photogeologic analysis of impact melt rich lithologies in kepler crater that could be sampled by future missions 1 kepler is a 31 km diameter copernican age complex impact crater located on the nearside maria of the moon we used lunar reconnaissance orbiter imagery and topographic data in combination with kaguya terrain camera and other image data sets to construct a new geomorphologic sketch map of the kepler crater with a focus on impact melt rich lithologies most of the interior melt rocks are preserved in smooth and hummocky floor materials smaller volumes of impact melt were deposited in rim veneer interior and exterior ponds and lobe like overlapping flows on the upper crater wall based on shadow lengths typical flows of melt rich material on crater walls and the western rim flank are 1 5 m thick and have yield strengths of 1 10 kpa the melt rock distribution is notably asymmetric with interior and exterior melt rich deposits concentrated north and west of the crater center this melt distribution and the similarly asymmetric ray distribution imply a slightly less than 45 impact trajectory from the southeast the exposed wall of kepler displays distinct layering with individual layers having typical thicknesses of 3 5 m these are interpreted as flows of procellarum mare basalts in the impact target from the point of view of exploration numerous fractures and pits in the melt rich floor materials not only enable detailed studies of melt related processes of impact crater formation but also provide potential shelters for longer duration manned lunar missions

physical constraints on impact melt properties from lunar reconnaissance orbiter camera images abstract impact melt flows exterior to copernican age craters are observed in high spatial resolution 0 5 m pixel images acquired by the lunar reconnaissance orbiter camera lroc narrow angle camera nac impact melt is mapped in detail around 15 craters ranging in diameter from 2 4 to 32 5 km this survey supports previous observations suggesting melt flows often occur at craters whose shape is influenced by topographic variation at the pre impact site impact melt flows are observed around craters as small as 2 4 km in diameter and preliminary estimates of melt volume suggest melt production at small craters can significantly exceed model predictions digital terrain models produced from targeted nac stereo images are used to examine the three dimensional properties of flow features and emplacement setting enabling physical modeling of flow parameters qualitative and quantitative observations are consistent with low viscosity melts heated above their liquidii superheated with limited amounts of entrained solids

a transient heating event in the history of a highlands troctolite from apollo 12 soil 12033 a 1 5 mm clast of a highlands troctolite attached to a glassy alkali rich soil breccia was identified in a thin section of 1 2 mm particles from apollo 12 soil sample 12033 the troctolite consists of euhedral olivines fo89 in a groundmass of granulitic plagioclase an95 each olivine grain is rimmed by a thin selvage of olivine plagioclase glass containing vesicles and minute crystallites of spinel olivine and plagioclase this unique texture records a complex history beginning with the formation of the troctolite as a plutonic cumulate followed by subsolidus metamorphism partial remelting vesculation crystallite growth and quenching experimental runs on plagioclase olivine melting rates show that at temperatures above incipient melting the grain boundary selvages in the lunar troctolite would have formed very rapidly in less than about 10 min preservation of selvage glass required rapid cooling the troctolite was subject to a heat pulse most likely accompanying an impact event the same event or more probably a later one welded the troctolite to the soil breccia inasmuch as this particle was found on oceanus procellarum at a site crossed by a ray from copernicus and because olivine has been identified by remote sensing experiments as the dominant mafic mineral in the central peak of copernicus we suggest that the troctolite is a fragment of copernicus ejecta

zn he ar and sr nd isotopic compositions of the tongkeng tin polymetallic ore deposit in south china implication for ore genesis abstract the tongkeng tin polymetallic ore deposit in nandan county guangxi zhuang autonomous region southern china is the representative deposit of the largest scale in the famous dachang tin polymetallic ore field it consists of the upper tin polymetallic ores and the lower newly found zinc copper ores with the sn metal reserve of 680 000 tons average grade 1 4 500 000 tons of zn average grade 4 and 80 000 tons of cu average grade 0 2 the orebodies occur as layers and veins within the middle to late devonian siliceous rocks and carbonate rocks in this paper the isotopic compositions of zn he ar and sr nd of the tongkeng deposit have been studied systematically the results show that the isotopic composition of zn is quite homogenous with 66zn 0 22 0 34 in sphalerite samples of various colors from brown to black collected from different orebodies upper tin polymetallic and lower zinc copper ores in the tongkeng deposit it indicates that zn source mainly came from magmatic fluid as the calculated 66zn 0 42 0 54 of ore forming fluid is almost same as that of the longxianggai granite 0 41 0 55 but quite different from that of the marine carbonate average 0 91 he ar isotope study of pyrite shows that the exhalative substances might have been involved in the mineralization with 3he 4he 1 2 ra 2 5 ra in the upper tin polymetallic ores and 3he 4he 0 8 ra 1 9 ra in the lower zinc copper ores in the tongkeng deposit which is different from that of the longxianggai granite 3he 4he 0 7 0 8 ra but close to that of the devonian liujiang formation exhalative sedimentary sequences with 3he 4he 1 5ra the longxianggai granite has isr 0 719 in average end t 7 9 9 6 and nd model age t2dm 1 54 1 68 ga based on the geochemical characteristics of granite and sr nd and o isotopes the source rocks of the longxianggai granite may be mainly derived from the continental crust which is a typical remelted s type granite based on the results of this study and the previous data in the literature it is concluded that the mineralization in the dachang ore field is closely related to the cretaceous longxianggai granite in time and space with the main metal substances of zn most likely derived from the magmatic fluid classified into the type of post magmatic hydrothermal filling metasomatism the admixing of the early devonian spouting sediments in the mineralization was evidenced in the study of source trace and has led to the longtime dispute over the ore genesis

liquidus phase relationships on the join anorthite forsterite quartz at 10 kbar with applications to basalt petrogenesis liquidus phase relationships determined on the join caal2si2o8 anorthite mg2sio4 forsterite sio2 quartz at 10 kbar show that increasing pressure causes the forsterite and anorthite primary phase fields to shrink and the spinel enstatite and silica fields to expand the boundary line between the enstatite and forsterite fields and that between the enstatite and quartz fields both move away from the sio2 apex as pressure increases therefore simplified source peridotite would yield simplified basaltic partial melts with decreasing silica as pressure increases as has been found in other studies also increasing pressure decreases the amount of silica enrichment in residual liquids produced by fractional crystallization although anorthite is unstable in simplified peridotite above 9 kbar in the system cao mgo al2o3 sio2 it is an important phase in the fractional crystallization of simplified basalts at 10 kbar and probably also in natural basalts

long term monitoring of creep rate along the hayward fault and evidence for a lasting creep response to 1989 loma prieta earthquake we present results from over 30 yr of precise surveys of creep along the hayward fault along most of the fault spatial variability in long term creep rates is well determined by these data and can help constrain 3d models of the depth of the creeping zone however creep at the south end of the fault stopped completely for more than 6 years after the m7 1989 loma prieta earthquake lpeq perhaps delayed by stress drop imposed by this event with a decade of detailed data before lpeq and a decade after it we report that creep response to that event does indeed indicate the expected deficit in creep

alha 81005 moon mars petrography and giordano bruno meteorite alha 81005 a glassy regolith breccia is beyond any reasonable doubt of lunar origin according to its petrographic chemical and isotopic characteristics the sample was shocked at most to 15 gpa during ejection and supports the possibility of some meteorites being of martian origin most lithic fragments are feldspathic granulitic impactites cataclastic anorthosites and impact melts all typical lunar lithologies mineral fragments are derived from plutonic troctolitic and noritic rocks varied mare basalt like extrusive rocks and the identified lithic fragment types neither petrographically nor chemically are there significant components in alha 81005 which were previously unknown a mare basalt component restricts the origin of the sample with remotely sensed data which eliminates most frontside as well as farside groundtrack regions it makes the probability of ejection from giordano bruno near the moon s ne limb far greater than from any other lunar crater

thermal limitations on incorporation of wall rock into magma incorporation of solid wall rocks is an oft cited process in the evolution of magmas but this process is severely limited by the energy required to dissolve xenoliths disaggregation without melting has been proposed as an alternative process for incorporating xenoliths into magma because disaggregation avoids expending the energy required for melting analysis of these processes using enthalpy composition diagrams shows that both processes rapidly lead to high crystal contents in the hybrid magma for example incorporation of 25 granite at 400 c into basalt magma at 1125 c produces a hybrid magma at 1050 c with 50 crystals if the granite disaggregates without melting the crystal content is 65 70 once the crystal content reaches 50 the viscosity of the magma is too high to allow further magma movement or xenolith incorporation thus both processes are self limiting and probably restricted in natural systems to at most a few tens of percent incorporation of xenoliths

northwest africa 482 a crystalline impact melt breccia from the lunar highlands northwest africa 482 nwa 482 is a crystalline impact melt breccia from the moon with highlands affinities the recrystallized matrix and the clast population are both highly anorthositic clasts are all related to the ferroan anorthosite suite and include isolated plagioclase crystals and lithic anorthosites troctolites and spinel troctolites potassium rare earth element and phosphorus bearing kreep and mare lithologies are both absent constraining the source area ofthis meteorite to a highland terrain with little to no kreep component most likely on the far side of the moon glass is present in shock veins cutting through the sample and in several large melt pockets indicating a second impact event there are two separate events recorded in the 40ar 39ar system one at 3750 ma which completely reset the k ar system and one at 2400 ma which caused onlypartial degassing these events could represent respectively crystallization ofthe impact melt breccia and later formation of the glass or the formation of the glass and a later thermal event the terrestrial age of the meteorite is 8 6 1 3 ka this age corresponds well with the modest amount ofweathering in the rock in the form ofsecondaryphyllosilicates and carbonates based on terrestrial age and location lithology and chemistry nwa 482 is unique among known lunar meteorites

cadmium and sulfur isotopic compositions of the tianbaoshan zn pb cd deposit sichuan province china abstract although zn pb deposits are one of the most important cd reservoirs in the earth few studies have focused on the cd isotopic fractionation in zn pb hydrothermal systems this study investigates the causes and consequences of cadmium and sulfur isotope fractionation in a large hydrothermal system at the tianbaoshan zn pb cd deposit from the sichuan yunnan guizhou syg metallogenic province sw china moderate variations in cd and s isotope compositions have been measured in sphalerite cover a distance of about 78 m sphalerite has 114 110cd values ranging from 0 01 to 0 57 and sulfides sphalerite galena and chalcopyrite have 34scdt values ranging from 0 2 to 5 0 although 34scdt and 114 110cd values in sphalerites have no regular spatial variations the 34scdt values in galena and calculated ore forming fluid temperatures decreased from 2 1 to 0 2 and from about 290 to 130 c respectively from the bottom to the top of the deposit heavy cd isotopes are enriched in early precipitated sphalerite in contrast to previous studies we suggest that cd isotopic compositions in ore forming fluids are heterogeneous which result in heavy cd isotope enrichment in early precipitated sphalerite in comparison with other zn pb deposits in the syg area the tianbaoshan deposit has moderate cd contents and small isotope fractionation suggesting differences in origin to other zn pb deposits in the syg province in the tianbaoshan deposit the calculated 34s s fluids value is 4 2 which is not only higher than the mantle derived magmatic sulfur 0 3 but also quite lower than those of ediacaran marine sulfates about 30 to 35 thus we suggest that reduced sulfur of ore forming fluids in the deposit was mainly derived from the leaching of the basement which contains large amount of volcanic or intrusive rocks based upon a combination of cd and s isotopic systems the tianbaoshan deposit has different geochemical characteristics from typical zn pb deposits e g the huize deposit in syg area indicating the unique origin of this deposit

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

spinel rich lithologies in the lunar highland crust linking lunar samples with crystallization experiments and remote sensing mg al spinel is rare in lunar rocks apollo and meteorite collections and occurs mostly in troctolites and troctolitic cataclastites recently a new lunar lithology rich in spinel and plagioclase and lacking abundant olivine and pyroxene was recognized in visible to near infrared vnir reflectance spectra by the moon mineralogy mapper m3 instrument on the chandrayaan 1 spacecraft at the moscoviense basin these outcrop scale areas are inferred to contain 20 30 mg al spinel possible explanations for the petrogenesis of spinel bearing and spinel rich lithology s range from low pressure near surface crystallization to a deep seated origin in the lower lunar crust or upper mantle here we describe 1 bar crystallization experiments conducted on rock compositions rich in olivine and plagioclase that crystallize spinel this would be equivalent to impact melting which is moderately common among lunar plutonic rocks and granulites to explore possible precursor materials and the maximum amount of spinel that could be crystallized a lunar troctolitic composition similar to apollo pink spinel troctolite 65785 and a composition similar to alha81005 as analog to the source region of this meteorite have been chosen the crystallization experiments on the composition of ahla 81005 did not yield any spinel experiments on the composition similar to apollo 65785 crystallized a maximum of 8 wt spinel much less than the suggested 20 30 spinel of the new lithology detected by m3 however our vnir spectral reflectance analyses of the experimental run products indicate that the spinel composition of the experimental run products not only appears to be similar to the composition of the spinel lithology detected by m3 characteristics of the spinel absorption but also that the modal abundances of coexisting phases e g mafic glass influence the spectral reflectance properties thus the spinel rich deposits detected by m3 might not be as spinel rich as previously thought and could contain as little as 4 5 wt spinel however the effect of space weathering on spinel is unknown and could significantly weaken its 2 m absorptions if this occurs weathered lunar rocks could contain more spinel than a comparison with our unweathered experimental charges would suggest

coupled thermal orbital evolution of the early moon abstract coupled thermal orbital histories of early lunar evolution are considered in a simple model we consider a plagioclase lid overlying a magma ocean overlying a solid mantle tidal dissipation occurs in the plagioclase lid and heat transport is by conduction and melt migration we find that large orbital eccentricities can be obtained in this model we discuss possible consequences of this phase of large eccentricities for the shape of the moon and geochronology of lunar samples we find that the orbit can pass through the shape solution of garrick bethell et al garrick bethell i wisdom j zuber m 2006 science 313 652 but we argue that the shape cannot be maintained against elastic deformation as the orbit continues to evolve

creep response of the hayward fault to stress changes caused by the loma prieta earthquake in 1996 an 18 millimeter creep event the largest ever observed on the hayward fault occurred between surveys 63 days apart this event marked the end of a period of severely reduced creep on the southern part of the fault that began after the 1989 loma prieta california earthquake the reduction in creep was consistent with elastic models for earthquake induced static stress changes on the hayward fault these data suggest that creep observations can indicate regional stress changes of about 1 bar or less

carbon isotope variability across the ediacaran yangtze platform in south china implications for a large surface to deep ocean δ13c gradient new isotope data obtained from relatively conformable carbonate rich strata of the ediacaran yangtze platform in south china reveal substantial 13 c variability in platform sections four negative 13 c anomalies with a nadir down to 8 pdb are present in the interval between the cap carbonate level 635 ma and the precambrian cambrian boundary 542 ma while in slope and basinal sections 13 c values are negative through the entire doushantuo formation 635 551 ma if these 13 c values are close to their primary seawater signature they imply a strong 10 surface to deep ocean 13 c gradient that is consistent with long term deep ocean anoxia and the presence of a large dissolved organic carbon doc reservoir the two prominent negative 13 c excursions within the doushantuo formation above the cap carbonate level are associated with shoaling and local exposure of the platform the anomalies may thus record remineralization of a large oceanic doc pool via sulfate reduction that transferred 13 c depleted carbon from the oceanic doc reservoir to the surface ocean during regression inconsistencies in ediacaran 13 c profiles globally and variations in south china in particular highlight the need for further evaluation of local departures in 13 c from an inferred average seawater signature

pb isotopes in the impact melt breccia 66095 association with the imbrium basin and the isotopic composition of lithologies at the apollo 16 landing site recent in situ secondary ion mass spectrometry sims pb isotope analyses of lunar basalts have provided precise crystallisation ages and initial pb isotopic compositions for these samples in this

a previously unrecognized high temperature impactite from the steen river impact structure alberta canada here we report a previously unrecognized impactite from the steen river impact structure in alberta canada which was intersected by continuous diamond drill core into the allochthonous proximal deposits of this buried 25 km diameter complex crater a suite of high temperature minerals defines the matrix formed by grain growth in a solid state by static recrystallization of an originally clastic matrix deposited at temperatures 800 c this rock type is predominantly a result of the recrystallization of target material driven by the acceleration of hot gasses from volatilized sedimentary cover mixed with variably shocked crystalline basement approximately one third of terrestrial impact structures occur in mixed target rocks therefore this type of impactite may be more common than previously realized contact metamorphism between entrained sedimentary target rocks and the juxtaposed hot matrix resulted in carbonate decomposition to form a rare spinel group mineral magnesioferrite in crater environments magnesioferrite has been found in the distal chicxulub mexico ejecta and may prove a novel indicator mineral for impact into carbonate bearing target rocks

magnesian anorthositic granulites in lunar meteorites allan hills a81005 and dhofar 309 geochemistry and global significance abstract fragments of magnesian anorthositic granulite are found in the lunar highlands meteorites allan hills alh a81005 and dhofar dho 309 five analyzed clasts of meteoritic magnesian anorthositic granulite have mg molar mg mg fe 81 87 feo 5 wt al2o3 22 wt rare earth elements abundances 0 5 2 ci except eu 10 ci and low ni and co in a non chondritic ratio the clasts have nearly identical chemical compositions even though their host meteorites formed at different places on the moon these magnesian anorthositic granulites are distinct from other highlands materials in their unique combination of mineral proportions mg ree abundances and patterns ti sm ratio and sc sm ratio their mg is too high for a close relationship to ferroan anorthosites or to have formed as flotation cumulates from the lunar magma ocean compositions of these magnesian anorthositic granulites cannot be modeled as mixtures of or fractionates from known lunar rocks however compositions of lunar highlands meteorites can be represented as mixtures of magnesian anorthositic granulite ferroan anorthosite mare basalt and kreep meteoritic magnesian anorthositic granulite is a good candidate for the magnesian highlands component inferred from apollo highland impactites magnesian feldspathic and ree poor bulk compositions of meteorite magnesian anorthositic granulites are comparable to those inferred for parts of the lunar farside the feldspathic highlands terrane 4 5 wt feo 28 wt al2o3 and th 1 ppm thus magnesian anorthositic granulite may be a widespread and abundant component of the lunar highlands

petrogenesis of lunar troctolites models of petrogenesis for lunar troctolites are severely constrained by the high mg 88 values of the most primitive members of the mg rich suite melts derived by partial melting of olivine cumulates to the lunar magma ocean have high mg but are strongly undersaturated with respect to plagioclase assimilation of lunar crust cannot bring these melts to the plagioclase liquidus without unduly reducing the mg values of olivine partial melts derived by melting a iherzolite primitive interior have higher normative plagioclase contents but require sources with mg 90 more terrestrial like mg 88 values are permitted if rising thermal plumes are capable of entraining the most mg rich cumulates of the magma ocean the mg values of lunar troctolites may therefore reflect a hybrid source composed of primitive mantle and mg rich cumulates of the magma ocean higher mg values may also arise from the reduction of small amounts of feo to fe alternatively the parent magmas to lunar troctolites may be impact melts of the anorthositic crust and the mg rich dunite cumulates of the magma ocean the latter were brought to the upper mantle during the overturn of the unstable cumulate pile of the magma ocean

variations in creep rate along the hayward fault california interpreted as changes in depth of creep variations in surface creep rate along the hayward fault are modeled as changes in locking depth using 3d boundary elements model creep is driven by screw dislocations at 12 km depth under the hayward and other regional faults inferred depth to locking varies along strike from 4 12 km 12 km implies no locking our models require locked patches under the central hayward fault consistent with a m6 8 earthquake in 1868 but the geometry and extent of locking under the north and south ends depend critically on assumptions regarding continuity and creep behavior of the fault at its ends for the northern onshore part of the fault our models contain 1 4 1 7 times more stored moment than the model of burgmann et al 2000 45 57 of this stored moment resides in creeping areas it is important for seismic hazard estimation to know how much of this moment is released coseismically or as aseismic afterslip

chronology and petrogenesis of the lunar highlands alkali suite cumulates from kreep basalt crystallization alkalic rocks from the highlands of the moon though relatively minor in volume yield important information in understanding the later development of the lunar crust however until recently little information has been available on the crystallization ages of samples from this diverse suite of rocks previous workers suggested a link between pristine kreep basalts and lunar quartz monzodiorites and granites through mineral and chemical modelling of all known pristine highlands alkali suite has rocks and radiogenic isotopic analyses of rather large has clasts from the apollo 14 landing site we explore further this potential link two clasts of alkalic affinity from the western highlands of the moon have been analyzed for their neodymium and strontium isotopic compositions an alkali anorthosite 14304 267 yields a smnd mineral isochron of 4108 53 ma mswd 0 06 and an end t of 1 0 0 2 two splits of the same alkali norite clast 14304 270 and 14304 272 yield similar end values when calculated for this age rbsr systematics for alkali anorthosite 14304 267 scatter about a line which yields an age of 4336 81 ma however the large mean square of weighted deviates mswd for this line 12 3 indicates that the age is suspect and that rbsr sytematics may have been disturbed the smnd age for 14304 267 in conjunction with upb zircon ages for two other highlands alkali suite has rocks from the apollo 14 landing site and one from the apollo 16 landing site indicate production of has rocks over an extended time period spanning at least 300 million years from 4 34 to 4 02 ga since the last dregs of the lunar magma ocean lmo likely crystallized prior to 4 3 ma all rocks from this alkalic period cannot represent direct remnants of the late lmo and may include material resulting from the remelting of evolved portions of the moon by upward moving basaltic melts from the deep lunar interior these contaminated melts may be represented by pristine kreep basalts from the apollo 15 landing site these kreep basalt melts could have crystallized within the crust to form cumulate gabbros norites anorthosites monzodiorites and possibly granites with the proportion of trapped kreepy residual liquid determining the large ion lithophile element enrichment of the rock generally the proportion of trapped kreepy liquid is small 2 15 the broad age range for the lunar has indicates that parental kreep basalt magmatism was not a unique event but was an important process possibly repeated several times throughout the first 600 to 700 million years of lunar history

magnesian anorthosites and a deep crustal rock from the farside crust of the moon abstract among over thirty lunar meteorites recovered from the hot deserts and antarctica dhofar 489 is the most depleted in thorium 0 05 ppm feo and rare earth elements ree dhofar 489 is a crystalline matrix anorthositic breccia and includes clasts of magnesian anorthosites and a spinel troctolite the mg mg fe mol mg numbers 75 85 of olivine and pyroxene grains in this meteorite are higher than those of the apollo ferroan anorthosites such materials were not recovered by the apollo and luna missions however remote sensing data suggest that the estimated concentrations of th and feo are consistent with the presence of such samples on the farside of the moon the differentiation trend deduced from the mineralogy of the anorthositic clasts define a magnesian extension of the ferroan anorthosite fan trend constructed from the apollo samples the presence of magnesian anorthositic clasts in dhofar 489 still offers a possibility that the farside trend with magnesian compositions is more primitive than the fan trend and may require a revision of this classical differentiation trend the ar ar age of dhofar 489 is 4 23 0 034 gyr which is older than most ar ages reported for highland rocks returned by apollo the old ar ar age of impact formation of this breccia and the presence of a fragment of spinel troctolite of deep crustal origin suggest that a basin forming event on the farside excavated the deep crust and magnesian anorthosites before formation of imbrium

isotope geochemistry of zn pb and s in the ediacaran strata hosted zn pb deposits in southwest china abstract the sichuan yunnan guizhou syg area is a world class zn pb metallogenic zone and contains over four hundred of carbonate hosted hydrothermal zn pb deposits six of which are super large scale deposits with significant sources of cd ge and ag including the huize wusihe xiaoshifang maozu tianbaoshan and daliangzi deposits although previous studies focused fully on these deposits the ore genesis of which are still in controversial interestedly four of those super large scale deposits are hosted in the ediacaran dengying formation including the maozu wusihe tianbaoshan and daliangzi deposits based upon previous studies we investigate the extent causes and consequences of zn and pb isotope signatures at hand specimen scale and ore genesis of the daliangzi and tianbaoshan deposits associated with published data for the wusihe deposit lead isotope ratios coupled with published data demonstrate that pb in the studied deposits was predominantly derived from two components basements and sedimentary rocks meanwhile a strong positive linear correlation between 66zn and 34scdt values was observed in hand specimen d 2084 suggesting the variations may be resulted by fluid mixing furthuremore the zn isotope and cd zn dataset from the tianbaoshan daliangzi and wusihe deposits defines a logarithmic curve r2 0 82 which to our knowledege is firstly reported and lies between two indentified components a low cd zn end member with high 66zn values and a high cd zn end member with low 66zn values based upon previous studies we suggest that zn and pb in the wusihe and tianbaoshan deposits were predominantly derived from basements and ediacaran sediments in contrast zn and pb in the daliangzi deposit were predominantly derived from ediacaran sediments and upper sedimentary rocks but we cannot rule out metal contributions of the basements furthermore we suggest that fluid mixing is more propreate to better explain zn isotope signatures in the studied deposits in summary zn and pb isotope ratios reflect similar ore genesis and metal sources of the daliangzi tianbaoshan and wusihe zn pb deposits in the syg area the application to the studied deposits with the discovery of zn s and pb isotope compositions for sulfides indicates the potential of zn isotope combined with cd zn raito as new geochemical tracers which may be useful for distinguishing the metal sources in large hydrothermal systems as suggested previously

differentiation of the south pole aitken basin impact melt sheet implications for lunar exploration we modeled the differentiation of the south pole aitken spa impact melt sheet to determine whether noritic lithologies observed within spa formed as a result of the impact results indicate differentiation of spa impact melt can produce noritic layers that may accommodate observed surface compositions but only in specific scenarios one of nine modeled impact melt compositions yielded layers of noritic materials that account for observations of noritic lithologies at depths of 6 km in this scenario impact occurred before a hypothesized lunar magma ocean cumulate overturn the 50 km deep melt sheet would have formed an insulating quenched layer at the surface before differentiating the uppermost differentiated layers in this scenario have feo and tio2 contents consistent with orbital observations if they were subsequently mixed with the uppermost quenched melt layer and with less feo and tio2 enriched materials such as ejecta emplaced during younger impacts these results verify that noritic lithologies observed within spa could have formed as a direct result of the impact therefore locations within spa that contain noritic materials represent potential destinations for collecting samples that can be analyzed to determine the age of the spa impact potential destinations include central peaks of bhabha bose finsen and antoniadi craters as well as walls of leibnitz and schrodinger basins additionally potential remnants of the uppermost quenched melt may be preserved in gabbroic material exposed in mafic mound exploring and sampling these locations can constrain the absolute age of spa a task that ranks among the highest priorities in lunar science

on the petrogenesis of lunar troctolites new insights into cumulate mantle overturn mantle exposures in impact basins abstract we investigate lunar troctolite petrogenesis with a series of forward models we simulate the cumulate mantle overturn hypothesis by modeling the adiabatic ascent and decompression melting of primary mantle cumulates produced during differentiation of a lunar magma ocean lmo combined equilibrium and fractional crystallization of candidate liquids generated by the melting model can reproduce the predominant constituents of the lunar magnesian suite mg suite troctolites and norites contrary to previous hypotheses model results are consistent with previous studies challenging the proposed and long standing genetic relationship between mg suite and gabbronorites our mg suite petrogenetic model validates a direct temporal and chemical link between mg suite melt production and pressure release melting of primary lmo cumulates if so mg suite crystallization ages 4345 15 ma can be used to constrain the onset and duration of melting associated with mantle overturn based on our model results we propose an alternative mantle overturn hypothesis whereby upwelling olivine dominated cumulates experience decompression melting to produce the mg suite primary melt 1 9 melt at 2 1 gpa but that this melt was extracted from depth akin to lunar picritic glass magmas low degree partial melts at depths corresponding to 1 3 2 5 gpa thus our revised mantle overturn hypothesis reconciles mg suite petrogenesis without the expanse of an olivine dominated upper mantle as suggested by the current paradigms but contradicted by orbital data this hypothesis supports the presence of a low ca pyroxene dominated upper mantle consistent with mantle stratigraphy constrained by experimental and numerical simulations of lmo differentiation and proposed mantle exposures within impact basins

the system mg2sio4 ca2sio4 caal2o4 naalsio4 sio2 one atmosphere liquidus equilibria of analogs of alkaline mafic lavas one atmosphere liquidus relationships in the system mg2sio4 fo ca2sio4 la naalsio4 ne caal2o4 ca sio2 sil are presented as analogs for alkaline mafic lavas liquidus diagrams are constructed from electron microprobe analyses of quenched liquids and coexisting mineral phases produced in melting experiments and they are depicted in terms of sub projections within the pseudo quaternary system fo la ne ca sil the ne and ca components are combined to create a normative feldspathoid component defined as ne ne ne ca liquidus relations at ne 0 5 from this study are compared to relations at ne 0 0 and 1 0 from previous studies in general liquidus temperatures decrease and positions of liquidus boundaries involving feldspathic phases shift toward the ne ca component as ne increases the pseudoinvariant points fo di pl mel l and fo pl mel sp l exist at ne 0 5 these equilibria between forsterite plagioclase melilite liquid are not present in the system when ne 1 0 because a boundary curve fo di ne l separates the plagioclase and melilite liquidus fields the liquidus diagrams provide useful analogs for the crystallization sequences of natural primary alkali olivine basalts basanitoids basanites olivine nephelinites olivine melilite nephelinites and olivine melilitites

early crust building enhanced on the moon s nearside by mantle melting point depression the moon s earth facing hemisphere hosts a geochemically anomalous region the procellarum kreep terrane which is widely thought to have provided radiogenic heat for mantle melting from 3 9 to 1 billion years ago however there is no agreement on such a link between this region and the earliest pulse of post differentiation crust building magmatism on the moon at 4 37 billion years ago whether this early magmatism was global or regional has been debated here we present results of high temperature experiments that show the nearside geochemical anomaly may have caused asymmetric early crust building via mantle melting point depression our results demonstrate that the anomalous enrichment in incompatible elements of this nearside reservoir dramatically lowers the melting temperature of the source rock for these magmas and may have resulted in 4 to 13 times more magma production under the nearside crust even without any contribution from radioactivity from thermal numerical modelling we show that radiogenic heating compounds this effect and may have resulted in an asymmetric concentration of post magma ocean crust building on the lunar nearside our findings suggest that the nearside geochemical anomaly has influenced the thermal and magmatic evolution of the moon over its entire post differentiation history early magmatism on the moon s nearside may have been enhanced by a geochemical anomaly lowering the melting point of the mantle source region according to high temperature experiments and thermal numerical modelling

unique spinel rich lithology in lunar meteorite alha 81005 origin and possible connection to m3 observations of the farside highlands 1 a new lunar rock type rich in mg fe al spinel and lacking abundant olivine and pyroxene was recently detected by near infrared reflectance spectroscopy by the m3 instrument on the chandrayaan 1 spacecraft no such material has been described from lunar rocks either returned samples or meteorites here we describe a fragment of rock containing 30 mg fe al spinel from the lunar meteorite alha 81005 although the fragment is not identical to the material detected by m3 it contains 20 olivine pyroxene both share the defining feature of an unusual enrichment in spinel the fragment 350 150 m is so fine grained that it reasonably could represent a larger rock body it is not spinel rich merely by chance incorporation of a few spinel grains the fragment is so rich in spinel and consequently in al2o3 that it could not have formed by melting a peridotitic mantle or a basaltic lunar crust the clast s small grain size and its apparent disequilibrium between spinel and pyroxene suggest fairly rapid crystallization at low pressure it could have formed as a spinel cumulate from an impact melt of troctolitic composition or from a picritic magma body that assimilated crustal anorthosite on its margins the latter mechanism is preferred because it not only explains the petrographic and chemical features of our clast but is also consistent with the regional setting of the moscoviense spinel deposit in that area m3 spectra have defined areas rich in olivine and in orthopyroxene these could represent igneous cumulate rocks formed during crystallization and differentiation of a picritic magma body and thus suggests a possible link between the analyzed clast and the observed spinels at moscoviense

assimilation by lunar mare basalts melting of crustal material and dissolution of anorthite we discuss techniques for calculating the amount of crustal assimilation possible in lunar magma chambers and dikes based on thermal energy balances kinetic rates and simple fluid mechanical constraints assuming parent magmas of picritic compositions we demonstrate the limits on the capacity of such magmas to melt and dissolve wall rock of anorthitic troctolitic noritic and kreep quartz monzodiorite compositions significant melting of the plagioclase rich crustal lithologies requires turbulent convection in the assimilating magma and an efficient method of mixing in the relatively buoyant and viscous new melt even when this occurs the major element chemistry of the picritic magmas will change by less than 1 2 wt diffusion coefficients measured for al2o3 from an iron free basalt and an orange glass composition are 10 12 m2 s 1 at 1340 c and 10 11 m2 s 1 at 1390 c these rates are too slow to allow dissolution of plagioclase to significantly affect magma compositions picritic magmas can melt significant quantities of kreep which suggests that their trace element chemistry may still be affected by assimilation processes however mixing viscous melts of kreep composition with the fluid picritic magmas could be prohibitively difficult we conclude that only a small part of the total major element chemical variation in the mare basalt and volcanic glass collection is due to assimilation fractional crystallization processes near the lunar surface instead most of the chemical variation in the lunar basalts and volcanic glasses must result from assimilation at deeper levels or from having distinct source regions in a heterogeneous lunar mantle

the univariant curve liquid forsterite anorthite diopside in the system cmas at 1 bar solid solutions and melt structure one atmosphere liquid present experiments were carried out in the cmas system using an ordinary quench furnace apparatus the runs including reversal and duplicate experiments describe the univariant curve l fo an di between the invariant points q l fo an di sp and f l fo an di oen located respectively at 1245 1 c and 1244 1 c the thermal divide on this curve m3 l fo an di is located at 1275 1 c and plots well within the silica saturated field in agreement with longhi s 1987 experiments along the univariant curve l fo an di liquid composition evolves away from the thermal divide either toward invariant points q or f and pierces the silica saturation plane i e the join di an en in the silica saturated field in this compositional range the al solubility in clinopyroxene changes drastically from one side of the thermal divide to the other with great increase of al solubility in the silica undersaturated field four endmembers must be used to describe the complex solid solution of anorthite caal2si2o8 camgsi3o8 mgal2si2o8 and si4o8 the last two of these are present only within the silica saturated field unlike clinopyroxene the mg content of anorthite is insensitive to the thermal barrier but is only sensitive to silica saturation plane olivine composition can be described by a binary solid solution of forsterite and monticellite with no ca in the m2 site as with anorthite olivine compositions exhibit a marked change with crossing of the silica saturation plane the above features imply that the solubility of minor elements in crystalline phases al in clinopyroxene ca in olivine and mg in anorthite selectively respond to only one or another of these particular plane results have many important consequences one is the likelihood of changes in melt speciation depending on position with respect to the thermal divide and the silica saturation plane

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

petrography of impact glasses and melt breccias from the el gygytgyn impact structure russia the el gygytgyn impact structure 18 km in diameter and 3 6 ma old in arctic siberia russia is the only impact structure on earth mostly excavated in acidic volcanic rocks the late cretaceous volcanic target includes lavas tuffs and ignimbrites of rhyolitic dacitic and andesitic composition and local occurrence of basalt although the ejecta blanket around the crater is nearly completely eroded bomb shaped impact glasses redeposited after the impact event occur in lacustrine terraces within the crater here we present detailed petrographic descriptions of newly collected impact glass bearing samples the observed features contribute to constrain the formation of the melt and its cooling history within the framework of the impact process the collected samples can be grouped into two types characterized by specific features 1 pure glasses containing very few clasts or new crystals and which were likely formed during the early stages of cratering and 2 a second type which represents composite samples with impact melt breccia lenses embedded in silicate glass these mixed samples probably resulted from inclusion of unmelted impact debris during ejection and deposition after deposition the glassy portions continued to deform whereas the impact melt breccia inclusions that probably had already cooled down behaved as rigid bodies in the flow

zinc isotopes in sphalerite from base metal deposits in the red dog district northern alaska analyses of sphalerite samples from shale hosted massive sulfide and stratigraphically underlying vein breccia deposits in the red dog district in northern alaska show a range of 66zn values from zero to 0 60 per mil the lowest values are observed in the vein breccia deposits and the stratigraphically overlying but structurally displaced shale hosted massive sulfide deposits show a systematic trend of increasing 66zn values from south to north main aqqaluk paalaaq anarraaq the 66zn values are inversely correlated with sphalerite fe mn ratio and also tend to be higher in low cu sphalerite consistent with precipitation of lower 66zn sphalerite closer to the principal hydrothermal fluid conduits the most likely control on isotopic variation is rayleigh fractionation during sulfide precipitation with lighter zinc isotopes preferentially incorporated in the earliest sphalerite to precipitate from ore fluids at deeper levels vein breccias and close to the principal fluid conduits in the orebodies followed by precipitation of sulfides with higher 66zn values in shallower and or more distal parts of the flow path there is no systematic variation among the paragenetic stages of sphalerite from a single deposit suggesting an isotopically homogeneous zinc source and consistent transport deposition conditions and or dissolution reprecipitation of earlier sphalerite without significant fractionation decoupled zn and s isotope compositions are best explained by mixing of separate metal and sulfur bearing fluids at the depositional site the results confirm that zn isotopes may be a useful tracer for distinguishing between the central and distal parts of large hydrothermal systems as previously suggested and could therefore be of use in exploration

lunar highland meteorite dhofar 026 and apollo sample 15418 two strongly shocked partially melted granulitic breccias studies of lunar meteorite dhofar 026 and comparison to apollo sample 15418 indicate that dhofar 026 is a strongly shocked granulitic breccia or a fragmental breccia consisting almost entirely of granulitic breccia clasts that experienced considerable post shock heating probably as a result of diffusion of heat into the rock from an external hotter source the shock converted plagioclase to maskelynite indicating that the shock pressure was between 30 and 45 gpa the post shock heating raised the rock s temperature to about 1200 c as a result the maskelynite devitrified and extensive partial melting took place the melting was concentrated in pyroxene rich areas all pyroxene melted as the rock cooled the partial melts crystallized with fine grained subophitic poikilitic textures sample 15418 is a strongly shocked granulitic breccia that had a similar history but evidence for this history is better preserved than in dhofar 026 the fact that dhofar 026 was previously interpreted as an impact melt breccia underscores the importance of detailed petrographic study in interpretation of lunar rocks that have complex textures the name impact melt has in past studies been applied only to rocks in which the melt fraction formed by shock induced total fusion recently however this name has also been applied to rocks containing melt formed by heating of the rocks by conductive heat transfer assuming that impact is the ultimate source of the heat we urge that the name impact melt be restricted to rocks in which the bulk of the melt formed by shock induced fusion to avoid confusion engendered by applying the same name to rocks melted by different processes

the giant south china mesozoic low temperature metallogenic domain reviews and a new geodynamic model abstract the south china craton was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic during the mesozoic voluminous granitic plutons and associated w sn polymetallic deposits were formed in the cathaysia block the giant south china low temperature metallogenic domain ltmd includes an area of 500 000 km 2 in the yangtze block and is composed of the chuan dian qian pb zn youjiang au as sb hg and xiangzhong sb au metallogenic provinces the chuan dian qian pb zn province contains numerous mvt pb zn deposits whereas the other two provinces are characterized by carlin type au deposits and vein type sb hg and as deposits these epigenetic deposits which formed under low temperature conditions 100 250 c are typically hosted in sedimentary rocks and are locally controlled by faults and fractures the deposits formed dominantly at 200 230 ma and 130 160 ma corresponding to indosinian triassic and yanshanian jurassic to cretaceous orogenies respectively indosinian mineralization is recognized in all three provinces but yanshanian mineralization occurred only in the youjiang and xiangzhong provinces the indosinian orogeny which involved collision of the indochina block with the south china craton resulted in circulation of basinal brines that leached ore forming elements from adjacent sedimentary strata to form the chuan dian qian pb zn province deep seated granitic magmas generated during this orogeny caused extensive circulation of meteoric water that mobilized ore forming elements from the sedimentary strata to form the carlin type au deposits in the youjiang province and the sb au deposits in the xiangzhong province the indosinian orogeny was the key factor in establishing the metallogenic framework of the ltmd it produced widespread mineralization in the three metallogenic provinces each of which has unique features reflecting differences in the nature and composition of the basement rocks the yanshanian metallogeny was less important and overprinted the older ore deposits in the youjiang and xiangzhong provinces

chemical and mineralogical influences on concentrations of trace metals in hydrothermal fluids abstract concentrations of trace metals in hydrothermal solutions from the southern juan de fuca ridge sjfr and the tag hydrothermal field on the mid atlantic ridge are influenced by the combined effects of source rock composition brine seawater mixing and complex interplay among various metals and minerals deposited and remineralized in vent mounds and chimneys copper mo and co show predicted sharp decreases in concentration for vent fluids as temperatures decrease below 350 c however concentrations of cu in 363 c fluids at the tag site are well above values determined from seawater basalt interactions due to subseafloor refining processes and remineralization of chalcopyrite concentrations of zn cd pb as and ga do not show any temperature dependence between 214 to 363 c however zn values do correlate well with cl on an area by area basis due to subseafloor mixing of brine with altered seawater zinc levels also correlate well with concentrations of cd pb and as for all vent fluid samples as well as with basalt and zn rich sulfides implying some continuity in behavior from source rock to vent fluid to sulfide minerals gallium values correlate with zn and cl levels for the sjfr but are high relative to zn at the tag site due to subseafloor refining processes concentrations of tl follow cl k and rb consistent with the behavior predicted for tl overall the cl and zn rich fluids from the sjfr are characteristic of a brine dominated system formed during recent volcanism in contrast high temperature fluids from the tag area are representative of a system that has evolved over the past 100 000 yr with high concentrations of cu co and ga that result from higher temperatures and complex refining processes within a large vent mound

the lunar magma ocean reconciling the solidification process with lunar petrology and geochronology abstract the moon is thought to have originated with a magma ocean that produced a plagioclase flotation crust as solidification proceeded ages of anorthositic crust range over at least 200 million years the model for solidification presented here integrates chemical and physical constraints of lunar magma ocean solidification to determine 1 the final thickness of flotation crust generated by a fractionally solidifying magma ocean 2 the timescale of crystallization before plagioclase is a stable phase 3 the timescale of solidification after the formation of the plagioclase flotation crust and 4 the post overturn lunar mantle composition and structure we find that magma oceans of as much as 1000 km depth are consistent with creating an anorthositic crust 40 to 50 km in thickness solidification of the magma ocean prior to formation of the flotation crust may occur on the order of 1000 years and complete solidification would require additional ten to tens of millions of years reconciling these short model timescales with radiometric dates of crustal samples requires either a very late forming moon combined with finding older crustal ages to be incorrect or calling on tidal heating of the crust by the early earth to prolong solidification gravitationally driven overturn of cumulates during tidal heating provides a mechanism for creating the compositions and ages of the lunar mg suite of crustal rocks further we find that upon crystallization the moon likely began with an azimuthally heterogeneous gravitationally stable mantle after magma ocean cumulate overturn this result may help explain the experimentally determined origin of picritic glasses at similar depths but from different source materials

reflectance spectroscopy of chromium bearing spinel with application to recent orbital data from the moon visible to near infrared v nir remote sensing observations have identified spinel in various locations and lithologies on the moon experimental studies have quantified the feo content of these spinels jackson et al 2014 however the chromite component is not well constrained here we present compositional and spectral analyses of spinel synthesized with varying chromium contents at lunar like oxygen fugacity f o2 reflectance spectra of the chromium bearing synthetic spinels cr 1 29 have a narrow 130 nm wide absorption feature centered at 550 nm the 550 nm feature attributed to octahedral cr3 is present over a wide range in iron content fe 8 30 and its strength positively correlates with spinel chromium content ln reflectancemin 0 0295 cr 0 3708 our results provide laboratory characterization for the v nir and mid infrared mid ir spectral properties of spinel synthesized at lunar like f o2 the experimentally determined calibration constrains the cr of spinels in the lunar pink spinel anorthosites to low values potentially cr 1 furthermore the results suggest the absence of a 550 nm feature in remote spectra of the dark mantle deposits at sinus aestuum precludes the presence of a significant chromite component combined the observation of low chromium spinels across the lunar surface argues for large contributions of anorthositic materials in both plutonic and volcanic rocks on the moon

occurrence and mechanisms of impact melt emplacement at small lunar craters abstract using observations from the lunar reconnaissance orbiter camera lroc we assess the frequency and occurrence of impact melt at simple craters less than 5 km in diameter nine hundred and fifty fresh randomly distributed impact craters were identified for study based on their maturity albedo and preservation state the occurrence frequency and distribution of impact melt deposits associated with these craters particularly ponded melt and lobate flows are diagnostic of melt emplacement mechanisms like larger craters those smaller than a few kilometers in diameter often exhibit ponded melt on the crater floor as well as lobate flows near the crater rim crest the morphologies of these deposits suggest gravity driven flow while the melt was molten impact melt deposits emplaced as veneers and sprays thin layers of ejecta that drape other crater materials indicate deposition late in the cratering process the deposits of fine sprays are particularly sensitive to degradation exterior melt deposits found near the rims of a few dozen craters are distributed asymmetrically around the crater and are rare at craters less than 2 km in diameter pre existing topography plays a role in the occurrence and distribution of these melt deposits particularly for craters smaller than 1 km in diameter but does not account for all observed asymmetries in impact melt distribution the observed relative abundance and frequency of ponded melt and flows in and around simple lunar craters increases with crater diameter as was previously predicted from models however impact melt deposits are found more commonly at simple lunar craters i e those less than a few kilometers in diameter than previously expected ponded melt deposits are observed in roughly 15 of fresh craters smaller than 300 m in diameter and 80 of fresh craters between 600 m and 5 km in diameter furthermore melt deposits are observed at roughly twice as many non mare craters than at mare craters we infer that the distributions and occurrences of impact melt are strongly influenced by impact velocity and angle target porosity pre existing topography and degradation additionally areally small and volumetrically thin melt deposits are sensitive to mixing with solid debris and or burial during the modification stage of impact cratering as well as post cratering degradation thus the production of melt at craters less than 800 m in diameter is likely greater than inferred from the present occurrence of melt deposits which is rapidly affected by ongoing degradation processes

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

reflectance spectroscopy of plagioclase dominated mineral mixtures implications for characterizing lunar anorthosites remotely anorthositic rocks dominate the moon s upper crust as remnants of the lunar magma ocean lmo small variations in the mineralogy of these rocks may hold key information about the homogeneity of lmo composition and solidification processes orbital near infrared nir sensors are sensitive to mineralogy but technologic advances have only recently enabled detection of the plagioclase component in crustal rocks based on an absorption band centered near 1250 nm anorthosites occupy a unique mineralogic range that is well suited for nir studies the highly transparent component plagioclase is present in high abundances while the spectrally dominant mafic or oxide minerals are present in only minor abundance as a result spectra of anorthosites are more likely than many other rock types to contain visually discernable signatures from more than one mineral component facilitating their identification and characterization in nir data in support of new nir measurements for the moon we present laboratory spectral analyses of well controlled plagioclase dominated mineral mixtures we focus on the spectral effects of varying mafic and oxide composition and abundance in mixtures with a common plagioclase end member the results demonstrate that plagioclase can be a significant contributor to reflectance spectra when strongly absorbing minerals are present in low abundance we show that the contribution of plagioclase is more pronounced in mixtures with pyroxenes and certain spinels but more easily masked in mixtures containing small amounts of olivine differences in minor mineral composition are clearly expressed in bulk spectra modeling of mixtures using a hapke nonlinear approach accurately estimates mineral abundances in laboratory spectra to within 5 vol for mixtures with 90 vol plagioclase together these results imply that not only should orbital nir data sets be able to discern the presence of plagioclase in anorthositic crustal exposures but also that detailed information about anorthosite mineral assemblages can be reliably accessed in reflectance spectra

geological features and origin of the huize carbonate hosted zn pb ag district yunnan south china abstract the huize zn pb ag district in the sichuan yunnan guizhou zn pb ag metallogenic region contains significant high grade zn pb ag deposits the total metal reserve of zn and pb exceeds 5 mt the district has the following geological characteristics 1 high ore grade zn pb 25 wt 2 enrichment in ag and a range of other trace elements ge in ga cd and tl with galena sphalerite and pyrite being the major carriers of ag ge cd and tl 3 ore distribution controlled by both structural and lithological features 4 simple and limited wall rock alteration 5 mineral zonation within the orebodies and 6 the presence of evaporite layers in the ore hosting wall rocks of the early carboniferous baizuo formation and the underlying basement fluid inclusion and isotope geochemical data indicate that the ore fluid has homogenisation temperatures of 165 220 c and salinities of 6 6 12 wt nacl equiv and that the ore forming fluids and metals were predominantly derived from the kunyang group basement rocks and the evaporite bearing rocks of the cover strata ores were deposited along favourable specific ore controlling structures the new laboratory and field studies indicate that the huize zn pb ag district is not a carbonate replacement deposit containing massive sulphides but rather the deposits can be designated as deformed carbonate hosted mvt type deposits detailed study of the deposits has provided new clues to the localisation of concealed orebodies in the huize zn pb ag district and of the potential for similar carbonate hosted sulphide deposits elsewhere in ne yunnan province as well as the sichuan yunnan guizhou zn pb ag metallogenic region

earthquake potential along the northern hayward fault california the hayward fault slips in large earthquakes and by aseismic creep observed along its surface trace dislocation models of the surface deformation adjacent to the hayward fault measured with the global positioning system and interferometric synthetic aperture radar favor creep at 7 millimeters per year to the bottom of the seismogenic zone along a 20 kilometer long northern fault segment microearthquakes with the same waveform repeatedly occur at 4 to 10 kilometer depths and indicate deep creep at 5 to 7 millimeters per year the difference between current creep rates and the long term slip rate of 10 millimeters per year can be reconciled in a mechanical model of a freely slipping northern hayward fault adjacent to the locked 1868 earthquake rupture which broke the southern 40 to 50 kilometers of the fault the potential for a major independent earthquake of the northern hayward fault might be less than previously thought

visible infrared spectral properties of iron bearing aluminate spinel under lunar like redox conditions remote sensing observations have identified aluminate spinel in the absence of measureable olivine and pyroxene as a globally distributed component of the lunar crust earlier remote sensing observations and returned samples did not indicate the presence of this component leaving its geologic significance unclear here we report visible to mid infrared v ir reflectance 300 25 000 nm and mossbauer spectra of aluminate spinels synthesized at lunar like oxygen fugacity o2 that vary systematically in fe abundance reflectance spectra of particulate 6 fe although the 2000 and 2800 nm bands are assigned to fe 2 iv electronic transitions spectra of aluminate spinels with excess al2o3 demonstrate that the strengths of the 1000 nm bands are related to the abundance of fe 2 vi the abundance of fe 2 vi depends on bulk fe content as well as factors that control the degree of structural order disorder such as cooling rate consequently the strength of the 1000 nm bands are useful for constraining the fe content and cooling rate of remotely sensed spinel controlling for cooling rate particle size and o2 we conclude that spinels with 12 fe 88 mg have observable 1000 nm bands under ambient lunar conditions and that only very mg rich spinels lack 1000 nm bands in their spectra this links remote observations of spinel anorthosite to mg suite magmatism the combined effects of fe oxidation state abundance of coexisting plagioclase and space weathering have not been explored here and may add additional constraints the relative strengths of the distinctive 1000 and 2000 nm bands of the spinels associated with pyroclastic deposits at sinus aestuum suggest fast cooling rates possibly in the absence of an extensive vapor cloud

lunar magma ocean crystallization revisited bulk composition early cumulate mineralogy and the source regions of the highlands mg suite abstract crystallization of the lunar magma ocean lmo has been numerically modeled and its products inferred from sample observations but it has never been fully tested experimentally this study is a reexamination of the lmo hypothesis by means of the first experimental simulation of lunar differentiation two end member bulk moon compositions are considered one enriched in refractory lithophile elements relative to earth and one with no such enrichment a two stage model of magma ocean crystallization based on geophysical constraints is simulated and features early crystal suspension and equilibrium crystallization followed by fractional crystallization of the residual magma ocean an initially entirely molten moon is assumed part 1 of this study presented here focuses on stage 1 of this model and considers the early cumulates formed by equilibrium crystallization differences in mantle mineralogy resulting from different bulk moon compositions and implications for the source regions of the highlands mg suite refractory element enriched bulk moon compositions produce a deep mantle that contains garnet and trace cr spinel in addition to low ca pyroxene and olivine in contrast compositions without refractory element enrichment produce a deep dunitic mantle with low ca pyroxene but without an aluminous phase the differences in bulk composition are magnified in the residual melt the residual lmo from the refractory element enriched composition will likely produce plagioclase and ilmenite earlier and in greater quantities both compositions produce mg rich early cumulate piles that extend from the core mantle boundary to 355 km depth if 50 equilibrium crystallization and whole moon melting are assumed these early lmo cumulates provide good fits for the source regions for a component of the high mg ni and co poor parental magmas of the mg suite cumulates if certain conditions are called upon the olivine in early lmo cumulates produced by either bulk moon composition is far too rich in cr to be reasonable for the source regions of the mg suite meaning either core formation in the presence of s and or c must be invoked to deplete the lmo and the crystallizing olivine in cr or that current estimates of the bulk lunar cr content are too high we infer that melts meeting the criteria of the mg suite parents could be produced from early lmo cumulates by solid state kreep and plagioclase hybridization near the base of the crust and subsequent partial melting additionally we propose a revised model for mg suite petrogenesis

cadmium isotope fractionation in the fule mississippi valley type deposit southwest china high precision cadmium cd isotope compositions are reported for sphalerite galena and smithsonite from the fule zn pb cd deposit a typical mississippi valley type deposit in southwest china dark sphalerite has lighter 114 110cd values 0 06 to 0 46 than light sphalerite 0 43 to 0 70 and the cd in galena is primarily in the form of sphalerite micro inclusions with 114 110cd of 0 35 to 0 39 from early to late stages 114 110cd values of smithsonite regularly increase from 0 19 to 0 42 whereas cd zn ratios decrease from 252 to 136 the 114 110cd variation pattern of supergene smithsonite reflects kinetic rayleigh fractionation during low temperature processes from the bottom to the top of the orebody the dark sphalerite has different patterns in 114 110cd values cd zn ratios 34s values and fe concentrations compared to the light sphalerite indicating that dark and light sphalerite formed by different processes the varying patterns of 144 110cd values and cd zn ratios within light sphalerite are similar to those of layered smithsonite and the 144 110cd values have a positive correlation with 34s values indicating that cd isotope fractionation in the light sphalerite was due to kinetic rayleigh fractionation instead in dark sphalerite the 144 110cd values have a negative correlation with 34s values and a positive correlation with the cd zn ratio thus it can be concluded that dark sphalerite could be modeled in terms of two component mixing basement fluid and host rock fluid which is in agreement with previous explanations for the negative correlation between 66zn and 34s in some typical zn pb deposits we propose that the significant variation in cd isotope composition observed in the fule zn pb cd deposit confirms that cd isotopes can be used for tracing fluid evolution and ore formation

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

zinc sulfur and lead isotopic variations in carbonate hosted pb zn sulfide deposits southwest china abstract the sichuan yunnan guizhou pb zn metallogenic province in the western yangtze block southwest china contains more than four hundred pb zn deposits with more than 200 million tons of pb zn ores at mean grades of 5 wt pb and 10 wt zn these deposits are hosted in sinian ediacaran to permian carbonate rocks and are structurally controlled by thrust fault fold structures and are spatially associated with the late permian 260 ma emeishan flood basalts two representative low temperature hydrothermal pb zn sulfide deposits the tianqiao and banbanqiao deposits in the southeastern part of the sichuan yunnan guizhou pb zn metallogenic province are selected for zn s pb isotopic analyses sphalerite from the tianqiao deposit has 66 zn values ranging from 0 26 to 0 58 relative to the jmc 3 0749l zinc isotope standard whereas 66 zn values of sphalerite from the banbanqiao deposit range from 0 07 to 0 71 the zinc isotopic composition of sphalerite from both deposits increase from early to final mineralization stage in addition sphalerite from the center near to bottom part of the no 1 ore body in the tianqiao deposit has lower 66 zn values 0 01 to 0 43 than those 0 11 to 0 57 in the periphery near to top sinian to permian sedimentary rocks and permian emeishan flood basalts the potential zinc metal source rocks have 66 zn values range from 0 24 to 0 17 and from 0 32 to 0 44 respectively the majority of the hydrothermal sphalerite has heavier zinc isotope than the country rocks precluding the mixing of multiple zinc sources as the key factor controlling the spatial and temporal variations of zinc isotope therefore the increased 66 zn values from the early to late stage and from the center to top could be due to kinetic raleigh fractionation sphalerite from the tianqiao and banbanqiao deposits has 34 s values ranging from 10 9 to 14 8 and from 3 9 to 9 0 respectively lower than cambrian to permian marine sulfates 15 to 35 and sulfate bearing evaporates 15 to 28 in the devonian to permian carbonate host rocks sulfur of the pb zn ores from both deposits is interpreted as the result of thermal chemical sulfate reduction of evaporates in the sedimentary rocks most likely the host rocks sphalerite from the tianqiao deposit has pb isotope similar to that of age corrected devonian to permian carbonate host rocks whereas sphalerite from the banbanqiao deposit has pb isotope similar to that of age corrected underlying precambrian basement rocks therefore at least lead in the tianqiao and banbanqiao deposits was mainly originated from the host rocks and the underlying basements respectively zn s pb isotopic studies of sphalerite from both deposits indicate that sources of metals and sulfur in the hydrothermal fluid for the tianqiao deposit are the paleozoic carbonate host rocks whereas for the banbanqiao deposit the sources are the precambrian basements and the paleozoic carbonate host rocks respectively

on the potential for lunar highlands mg suite extrusive volcanism and implications concerning crustal evolution abstract the lunar magnesian suite mg suite was produced during the earliest periods of magmatic activity on the moon based on the cumulate textures of the samples and a lack of evidence for mg suite extrusives in both the sample and remote sensing databases several petrogenetic models deduce a predominantly intrusive magmatic history for mg suite lithologies considering that 18 of the lunar surface is covered by mare basalt flows which are substantially higher in density than estimated mg suite magmas 2900 versus 2700 kg m3 the apparent absence of low density mg suite volcanics is surprising were mg suite magmas predominantly intrusive or have their extrusive equivalents been covered by subsequent impact ejecta and or later stage volcanism if mg suite magmas were predominantly intrusive what prevented these melts from erupting or if they are present as extrusives what regions of the moon are most likely to contain mg suite volcanic deposits this study investigates buoyancy driven ascent of mg suite parental melts and is motivated by recent measurements of crustal density from grail mg suite dunite troctolite and spinel anorthosite parental melts 2742 2699 and 2648 kg m3 respectively are considered all of which have much lower melt densities relative to mare basalts and picritic glasses mg suite parental melts are more dense than most of the crust and would not be expected to buoyantly erupt however about 10 of the lunar crust is greater in density than mg suite melts these areas are primarily within the nearside southern highlands and south pole aitken sp a basin mg suite extrusions and or shallow intrusions were possible within these regions assuming crustal density structure at 4 1 ga was similar to the present day crust we review evidence for mg suite activity within both the southern highlands and sp a and discuss the implications concerning crustal evolution as well as mg suite petrogenesis lower crustal densities measured by grail are consistent with the lack of observed mg suite extrusives if mg suite extrusive volcanism was prevented by the low density of the crust it would suggest the lunar crust was fractured shortly after solidification 4 3 ga the thermal and stress state of the lunar crust may have also inhibited mg suite extrusion

historic creep rate and potential for seismic slip along the hayward fault california the hayward fault is considered the most likely source of one or more major earthquakes in the san francisco bay area in the next few decades historically at least one and probably two major earthquakes about m 6 8 occurred along the hayward fault one in 1836 and another in 1868 little is known about the 1836 event but the 1868 earthquake was accompanied by a surface rupture that extended as much as 41 km along the southern part of the fault although the amount of surface slip in 1868 is uncertain right slip including afterslip reached at least several centimeters and possibly several decimeters in places this paper documents the spatial variation of creep rate along the hayward fault since the 1868 earthquake creep aseismic fault slip occurs over at least 66 km and may extend over the fault s entire 82 km length of which about 13 km lies underwater creep rate seems nearly constant over decades but short term variations occur we derive creep rate mainly from our own systematic surveying of offset cultural features curbs fences and buildings on each feature we solve directly for accumulated creep by using multiple linear regression creep rate mostly falls in the range of 3 5 6 5 mm yr but systematic variation occurs along strike fault segments with distinctly higher and lower rates generally correspond to parts of the fault most salient from the overall average alinement of the fault most distinctive is a 4 km long section near the south end of the fault that creeps at about 9 mm yr such a high rate has occurred there at least since the 1920s and probably since the 1868 earthquake as indicated by an offset railroad track built in 1869 we suggest that this 9 mm yr slip rate may approach the long term or deep slip rate that controls average recurrence interval between major earthquakes if so assuming an elastic rebound model the potential for slip in large earthquakes below the surficial creeping zone is now 1 1 m in the southern 1868 segment of the fault and 1 4 m in the northern 1836 segment subtracting surface creep rates from a long term slip rate of 9 mm yr gives present potential for surface slip in large earthquakes of up to 0 8 m with an average of 0 6 m in the northern segment and 0 4 m in the southern segment we present a simple hypothesis for rupture potential that is compatible with historic creep rate microseismicity distribution and geodetic data if seismic rupture occurs on segments 41 km long by 10 km deep 7 km fully locked 3 km creeping today s potential for seismic moment release is 1 4 1019 and 1 1 1019 n m for both 1836 and 1868 segments respectively and 2 5 1019 n m for both segments jointly converting moment to magnitude gives ml 6 8 in the northern segment ml 6 7 in the southern segment and ml 7 0 for simultaneous rupture of both

mg spinel lithology a new rock type on the lunar farside 1 high resolution compositional data from moon mineralogy mapper m3 for the moscoviense region on the lunar farside reveal three unusual but distinctive rock types along the inner basin ring these are designated oos since they are dominated by high concentrations of orthopyroxene olivine and mg rich spinel respectively the oos occur as small areas each a few kilometers in size that are widely separated within the highly feldspathic setting of the basin rim although the abundance of plagioclase is not well constrained within the oos the mafic mineral content is exceptionally high and two of the rock types could approach pyroxenite and harzburgite in composition the third is a new rock type identified on the moon that is dominated by mg rich spinel with no other mafic minerals detectable 5 pyroxene olivine all oos surfaces are old and undisturbed since basin formation they are effectively invisible in image data and are only recognized by their distinctive composition identified spectroscopically the origin of these unusual lithologies appears to be linked to one or more magmatic intrusions into the lower crust perhaps near the crust mantle interface processes such as fractional crystallization and gravity settling within such intrusions may provide a mechanism for concentrating the mafic components within zones several kilometers in dimension the oos are embedded within highly anorthositic material from the lunar crust they may thus be near contemporaneous with crustal products from the cooling magma ocean

origin of large volume pseudotachylite in terrestrial impact structures large volume pseudotachylite bodies in impact structures are dike like and consist of angular and rounded wall rock fragments enveloped by a microcrystalline and sporadically glassy matrix that crystallized from a melt knowledge of the formation of pseudotachylite bodies is important for understanding mechanics of complex crater formation most current hypotheses of pseudotachylite formation inherently assume that fragmentation and melt generation occur during a single process based on the structure of pseudotachylite bodies at sudbury canada and vredefort south africa we show that these processes differ in time and space we demonstrate that the centimeter to kilometer scale bodies are effectively fragment and melt fi lled tension fractures that formed by differential rotation of target rock during cratering highly variable pseudotachylite characteristics can be accounted for by a single process i e drainage of initially superheated impact melt into tension fractures of the crater fl oor

on some fundamentals of igneous petrology the age old process of crystal fractionation leading to the diversity of the igneous rocks and earth itself is an exceedingly well understood chemical process in magmatism and physical chemistry but the broader physical aspects of this and related processes have proven elusive on many fronts especially in its relation to the spatial variations in rock composition texture and macroscopic features like layering magmatic systems be they volcanic dikes sills or plutons are generally analyzed with a problem at hand and an end result in mind the processes invoked to solve these problems which are most often purely chemical are often unique to each problem with few if any general principles emerging that are central to understanding the wider perspective of magmatic processes and problems an attempt is made at the outset to provide a list of inviolate magmatic first principles that are relevant to analyzing most magmatic problems these involve initial conditions critical crystallinity solidification fronts transport and emplacement fluxes phenocrysts xenocrysts primocrysts crystal size layering and crystal sorting thermal convection magmatic processes are physical along with these principles two reference magmatic systems are suggested where the initial conditions and outcome are unequivocal the sudbury impact melt sheet and the hawaiian lava lakes sudbury formed in 5 min by superheated magma crystallized to a near uniform sequence while the tiny lava lakes formed of crystal laden slurries form a highly differentiated layered sequence the major difference is in the initial conditions of formation especially the nature of the input materials the challenge is to construct and analyze magmatic systems i e magma chambers sills dikes and lavas using these reference end members and the suggested principles the hawaiian 500 000 year volcanic record exhibits what can be expected as input materials namely a highly varied output of magma of an overall composition reflecting the abundance of entrained olivine primocrysts the provenance of these crystals is varied and within any single sample the population may be highly heterogeneous in composition from crystal to crystal yet the overall pattern of chemical fractionation is exceedingly regular and well defined if similar inputs go to form large intrusions these systems will undoubtedly be dominated by crystal rich slurries which provide a vast set of physical processes promoting exotic layering and at the same time given the effects of annealing and continued crystal growth a final chemical record adhering to all the time honored effects of crystal fractionation the long assumed initial condition of instantaneously emplaced crystal free magmas cannot reasonably produce the observed rock records

cordierite spinel troctolite a new magnesium rich lithology from the lunar highlands a clast of spinel troctolite containing 8 percent cordierite mg2al4si5o18 has been identified among the constituents of apollo 15 regolith breccia 15295 the cordierite and associated anorthite forsteritic olivine and pleonaste spinel represent a new mg rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate the cordierite forsterite pair in the assemblage is stable at a maximum pressure of 2 5 kilobars equivalent to a depth of 50 kilometers or 10 kilometers above the lunar crust mantle boundary the occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized the rarity of cordierite spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events such as the one that formed the adjacent imbrium basin

the reaction forsterite cordierite aluminous orthopyroxene spinel in the system mgo al2o3 sio2 reversal experiments at 1 150 1 300 c on the reaction forsterite cordierite aluminous orthopyroxene spinel in the system mgo al2o3 sio2 show the equilibrium to have a negativedt dp the slope andt p location of this equilibrium have been modelled using available heat capacity data and various structural models which explore the configurational entropy contributions to the total s the experimental data are consistent with the aluminous orthopyroxene model of ganguly and ghose 1979 where limited al disorder occurs between them1 andm2 sites al si mixing occurs on the tetrahedralb site with the aluminum avoidance principle maintained and mg al disorder occurs in spinel with an interchange enthalpy of 9 12 kcal mol 1 additionally al si disordering which occurs in the indialite structure of cordierite is inconsistent with the experimental data and all pyroxene and spinel mixing models consequently si and al in anhydrous cordierites to 1 300 c in the system mgo al2o3 sio2 must be largely ordered

detection of mg spinel bearing central peaks using m 3 images implications for the petrogenesis of mg spinel abstract mg spinel bearing lithologies lacking abundant mafic materials have been discovered with images acquired by the moon mineralogy mapper m3 aboard chandrayaan 1 we conducted a systematic screening of lunar crater central peaks for the presence of mg spinel to address its distribution and petrogenesis 38 mg spinel bearing crater central peaks were identified in this study out of 166 craters investigated the results suggest that mg spinel is common in the lunar crust and appears to be extensive in the middle part of the lunar crust underneath procellarum kreep terrane pkt mg spinel neither exclusively originated from deep layers 10 km nor necessarily coexist with the appearance of olivine or pyroxene 15 mg spinel bearing central peaks originated from depth less than 10 km nine investigated central peaks only contain mg spinel and plagioclase without any detectable mafic materials all those observations imply that the origin of mg spinel is possibly related to mg suite plutonism and assimilation between high mg magma with anorthositic crust the extensive distribution and mg suite related petrogenesis indicates that mg spinel bearing lithologies might represent a new member of mg suite rocks

geology and petrology of enormous volumes of impact melt on the moon a case study of the orientale basin impact melt sea abstract lunar basin forming impacts produce enormous volumes 10 5 km 3 of impact melt all known basin forming impacts combined may produce 10 8 km 3 of impact melt 1 20th the volume of the lunar crust despite their volumetric importance the geology and petrology of massive deposits of impact melt on the moon have been little studied in part because most basin impact melt deposits are old and have been obscured or buried by subsequent impact cratering and mare infill we investigate the geology and model the petrology of fresh massive impact melt deposits in the relatively young 930 km diameter orientale basin models of impact melt production combined with geologic analyses based on new lola topographic data suggest that most of the impact melt 2 3 produced by the orientale forming impact occurs in a 15 km thick impact melt sheet better described as an impact melt sea 350 km in diameter with a volume of 10 6 km 3 we anticipate that the orientale melt sea has undergone large scale igneous differentiation since terrestrial impact melt sheets such as manicouagan sudbury and morokweng less than a tenth of the thickness and a hundredth of the volume of the orientale melt sea have differentiated we develop a model for the cumulate stratigraphy of the solidified orientale impact melt sea a modeled cumulate stratigraphy occurring below a quench crust and anorthositic fallback breccia with an 8 km thick layer of norite overlying a 4 km layer of pyroxenite and a basal 2 km thick layer of dunite produced by equilibrium crystallization of a homogenized melt sea consistent with vigorous convection in that melt sea is supported by remotely sensed norite excavated by the central peak of maunder crater from 4 km depth generally we predict that very large basin forming impacts including the south pole aitken spa basin forming impact produce melt seas with a cumulate stratigraphy similar to that of the orientale melt sea impact melt differentiation may explain apparently anomalous lithologies excavated in the spa basin interior we note that impact melt differentiates are slow cooled the orientale melt sea took on the order of 10 5 years to solidify and if meteoritic siderophiles fractionate into metal or sulfide layers may not be siderophile enriched therefore impact melt differentiates may pass for pristine highland plutonic rocks in the lunar sample suite these predictions can be tested with current and future mission data

graphical analysis of enthalpy composition relationships in mixed magmas enthalpy composition diagrams h x calculated from existing temperature composition t x phase diagrams and thermodynamic data provide a simple and effective means for evaluating the enthalpy temperature effects of magma mixing if athermal mixing is assumed adiabatic mixing lines on h x diagrams are straight lines because enthalpy unlike temperature is an extensive property of a system comparison of binary t x diagrams with their derivative h x diagrams shows that incorrect predictions can be obtained when t x diagrams are used to analyze mixing problems an h x diagram calculated using experimentally determined phase equilibria for anhydrous basalt rhyolite mixtures predicts that adiabatic mixing of basalt and rhyolite at their respective liquidus temperatures will result in small amounts of crystallization 2 wt because the phase equilibria of hydrous basalt rhyolite mixtures have not yet been determined an h x diagram for such mixtures cannot be constructed however existing hydrous phase equilibria can be used to predict whether adiabatic mixtures of anhydrous basalt and hydrous rhyolite will be super or subliquidus calculations at ptotal 200 mpa show that on an h x diagram a mixing chord drawn between anhydrous basalt and water saturated rhyolite at their respective liquidus temperatures lies below the enthalpy values calculated for a paricutin andesite and mt st helens dacite at their estimated liquidus temperatures this indicates that the liquidus for mixtures of anhydrous basalt and water saturated rhyolite is noticeably convex upward suggesting that larger amounts of crystallization will occur than in the anhydrous case

sixth foray for pristine nonmare rocks and an assessment of the diversity of lunar anorthosites eleven nonmare samples are characterized generally both compositionally and petrographically five are almost certainly pristine ferroan anorthosite 10056c alkali anorthosite 14047c ferroan anorthosite 14312c anorthositic troctolite 14321c3 and granite 14321c4 and four are probably pristine norite 14318c noritic anorthosite 67215 quasi pristine ferroan anorthosite 73217c and norite 78527 five are unique anorthosites extending the diversity of lunar anorthosites considerably alkali anorthosites particularly 14047c are extremely rich in incompatible elements the first anorthosite from apollo 11 with manifestations of pristinity 10056c appears to be a normal member of the ferroan group however the first pristine ferroan anorthosites from apollo 14 and 17 to be studied in detail 14312c and 73217c both have unusually sodic plagioclase by ferroan standards with only 75 plagioclase 67215 is the first large 273 g probably pristine ferroan sample with less than 83 plagioclase the nature of the correlations between longitude and such parameters as eu and sm concentrations and sc sm ti sm and ca na ratios among pristine ant samples has been elucidated because five of the new pristine samples are from a western site apollo 14 interestingly ferroan anorthosite 14312c has ca na sc sm and ti sm ratios close to the normal ferroan values but significantly displaced in the direction of the nonferroan western pristine rocks this suggests that the composition longitude relationships are as old as the late stages of the crystallization of the putative magma ocean

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

zn fe and s isotope fractionation in a large hydrothermal system abstract the genesis of hydrothermal ore deposits is of crucial economic importance this study investigates the extent causes and consequences of zinc and iron isotope fractionation in a large hydrothermal system at the world class navan zn pb orebody ireland large variations in zn fe and s isotope compositions have been measured in microdrilled sphalerite zns at the millimetre scale 66 zn and 56 fe display a well defined positive correlation and both also correlate with 34 s these relationships represent the combined effects of kinetic zn and fe isotope fractionation during sphalerite precipitation and s isotope variation through mixing of hot metal rich hydrothermal fluids and cool bacteriogenic sulfide bearing brines combined with s isotope data 56 fe and 66 zn data on mine concentrates confirm that hydrothermal sulfide is a minor component of the overall deposit signature our data suggest that incoming pulses of metal rich hydrothermal fluid triggered sulfide mineralisation and that rapid precipitation of sphalerite from hydrothermal fluids will lead to strong kinetic fractionation of zn and fe isotopes at very short time and length scales thereby limiting the use of fe and zn isotopes as exploration tools within deposits but revealing the possibility of detecting new deposits from isotopically heavy zn fe geochemical halos

the sudbury igneous complex viscous emulsion differentiation of a superheated impact melt sheet the sudbury igneous complex of ontario canada is the remnant of a voluminous melt sheet produced in a few minutes by impact of a massive meteorite into continental crust 1 85 ga ago the transient cavity and melting zone reached the moho and instantly 2 min relaxed to form a more familiar large shallow crater holding a thick superheated 1700 c melt sheet covered by 2 km of breccia there is little about the resulting bimodal igneous complex that resembles crystallization of well known sheet like bodies of similar composition yet the norite and granophyre exhibit a remarkable similarity in isotopic and trace element compositions suggesting an intimate common parentage from the surrounding crust this petrogenetic enigma is explained here as a natural unavoidable consequence of the impact process in the rapid formation of a superheated magmatic emulsion which we take as the high temperature equivalent of breccia a wide spectrum of viscously discrete interdispersed parcels of mafic and felsic liquids reflecting the compositional heterogeneity of the target crustal materials formed the emulsion within days to months the emulsion components separated according to their relative densities into a bimodal norite granophyre assemblage that formed the basic structure of the present sudbury igneous complex there is clear evidence of this emulsion in the earliest dikes i e offsets which likely give the earliest state of the nascent melt sheet immediately following emulsion separation the strongly superheated bimodal melt sheet underwent vigorous thermal convection in each layer these convective motions homogenized and rapidly cooled the magma to the liquidus temperatures whereupon convection ceased the pattern of convection was pinned in place by the embayment topography of the crater floor which in turn played a pivotal role in directing sulfide deposition into the embayments all further cooling was by conduction of heat through the upper and lower boundaries during which time solidification fronts were established and propagated inward from the upper and lower margins there is clear evidence of solidification from the floor upward and the roof downward minimal differentiation and compositional modification took place throughout cooling and solidification nevertheless during the solidification stage granitic rock fragments on the crater floor and rafts of fallback breccia from the thick overlying onaping formation became unstable and entered the melt sheet and the partially melted remnants collected at the interface between the norite and granophyre some interstitial melt from the norite also percolated upward and altogether the blocks and melt produced the distinctive chemical and physical characteristics of the unusual transition zone the sudbury melt sheet is in essence a full scale magmatic experiment the conditions of formation relative to any other large terrestrial magma are precisely known thus the clear lack of any significant modal layering the overall homogeneous nature of each unit and the lack of any significant chemical differentiation through crystal fractionation establish sudbury as a valuable example of what does not happen under the initial conditions long assumed to prevail at the formation of most large magma chambers

chemical composition and origin of apollo 15 impact melts to better understand the apennine front we have analyzed 14 apollo 15 impact melt rocks including hand samples rake samples and coarse fines for major fused bead microprobe and trace element inaa abundances the melt rocks show a remarkable diversity of chemical composition although all but one have typical kreep incompatible element patterns they appear to form five chemical groups all but the most kreep rich of which may represent single impacts three groups are of low k fra mauro composition none correspond to very high alumina vha compositions the compositions are unlike nearly all other impact melts and regoliths from highland sites indicating a distinct provenance for the apollo 15 samples serenitatis basin impact melt compositions apollo 17 poikilitic boulders are not duplicated although one apollo 17 aphanitic melt sample 73215 is similar to one of the apollo 15 groups the apollo 15 group consisting only of 15445 and 15455 remains the best candidate for imbrium basin impact melt while the most kreep rich group probably consists of melts produced in varied post imbrium impacts into the apennine bench formation apollo 15 kreep basalt flows the most populated group was previously unrecognized and could be either pre or post imbrium basin it is possible that it not 15445 15455 represents imbrium melt one unique sample has a non kreep incompatible element pattern with low abundances and a positive eu anomaly its target was rather primitive and would not appear to be of regional extent or present in the area in post imbrium times it is either a pre imbrian melt or exotic the apennine front does not consist of a monolithic lkfm composition but shows a much wider diversity of compositions than was previously recognized

large mineralogically distinct impact melt feature at copernicus crater evidence for retention of compositional heterogeneity 1 despite several lines of evidence for efficient mixing of impact melt in complex craters we document mineralogical heterogeneity in impact melt deposit on a scale of tens of kilometers on the moon in the 96 km diameter copernicus crater this heterogeneity is in the form of a large sinuous impact melt feature on the floor and northern wall that is spectrally distinct from melt in its immediate vicinity this melt feature spanning 30 km in length and 0 5 5 km in width has relatively short wavelength narrow ferrous absorption bands near 900 nm and 2000 nm indicating a more mg rich pyroxene composition as compared to impact melt deposit in the vicinity which is relatively rich in fe ca pyroxenes this distinction provides evidence for the preservation of compositional heterogeneity in impact melt in complex craters on the moon and documents an example of inefficient mixing of melt during the cratering process

anorthosite assimilation and the origin of the mg fe related bimodality of pristine moon rocks support for the magmasphere hypothesis the lunar magma ocean or magmasphere hypothesis always controversial has required considerable revision in recent years the geochemical bimodality of pristine rocks epitomized by a diagram of na na ca versus mg ratio has led to proposals that a major fraction of the crust the mg rich suite formed as cumulates in numerous intrusions slightly younger than the magmasphere the precise origin of the bimodality has been elusive however one previous suggestion was that na was lost as a volatile before the ferroan anorthosites crystallized from the magmasphere whereas the mg rich intrusives retained all of their original na however this model cannot fully explain the bimodality because the same bimodal pattern is manifested by plotting eu al a ratio of involatile elements versus mg ratio assimilation probably helped to engender the bimodal patterns mass energy balance calculations indicate that large proportions of plagioclase were probably assimilated from the older magmasphere generated ferroan anorthosite crust by most of the mg rich intrusive melts the magmasphere in the absence of assimilation probably did not yield appreciable plagioclase the ferroan anorthosite crust until fractional crystallization of mafic silicates had diminished the melt mg ratio to about 0 42 however assuming identical initial melt composition an mg rich intrusion assimilating ferroan anorthosite and perhaps also a small proportion of urkreep would have reached plagioclase saturation at much higher mg about 0 66 the current version of the magmasphere hypothesis ferroan anorthosites magmasphere flotation cumulates mg rich rocks products of slightly younger localized intrusions appears to be the only plausible mechanism for engendering the mg fe related bimodality

the distribution of mg spinel across the moon and constraints on crustal origin a robust assessment is made of the distribution and spatially resolved geologic context for the newly identified rock type on the moon a mg spinel bearing anorthosite pink spinel anorthosite psa essential criteria for confirmed detection of mg spinel using spectroscopic techniques are presented and these criteria are applied to recent data from the moon mineralogy mapper altogether 23 regions containing confirmed exposures of the new mg spinel rock type are identified all exposures are in highly feldspathic terrain and are small a few hundred meters but distinct and verifiable most resulting from multiple measurements each confirmed detection is classified according to geologic context along with other lithologies identified in the same locale confirmed locations include areas along the inner rings of four mascon basins knobs within central peaks of a few craters and dispersed exposures within the terraced walls of several large craters unexpected detections of mg spinel are also found at a few areas of hypothesized non mare volcanism the small mg spinel exposures are shown to be global in distribution but generally associated with areas of thin crust confirmation of mg spinel exposures as part of the inner ring of four mascon basins indicates this psa rock type is principally of lower crust origin and predates the basin forming era

cubic zirconia in 2370 c impact melt records earth s hottest crust abstract bolide impacts influence primordial evolution of planetary bodies because they can cause instantaneous melting and vaporization of both crust and impactors temperatures reached by impact generated silicate melts are unknown because meteorite impacts are ephemeral and established mineral and rock thermometers have limited temperature ranges consequently impact melt temperatures in global bombardment models of the early earth and moon are poorly constrained and may not accurately predict the survival stabilization geochemical evolution and cooling of early crustal materials here we show geological evidence for the transformation of zircon to cubic zirconia plus silica in impact melt from the 28 km diameter mistastin lake crater canada which requires super heating in excess of 2370 c this new temperature determination is the highest recorded from any crustal rock our phase heritage approach extends the thermometry range for impact melts by several hundred degrees more closely bridging the gap between nature and theory profusion of 2370 c superheated impact melt during high intensity bombardment of hadean earth likely facilitated consumption of early formed crustal rocks and minerals widespread volatilization of various species including hydrates and formation of dry rigid refractory crust

trace and minor elements in sphalerite from base metal deposits in south china a la icpms study laser ablation icp mass spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine zn pb deposits in south china the deposits which are of different ages and belong to different metallogenic provinces have been assigned to the following genetic types skarn hetaoping luziyuan syngenetic massive sulphide dabaoshan laochang and bainiuchang and mississippi valley type huize mengxing niujiaotang based on the features of the ore even though their origin is heavily debated based on other criteria the giant jinding deposit is considered separately sphalerite from each genetic class of deposit shows a distinct chemical signature sphalerite from the skarn deposits is characterised by elevated lattice bound concentrations of co and mn the distal character of these skarn systems is reflected by the low in content of sphalerite the three syngenetic massive sulphide deposits feature sphalerite strongly enriched in in sn and ga whereas the deposits of mvt type are typically enriched in ge cd tl and as these divergent characters are reflected in absolute element abundances as well as in element ratios time resolved depth profiles for sphalerite from the chinese deposits confirm the presence of elements such as co in ge ga and cd in solid solution but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements whose ability to enter the crystal structure of sphalerite has been previously debated ag sn tl sb may also be in solid solution sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as south china and help resolve the mechanism by which many of the debated ore deposits were formed

lunar mg suite thermobarometry and petrogenesis of parental magmas using compilations of internally consistent thermodynamic data on minerals and advances in quantifying the energetics of crystalline solid solutions we have recalculated the pressures and temperatures of equilibration of troctolite sample 76535 and a number of spinel cataclasites the five phase assemblage olivine orthopyroxene clinopyroxene cr spinel plagioclase which occurs in symplectite assemblages in 76535 gives equilibration temperatures from 800 900 c and pressures from 200 to 250 mpa indicating a deep 40 50 km crustal source spinel cataclasite assemblages give minimum pressures of 100 mpa mg suite magmas were apparently intruded throughout the lunar crust early in lunar history the textures and equilibration temperatures in many mg suite samples are consistent with sub solidus recrystallization and the mg rich minerals of some refractory troctolites and dunites may be residues of a crustal melting process or products of subsolidus elemental redistribution the sm nd age of 4 26 0 06 ga of troctolite 76535 most likely represents the time of sub solidus recrystallization and or partial melting in an attempt to identify the primary source material for the mg suite magmas a variety of models were tested using the melts and magfox codes a good fit between mineral compositions and crystallization sequences is obtained by 20 batch melting at 0 5 gpa of an average whole moon composition with an mg of 0 85 melts formed by batch melting at higher pressures and melts formed by poly baric partial fusion over the pressure range from 2 0 to 0 3 gpa were either too poor in mg and or crystallized clinopyroxene before orthopyroxene mixing with 10 20 urkreep which is required to satisfy the ree constraints of the mg suite reduces the mg of the parental magmas and requires a whole moon mg closer to that of the terrestrial mantle

low pressure phase equilibria of anhydrous anorthite bearing mafic magmas 1 one of the most persistent questions regarding the phase equilibria of mid ocean ridge basalts morb pertains to the petrogenesis of the anorthitic plagioclase phenocrysts an90 that are characteristic of the more primitive members of such suites anorthitic phenocrysts are present in many if not most morb suites in spite of the fact that no naturally occurring morb glasses have ever been discovered to be in equilibrium with plagioclase more calcic than an85 we have addressed this paradox by attempting to saturate natural basalts with anorthite in a series of 1 atm experiments using three different natural basaltic starting compositions an n morb an e morb and a continental high alumina basalt to ensure duplication of the olivine and anorthite saturation observed in natural anorthite bearing basalt the experiments were run in an93 6 capsules with fo92 olivine added to the starting glass the compositions of experimental liquids are generally colinear with the trends observed in the lava suites used as the source material for the starting glasses significantly aluminous spinel al2o3 contents of 61 68 wt was produced at 1290 c in all compositions and chromites al2o3 contents of 33 42 wt at lower temperatures in n morb derived liquids despite no spinel having been added to the starting mixture in addition the experiments produced basaltic liquid in equilibrium with both fo89 olivine and an85 feldspar at temperatures of 1230 and 1210 these liquids have compositions with mg at mg mg fet 100 that range from 63 to 85 the tio2 mgo correlation indicates large 16 23 amounts of crystallization for each percent decrease in mgo these results suggest the possibility that dry anorthite bearing basaltic magmas are the product of the interaction between primary melt and al spinel bearing upper mantle in addition the results indicate that morb magmas can undergo a large amount 50 of crystallization prior to reaching 8 mgo further although anorthite bearing magmas have characteristics consistent with their being a significant volumetric component of morb parent magmas the reaction mechanism suggested for their petrogenesis indicates that they are not necessarily primary magmas

spatial evolution of zn fe pb isotopes of sphalerite within a single ore body a case study from the dongshengmiao ore deposit inner mongolia china analyses of sphalerite minerals from the characteristic brecciated zn pb ores of the main ore body in the giant dongshengmiao deposit have revealed variations in 66zn from 0 17 to 0 40 and in 56fe from 1 78 to 0 35 further the investigated pyrrhotite samples have iron that is isotopically similar to that of associated sphalerite minerals the most distinctive pattern revealed by the zinc and iron isotope data is the lateral trend of increasing 66zn and 56fe values from southwest to northeast within the main ore body the lead isotopic homogeneity of ore sulfides from the main ore body suggests that there is only one significant source for metal thus precluding the mixing of multiple metal sources as the key factor controlling spatial variations of zinc and iron isotopes the most likely control on spatial variations is rayleigh fractionation during hydrothermal fluid flow with lighter zn and fe isotopes preferentially incorporated into the earliest sulfides to precipitate from fluids precipitations of sphalerite and pyrrhotite have played vital roles in the zn and fe isotopic variations respectively of the ore forming system accordingly the larger isotopic variability for fe than zn within the same hydrothermal system perhaps resulted from a larger proportion of precipitation for pyrrhotite than for sphalerite the lateral trend pattern revealed by the zinc and iron isotope data is consistent with the occurrence of a cystic shaped breccia zone which is characterized by marked elevation in cu the results further confirm that zn and fe isotopes can be used as a vectoring tool for mineral prospecting

the pattern of ni and co abundances in lunar olivines abstract near liquidus experiments on peridotite and other olivine normative compositions from 1 7 to 6 gpa confirm the applicability of exchange based empirical models of ni and co partitioning between olivine and silicate liquids with compositions close to the liquidus of peridotite given that most estimates of lunar bulk composition are peridotitic the partitioning models thus lend themselves to calculation of olivine compositions produced during the early stages of magma ocean crystallization calculation of olivine compositions produced by fractional crystallization of a model lunar magma ocean initially 700 km deep reveals a prominent maximum in ni concentration versus fraction crystallized or mg molar mgo mgo feo but a pattern of monotonically increasing co concentration these patterns qualitatively match the puzzling patterns of ni and co concentrations observed in lunar rocks in which forsteritic olivines in magnesian suite cumulates have lower ni and co abundances than do less magnesian olivines from low ti mare basalts and olivines from the ferroan anorthosite suite fas have lower ni but similar co to mare basalt olivines the ni and co abundances in olivines from the magnesian suite cumulates can be reconciled in terms of fractional crystallization of a deep magma ocean which initially produces a basal dunite comprised of the hottest and most magnesian olivine overlain by an olivine orthopyroxene harzburgite layer that is in turn overlain by an upper zone of plagioclase bearing cumulates the ultramafic portion of the cumulate pile overturns sending the denser harzburgite layer which later becomes a portion of the green glass source region to the bottom of the cumulate pile with ni and co rich olivine meanwhile the less dense but hottest most magnesian olivines with much lower ni and co abundances are transported upward to the base of the plagioclase bearing cumulates where subsequent heat transfer leads to melting of mixtures of primary dunite norite and gabbronorite with kreep a k ree p enriched component widely believed to be derived from the very latest stage magma ocean liquid these hybrid melts have al 2 o 3 ni and co abundances and mg appropriate for parent magmas of the magnesian suite ni and co abundances in the fas are consistent with either direct crystallization from the magma ocean or crystallization of melts of primary dunite norite mixtures without kreep

zinc isotope variation in hydrothermal systems preliminary evidence from the irish midlands ore field little is known about the range or controls on the zinc isotope composition of terrestrial materials and no systematic studies have been carried out on ore forming systems we have obtained zinc isotope data from 19 sphalerite samples formed over a range of well constrained precipitation conditions from the irish zn pb ore field the results reveal variation in 66zn where 66zn 66zn 64zn sample 66zn 64zn standard 1 1000 from 0 17 to 1 33 per mil relative to the lyon jmc 3 0749l zinc standard this variation is significant compared to the external reproducibility 0 12 2 and the data show very good mass dependency with 67zn and 68zn values thus natural variations in the zinc isotope composition of these ore minerals can be resolved our results span the entire range of 66zn values measured on terrestrial geologic samples to date the data suggest that variations in the primary source rock composition or precipitation temperature are unlikely to be important controls on the zinc isotope composition of sphalerite in the ore field we suggest that the variation is most likely due to a kinetic fractionation involving the preferential incorporation of light zinc isotopes in sphalerite precipitated rapidly under disequilibrium conditions however we cannot rule out the possibility of mixing of zinc derived from two isotopically distinct sources the significant variation in zinc isotope compositions we have observed in the irish ore field confirms that such fractionations can provide new insights into mineralizing processes in the earth s crust

on the origin of impact glass in the apollo 16 regolith this study addresses the issue of what fraction of the impact glass in the regolith of a lunar landing site derives from local impacts those within a few kilometers of the site as opposed to distant impacts 10 or more kilometers away among 10 323 fragments from the 64 210 lm grain size fraction of three apollo 16 regolith samples 14 are impact glasses that is fragments consisting wholly or largely of glass produced in a crater forming impact another 16 are agglutinates formed by impacts of micrometeorites into regolith we analyzed the glass in 1559 fragments for major and minor element concentrations by electron probe microanalysis and a subset of 112 of the fragments that are homogeneous impact glasses for trace elements by secondary ion mass spectrometry of the impact glasses 75 are substantially different in composition from either the apollo 16 regolith or any mixture of rocks of which the regolith is mainly composed about 40 of the impact glasses are richer in fe mg and ti as well as k p and sm than are common rocks of the feldspathic highlands these glasses must originate from craters in maria or the procellarum kreep terrane of the feldspathic impact glasses some are substantially more magnesian greater mgo feo or have substantially lower concentrations of incompatible elements than the regolith of the apollo 16 site many of these however are in the range of feldspathic lunar meteorites most of which derive from points in the feldspathic highlands distant from the procellarum kreep terrane these observations indicate that a significant proportion of the impact glass in the apollo 16 regolith is from craters occurring 100 km or more from the landing site in contrast the composition of glass in agglutinates on average is similar to the composition of the apollo 16 regolith consistent with local origin 2010 elsevier ltd all rights reserved

slip in the 1868 hayward earthquake from the analysis of historical triangulation data despite the importance of the hayward fault for earthquake hazards in the san francisco bay area neither the rupture length nor the average coseismic slip in the most recent major earthquake which occurred in 1868 is well known we estimate slip in the 1868 earthquake by analyzing triangulation data collected between 1853 1860 and 1876 1891 we apply a denuisancing procedure that projects out the dependence of that data on station coordinates allowing their displacements to be estimated directly the best fit to the data is obtained with a 52 km long by 10 km deep rupture that extends from warm springs to near berkeley considerably longer than the 30 km of reported surface breakage the estimated slip for an earthquake of this length is 1 9 0 4 m and the seismic moment is m0 3 0 0 7 1019 n m corresponding to mw 7 0 the data are inconsistent with regionally high strain rate prior to the 1906 earthquake as had been previously suggested the triangulation data record northeastward displacement of station loma prieta presumably as a result of the 1865 earthquake the fault normal displacement is not easily explained by slip on either the san andreas fault or the 1989 loma prieta rupture surface this observation is however consistent with an mw 6 3 4 thrust event northeast of the san andreas fault in the southern santa cruz mountains thrust belt

compositional diversity at theophilus crater understanding the geological context of mg spinel bearing central peaks 1 analysis of high resolution moon mineralogy mapper m3 data reveals the presence of a prominent mg spinel rich lithology in the central peaks of theophilus crater on the lunar nearside other peak associated lithologies are comprised of plagioclase olivine and pyroxene bearing materials a consistent spatial association of mg spinel with mafic free anorthosite is recognized documentation of theophilus central peaks brings the global inventory of mg spinel rich lithology to two widely separated occurrences namely theophilus on the lunar nearside and moscoviense basin on the farside the theophilus crater target region lies on one of the inner rings of the nectaris basin indicating that the mg spinel bearing lithology source was deep in the lunar crust

mineral chemical investigation on sulfide mineralization of the istala deposit gumushane ne turkey abstract the mineralogy of the istala deposit gumushane northeastern turkey was studied in detail and a geochemical investigation was carried out using electron probe micro analysis epma sphalerite galena chalcopyrite and pyrite are the major sulfide minerals found in the istala deposit with minor amounts of bornite idaite tetrahedrite tennantite anilite yarrowite mckinstryite covellite and chalcocite in addition to these barite and a small quantity of quartz occur as gangue minerals based on the textural relations and mineral assemblages five different stages of crystallization have been recognized mineral paragenesis of the first four stages has been found to be similar whereas clear enrichment has been observed in the modal abundance of the copper sulfide mineral assemblage at the fifth stage ore formation whole rock geochemical analyses of the istala ore show an enrichment of ag content up to 3328 ppm optical observations and epma study indicated that abundant silver mineralization was found in the istala ore especially during the later stage ore deposition repetition to the presence of native silver in the samples a significant amount of silver was incorporated in bornite idaite tetrahedrite tennantite anilite yarrowite mckinstryite covellite and chalcocite whereas a trace amount of silver has been detected in sphalerite galena chalcopyrite and pyrite the homogenization temperatures th of the primary fluid inclusions were measured between 98 and 284 c with frequency peaks around 140 c 190 c and 240 c all data obtained support the theory that later stage copper rich sulfides formed under the low temperature conditions are responsible for the large amounts of silver content in the istala mine