evidence of greenland sea water in the iceland basin 1 this study evaluates the presence of intermediate water from the greenland sea in the iceland basin deduced from the observed excess of the tracer sulphur hexafluoride sf6 released in the central greenland sea in 1996 the large tracer release experiment has served a unique opportunity to follow the spread of greenland sea intermediate water to the adjacent basins of the nordic seas and to the areas bordering this region in the present study using data from may june 2001 the released tracer was detected at the sill in the faroe bank channel and at several locations in the iceland basin of the north atlantic just downstream the sill and southeast of iceland the estimated excess of the released tracer at the icelandic slope combined with reported values of the volume flow at this location suggest an annual transport rate of approximately 1 4 kg excess sf6 the results suggest an upper transit time from the central greenland sea to the area southeast of iceland of approximately 4 years

geochemistry zircon u pb and hf isotope for granitoids nw sanandaj sirjan zone iran implications for mesozoic cenozoic episodic magmatism during neo tethyan lithospheric subduction abstract the sanandaj sirjan zone ssz of iran comprises sedimentary and metamorphic basement rocks which are generally regarded as having been derived from the southern active margin of the eurasian plate within the ssz a number of mesozoic to cenozoic granitoid intrusions of various size elongated in a nw se direction are exposed with the benefit of precise age dating geochemical and isotopic data over the past decade the magmatic history of these intrusions has become clearer this study presents further geochronological and geochemical data for previously dated and undated granitoids together with considerable zircon lu hf isotopic data which were limited in the past combined with previous work these new data including the finding of ca 170 ma adakite lead to improved constraints on the meso cenozoic tectonic evolution of neo tethyan lithospheric subduction the dominant early middle jurassic magmatism is proposed to have occurred with a major contribution of crustal components during the initiation of neo tethyan subduction subsequent late jurassic magmatism suggests the involvement of lower crust partial melting in an extensional tectonic setting cretaceous magmatism almost ceased after formation of a flat slab caused by a trench retreat rate exceeding that of slab roll back late paleocene eocene magma sources in the ssz are dominated by mantle derived input through an asthenospheric window with subordinate crustal contamination during the subduction of the neo tethyan ridge spreading center this interpretation differs from paleocene eocene magmatic flare up proposed for the northern iranian interior which may have been driven by an episode of slab retreat or slab roll back following cretaceous flat slab subduction

the lunar far uv albedo indicator of hydration and weathering 1 we present an analysis of lunar reconnaissance orbiter lro lyman alpha mapping project lamp measurements of the dayside lunar surface at far ultraviolet wavelengths we use the strong 165 nm h2o absorption edge to look for diurnal variations in hydration we find that diurnal variations in spectral slope are indeed present they are superimposed on latitudinal and spatial variations related to composition and weathering we use two different spectral regions 164 173 nm and 175 190 nm to separate out these effects highlands and mare regions have distinct reflectance spectra with mare regions being spectrally bluer than highlands regions a consequence of the greater abundance of opaque minerals in mare regions bright ray terrains and areas known to be young such as giordano bruno crater are found to be relatively spectrally flat or red in the far uv this is consistent with a lack of space weathering which tends to make the far uv spectrum bluer due to the spectral behavior of nanophase iron large scale latitudinal variations in fuv slope are distinct and are likely due to a gradient in space weathering the diurnal variation in hydration is consistent with a solar wind origin and with loss of h2o at temperatures above 320 k far uv spectroscopy is thus shown to represent a viable method for mapping aqueous alteration even on the dayside of the moon and potentially elsewhere in the solar system

global distribution of large lunar craters implications for resurfacing and impactor populations by using high resolution altimetric measurements of the moon we produced a catalog of all impact craters 20 kilometers in diameter on the lunar surface and analyzed their distribution and population characteristics the most densely cratered portion of the highlands reached a state of saturation equilibrium large impact events such as orientale basin locally modified the prebasin crater population to 2 basin radii from the basin center basins such as imbrium orientale and nectaris which are important stratigraphic markers in lunar history are temporally distinguishable on the basis of crater statistics the characteristics of pre and postmare crater populations support the hypothesis that there were two populations of impactors in early solar system history and that the transition occurred near the time of the orientale basin event

initial observations of lunar impact melts and ejecta flows with the mini rf radar 1 the mini rf radar on the lunar reconnaissance orbiter spacecraft has revealed a great variety of crater ejecta flow and impact melt deposits some of which were not observed in prior radar imaging the craters tycho and glushko have long melt flows that exhibit variations in radar backscatter and circular polarization ratio along the flow comparison with optical imaging reveals that these changes are caused by features commonly seen in terrestrial lava flows such as rafted plates pressure ridges and ponding small 20 km sized craters also show a large variety of deposits including melt flows and ponds two craters have flow features that may be ejecta flows caused by entrained debris flowing across the surface rather than by melted rock the circular polarization ratios cprs of the impact melt flows are typically very high even ponded areas have cpr values between 0 7 and 1 0 this high cpr suggests that deposits that appear smooth in optical imagery may be rough at centimeter and decimeter scales in some places ponds and flows are visible with no easily discernable source crater these melt deposits may have come from oblique impacts that are capable of ejecting melted material farther downrange they may also be associated with older nearby craters that no longer have a radar bright proximal ejecta blanket the observed morphology of the lunar crater flows has implications for similar features observed on venus in particular changes in backscatter along many of the ejecta flows are probably caused by features typical of lava flows

comparisons between tethyan anorthosite bearing ophiolites and archean anorthosite bearing layered intrusions implications for archean geodynamic processes

how old are young lunar craters 1 the accurate definition of the lunar cratering chronology is important for deriving absolute model ages across the lunar surface and throughout the solar system images from the lunar reconnaissance orbiter narrow angle cameras and wide angle camera and the selene kaguya terrain camera provide new opportunities to investigate crater size frequency distributions csfds on individual geological units at lunar impact craters we report new csfd measurements for the copernican aged craters north ray tycho and copernicus which are crucial anchor points for the lunar cratering chronology we also discuss possible reasons for an age discrepancy observed between the impact melt and ejecta units our csfds for north ray and tycho crater ejecta deposits are consistent with earlier measurements however for copernicus crater and one of its rays we find significantly lower cumulative crater frequencies than previous studies our new results for copernicus crater fit the existing lunar absolute chronologies significantly better than the previous counts our derived model ages of the ejecta blankets of north ray tycho and copernicus agree well with radiometric and exposure ages of the apollo 16 17 and 12 landing sites respectively and are generally consistent with a constant impact rate over the last 3 ga however small variations of the impact rate cannot be resolved in our data and require further investigations

the transition from complex craters to multi ring basins on the moon quantitative geometric properties from lunar reconnaissance orbiter lunar orbiter laser altimeter lola data united states national aeronautics and space administration nasa lunar reconnaissance orbiter lunar orbiter laser altimeter lola experiment nnx09am54g

jurassic granitoids in the northwestern sanandaj sirjan zone evolving magmatism in response to the development of a neo tethyan slab window abstract voluminous jurassic granitoids within the sanandaj sirjan zone ssz provide insight into the magmatic arc formed in the active margin of eurasia here we present new in situ zircon u pb whole rock major and trace element and sr nd isotopic data for the gorveh plutonic complex gpc of the northwestern ssz in iran six samples from the plutons within the gpc yielded zircon u pb ages that range from 151 to 146 ma these plutons can be subdivided into two groups based on their geochemistry group 1 rocks the mobarak abad diorites and the gorveh gabbros and diorites contain relatively high concentrations of the high field strength elements hfse nb ta zr and ti and have low th nb 0 20 0 56 and moderate sm yb ratios 1 51 2 32 low 87sr 86sr i values 0 70354 0 70622 and high end t values 2 3 5 4 these features indicate that the group 1 rocks formed from magmas derived from a subduction modified region of the subcontinental lithospheric mantle the group 2 plutons the bolban abad granites and the gorveh quartz monzonites have a type granites affinities including high k2o na2o and zr nb ce y concentrations and high feotot mgo and 10 000 ga al ratios these a type rocks are enriched in rb th and k and depleted in ba u nb ta sr p and ti the group 2 plutons have different sr nd isotopic compositions to each other indicating they were derived from different sources and record different igneous processes the gorveh quartz monzonites have high 87sr 86sr i ratios 0 70552 0 70617 negative end t values 1 1 to 5 4 and extremely low concentrations of mgo 0 32 0 35 wt suggesting they were derived from an igneous quartzo feldspathic crustal source in comparison the bolban abad granites have positive end t values and contain high concentrations of sio2 and low concentrations of mgo suggesting that they formed from group 1 magmas that subsequently underwent assimilation and fractional crystallization processes combining these new data with the results of previous research we conclude that this jurassic magmatism was the result of the formation of a slab window within the subducting neo tethys slab a process that caused the partial melting of overlying continental lithospheric material

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

testing polar spots of water rich permafrost on the moon lend observations onboard lro 1 results are presented for the lend instrument onboard lro for the detection of local spots of suppression and excess of epithermal neutron emission at the lunar poles twelve local neutron suppression regions nsrs and neutron excess regions ners are detected it is shown using the data from the lola and diviner instruments that six nsrs have the empirical property less local irradiation and lower temperature fewer local neutrons these nsrs may be identified with spots of water ice rich permafrost on the moon it is shown that detected nsrs are include in both permanently shadowed and illuminated areas and they are not coincident with permanently shadowed regions psrs at the bottom of polar craters as has been commonly expected before lend presented neutron data with high spatial resolution

u pb dating and emplacement history of granitoid plutons in the northern sanandaj sirjan zone iran abstract the sanandaj sirjan zone ssz which runs parallel to the zagros fold and thrust belt of iran underwent a multistage evolution starting with neotethys initiation its subsequent subduction below the iranian continental crust and eventual closure during convergence of arabia towards central iran plutonic complexes are well developed in the northern part of the ssz and we have dated a number of them by id tims u pb on zircon the new data record the following events a mid jurassic period that formed the boroujerd plutonic complex 169 ma the astaneh pluton 168 ma and the alvand pluton 165 ma late jurassic emplacement of the gorveh pluton 157 149 ma mid cretaceous 109 ma formation of a i type phase in the hasan salary pluton near saqqez followed by early paleocene 60 ma intrusion of a type granite in the same pluton and the youngest intrusive event recorded so far in the ssz with the intrusion of granite in the gosheh tavandasht complex near boroujerd at 34 9 ma these different events reflect specific stages of subduction related magmatism prior to the eventual miocene collision between the two continental blocks

characterization of previously unidentified lunar pyroclastic deposits using lunar reconnaissance orbiter camera data 1 we used a lunar reconnaissance orbiter camera lroc global monochrome wide angle camera wac mosaic to conduct a survey of the moon to search for previously unidentified pyroclastic deposits promising locations were examined in detail using lroc multispectral wac mosaics high resolution lroc narrow angle camera nac images and clementine multispectral ultraviolet visible or uvvis data out of 47 potential deposits chosen for closer examination 12 were selected as probable newly identified pyroclastic deposits potential pyroclastic deposits were generally found in settings similar to previously identified deposits including areas within or near mare deposits adjacent to highlands within floor fractured craters and along fissures in mare deposits however a significant new finding is the discovery of localized pyroclastic deposits within floor fractured craters anderson e and f on the lunar farside isolated from other known similar deposits our search confirms that most major regional and localized low albedo pyroclastic deposits have been identified on the moon down to 100 m pix resolution and that additional newly identified deposits are likely to be either isolated small deposits or additional portions of discontinuous patchy deposits

morphometric analysis of small scale lobate scarps on the moon using data from the lunar reconnaissance orbiter 1 prior to lunar reconnaissance orbiter lro the morphology and dimensions of only a limited number of lobate scarps all located near the equator within 21 had been characterized topography derived from lro camera stereo images and lunar orbiter laser altimeter lola ranging is used to measure the relief and analyze the morphology of previously known and newly detected low and high latitude lobate scarps the asymmetric profiles and maximum slopes on scarp faces 5 to 29 of lunar lobate scarps are similar to those of lobate scarps observed on mars and mercury scarp lengths range from 0 6 to 21 6 km mean 6 0 km median 4 4 km n 79 and measured relief ranges from 5 to 150 m mean 35 m median 20 m n 26 assuming a range of 20 to 40 for the fault plane dip estimated lower limits for the horizontal shortening s expressed by the lobate scarp thrust faults range from 10 to 410 m the range in s estimated for the lunar scarps is roughly an order of magnitude lower than estimates of s for lobate scarp thrust faults on mars and mercury the relatively small range of s estimated for the growing number of well characterized lunar scarps is consistent with a small amount of global contraction

persistently illuminated regions at the lunar poles ideal sites for future exploration abstract the lunar reconnaissance orbiter camera lroc provides multi temporal and high resolution imaging of the north and south polar regions these images delimit illuminated areas from those in shadow and are used to analyze the illumination environment of the polar regions over the course of a lunar year the wide angle camera wac provides repeat imaging of the north and south pole at a frequency of roughly 2 h with a ground sampling distance of 100 m the lroc narrow angle camera nac acquires images with a ground sampling distance of 0 5 2 0 m providing the means to construct high resolution maps that reveal illuminated terrain under varying lighting conditions with the multi temporal coverage provided by the wac and the high resolution images from the nac the lroc dataset enables a more comprehensive analysis of the illumination conditions near the lunar poles than any previous image based dataset furthermore these images are used to validate previously published numerical models that simulate polar illumination conditions from our analysis of the lroc images we identified localized regions where the lunar surface remains illuminated for nearly 94 of the year with the longest eclipsed period lasting only 43 h we also identified small illuminated peaks tens of meters across in areas previously modeled to be in shadow together the wac and nac dataset provide direct high resolution observations of the actual surface illumination environment of potential exploration sites near the lunar poles

fluxes of fast and epithermal neutrons from lunar prospector evidence for water ice at the lunar poles maps of epithermal and fast neutron fluxes measured by lunar prospector were used to search for deposits enriched in hydrogen at both lunar poles depressions in epithermal fluxes were observed close to permanently shaded areas at both poles the peak depression at the north pole is 4 6 percent below the average epithermal flux intensity at lower latitudes and that at the south pole is 3 0 percent below the low latitude average no measurable depression in fast neutrons is seen at either pole these data are consistent with deposits of hydrogen in the form of water ice that are covered by as much as 40 centimeters of desiccated regolith within permanently shaded craters near both poles

non mare silicic volcanism on the lunar farside at compton belkovich non basaltic volcanism is rare on the moon and has been found predominantly on the lunar nearside analysis of lunar reconnaissance orbiter camera images and spectral data reveal the presence of compositionally evolved non basaltic volcanism on the lunar farside

late permian to late triassic palaeomagnetic data from iran constraints on the migration of the iranian block through the tethyan ocean and initial destruction of pangaea summary a palaeomagnetic study of late permian to early jurassic rocks from the alborz and sanandaj sirjan zones in iran and a compilation of selected palaeopoles from the carboniferous to the present provide an updated history of the motion of the iranian block within the tethys ocean the iran assemblage part of gondwana during the palaeozoic rifted away by the end of the permian we ascertain the southernhemisphere palaeoposition of iran at that time using magnetostratigraphy and show that it was situated close to arabia near to its relative position today a northward transit of this block during the triassic is shown with an estimated expansion rate of the neotethyan ridge of 100 140 km myr 1 the northward convergence with respect to eurasia ended during the ladinian middle triassic and is marked by a collision in the northern hemisphere with the turan platform which was the southern margin of the eurasian continent at that time no north south component of shortening is evidenced north of iran afterwards an analysis of the declinations from the late permian to the present shows diverent large rotations emphasizing the important tectonic phases suvered since the triassic finally we propose palaeomagnetic reconstructions of the tethys area during the late permian and the late triassic showing that the palaeotethys ocean was narrower than previously thought and did not widen its gate to the panthalassa before the triassic period

initial results for the north pole of the moon from mini sar chandrayaan 1 mission 1 we present new polarimetric radar data for the surface of the north pole of the moon acquired with the mini sar experiment onboard india s chandrayaan 1 spacecraft between mid february and mid april 2009 mini sar mapped more than 95 of the areas polewards of 80 latitude at a resolution of 150 meters the north polar region displays backscatter properties typical for the moon with circular polarization ratio cpr values in the range of 0 1 0 3 increasing to over 1 0 for young primary impact craters these higher cpr values likely reflect surface roughness associated with these fresh features in contrast some craters in this region show elevated cpr in their interiors but not exterior to their rims almost all of these features are in permanent sun shadow and correlate with proposed locations of polar ice modeled on the basis of lunar prospector neutron data these relations are consistent with deposits of water ice in these craters

archaean boninite like rocks in an intracratonic setting abstract boninites and high mg norites show considerable compositional overlap while the petrogenesis of both may involve large ion lithophile element lile replenishment of a mantle source boninites appear restricted to convergent margin settings while many high mg norite suites intrude intracratonic rifts rocks with boninitic compositions are extremely rare in archaean terranes where they are also interpreted to have formed at convergent margins high mg lile enriched basaltic rocks form a ca 2950 ma sub volcanic sill within the 3010 2935 ma mallina basin of the pilbara craton northwest australia they are spatially associated with low ti tholeiitic intrusions and a high mg diorite sanukitoid suite they have a strong boninitic affinity with high sio 2 52 54 wt mg 62 67 and al 2 o 3 tio 2 62 73 low tio 2 0 24 0 28 wt and strong lile enrichments primitive mantle normalised la gd and gd yb ratios of 4 5 and 0 6 respectively produce prominent u shaped normalised trace element patterns despite such close compositional affinity to boninite these rocks probably formed more than 40 myr after regional magmatism and 60 myr after the last regional event linked to subduction geological evidence suggests that the mallina basin formed in an intracontinental setting not at a convergent margin and so high mg norite provides a more realistic analogy for the mallina boninite like rocks in terms of tectonic setting in old terranes the tectonic setting of rocks with boninite like compositions must be interpreted with caution trace element modelling shows that contamination by felsic crust is a plausible explanation for lile enrichments in the mallina boninite like rocks but the scarcity of suitable contaminants makes this explanation unlikely petrogenesis of the boninite like rocks was closely associated with that of the high mg diorite sanukitoid suite lile enrichments in high mg diorite require that the mantle beneath the entire mallina basin was variably metasomatically enriched by an earlier subduction event at or before ca 3015 ma the refractory source for the boninite like rocks may have also been enriched during this event

geochemistry and isotopic characteristics of mafic phulad ophiolite and related rocks in the delhi supergroup rajasthan india implications for rifting in the proterozoic abstract regionally metamorphosed mafic rocks phulad ophiolite in the delhi supergroup n w india have tholeiitic compositions the data indicate that there are two independent rock suites phulad barr jetgarh pbj meta basalts with element abundances and ratios resembling midocean ridge basalts morb and ranakpur desuri r d meta basalts and meta gabbros with relatively high al2o3 and low tio2 for similar mgo and high lil element rb ba sr coupled with low hfs zr nb and ree sm nd abundances the compositions of these rocks are characteristic of ocean arc basalts dioritic rocks at ranakpur exhibit low k tholeiitic differentiation trends and have close chemical affinity with the spatially associated meta basalts ranakpur diorites define a sm nd whole rock isochron corresponding to an age of 1012 78 ma with an initial nd isotopic composition that is similar to bulk earth sm nd mineral isochrons for a meta gabbro diorite and quartz diorite at ranakpur correspond to ages of 838 36 835 43 and 791 43 ma respectively these younger ages reflect metamorphic re equilibration of isotope compositions during widespread granite and granodiorite emplacement in this region during the late proterozoic model sm nd ages for the meta basalts calculated relative to undepleted mantle vary between 1300 1700 ma the chemistry of both mafic rock suites indicates derivation from source regions which had been depleted during previous melting episodes so the model ages are a maximum age constraint ranakpur desuri mafic rocks have negative initial nd 1 0 to 4 5 and low sm nd ratios suggesting crustal contamination or reworking with a few exceptions the pbj meta basalts have positive initial nd 1 5 to 4 8 indicating that they were derived from heterogeneously enriched although longterm depleted mantle the chemical data support the hypothesis that the pbj meta basalts are fragments of proterozoic ocean crust

geochemistry and u pb zircon geochronology of the alvand plutonic complex in sanandaj sirjan zone iran new evidence for jurassic magmatism abstract this paper presents geochemical sr nd isotopic and u pb zircon geochronological data on the alvand plutonic complex in sanandaj sirjan zone ssz western iran the gabbroic rocks show a trend of a calc alkaline magma suite and are characterized by low initial 87 sr 86 sr ratios 0 7023 0 7037 and positive e nd t values 2 9 3 3 which suggest derivation from a moderately depleted mantle source geochemical features of the granites illustrate a high k calc alkaline magma series whereas the leucocratic granitoids form part of a low k series granites have intermediate 87 sr 86 sr ratios 0 707 0 719 and negative e nd t values 1 0 to 3 4 while leucocratic granitoids have higher initial 87 sr 86 sr ratio 0 713 0 714 and more negative e nd t values 3 5 to 4 5 potential basement source lithologies for the granites are proterozoic granites and orthogneisses and those for the leucocratic granites are plagioclase rich sources such as meta arkoses or tonalites the u pb dating results demonstrate that all granitoids were exclusively emplaced during the jurassic instead of being cretaceous or younger in age as suggested previously the pluton was assembled incrementally over c 10 ma gabbros formed at 166 5 1 8 ma granites between 163 9 0 9 ma and 161 7 0 6 ma and leucocratic granitoids between 154 4 1 3 and 153 3 2 7 ma granites and leucocratic granitoids show some a type affinity it is concluded that the alvand plutonic complex was generated in a continental arc related extensional regime during subduction of neo tethyan oceanic crust beneath the ssz the u pb zircon age data recently corroborated by similar results in the central and southern ssz indicate that jurassic granitoids are more areally extensive in this belt than previously thought

late cretaceous and early miocene andean type plutonic activity in northern makran and central iran two calc alkaline plutonic complexes bazman and natanz intruded through the south eastern active and south western ancient continental margins of central iran have been dated by the rb sr whole rock isochron method at 74 2 and 24 4 5 ma respectively detailed trace element studies together with low 87 sr 86 sr initial ratios 87 sr 86 sr ratios and the gabbros at least were intruded some 10 ma earlier

u pb zircon ages and geochemistry of kangareh and taghiabad mafic bodies in northern sanandaj sirjan zone iran evidence for intra oceanic arc and back arc tectonic regime in late jurassic abstract the northern sanandaj sirjan zone sasz in northwestern iran contains several granitoid and gabbroic bodies that are parallel to the zagros suture zone in a northwest southeast direction the fine grained taghiabad gabbro and coarse grained kangareh gabbroic bodies southwest of the ghorveh in the northern sasz were crystallized at 158 0 10 0 ma and 148 3 3 6 ma respectively based on u pb zircon dating the sio 2 contents of the kangareh and taghiabad rocks are similar and range from 45 5 to 51 5 wt and the al 2 o 3 contents vary from 14 to 24 wt with high mg number mg 61 72 and 46 63 respectively the taghiabad body has higher contents of tio 2 fe 2 o 3 and p 2 o 5 than the kangareh rocks the fe 2 o 3 contents of the taghiabad rocks vary from 6 to 15 wt whereas those of the kangareh rocks range from 5 to 9 wt the tio 2 concentrations of the taghiabad samples are high 1 3 wt and these rocks can be classified as high ti and fe rocks the chemical compositions of the two bodies show some clear differences positive end t values 3 to 8 and low initial 87 sr 86 sr ratios 0 7034 to 0 7054 indicate a depleted mantle source for both bodies the variation and distribution of trace elements rees patterns and initial 87 sr 86 sr 143 nd 144 nd ratios show that the kangareh and taghiabad bodies have high affinities to tholeiitic and alkaline magmatic series these results suggest an arc and back arc system regime in an intra oceanic system than the andean magmatic type regime for the origin of these bodies in the middle to late jurassic period these complexes merged with the northern sasz during accretion type continental growth in the late jurassic

relative rates of optical maturation of regolith on mercury and the moon 1 quantifying relative differences in regolith optical maturation rates is critical to interpreting multispectral reflectance measurements of airless bodies in this study normalized reflectance measurements of crater ejecta blankets and rays are used as indicators of the relative state of regolith maturation on mercury and the moon as well as for a comparison of surface reflectance characterization of craters with high reflectance ejecta from lunar reconnaissance orbiter camera and mercury dual imaging system orbital mosaics indicates that the optical maturation rate is up to 4 times faster on mercury than on the moon observations also show that there are fewer immature craters per unit area on mercury than on the moon and suggest a younger average age for mercurian rayed craters than for lunar rayed craters a comparison of crustal reflectance of immature material yields a ratio of 1 9 0 4 for the average photometrically normalized reflectance of lunar material to that of mercurian material the difference in reflectance is attributed primarily to differences in composition between the lunar highlands and average surface material on mercury the new observations of immature craters per unit area and surface reflectance of immature materials are consistent with previous proposals that regolith maturation rates are faster on mercury than the moon and but here we quantify the relative rate from empirical observations for the first time

thickness of proximal ejecta from the orientale basin from lunar orbiter laser altimeter lola data implications for multi ring basin formation 1 quantifying the ejecta distribution around large lunar basins is important to understanding the origin of basin rings the volume of the transient cavity the depth of sampling and the nature of the basin formation processes we have used newly obtained altimetry data of the moon from the lunar orbiter laser altimeter lola instrument to estimate the thickness of ejecta in the region surrounding the orientale impact basin the youngest and best preserved large basin on the moon our measurements yield ejecta thicknesses of 2900 m near the cordillera mountains the topographic rim of orientale decaying to 1k m in thickness at a range of 215 km these measurements imply a volume of ejecta in the region from the cordillera ring to a radial range of one basin diameter of 2 9 10 6 km 3 and permit the derivation of an ejecta thickness decay model which can be compared with estimates for the volume of excavation and the size of the transient cavity these data are consistent with the outer rook mountains as the approximate location of the transient cavity s rim crest and suggest a volume of 4 8 10 6 km 3 for the total amount

formation of lunar mare domes along crustal fractures rheologic conditions dimensions of feeder dikes and the role of magma evolution abstract in this study we examine a set of lunar mare domes located in the hortensius milichius t mayer region and in northern mare tranquillitatis with respect to their formation along crustal fractures their rheologic properties the dimensions of their feeder dikes and the importance of magma evolution processes during dome formation many of these domes display elongated summit vents oriented radially with respect to major impact basins and several dome locations are also aligned in these preferential directions analysis of clementine uv vis and lunar prospector gamma ray spectrometer data reveals that the examined mare domes formed from low si basaltic lavas of high feo and low to moderate tio2 content based on their morphometric properties diameter height volume obtained by photoclinometric and shape from shading analysis of telescopic ccd images we derive rheologic quantities lava viscosity during eruption effusion rate duration of the effusion process magma rise speed and the dimensions of the feeder dikes we establish three rheologic groups characterised by specific combinations of rheologic properties and dike dimensions where the most relevant discriminative parameter is the lava viscosity the first group is characterised by 10 4 pa s 10 6 pa s and contains the domes with elongated vents in the milichius t mayer region and two similar domes in northern mare tranquillitatis the second group with 10 2 pa s 10 4 pa s comprises the very low aligned domes in northern mare tranquillitatis and the third group with 10 6 pa s 10 8 pa s the relatively steep domes near hortensius and in the t mayer region the inferred dike dimensions in comparison to lunar crustal thickness data indicate that the source regions of the feeder dikes are situated within the upper crust for six of the domes in northern mare tranquillitatis while they are likely to be located in the lower crust and in the upper mantle for the other examined domes by comparing the time scale of magma ascent with the time scale on which heat is conducted from the magma into the host rock we find evidence that the importance of magma evolution processes during ascent such as cooling and crystallisation increases with lava viscosity we conclude that different degrees of evolution of initially fluid basaltic magma are able to explain the broad range of lava viscosities inferred for the examined mare domes the spectral data reveal that differences in tio2 content may additionally account for the systematic difference in lava viscosity between the two examined lunar regions we show that the described mechanisms are likely to be valid also for other lunar mare domes situated near cauchy and arago regarded for comparison on the other hand we find for the gruithuisen and mairan highland domes that despite their inferred high lava viscosities of 10 8 10 9 pa s no significant magma cooling in the dike occurred during ascent supporting previous findings that the highland domes were formed during a specific phase of non mare volcanism by highly silicic viscous lavas

strike slip faulting in the central part of the sanandaj sirjan zone zagros orogen iran abstract the sanandaj sirjan zone ssz is one of the main basement tectonic blocks located close to the northeastern margin of the zagros orogenic belt new observations in the central part of the zone indicate that the fault pattern is dominated by nw trending longitudinal faults the components of movement on the fault planes are interpreted as dextral oblique thrusting and dextral strike slip the identified structures along the faults were associated with the strike slip faults e g hasan robat and najafabad dextral restraining stepovers and rotated tectonic blocks arranged in a domino configuration near to the foladshahr and kolah ghazi mountains along the longitudinal faults the dextral offsets of the rock units streams alluvial deposits and rivers were measured the dextral offset values range from 2 4 to 2 7 km while the estimated offsets based on the geomorphological features are between 50 and 61 m for streams up to approximately 50 m for alluvial deposits and up to 2 2 km for rivers the dextral strike slip component on the fault planes occurs along the northern and southern margins of the ssz as well as directly within the zone west and east of the study area the evidence for strike slip faulting in the internal part of the zone suggests that the central part of the ssz probably was horizontally sheared in a manner consistent with a simple shear card deck model

characterization of space weathering from lunar reconnaissance orbiter camera ultraviolet observations of the moon we investigate the effects of space weathering at ultraviolet wavelengths using a near global seven band 321 689 nm mosaic from the lunar reconnaissance orbiter camera lroc wide angle camera wac we confirm that for moderate to high iron compositions 5 wt feo the steeply positive uv slope at wavelengths 415 nm shallows with increasing exposure to space weathering we measure these differences in lroc wac data as variations in the 321 415 nm ratio which has low values for fresh craters in the mare and moderate iron highlands for low iron highland compositions the break in slope occurs at shorter wavelengths and it is instead the 321 360 nm ratio that increases with exposure to the space weathering environment whereas the 321 415 nm ratio appears to be largely controlled by the degree of shock experienced during the impact the effects of shock may be more important at highland craters because modest shock pressures result in the solid state transformation of plagioclase to its glass equivalent maskelynite and can help distinguish between primary shocked ejecta and locally exposed fresh material in rays while all of the fresh craters we examined have uv spectral properties consistent with substantial alteration due to space weathering the uv spectra of lunar swirls magnetically shielded from the solar wind are consistent with exposure of immature crystalline material together these results suggest that lunar space weathering is dominated by the solar wind and saturates in the uv at is feo values of 40 submature

geology of the king crater region new insights into impact melt dynamics on the moon 1 new geologic sketch maps and digital elevation models for king crater and the surrounding lunar farside highlands were created from lunar reconnaissance orbiter camera lroc wide angle camera wac and narrow angle camera nac images nac images reveal that high volume impact melt accumulations exhibit evidence of dynamic processes during and following emplacement that resulted in downwarped zones and other morphologic anomalies visible at the 50 cm pixel scale among the most significant of these forms are negative relief features some of which may represent evidence for near surface caverns offering points of access to subsurface environments and possible shelter from surface hazards other negative relief features may represent regions of extension and separation in response to possible subsurface drainage together with isostatic readjustments contraction and or compaction in the cooling impact melt crater counts on the continuous ejecta blanket suggest a late eratosthenian to copernican age for king crater which is older than the estimate of young 1977 but consistent with those of others

plate tectonic evolution of the southern margin of eurasia in the mesozoic and cenozoic abstract thirteen time interval maps were constructed which depict the triassic to neogene plate tectonic configuration paleogeography and general lithofacies of the southern margin of eurasia the aim of this paper is to provide an outline of the geodynamic evolution and position of the major tectonic elements of the area within a global framework the hercynian orogeny was completed by the collision of gondwana and laurussia whereas the tethys ocean formed the embayment between the eurasian and gondwanian branches of pangea during late triassic early jurassic times several microplates were sutured to the eurasian margin closing the paleotethys ocean a jurassic cretaceous north dipping subduction boundary was developed along this new continental margin south of the pontides transcaucasus and iranian plates the subduction zone trench pulling effect caused rifting creating the back arc basin of the greater caucasus proto south caspian sea which achieved its maximum width during the late cretaceous in the western tethys separation of eurasia from gondwana resulted in the formation of the ligurian penninic pieniny magura ocean alpine tethys as an extension of middle atlantic system and a part of the pangean breakup tectonic system during late jurassic early cretaceous times the outer carpathian rift developed the opening of the western black sea occurred by rifting and drifting of the western central pontides away from the moesian and scythian platforms of eurasia during the early cretaceous cenomanian the latest cretaceous paleogene was the time of the closure of the ligurian pieniny ocean adria alcapa terranes continued their northward movement during eocene early miocene times their oblique collision with the north european plate led to the development of the accretionary wedge of the outer carpathians and its foreland basin the formation of the west carpathian thrusts was completed by the miocene the thrust front was still propagating eastwards in the eastern carpathians during the late cretaceous the lesser caucasus sanandaj sirjan and makran plates were sutured to the iranian afghanistan plates in the caucasus caspian sea area a north dipping subduction zone jumped during paleogene to the scythian turan platform the shatski terrane moved northward closing the greater caucasus basin and opening the eastern black sea the south caspian underwent reorganization during oligocene neogene times the southwestern part of the south caspian basin was reopened while the northwestern part was gradually reduced in size the collision of india and the lut plate with eurasia caused the deformation of central asia and created a system of nw se wrench faults the remnants of jurassic cretaceous back arc systems oceanic and attenuated crust as well as tertiary oceanic and attenuated crust were locked between adjacent continental plates and orogenic systems

petrology and geochemistry of the central north fiji basin spreading centre southwest pacific between 16 s and 22 s abstract the north fiji basin nfb is a 12 m y old back arc basin that has a complex multi stage history the presently active spreading system can be divided into four segments between 16 s and 22 s which from north to south trend n160 n15 and n s the fourth segment is the n s trending segment located near 174e the main n s segment is morphologically similar to other medium rate oceanic ridges whereas the other segments have rougher morphologies which have been severely disturbed by a triple junction at 16 45 s and several instability features such as overlapping spreading centres oscs and propagating rifts the spreading rate seems to diminish from 7 8 cm yr near 20 s to 4 6 cm yr near 18 s mineralogical pertological and geochemical data were obtained on 24 new stations located along all the four segments the petrogenesis of the basalts collected is essentially controlled by low pressure crystal fractionation of plagioclase olivine clinopyroxene plagioclase olivine clinopyroxene with 52 of the nfb basalts reaching the four phase cotectic locally some magma mixing occurs but this is limited to magma batches of closely related composition as might be expected to occur inside a magma reservoir the n s segment which since 3 m y is the only steady state segment is also petrologically and geochemically very comparable to other medium rate oceanic spreading centres producing moderately evolved lile and lree depleted n morb in contrast the three other segments produce basalts of much more variable petrology and geochemistry characterized by lile and slightly lree enriched magmas cf back arc basin basalt babb affinity but not as enriched as for example the mariana babb morb is however also found on the n160 n15 and 174e segments diagrams using ba rb k p and k ti n normalized to the chondrites plotted against latitude clearly show along strike variations beneath the recently formed segments the mantle source is heterogeneous and locally has some babb affinities whereas beneath the more steady state n s segment the magma source is more homogeneous being generally depleted in lile and ree as is the case for classical n morb mantle sources simple evolution from an early stage of babb production to morb described in the lau basin and proposed for the nfb does not seem to occur present day activity still produces large amounts of babb along the less stable and more recently created segments and morb was produced in the earlier stages of the development of the nfb

the mairan domes silicic volcanic constructs on the moon 1 the mairan domes are four features located in northern oceanus procellarum at 312 3e 41 4n on the moon high resolution visible imagery visible to mid ir spectra and lunar prospector th abundance data all indicate that these four domes have a composition that is consistent with derivation from a si rich highly evolved magma

new insight into lunar impact melt mobility from the lro camera 1 the lunar reconnaissance orbiter camera lroc is systematically imaging impact melt deposits in and around lunar craters at meter and sub meter scales these images reveal that lunar impact melts although morphologically similar to terrestrial lava flows of similar size exhibit distinctive features e g erosional channels although generated in a single rapid event the post impact mobility and morphology of lunar impact melts is surprisingly complex we present evidence for multi stage influx of impact melt into flow lobes and crater floor ponds our volume and cooling time estimates for the post emplacement melt movements noted in lroc images suggest that new flows can emerge from melt ponds an extended time period after the impact event

predominance of high th u magmatic zircon in brazilian shield sandstones the strong predominance of magmatic th u 0 2 zircon grains in quartz sandstones from 10 locations in the brazilian shield as measured by sensitive high resolution ion microprobe shrimp introduces a strong bias in the tectonic interpretation of source terrains because the metamorphic sources remain undetected in the detrital population zircon grains from many mature and some immature sedimentary terrains show th u ratios 0 2 ratios commonly considered magmatic complemented by the near absence of metamorphic th u ratios 0 1 metamorphic rims on magmatic zircon grains from the brazilian shield are nearly absent from quartz sandstones only being present in shielded young cores of a few crystals high u metamorphic portions of zircon grains are more defective and liable to undergo comminution by abrasion during weathering and transport and they do not remain in the sand fraction ages obtained from detrital zircon in mature sandstones reflect magmatic sources not the full spectrum of orogenic events only less mature sedimentary rocks preserve a full record of orogenic rocks in the source mostly magmatic events were characterized in previous zircon provenance studies brazilian shield detrital zircon may be a proxy for equivalent investigations in other provinces of the world

petrogenesis of the carboniferous ghaleh dezh metagranite sanandaj sirjan zone iran constraints from new zircon u pb and 40ar 39ar ages and sr nd isotopes

lro observations of morphology and surface roughness of volcanic cones and lobate lava flows in the marius hills 1 the volcanic domes cones sinuous rilles and pyroclastic deposits of the marius hills region of the moon 13 4 n 304 6 e represent a significant episode of magmatic activity at or near the lunar surface that is still poorly understood comparisons between lroc nac block populations mini rf data and diviner derived rock abundances confirm that blocky lava flows comprise the domes of the marius hills 8 m features measured by diviner indicate that the domes are not rich in silica and are not significantly different than surrounding mare materials lroc observations indicate that some of the dome building lava flows originated directly from volcanic cones many of the cones are c shaped while others are irregularly shaped and local topography and lava eruptions affect cone shape in general the cones are morphologically similar to terrestrial cinder and lava cones and are composed of varying amounts of cinder spatter and lava many of the cones are found in local groupings or alignments the wide range of volcanic features from broad low domes to steep cones represents a range of variable eruption conditions complex morphologies and variable layering show that eruption conditions were variable over the plateau

subsurface migration of h2o at lunar cold traps 1 permanently shaded areas near the poles of the moon and mercury may harbor water ice we develop a physical model for migration of water molecules in the regolith and discover two pathways that can lead to accumulation of h2o in the subsurface a small fraction of water molecules delivered either continuously or abruptly to permanently cold areas diffuses into the regolith and can remain there longer than on the surface higher temperatures lead to deeper burial at constant temperature this diffusive migration produces less than one molecular layer of volatile h2o on grains because it is driven by differences in surface concentrations the water is therefore expected to be in adsorbed form and the amount stored in this fashion could be at most a few hundred ppm of h2o a second pathway is pumping by diurnal temperature oscillations from a transient ice cover that may have formed during a large comet impact it can lead to high ground ice densities but the ground ice layer lasts not long beyond the disappearance of the ice cover both types of subsurface charging mechanism work best for temperatures typical of permanently shaded areas with sunlit surfaces in their field of view

a new tectonic scenario for the sanandaj sirjan zone iran abstract recent geochemical studies of volcanic rocks forming part of the ophiolites within the zagros and naien baft orogen indicate that most of them were developed as supra subduction ophiolites in intra oceanic island arc environments intra oceanic island arcs and ophiolites now forming the naien baft zone were emplaced southwestward onto the northeastern margin of the south sanandaj sirjan zone while those now in the high zagros were emplaced southwestward onto the northern margin of arabia thereafter subduction continued on opposite sides of the remnant oceans the floor of neo tethys ocean was subducted at a low angle beneath the entire sanandaj sirjan zone and the floor of the naien baft ocean was subducted beneath the central iranian micro continent the naien baft ocean extended into north west iran only temporarily this failed ocean arm between the urumieh dokhtar magmatic assemblage and the main zagros thrust was filled by thick upper triassic upper jurassic sediments the naien baft ocean finally closed in the paleocene and neo tethys closed in the early to middle eocene after arabia was sutured to iran the urumieh dokhtar magmatic assemblage recorded slab break off in the middle eocene

lunar radiation environment and space weathering from the cosmic ray telescope for the effects of radiation crater 1 the cosmic ray telescope for the effects of radiation crater measures linear energy transfer by galactic cosmic rays gcrs and solar energetic particles seps on the lunar reconnaissance orbiter lro mission in a circular polar lunar orbit gcr fluxes remain at the highest levels ever observed during the space age one of the largest sep events observed by crater during the lro mission occurred on june 7 2011 we compare model predictions by the earth moon mars radiation environment module emmrem for both dose rates from gcrs and seps during this event with results from crater we find agreement between these models and the crater dose rates which together demonstrate the accuracy of emmrem and its suitability for a real time space weather system we utilize crater to test forecasts made by the relativistic electron alert system for exploration release which successfully predicts the june 7th event at the maximum crater observed gcr dose rate 11 7 cgy yr where gy is a unit indicating energy deposition per unit mass 1 gy 1 j kg gcrs deposit 88 ev molecule in water over 4 billion years causing significant change in molecular composition and physical structure e g density color crystallinity of water ice loss of molecular hydrogen and production of more complex molecules linking carbon and other elements in the irradiated ice this shows that space weathering by gcrs may be extremely important for chemical evolution of ice on the moon thus we show comprehensive observations from the crater instrument on the lunar reconnaissance orbiter that characterizes the radiation environment and space weathering on the moon

sequential magma injection with a wide range of mixing and mingling in late jurassic plutons southern ghorveh western iran abstract intrusive bodies with a wide ranging geology are distributed in the central part of the sanandaj sirjan zone c sasz in southern ghorveh western iran the zircon u pb ages were dated at 154 146 ma and were characterized by low 87sr 87sr i ratios and high 143nd 144nd i ratios that ranged from 0 7035 to 0 7061 and 0 51245 to 0 51271 respectively positive end t values magma differentiation and mixing formed different magmatic rocks that range widely from gabbro to granite in the meiham shirvaneh area in southern ghorveh however there was no clear evidence to support the slab role for the enrichment of large ion lithophile elements liles and light rare earth elements lrees in this area meanwhile there is a possibility that some ocean island basalt like melt which has been reported in the ghorveh area for the same period was involved in the minor enrichment of liles and lrees the high development of the released depleted mantle melts with a minor role played by crustal components accelerated the thinning of the continental crust in an extensional regime such as continental rift in the c sasz during the jurassic this rift was responsible for the sequential injection of mafic magma with a wide range of magma mixing and mingling in southern ghorveh during the late jurassic as a result we observed a wide range of intrusive rocks from gabbro to granite with different compositions which included some clear mixing and hybrid textures this finding demonstrated how the released mantle melt formed a thicker crust in western iran

large shield volcanoes on the moon 1 the volcanic style of the moon has long been understood to consist almost exclusively of flood basalts erupted from fissures along with minor pyroclastic activity large central vent shield volcanoes that characterize basaltic volcanism on the other terrestrial planets appeared to be absent small few kilometers diameter central vent constructs have long been recognized in the lunar maria and often are found clustered in fields throughout the lunar maria new global topographic data from the lola and lroc instruments on lro reveal that almost all of these volcanic complexes on the moon occur on large regional topographic rises in the lunar maria tens to hundreds of kilometers in extent and between several hundred to several thousand meters high we propose that these topographic swells are shield volcanoes and are the lunar equivalents of the large basaltic shields found on the earth venus and mars the newly recognized lunar shields are found peripheral to the large deeply flooded impact basins imbrium and serenitatis suggesting a genetic relation to those features loading of the lithosphere by these basalt filled basins may be responsible for inducing a combination of flexural and membrane stress inducing a pressure distribution on vertically oriented dikes favorable to magma ascent this condition would occur in a zone annular to the large circular loads produced by the basins where the shield volcanoes occur

the lunar reconnaissance orbiter mission six years of science and exploration at the moon abstract since entering lunar orbit on june 23 2009 the lunar reconnaissance orbiter lro has made comprehensive measurements of the moon and its environment the seven lro instruments use a variety of primarily remote sensing techniques to obtain a unique set of observations these measurements provide new information regarding the physical properties of the lunar surface the lunar environment and the location of volatiles and other resources scientific interpretation of these observations improves our understanding of the geologic history of the moon its current state and what its history can tell us about the evolution of the solar system scientific results from lro observations overturned existing paradigms and deepened our appreciation of the complex nature of our nearest neighbor this paper summarizes the capabilities measurements and some of the science and exploration results of the first six years of the lro mission

cretaceous tertiary convergence and continental collision sanandaj sirjan zone western iran abstract the sanandaj sirjan zone contains the metamorphic core of the zagros continental collision zone in western iran the zone has been subdivided into the following from southwest to northeast an outer belt of imbricate thrust slices radiolarite bisotun ophiolite and marginal sub zones which consist of mesozoic deep marine sediments shallow marine carbonates oceanic crust and volcanic arc respectively and an inner complexly deformed sub zone late palaeozoic mesozoic passive margin succession rifting and sea floor spreading of tethys occurred in the permian to triassic but in the sanandaj sirjan zone extension related successions are mainly of late triassic age subduction of tethyan sea floor in the late jurassic to cretaceous produced deformation metamorphism and unconformities in the marginal and complexly deformed sub zones deformation climaxed in the late cretaceous when a major southwest vergent fold belt formed associated with greenschist facies metamorphism and post dated by abundant palaeogene granitic plutons in the southwest of the zone a late cretaceous island arc passive margin collision occurred with ophiolite emplacement onto the northern arabian margin similar to that in oman final closure of tethys was not completed until the miocene when central iran collided with the northeast arabian margin

jurassic transgressions and regressions in the caucasus northern neotethys ocean and their influences on the marine biodiversity abstract in the jurassic the caucasus presently located in the southwest of russia georgia armenia and azerbaijan was located on the northern active margin of the neotethys ocean facies interpretation in all 62 areas distinguished by differences in facies allows to semi quantitatively evaluate jurassic regional transgressions and regressions for this region major transgressive regressive cycles took place in the hettangian aalenian bajocian bathonian and callovian tithonian each transgression was more extensive than the previous the same cycles are established in the greater caucasus basin deep marine environments were common in the pliensbachian late aalenian and late bathonian whereas they were very restricted in the late jurassic the jurassic transgressions and regressions in the caucasus coincided with the proposed global eustatic changes however some differences were caused by the regional tectonic activity although transgressions and regressions cause some changes in marine biodiversity it seems that only ammonites might have been directly influenced by them diversity of bivalves brachiopods and belemnites was driven by other factors however global changes in marine biodiversity were more closely related to the eustatic fluctuations than it was documented on a regional scale

dating small fresh lunar craters with mini rf radar observations of ejecta blankets 1 the ages of large impact craters on the moon can be estimated by measuring the size frequency distribution of smaller craters superimposed on their ejecta but applying this method to individual craters under 3 km in diameter remains difficult due to their limited areal extent the ejecta blankets of fresh lunar impact craters are expressed as halos of optical and radar bright material that gradually fade with time although compositional differences make inferring crater ages from optical albedo problematic radar is less sensitive to composition and thus may provide a more reliable means of estimating age in this work we use radar data from the miniature radio frequency mini rf instrument on the lunar reconnaissance orbiter lro to characterize the radar backscatter of large numbers of ejecta blankets by analyzing the size frequency distribution of these craters we show that the lifetime of the radar bright discontinuous ejecta blanket varies with crater diameter in a predictable way for craters with diameters between 0 45 and 5 km absolute ages of individual craters can then be estimated by combining this empirically derived model with estimates of the relative degradation state of each individual crater the lifetimes of radar bright discontinuous ejecta blankets are significantly shorter in the highlands than the maria although this is likely due to local topography creating difficulties in applying the method to the highlands the cosmic ray exposure age of south ray crater a fresh crater visited by apollo 16 provides confirmation of these results this method therefore provides a new way to accurately date small fresh craters using the mini rf data set

early permian pangea b to late permian pangea a the pre drift wegenerian model of pangea is almost universally accepted but debate exists on its pre jurassic configuration since tedirving introd ucedpangea b by placing gond wana farther to the east by v3000 km with respect to laurasia on the basis of paleomagnetic data new paleomagnetic data from radiometrically dated early permian volcanic rocks from parts of adria that are tectonically coherent with africa gondwana integrated with published coeval data from gondwana and laurasia again only from igneous rocks fully support a pangea b configuration in the early permian the use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for pangea b the ultimate option to reject pangea b is to abandon the geocentric axial dipole hypothesis by introducing a significant non dipole zonal octupole component in the late paleozoic time averaged geomagnetic field we demonstrate however by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from gondwana as well as laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for pangea b in the early permian we therefore regard the paleomagnetic evidence for an early permian pangea b as robust the transformation from pangea b to pangea a took place during the permian because late permian paleomagnetic data allow a pangea a configuration we therefore review geological evidence from the literature in support of an intra pangea dextral megashear system the transformation occurred after the cooling of the variscan mega suture andlasted v20 myr in this interval the neotethys ocean opened between india arabia and the cimmerian microcontinents in the east while widespread lithospheric wrenching and magmatism took place in the west around the adriatic promontory the general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right lateral shear couple between gondwana and laurasia during the permian transcurrent plate boundaries associated with the pangea transformation reactivated variscan shear zones andwere subsequently exploitedby the opening of western neotethyan seaways in the jurassic

the late jurassic panjeh submarine volcano in the northern sanandaj sirjan zone northwest iran mantle plume or active margin abstract the tectonic setting in which jurassic igneous rocks of the sanandaj sirjan zone sasz of iran formed is controversial sasz igneous rocks are mainly intrusive granodiorite to gabbroic bodies which intrude early to middle jurassic metamorphic basement jurassic volcanic rocks are rare here we report the age and petrology of volcanic rocks from the panjeh basaltic andesitic rocks complex in the northern sasz southwest of ghorveh city the panjeh magmatic complex consists of pillowed and massive basalts andesites and microdioritic dykes and is associated with intrusive gabbros the overall sequence and relations with surrounding sediments indicate that this is an unusually well preserved submarine volcanic complex igneous rocks belong to a metaluminous sub alkaline medium k to high k calc alkaline mafic suite characterized by moderate al2o3 13 7 17 6 wt and variable fe2o3 6 0 12 6 wt and mgo 0 9 11 1 wt contents zircon u pb ages 145 149 ma define a late jurassic tithonian age for magma crystallization and emplacement whole rock compositions are enriched in th u and light rare earth elements lrees and are slightly depleted in nb ta and ti the initial ratios of 87sr 86sr 0 7039 0 7076 and end t values 1 8 to 4 3 lie along the mantle array in the field of ocean island basalts and subcontinental metasomatized mantle immobile trace element ti v zr y nb yb th and co behavior suggests that the mantle source was enriched by fluids released from a subducting slab i e deep crustal recycling with some contribution from continental crust for andesitic rocks based the chemical composition of panjeh mafic and intermediate rocks in combination with data for other gabbroic to dioritic bodies in the ghorveh area we offer two interpretations for these and other jurassic igneous rocks of the sasz as reflecting melts from a subduction modified oib type source above a neo tethys subduction zone or b plume or rift tectonics involving upwelling metasomatized mantle mostly reflecting the 550 ma cadomian crust forming event