs as the seismically fast directions can indicate preferred directions of fluid flow this paper presents innovative methods for anisotropy analysis in both vertical and horizontal plane integrated seismic anisotropy interpretation clearly indicates distinguished strain orientations forming fractures in oligocenic miocenic and pliocenic sediment in the edge of the extensional basin immediately next to tan lu fault an active continental strike slip fault zone

os os dating of copper and molybdenum deposits along the middle and lower reaches of the yangtze river china the 186 os 187 os and 188 os 187 os dating techniques were modified and applied to molybdenites from two cu vein deposits and three mo skarn deposits along the middle and lower reaches of the yangtze river china the results show that these deposits formed at 138 to 133 ma identical to the ages of 140 to 130 ma for the host granitoids re os and os os ages of two of the samples agree within analytical uncertainties the close temporal relationship between the granitoid intrusions and the formation of the deposits supports a magmatic model for the origin of these deposits the results show that the novel os os dating technique is capable of resolving geologic problems although the accuracy obtained by the present work 1 2 is lower than that of the re os method

fine scale heterogeneity in the earth s inner core the seismological properties of the earth s inner core have become of particular interest as we understand more about its composition and thermal state1 2 observations of anisotropy and velocity heterogeneity in the inner core are beginning to reveal how it has grown and whether it convects3 4 the attenuation of seismic waves in the inner core is strong and studies of seismic body waves5 6 have found that this high attenuation is consistent with either scattering or intrinsic attenuation5 the outermost portion of the inner core has been inferred to possess layering and to be less anisotropic than at greater depths7 8 9 10 here we present observations of seismic waves scattered in the inner core which follow the expected arrival time of the body wave reflection from the inner core boundary the amplitude of these scattered waves can be explained by stiffness variations of 1 2 with a scale length of 2 kilometres across the outermost 300 km of the inner core these variations might be caused by variations in composition by pods of partial melt in a mostly solid matrix or by variations in the orientation or strength of seismic anisotropy

a type granites in northeastern china age and geochemical constraints on their petrogenesis abstract a type granites are widely distributed in northeastern china ne china they were emplaced during three major episodes the permian late triassic to early jurassic and early cretaceous and evolved in different tectonic regimes according to their mineralogical and geochemical characteristics two subgroups of a type granites aluminous and peralkaline can be recognized the peralkaline subgroup contains alkali mafic minerals such as riebeckite arfvedsonite and sodic pyroxene while the aluminous subgroup contains annite and fe rich calcic or sodic calcic amphibole with respect to the aluminous subgroup the peralkaline granites contain higher rb ga and total rare earth elements ree but lower mgo cao al 2 o 3 ba and sr based on the discrimination criteria of eby geology 20 1992 641 the permian and late triassic to early jurassic a type granites belong to the a 2 post orogenic type whereas the early cretaceous granites are of the a 1 anorogenic type nd isotopic compositions of these a type granites indicate their derivation from a dominantly juvenile crustal source their origin is thought to have involved partial melting of an underplated lower crustal source because the generation of a type granites requires high melting temperature we propose models involving slab break off lithospheric delamination and extension the permian a type granites have the same age range as those in eastern junggar southern mongolia and central inner mongolia they occur along a major suture and form a narrow belt between the north china and siberian cratons we suggest that their formation was associated with post collisional slab break off the late triassic to early jurassic a type granites are likely to be the product of lithospheric delamination after the final collision of the major crustal blocks in the late paleozoic to early triassic the early cretaceous a type granites have an anorogenic affinity and were possibly associated with rifting in eastern china at this time associated with the onset of paleo pacific subduction consequently we conclude that the a type granites in ne china were generated at three different times involving multiple processes operative in different tectonic environments

hemispherical variations in seismic velocity at the top of the earth s inner core knowledge of the seismic velocity structure at the top of the earth s inner core is important for deciphering the physical processes responsible for inner core growth1 2 3 previous global seismic studies4 5 6 7 8 9 have focused on structures found 100 km or deeper within the inner core with results for the uppermost 100 km available for only isolated regions10 11 12 here we present constraints on seismic velocity variations just beneath the inner core boundary determined from the difference in travel time between waves reflected at the inner core boundary and those transmitted through the inner core we found that these travel time residuals observed on both global seismograph stations and several regional seismic networks are systematically larger by about 0 8 s for waves that sample the eastern hemisphere of the inner core 40 e to 180 e compared to those that sample the western hemisphere 180 w to 40 e these residuals show no correlation with the angle at which the waves traverse the inner core this indicates that seismic anisotropy is not strong in this region and that the isotropic seismic velocity of the eastern hemisphere is about 0 8 higher than that of the western hemisphere

isotopic studies of ferroan anorthosite 62236 a young lunar crustal rock from a light rare earth element depleted source isotopic analyses of mineral fractions and whole rocks from the ferroan anorthosite 62236 yield a sm nd isochron with an age of 4 29 0 06 ga and an initial end143 value of 3 1 0 9 we have also measured end142 anomalies of 0 25 on two fractions of 62236 these values are higher than the value of 0 1 predicted if 62236 was derived from a chondritic source at 4 29 ga but are consistent with the positive initial end143 value the sm nd isotopic composition of 62236 has been modified by the capture of thermal neutrons such that the 147sm 144nd 143nd 144nd and 142nd 144nd ratios measured on the mineral fractions and whole rocks must be corrected the corrections do not significantly alter the sm nd isotopic results determined on 62236 despite the fact that the ar ar and rb sr isotopic systematics of 62236 have been reset by impact metamorphism at 3 93 0 04 ga the sm nd systematics appear to have been unaffected the sm nd isotopic systematics of 62236 provide several constrains on models of lunar crustal differentiation provided they have not been reset since crystallization first the relatively young age of 62236 as well as the old ages determined on several crustal plutonic rocks of the mg suite require multiple sources of magmas on the moon very early in its history second positive end143 values determined on all analyzed ferroan anorthosites suggest that they were derived from sources depleted in light rare earth elements and third models based on initial end143 and present day end142 values suggest that the source of 62236 was depleted in light rare earth elements at 4 46 ga in order to reconcile these observations with the lunar magma ocean model 1 the magma ocean must have existed for a very short period of time and may have had a sub chondritic nd sm ratio and 2 the youngest ferroan anorthosites such as 62236 cannot be cumulates from the magma ocean but must form by other processes

the bombardment history of the moon as recorded by 40 ar 39 ar chronology new petrography and 40ar 39ar ages have been obtained for 1 3 mm sized rock fragments from apollo 16 station 13 soil 63503 north ray crater ejecta and chips from three rocks collected by apollo 16 and apollo 17 missions selection of these samples was aimed at the old 40ar 39ar ages to understand the early history of the lunar magnetic field and impact flux fifteen samples were studied including crustal material polymict feldspathic fragmental breccias and impact melts the impact ages obtained range between approximately 3 3 and 4 3 billion years ga polymict fragmental breccia 63503 1 exhibits the lowest signs of recrystallization observed and a probable old relic age of 4 547 0 027 the plateau age of 4 293 0 044 ga obtained for impact melt rock 63503 13 represents the oldest known age for such a lithology possibly this age represents the minimum age for the south pole aitken spa basin in agreement with literature data these results show that impact ages 3 9 ga are found in lunar rocks especially within soil 63503 impact exhumation of deep seated warm crustal material onto the lunar surface is considered to explain the common 4 2 ga ages obtained for weakly shocked samples from soil 63503 and apollo 17 this would directly imply that one or more basin forming events occurred at that time some rock fragments showing none to limited petrologic features indicate thermal annealing these rocks may have lost ar while resident within the hot ejecta of a large basin concurrent with previous studies these results lead us to advocate for a complex impact flux in the inner solar system during the initial approximately 1 3 ga

support for equatorial anisotropy of earth s inner inner core from seismic interferometry at low latitudes abstract anisotropy of earth s inner core provides a key role to understand its evolution and the earth s magnetic field recently using autocorrelations from earthquake s coda we found an equatorial anisotropy of the inner inner core iic in apparent contrast to the polar anisotropy of the outer inner core oic to reduce the influence of the polar anisotropy and reduce possible contaminations from the large fresnel zone of the pkikp 2 and pkiikp 2 phases at low frequencies we processed coda noise of large earthquakes 10 000 40 000 s after magnitude 7 0 from stations at low latitudes within 35 during 1990 2013 using a number of improved procedures of both autocorrelation and cross correlation we extracted 52 array stacked high quality empirical green s functions egfs an increase of over 60 from our previous study the high quality data allow us to measure the relative arrival times by automatic waveform cross correlation the results show large variation 10 9 s in the differential times between the pkikp 2 and pkiikp 2 phases the estimated influence of the fresnel zone is insignificant

heterogeneity and anisotropy of earth s inner core seismic observations provide strong evidence that earth s inner core is anisotropic with larger velocity in the polar than in the equatorial direction the top 60 80 km of the inner core is isotropic evidence for an innermost inner core is less compelling the anisotropy is most likely due to alignment of hcp hexagonal close packed iron crystals aligned either during solidification or by deformation afterward the existence of hemispherical variations used to be controversial but there is now strong evidence from both seismic body wave and normal mode observations showing stronger anisotropy less attenuation and a lower isotropic velocity in the western hemisphere two mechanisms have been proposed to explain the hemispherical pattern either a inner core translation wherein one hemisphere is melting and the other is solidifying or b thermochemical convection in the outer core leading to different solidification conditions at the inner core boundary neither is yet able to explain all se

earthʼs inner core innermost inner core or hemispherical variations the structure of earth s deep inner core has important implications for core evolution since it is thought to be related to the early stages of core formation previous studies have suggested that there exists an innermost inner core with distinct anisotropy relative to the rest of the inner core using an extensive new data set of handpicked absolute travel time observations of the inner core phase pkikp we find that the data are best explained by variations in anisotropy between two hemispheres and do not require an innermost inner core we demonstrate that observations of an innermost inner core are an artifact from averaging over lateral anisotropy variations more significantly we show that hemispherical variations in anisotropy previously only imaged in the upper inner core continue to its centre the eastern region has 0 5 1 5 anisotropy whereas the western region has 3 5 8 8 anisotropy increasing with depth with a slow direction at 57 61 to the earth s rotation axis at all depths such anisotropy is consistent with models of aligned hcp or bcc iron aggregates