great thrust earthquakes and aseismic slip along the plate boundary of the makran subduction zone the makran subduction zone of iran and pakistan exhibits strong variation in seismicity between its eastern and western segments and has one of the world s largest forearcs we determine the source parameters for 14 earthquakes at makran including the great mw 8 1 earthquake of 1945 the only instrumentally recorded great earthquake at makran we determine the loci of seismic and aseismic slip along the plate boundary and we assess the effects of the large forearc and accretionary wedge on the style of plate boundary slip we apply body waveform inversions and for small magnitude events use first motions of p waves to estimate earthquake source parameters for the 1945 event we also employ dislocation modeling of uplift data we find that the earthquake of 1945 in eastern makran is an interplate thrust event that ruptured approximately one fifth the length of the subduction zone nine smaller events in eastern makran that are also located at or close to the plate interface have thrust mechanisms similar to that of the 1945 shock seaward of these thrust earthquakes lies the shallowest 70 80 km of the plate boundary we find that this segment and the overlying accretionary wedge remain aseismic both during and between great earthquakes this aseismic zone as in other subduction zones lies within that part of the accretionary wedge that consists of largely uconsolidated sediments seismic velocities less than 4 0 km s the existence of thrust earthquakes indicates that either the sediments along the plate boundary in eastern makran become sufficiently well consolidated and de watered about 70 km from the deformation front or older lithified rocks are present within the forearc so that stick slip sliding behavior becomes possible this study shows that a large quantity of unconsolidated sediment does not necessarily indicate a low potential for great thrust earthquakes in contrast to the east the plate boundary in western makran has no clear record of historic great events nor has modem instrumentation detected any shallow thrust events for at least the past 25 years most earthquakes in western makran occur within the downgoing plate at intermediate depths the large change in seismicity between eastern and western makran along with two shallow events that exhibit right lateral strike slip motion in central makran suggest segmentation of the subduction zone two paleozoic continental blocks dominate the overriding plate the boundary between them is approximately coincident with the transition in seismicity although relative motion between these blocks may account for some of the differing seismic behavior the continuity of the deformation front and of other tectonic features along the subduction zone suggests that the rate of subduction does not change appreciably from east to west the absence of plate boundary events in western makran indicates either that entirely aseismic subduction occurs or that the plate boundary is currently locked and experiences great earthquakes with long repeat times evidence is presently inconclusive concerning which of these two hypotheses is most correct the presence of well defined late holocene marine terraces along portions of the coasts of eastern and western makran could be interpreted as evidence that both sections of the arc are capable of generating large plate boundary earthquakes if that hypothesis is correct then western makran could produce a great earthquake or it could rupture as a number of segments in somewhat smaller magnitude events alternatively it is possible that western makran is significantly different from eastern makran and experiences largely aseismic slip at all times a knowledge of the velocity structure and nature of the state of consolidation or lithification of rocks at depth in the interior portion of the forearc of western makran should help to ascertain whether that portion of the plate boundary moves aseismically or ruptures in large to great earthquakes a resolution of this question has important implications for seismic hazard not only for western makran but also for other margins such as the cascadia subduction zone of western north america where historical thrust events have not occurred

metasomatic control of k rb ratios in amphibolites abstract amphibolite facies metamorphism of gabbroic dykes together with their quartzo feldspathic granulite facies country rock archean basement west greenland transformed the gabbroic rocks into amphibolites with remarkably high k rb values up to 2300 average 727 reflecting correspondingly high k rb values in the country rock a similar dyke transformation in an amphibolite facies complex precambrian basement southwest sweden produced amphibolites with more common k rb values average 375 similar to those found in the country rock as the protolith chemistry and the p t conditions of origin for the two amphibolite occurrences are very similar it is concluded that the difference in k rb distribution is caused by the difference in country rocks the k and rb values in the two amphibolite occurrences lie between protolith and country rock values suggesting an exchange of k and rb between basic rock and quartzo feldspathic country rock probably through the hydrothermal fluids which assisted in the amphibolite formation

destructive earthquake and disastrous tsunami in the indian ocean what next abstract a major earthquake event and a disastrous tsunami struck on december 26 2004 in the indian ocean which led to the death of nearly 250 000 people within a short period of time this has given a major jolt not only to the scientists but also to the authorities planners and various national and international organizations discussions regarding what to do and how to cope with such situations are taking place and also on various plans and programmes for the future we have analyzed the available scientific data related to the sumatra earthquake and tsunami and also the earlier disastrous events of the tsunami this includes seismicity of the region numerical modeling studies and crustal deformation studies based on earlier reports of disastrous events warning systems related to earthquakes and tsunamis we suggest scientific studies that need to be taken up in the near future in the region our study will provide some direction for the ongoing discussions to prepare better plans and programmes in the indian ocean by various south east asian countries

high resolution palynological analysis in lake sapanca as a tool to detect recent earthquakes on the north anatolian fault high resolution palynological analysis of a 38 cm long core collected from lake sapanca northwest turkey reveals large earthquakes that occurred during the second half of the 20th century along the north anatolian fault zone four events have disturbed the lacustrine sedimentary sequence three of the four events are historical earthquakes in 1999 in izmit 1967 in mudurnu and 1957 in abant these events are recorded in the core by turbiditic deposits and reworked sediment and by low overall palynomorph concentrations but high values of thick exined pollen fern spores and fungal spores palynomorphs in the event beds have been grouped based on their associations in modern moss river and lake samples the inferred mechanisms of transport and sources for the palynomorphs are 1 lake sediment displaced by slump 2 collapsed shoreline sediment owing to seiche waves and sudden lake level changes 3 subsidence of deltas and 4 river transported soil and sediment from upland areas the 1999 izmit earthquake is only weakly recorded by palynomorphs probably due to recent engineering control on the rivers the 1967 mudurnu earthquake had the strongest effect on the lake introducing successive packages of sediment to the centre of the lake from underwater slopes the lakeshore and rivers

spatially averaged open channel flow over rough bed in this paper it is suggested that the double averaged in temporal and in spatial domains momentum equations should be used as a natural basis for the hydraulics of rough bed open channel flows especially with small relative submergence the relationships for the vertical distribution of the total stress for the simplest case of 2d steady uniform spatially averaged flow over a rough bed with flat free surface are derived these relationships explicitly include the form induced stresses and form drag as components of the total stress using this approach we define three types of rough bed flows 1 flow with high relative submergence 2 flow with small relative submergence and 3 flow over a partially inundated rough bed the relationships for the double averaged velocity distribution and hydraulic resistance for all three flow types are derived and compared with measurements where possible the double averaged turbulent and form induced intensities and stresses for the case of regular spherical segment type roughness show the dominant role of the double averaged turbulence stresses and form drag in momentum transfer in the near bed region

contrasting behaviour of boron during crustal anatexis the study of volatile elements in crustal anatectic terranes may provide information about the role of fluid flow and fluid pathways during high temperature metamorphism we have studied the distribution of li and b in two migmatitic areas the pena negra anatectic complex central spain and the migmatites and leucogranites associated with the ronda peridotites southern spain they represent two contrasting cases in the behaviour of volatiles particularly b during anatexis the pena negra migmatites are dominated by diatexites where it is possible to distinguish granitic leucosomes melanosomes metric to decimetric leucogranitic segregates and decimetric to metric sillimanite rich restitic enclaves all lithologies are characterized by low b concentrations mean values 30 ppm and b is enriched in melanosomesrrestites with respect to leucosomesrleucogranites this may be due to the fact that a notable proportion of b can reside in restitic sillimanite b concentrations in leucosomes and leucogranites can be explained by closed system anatexis at ronda metatexitic and diatexitic migmatites underlie the ronda peridotites and diatexite and leucogranite dikes intrude the peridotites diatexites underlying the peridotites are characterized by cordierite q biotite garnet as ferromagne sian phases with rare or absent tourmaline low b contents 10 ppm and cordierite garnet leucosomes leucogranite dikes have high b concentrations mean valuef 400 ppm with tourmaline being a common and sometimes the most abundant ferromagnesian phase a genetic relationship between diatexites and leucogranites is strongly suggested by the presence of dikes of diatexites intruding the bottom of the peridotites we conclude that b in the leucogranites may stem from the dissolution of tourmaline originally present in the metasediments or infiltration of b rich aqueous fluids into the anatectic zone according to recent experimental work textures in some tourmaline rich ronda leucogranites suggest initial b o 23 contents in the melt higher than the present measured concentrations preliminary experimental results presented in this paper propose that this difference is not due to water activities in the melt rapid crystallization of the melts following undercooling may explain the existence of abundant euhedral tourmaline in leucogranites with low aluminium saturation index asis molar al o r caoq na oq k o and relatively low b contents q 2001 elsevier science b v all rights 23 2 2 reserved

sedimentology and paleontology of a tsunami deposit accompanying the great chilean earthquake of february 2010 abstract at pichilemu in the northern third of the rupture area of the moment magnitude scale mw 8 8 2010 chile earthquake deposits of the tsunami accompanying the earthquake consist of a lower layer of medium to fine sand mean grain size of 200 m containing rock clasts overlain by a thin silty very fine sand mean grain size of 125 m layer based on a sedimentological model most 90 of the deposit is finer than 401 408 m suggesting tsunami flow velocities were between 7 m s and 13 5 m s ostracods were common in the upper layer along with a small number of broken benthic foraminifera and a single planktonic foraminifera diatoms were abundant throughout species assemblages represent a mixture of diatoms from differing environments life forms and substrate preferences we attribute the mixed assemblages to turbulence within the water column during tsunami inundation with erosion of beaches and salt marshes followed by redeposition of sand and mud inland breakage of fragile diatom valves in the lower layer may also support transport by turbulent flow a higher abundance of diatom species with mud substrate preferences in the upper layer implies a decrease in flow velocity from lower to upper layers

dinoflagellate cyst distribution in surface sediments from the arabian sea northwestern indian ocean in relation to temperature and salinity gradients in the upper water column abstract surface sediment samples from the arabian sea indian ocean have been investigated for their dinoftagellate cyst content to obtain information about the environmental affinity and potential palaeo environmental significance of the cyst species their distribution is compared with the environmental characteristics of the overlying water column using detrended correspondence analysis and canonical correspondence analysis the distribution patterns of individual species are compared with temperature and salinity gradients over four seasons the main variation in cyst association appears to be related to variation in those gradients affected by the sw and ne monsoons on the basis of this relationship four groups of species can be recognised 1 central arabian sea species 2 sw monsoon upwelling species 3 ne monsoon eutrophic species 4 species with no distinct relationship with monsoon related gradients the downcore occurrences of species from groups 1 2 and 3 have potential as indicators for palaeo sw and ne monsoon strength

origin of k poor leucosomes in a metasedimentary migmatite complex by ultrametamorphism syn metamorphic magmatism and subsolidus processes two types of stromatic leucosomes are identified in metasedimentary rocks from the skagit migmatite complex north cascades washington state u s a both types are trondhjemitic and appear similar in outcrop but although both contain low abundances of ree one type consists of leucosomes that are relatively ree enriched compared to the other and contains 1 small 700 c water rich fluid present inferences about the origin of the above listed mineralogical and fluid inclusion features and modeling of leucosome trace element abundances the second type of leucosome is interpreted to have formed entirely by subsolidus processes e g metamorphic differentiation because these leucosomes lack features consistent with an origin by partial melting k poor tonalitic trondhjemitic leucosomes associated with metasedimentary biotite bearing source rocks may form by water saturated partial melting or by subsolidus processes both general leucosome forming mechanisms may operate at different times during upper amphibolite facies regional metamorphism partial melting may be initiated by syn metamorphic magmatic activity if crystallizing plutons serve as external sources of the water rich fluid necessary for ultrametamorphism in the middle crust during orogenesis large scale migmatite complexes such as the skagit migmatites may form at least in part in response to contact effects of plutonism associated with high grade metamorphism so although migmatite complexes are a volumetrically substantial part of many orogenic belts they may not themselves represent a significant original source of magma for larger scale igneous bodies

makran continental margin sedimentation during the late holocene sedimentation in the makran active margin is governed by a complex interaction of atmospheric tectonics and hydrodynamic setting of the northern flank of the gulf of oman the mixed clastic carbo

geochemical constraints on restite composition and unmixing in the velay anatectic granite french massif central the main anatectic granite of the velay complex is unique among major french massif central hercynian granitoids in that rather than having an entirely lower crustal source it formed by mixing between partial melts of the meta igneous lower crust and upper crustal country rock schists and orthogneisses the geochemical variations in the velay main anatectic granites cannot however be explained by mixing alone as their compositions range to lower sio2 with higher al2o3 fe2o3 and tio2 and lower na2o and cao than either end member in mixing the variations are interpreted as being due to the presence of up to 35 restite in minimum melts of country rock compositions primary restites form equilibrium assemblages represented by biotite ilmenite and surmicaceous enclaves which consist of biotite apatite zircon and almandine the main anatectic granites more rarely contain schist and gneiss enclaves quartz resisters and plagioclase restites secondary restites are mainly represented by cordierite and possibly k feldspar which formed by recrystallisation of primary biotite rich restites the unique characteristics of the velay main anatectic granites are likely to be due in part to its late formation close to the end of the hercynian orogeny the metasedimentary lower crust may have become too refractory to yield large volumes of melt following partial melting to form the other major massif central granitoids the heat necessary for partial melting at higher crustal levels was transferred from the lower crust by the intrusion of i type granites and low volume diorites from the mantle upper crustal anatexis was mainly controlled by muscovite breakdown reactions 830 to 850 c and the liberation of water due to the recrystallisation of biotite to cordierite the temperatures necessary for biotite breakdown were only achieved locally and resulted in the formation of high lree granites

the geochemistry of phosphorus in granite rocks and the effect of aluminium phosphorus has been shown to have a profound influence on the evolution of silicate melt systems it also controls the geochemical behavior of rare earths uranium thorium strontium and other elements through the relationships between melt and accessory phosphates based on experimental data harrison and watson 1984 proposed a model of saturation behavior of apatite in crustal melts as a function of temperature and silica content subaluminous granites fit in well with such a model but departures are evident in the case of peraluminous granites a systematic study of the distribution of p2o5 in granitoids from all over the world shows that there are two modes to describe phosphorus enrichment in peraluminous granitic rocks 1 the hoyos type trend which is parallel to the one in harrison and watson s hw model but with higher p2o5 concentrations at the same silica contents and 2 the pedrobernardo type trend implying an increase in phosphorus in the most sio2 rich differentiates of strongly peraluminous low ca granites pedrobernardo type leucogranites are characterized by the presence of rare phosphates or p rich feld spars since they have excess p2o5 over cao to form normative apatite we here propose the term perphosphorous granites high phosphorus contents appear to be due to elevated apatite solubility in peraluminous granitic melts rather than to high amounts of restitic apatite both the hoyos and pedrobernardo type departures from the hw model can be corrected by using the expression p2o5corrected p2o5hw efactor where p2o5hw is the prediction according to the hw model and factor is asi 1 6429t asi being the al2o3 cao na2o k2o molar ratio we suggest that such departures could be caused by a decrease in the ca activity in the melt as a result of increased peraluminousity the pedrobernardo type trend is a limiting case in which ca activity in the melt is nearly zero and calcium instead of phosphorus becomes the essential structural constituent esc of the apatite when this happens phosphorus starts behaving as an incompatible element that is concentrated in late fluids high p2o5 contents are more characteristic of s than other granite types no significant departures from the hw model have been found for i a or m type granites in central iberia granites associated with u sn and w mineralizations usually have high phosphorus contents values of p2o50 5 wt at sio270 wt are good indicators of economic mineralization

multi proxy evidence for trans pacific tsunamis in the hawai ian islands abstract the origin of two sand layers buried in polol wetland on the northeast coast of the island of hawai i was investigated using a multi proxy approach including radiometric dating sedimentology geochemistry micropalaeontology palynology and historical records based on 210 pb 137 cs and pollen data the lower sand unit extending 250 to 350 m inland is attributed to the 1946 aleutian tsunami while the upper sand unit was laid down by the 1957 aleutian tsunami chronological information does not appear to support any link between these deposits and historical storm events furthermore sedimentological geochemical diatom and pollen results suggest deposition of marine and near beach sediments under high energy conditions typically associated with tsunami inundation this work presents the first conclusive sedimentary evidence for distantly generated tsunamis on the hawai ian islands opening the way for more comprehensive historical and palaeotsunami studies indeed a brief review of archaeological data suggests that the hawai ian coast may have experienced similar large magnitude events in the past from both local and distant sources

coastal boulders as evidence for high energy waves on the iranian coast of makran abstract coastal boulder deposits attesting to large waves are found along the rocky coast of makran iran from chabahar to lipar boulders are either scattered on the rocky coastal platform or accumulated in imbricated clusters the boulders are mostly rectangular and composed of biogenic calcarenite deriving from the present coastal platform significant morphological features observed on the boulders include supratidal karstic pools sharp broken edges and fractures some boulders contain boreholes and shells of marine bivalves suggesting detachment and transportation from the subtidal zone the dimensions elevation and distance from the coastline of 58 representative boulders are documented to estimate their volume weight and inland displacement the boulders weighing up to 18 t are found up to 6 m above present mean sea level and up to 40 m from the present shoreline we applied hydrological models to estimate and compare the wave height and inundation distance required to transport the boulders inland our results demonstrate that no known or probable storm event on the makran coast is capable of detaching and transporting the boulders in contrast tsunami wave height of 4 m is enough to detach all the boulders from the rocky coast and transport them inland we conclude that a tsunamigenic origin for boulder deposits is most plausible our results imply that the western part of the makran coast has archived evidence of paleotsunami events probably generated by large earthquakes at the makran subduction zone

experimental investigation of the impact of macroalgal mats on flow dynamics and sediment stability in shallow tidal areas abstract this study aims to quantify the impact of macroalgal mats of ulva intestinalis on flow dynamics and sediment stability such mats are becoming increasingly common in many coastal and estuarine intertidal habitats thus it is important to determine whether they increase flow resistance promote bed stability and therefore reduce the risk of erosion leading to tidal flooding or to degradation of coastal lagoons the study has been carried out through a systematic series of experiments conducted in the large open channel flume of the total environment simulator tes facility university of hull uk the experimental facility was set up with a bed of fine sand partially covered by strands of u intestinalis living individuals attached to large clasts were collected from budle bay in the lindisfarne national nature reserve uk and transplanted to the flume the tes was equipped with acoustic doppler velocimetry adv and acoustic backscatter abs sensors which measured current velocity water level bed level and suspended sediment concentration the experiments consisted of several unidirectional flow runs firstly with a mobile sediment bed covered with u intestinalis then with a bare sediment surface conducted at three different water depths under the investigated experimental range of velocities typical of tidal environments the macroalgal filaments were bent parallel to the sediment bed the resulting velocity profile departed from the classical logarithmic trend implying an increase of the overall roughness this result reflects the different vertical reynolds shear stress profiles and energy spectra features of the turbulent flow with respect to a bare sandy bed configuration macroalgae are also found to affect the morphological configuration of bedforms the overall result is significant bio stabilization with increased flow resistance and reduced sediment transport

flow turbulence over fixed and weakly mobile gravel beds characteristics of turbulence structure in quasi 2d flows with static and weakly mobile gravel beds are presented three sets of measurements with acoustic doppler velocimeters in an irrigation canal were used two with subcritical bed shear stress static beds and one with the bed shear stress o close to critical oc weakly mobile bed the analyses included vertical distributions of local mean velocities turbulence intensities turbulent shear stresses velocity auto and cross spectra the quadrant method and high order velocity moments a number of properties of turbulence intensities high order moments streamwise bursting parameters and velocity spectra appeared to be similar for all three flows but some properties were different the most important one was an observed reduction in the von karman constant for the flow with weakly mobile bed comparison of these results with other studies and analogies with drag reducing flows suggest that at o oc 1 the drag on the bed for a given granula

geochemical modeling of low melt fraction anatexis in a peraluminous system the pena negra complex central spain abstract a study was made of the chemical fractionation associated with four cases of anatectic segregation of low melt fraction cordieritic granites from migmatized meta greywackes the aims of the study were to 1 reveal the fractionation patterns of major and trace elements 2 compare the major element chemistry of leucogranites and the quantitative behavior of source minerals during anatexis inferred by mass balance adjustment with available experimental data for peraluminous systems and 3 discuss the behavior of trace elements in crustal melting by comparing the chemically determined composition of leucogranites with the results of three fractionation models two of these assume a perfect diffusive behavior of trace elements within residual solids but they use a different set of distribution coefficients the third assumes a perfect nondiffusive behavior in relation to their source rocks the leucogranites are strongly depleted in li transition elements and light rare earth elements but enriched in k2o sio2 and ba the k rb ratio in leucogranites is higher than in sources and reaches values typical of high grade metamorphism mass balance analysis using the anatexis mixing model shows that the chemistry of cordierite leucogranites is compatible with its having originated by closed system water undersaturated anatexis on previously migmatized meta greywackes leaving a residue enriched in cordierite plus biotite and exhausted in k feldspar biotite melts congruently unless important amounts of sillimanite were also present in the source compared with experimental melts obtained from sources with the same chemical composition but with a different femic mineralogy biotite sillimanite instead of cordierite biotite the pena negra leucogranites are richer in k2o and mgo with a lower fe fe mg ratio the differences in magnesium are believed to result from the changes in the mineral assemblage of the source rocks however the differences in potassium contents are still not well understood the behavior of trace elements during anatexis cannot be modeled by trace element fractionation equations because of the sluggish diffusion kinetics of trace elements at the temperature of anatexis making the melting rate of minerals greater than the diffusion rate of trace elements within minerals the behavior of trace elements essentially consists in following that of the minerals containing them

hybridization of a shallow i type granitoid pluton and its host migmatite by magma chamber wall collapse the tokuwa pluton central japan the miocene tokuwa pluton of i type granitoid affinity was emplaced discordantly into a cretaceous to paleogene accretionary complex and induced a contact aureole in which various thermally metamorphosed rocks were developed including hornfels metatexite diatexite and cordierite bearing tonalite crd tonalite of s type granite affinity the thermally metamorphosed rocks show low pressure reaction textures culminating in partial melting peak p t conditions of 3 kbar at 7808c are estimated on the basis of the twq thermobarometer for the garnet bearing rocks the rocks in the contact aureole exhibit a gradual transition from hornfels through metatexite and diatexite to crd tonalite the sr isotopic composition at the time of tokuwa pluton emplacement at 12 ma decreases systematically from metatexite 0 7100 0 7112 through diatexite 0 7078 0 7094 to crd tonalite 0 7067 0 7068 this trend is interpreted in terms of mixing between the tokuwa magma and the aureole migmatites the field relationships geochemical data and isotopic data collectively suggest that the emplacement of the tokuwa pluton triggered partial melting of the surrounding metasedimentary rocks subsequent hybridization of the tokuwa magma with the metatexite in variable proportions produced the crd tonalite and diatexite the hybridization was caused by invasion of the tokuwa magma into the migmatite zone accompanied by gravitational collapse of the previously crystallized wall of the magma chamber the data presented demonstrate that even a relatively low temperature shallow i type granitoid pluton can induce contact anatexis and hybrid s type granitoid formation at the intrusive contact

cyclone gonu storm surge in oman super cyclone gonu is the strongest tropical cyclone on record in the arabian sea gonu caused coastal damage due to storm surge and storm wave impact as well as wadi flooding high water marks overland flow depths and inundation distances were measured in the coastal flood zones along the gulf of oman from 1 to 4 august 2007 the high water marks peaked at ras al hadd at the eastern tip of oman exceeding 5 m the storm surge of gonu is modeled using the advanced circulation model adcirc the multi hazard aspect is analyzed by comparing observations from cyclone gonu with the 2004 indian ocean tsunami

the tsunami phenomenon abstract with human activity increasingly concentrating on coasts tsunamis from japanese tsu harbour nami wave are a major natural hazard to today s society stimulated by disastrous tsunami impacts in recent years for instance in south east asia 2004 or in japan 2011 tsunami science has significantly flourished which has brought great advances in hazard assessment and mitigation plans based on tsunami research of the last decades this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view starting with the wave features tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss at the coast tsunamis typically show wave shoaling funnelling and resonance effects as well as a significant run up and backflow tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms such are earthquakes as the main trigger submarine and subaerial mass wastings volcanic activity atmospheric disturbances meteotsunamis and cosmic impacts as is demonstrated by giving corresponding examples from the past tsunamis are known to have a significant sedimentary and geomorphological off and onshore response so called tsunamites form allochthonous high energy deposits that are left at the coast during tsunami landfall tsunami deposits show typical sedimentary features as basal erosional unconformities fining upward and landward a high content of marine fossils rip up clasts from underlying units and mud caps all reflecting the hydrodynamic processes during inundation the on and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro and morphodynamic numerical models the paper provides an overview of the basic tsunami modelling techniques including discretisation guidelines for appropriate temporal and spatial resolution as well as the nesting method furthermore the boussinesq approximation a simplification of the three dimensional navier stokes equations is presented as a basic theory behind numerical tsunami models which adequately reflects the non linear dispersive wave behaviour of tsunamis the fully non linear boussinesq equations allow the simulation of tsunamis e g in the form of n waves based on the various subtopics presented recommendations for future multidisciplinary tsunami research are made it is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre history and physiogeographical setting of a specific region

formation of diatexite migmatite and granite magma during anatexis of semi pelitic metasedimentary rocks an example from st malo france petrological and geochemical variations are used to investigate the introduction formation of granite magma from diatexite migmatites derived from partial melting experiments show that protoliths of pelite metasedimentary rocks of pelitic to greywacke composition at st and greywacke composition yield up to 40 vol malo france anatexis occurred at relatively low temperatures granite melt over the temperature range 650 900 c and pressures 800 c 4 7 kbar principally through muscovite typical of anatexis of the continental crust conrad et dehydration melting biotite remained stable and serves as a tracer al 1988 vielzeuf holloway 1988 patino douce for the solid fraction during melt segregation the degree of partial johnston 1991 vielzeuf montel 1994 patino douce melting calculated from modal mineralogy and reaction stoichiometry harris 1998 therefore to make a granite magma was 40 vol there is a continuous variation in texture the melt fraction must be segregated from a solid fraction mineralogy and chemical composition in the diatexite migmatites of much greater volume and then collected together mesocratic diatexite formed when metasedimentary rocks melted the type of melt residuum separation process depends sufficiently to undergo bulk flow or magma flow but did not on the melt fraction present experience significant melt residuum separation mesocratic diatexite melt residuum separation at low degrees of partial that underwent melt segregation during flow generated 1 memelting f and consequently low melt fraction mf lanocratic diatexites at the places where the melt fraction was has been documented from metatexite migmatites in removed leaving behind a biotite and plagioclase residuum enriched these rocks melt segregation produced centimetre scale in tio2 feot mgo cao sc ni cr v zr hf th u and leucosomes distributed in a host composed of layers that ree and 2 a complementary leucocratic diatexite enriched in have melted and others that have not e g henkes sio2 k2o and rb where the melt fraction accumulated leucocratic johannes 1981 gupta johannes 1982 dougan 1983 diatexite still contained 5 15 vol residual biotite mg number sawyer 1987 tait harley 1988 barbey et al 1990 40 44 and 10 20 vol residual plagioclase an22 anatectic brown 1994 leucosomes represent small volumes of granite magma developed from the leucodiatexite first by further felsic magma formed when melt was squeezed out of the melt residuum separation then through fractional crystallization deforming matrix mclellan 1988 sawyer 1991 1994 most biotite in the anatectic granite is magmatic mg number brown 1994 brown et al 1995 and collected in low18 22 pressure sinks such as shear bands and inter boudin

tourmaline occurrences within the penamacor monsanto granitic pluton and host rocks central portugal genetic implications of crystal chemical and isotopic features tourmalinization associated with peraluminous granitic intrusions in metapelitic host rocks has been widely recorded in the iberian peninsula given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of sn w mineralizations in the penamacor monsanto granite pluton central eastern portugal central iberian zone tourmaline occurs 1 as accessory phase in two mica granitic rocks muscovite granites and aplites 2 in quartz mica tourmaline rocks tourmalinites in several exocontact locations and 3 as a rare detrital phase in contact zone hornfels and metapelitic host rocks electron microprobe and stable isotope 18o d 11b data provide clear distinctions between tourmaline populations from these different settings a schorl oxyschorl tourmalines from granitic rocks have variable foititic component x 17 57 and mg mg fe ratios 0 19 0 50 in two mica granitic rocks and 0 05 0 19 in the more differentiated muscovite granite and aplites granitic tourmalines have constant 18o values 12 1 0 1 with wider ranging d 78 2 4 7 and 11b 10 7 to 9 0 values b vein breccia oxyschorl mg mg fe 0 31 0 44 results from late b and fe enriched magma derived fluids and is characterized by 18o 12 4 d 29 5 and 11b 9 3 while replacement tourmalines have more dravitic compositions mg mg fe 0 26 0 64 close to that of detrital tourmaline in the surrounding metapelitic rocks and yield relatively constant 18o values 13 1 13 3 though wider ranging d 58 5 to 36 5 and 11b 10 2 to 8 8 values and c detrital tourmaline in contact rocks and regional host metasediments is mainly dravite mg mg fe 0 35 0 78 and oxydravite mg mg fe 0 51 0 58 respectively boron contents of the granitic rocks are low 650 ppm compared to the minimum b contents normally required for tourmaline saturation in granitic melts implying loss of b and other volatiles to the surrounding host rocks during the late magmatic stages this process was responsible for tourmalinization at the exocontact of the penamacor monsanto pluton either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin vein breccia tourmalinites or as replacement of mafic minerals chlorite or biotite in the host rocks replacement tourmalinites along the exocontact of the granite thermometry based on 18o equilibrium fractionation between tourmaline and fluid indicates that a late b enriched magmatic aqueous fluid av 18o 12 1 at 600 c precipitated the vein breccia tourmaline 18o 12 4 at 500 550 c and later interacted with the cooler surrounding host rocks to produce tourmaline at lower temperatures 400 450 c and an average 18o 13 2 closer to the values for the host rock although b metasomatism associated with some granitic plutons in the iberian peninsula seems to be relatively confined in space extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of variscan magmatism and related mineralizations

mineral leucosome trace element partitioning in a peraluminous migmatite a laser ablation icp ms study abstract low pressure peraluminous migmatites from the pena negra complex central spain stayed partially molten for 5 10 ma until the latest hercynian deformations allowed the segregation of melt as discordant leucosome veins due to long residence within its source the melt had time enough to equilibrate with residual phases other than accessories included within major refractory minerals we estimated crystal melt partition coefficients as the concentration ratios between leucosome samples appearing to be pure melts and mesosome minerals which were analyzed for trace elements with a laser probe coupled to an icp mass spectrometer our data reveal that when biotite is stable li rb cs tl sc v cr ni nb and ta become strongly compatible the role of biotite in fractionating y th u and the ree is insignificant cordierite strongly fractionates li and be and also has some effect on the hree and u garnet produces extreme fractionation of sc y and the hree the ree partition coefficients for ferromagnesian silicates increase with the atomic number this effect being progressively more important through biotite cordierite and garnet k feldspar strongly fractionates ba and pb but plays a secondary role to biotite for rb and cs k feldspar fractionation does not change the lree hree ratio but plagioclase fractionation produces a significant decrease in the lree hree ratio both feldspars greatly fractionate sr and eu monazite fractionation produces a dramatic depletion in ree th and u as well as a decrease in the lree hree and th u ratios apatite also fractionates the ree although in contrast with monazite it increases the lree hree ratio and does not affect the th u ratio zircon fractionation like apatite and garnet produces a strong depletion in the hree and a concomitant increase in the lree hree ratio in contrast with monazite zircon fractionation causes the th u ratio to increase

melting reactions and trace element relationships in selected specimens of migmatitic pelites from new hampshire and maine leucosomes and melanosomes in selected specimens of migmatitic sillimanite zone pelitic schists are modal and chemical complements formed by segregation within originally homogeneous paleosomes systematic bulk chemical and modal variations in melanosomes can be used to infer the reactions by which leucosomes were generated

extreme wave deposits on the pacific coast of mexico tsunamis or storms a multi proxy approach abstract historical and instrumental data show that the pacific coast of mexico has been exposed to destructive tsunamis over at least the past 500 years this coast is also affected by hurricanes generated in the eastern pacific the great 1985 mexico earthquake and its aftershock generated tsunamis that affected the ixtapa zihuatanejo and michoacan coast the purpose of our study was two fold a to determine whether storm and tsunami deposits could be distinguished and b whether tsunami deposits from historical events are preserved in the tropical environments of the ixtapa zihuatanejo coast two anomalous sand units in the ixtapa estuary are interpreted to be the result of high energy marine inundation events that occurred in the last century several lines of evidence using a multi proxy approach historical studies interviews with local witnesses geomorphological and geological surveys coring and trenching laboratory analyses including grain size micropaleontology geochemistry magnetic susceptibility and radiometric dating and numerical modeling indicate the occurrence of two tsunamis that we link to local events the 21st september 1985 mexico and possibly the 14th march 1979 petatlan earthquakes we thereby provide the first onshore geological evidence of historical tsunamis on the pacific coast of mexico

expanding the proxy toolkit to help identify past events lessons from the 2004 indian ocean tsunami and the 2009 south pacific tsunami article i nfo some of the proxies used to identify palaeotsunamis are reviewed in light of new findings following the 2004 indian ocean tsunami and the 2009 south pacific tsunami and a revised toolkit provided the new application of anisotropy of magnetic susceptibility ams to the study of tsunami deposits and its usefulness to determine the hydrodynamic conditions during the emplacement of tsunami sequences together with data from grain size analysis are presented the value of chemical proxies as indicators of saltwater inundation associated marine shell and or coral high energy depositional environment and possible contamination is demonstrated and issues of preservation addressed we also provide new findings from detailed studies of heavy minerals new information gathered during the unesco international oceanographic commission ioc international tsunami survey of fine onshore sediments following the 2009 south pacific tsunami is presented and includes grain size chemical diatom and foraminifera data the tsunami deposit varied ranging from fining upward sand layers to thin sand layers overlain by a thick layer of organic debris and or a mud cap grain size characteristics chemical data and microfossil assemblages provide evidence for marine inundation from near shore and changes in flow dynamics during the tsunami

manaslu leucogranite a collision signature of the himalaya a model for its genesis and emplacement the manaslu pluton is one of 10 leucogranites that formed in the overthrusted higher himalaya after the indo eurasian collision field and analytical data indicate that the underlying migmatites of the tibetan slab may be where the leucogranitic melts were generated the himalayan crustal thrusting of a hot slab over a rather cold volcano sedimentary pile le fort 1975a provides the necessary release of fluids these fluids cross the main central thrust mct induce the partial anatexis of the overheated tibetan slab and produce a leucogranitic magma the emplacement of the magma at first is located along the main disharmonic plane above the mct between the infrastructure and the superstructure there it generates a convective hydrothermal system extending very far laterally according to the stratification of permeabilities progressive emplacement of the granite proceeds as the convected fluids including the fluids released by the saturated magma dissolve the mainly calcareous host rocks of tibetan sedimentaries a frozen image of this caving out progression is given by the extensive network of granitic dikes outside the pluton the two quite independant fluid cycles of the generation and of the emplacement were triggered or guided by the tectonics due to collision this two fold model dominated by fluid activity may be of importance for other leucogranites and granites

large scale melt depletion in granulite terranes an example from the archean ashuanipi subprovince of quebec this study uses field petrographic and geochemical methods to estimate how much granitic melt was formed and extracted from a granulite facies terrane and to determine what the grain and outcrop scale melt flow paths were during the melt segregation process the ashuanipi subprovince located in the north eastern superior province of quebec is a large 90 000 km2 metasedimentary terrane in which 85 of the metasediments are of metagreywacke composition that was metamorphosed at mid crustal conditions 820 900 c and 6 7 kbar in a late archean dextral transpressive orogen decrease in modal biotite and quartz as orthopyroxene and plagioclase contents increase together with preserved former melt textures indicate that anatexis was by the biotite dehydration reaction biotite quartz plagioclase melt orthopyroxene oxides using melt orthopyroxene ratios for this reaction derived from experimental studies the modal orthopyroxene contents indicate that the metagreywacke rocks underwent an average of 31 vol partial melting the metagreywackes are enriched in mgo cao and feot and depleted in sio2 k2o rb cs and u have lower rb sr higher rb cs and th u ratios and positive eu anomalies compared to their likely protolith these compositions are modelled by the extraction of between 20 and 40 wt granitic melt from typical archean low grade metagreywackes a simple mass balance indicates that about 640 000 km3 of granitic melt was extracted from the depleted granulites the distribution of relict melt at thin section and outcrop scales indicates that in layers without leucosomes melt extraction occurred by a pervasive grain boundary porous flow from the site of melting across the layers and into bedding planes between adjacent layers in other rocks pervasive grain boundary flow of melt occurred along the layers for a few to tens of centimetres followed by channelled flow of melt in a network of short interconnected and structurally controlled conduits visible as the net like array of leucosomes in some outcrops the leucosomes contain very little residual material 5 biotite orthopyroxene indicating that the melt fraction was well separated from the residuum left in situ as melt depleted granulite only 1 3 vol percentage melt remained in the melt depleted granulites hence the extraction of melt generated by biotite dehydration melting in these granulites was virtually complete under conditions of natural melting and strain rates in a contractional orogen

the limited growth of vegetated shear layers 1 in contrast to free shear layers which grow continuously downstream shear layers generated by submerged vegetation grow only to a finite thickness because these shear layers are characterized by coherent vortex structures and rapid vertical mixing their thickness controls exchange between the vegetation and the overlying water experiments conducted in a laboratory flume show that the growth of these obstructed shear layers is arrested once the production of shear layer scale turbulent kinetic energy ske is balanced by dissipation of ske within the canopy this equilibrium condition along with a mixing length closure scheme was used in a one dimensional numerical model to predict the mean velocity profiles of the experimental shear layers the agreement between model and experiment is very good but field application of the model is limited by a lack of description of the drag coefficient in a submerged canopy

the extent of equilibration between melt and residuum during regional anatexis and its implications for differentiation of the continental crust a study of partially melted metapelitic enclaves thisstudy presentsthefirst precise evaluation of the extent ofchem ical equilibrium between felsic melt and crystalline residuumduring the crustal anatexis of metasediments the high precision ofthese resultsstemsfrom thefactthat in thiscase the meltsare repre sented by pristine glasses that occur in the matrices of partiallymelted metapelitic enclaves and as abundant glassy melt inclusionstrapped by different minerals in the same enclaves in previous stu dies of anatexis the composition of the melt has been approximatedby that of leucosomes in migmatites which do not necessarily repre sent the composition of the melt very well the present study isbased on laser ablation analyses of 35 trace elements in the glassand principal minerals of enclaves included within neogene peralu minous dacites exposed at el hoyazo se spain the enclaves which contain the assemblage plagioclase biotite sillimanite garnet glass ilmenite graphite k feldspar cordieritequartz represent fragments of metapelitic continental crust thatwaspartiallymeltedatpressuresof5 7kbarduringaregionalmeta morphic event matrix melt and melt inclusions within the enclaveswere quenched to glass upon eruption of the dacite the glasses inthe melt inclusions are interpreted as the remains of melt producedby an initial melting reaction involving a muscovite rich assemblageat 700 7508c whereasthe matrixglassesare consistent with con tinuedmeltingand oralatermeltdominatedbytheincipientmeltingof biotite at 800 8508c the distribution of trace elements be tween residuum and melt duringanatexis of the enclaves isdifferentfrom that predicted by disequilibrium models that consider effectivedistribution coefficients close to unity instead the bulk melt andthe major minerals plagioclase biotite alkali feldspar cordierite were close to equilibrium except for the case of garnet duringthe generation of the melt inclusions and matrix glasses thequenchedmelts meltinclusionsandparticularlythematrixglasses were not in equilibrium with accessory zircon and monazite andare depleted in zirconium and the light rare earth elements recrystallization of mineralsand diffusion in the melt were import ant controls during the redistribution of trace elements betweenthe solids and the bulk melt local disequilibrium processes alsotook place at mineral melt interfaces during the crystallizationof peritectic minerals and the recrystallization of residual phases as shown by the depletion of compatible elements in the meltinclusions

depositional events and their records an introduction abstract event deposits of some lateral extent as defined here occur almost in all types of sedimentary basins the reflect either local intra basinal processes or they are associated with regional or global mechanisms some types of event beds such as sediment gravity flows sandy and muddy turbidites are common and usually well preserved they make up large proportions of basin fills whereas others e g tsunami deposits and in situ earthquake structures appear to be less frequent or rare in the geological record volume frequency and facies of event deposits are controlled by several processes pre event sediment accumulation triggering and transport mechanisms and mode of final deposition

geochronology and petrology of migmatites from the proterozoic damara belt importance of episodic fluid present disequilibrium melting and consequences for granite petrology abstract the oetmoed granite migmatite complex ogmc central damara orogen namibia consists of grt and crd bearing s type granites and hbl and titanite bearing a type granites that intruded into crd sil kfs bearing metasedimentary rocks stromatic migmatites and nebulites stromatic migmatites formed by limited in situ partial melting of metapelites under h2o saturated conditions at 700 c and 4 5 kbar this partial melting event took place close to the peak of regional metamorphism at 510 ma as revealed by sm nd garnet whole rock ages as well as u pb monazite ages the newly formed melt remained more or less at the site of origin melanosomes of the stromatic migmatites do not resemble true residues instead they represent reaction zones between in situ melt and the metasedimentary host rock leucosomes from the stromatic migmatites are lree and hfse depleted which is typical for the low melt fractions generally observed in migmatite terranes mass balance calculations suggest that these leucosomes may be disequilibrium melts similar 18 o whole rock values between 13 and 14 observed in leucosomes and corresponding melanosomes suggest homogenization of oxygen isotopes between the different rock types via the melt and an internal fluid phase during melting other leucosomes with a major element chemistry similar to the leucosomes from the stromatic migmatites but higher ree contents suggest significant incorporation of lree enriched phases monazite from the country rocks for these leucosomes sm nd garnet whole rock ages are 473 ma indicating a second phase of melting nebulites mainly result from injection of granitic melts into the country rocks but their residual chemistry indicates that partial melting and limited melt removal must have occurred monazites from these nebulites record concordant u pb ages between 540 ma and 470 ma indicating episodic migmatization during high grade regional metamorphism intrusive peraluminous granites are likely generated by partial melting of pelitic sources in the lower crust and different source rocks are probably not the controlling factor for the different chemistry of leucosomes and granites therefore different melting conditions fluid absent vs fluid present and different modes of entrainment and solubilities of accessory phases control the elemental budgets of the leucosomes large scale migmatite granite complexes are a substantial part of some high grade terrains but the distinctive geochemical composition of some leucosomes make these rocks unlikely precursors of large scale granitic bodies

55 million years of continuous anatexis in central iberia single zircon dating of the pena negra complex single zircon evaporation and ion microprobe dating of migmatites and anatectic granites in the pena negra complex of central iberia reveal that the variscan anatexis occurred continuously from 352 to 297 ma with a maximum at 335 305 ma anatexis began coeval with the main collision of continental masses a limited melting event probably related to syncollision crustal scale shear zones produced a population of zircons with ages of c 350 ma the production of new zircons decreased to a minimum at c 343 ma but then increased swiftly as the internal thermal evolution of the thickened central iberian crust led to widespread anatexis in the pena negra region at 332 ma shortly after this the melt resident in the migmatites was locally segregated into small bodies that crystallized as cordierite leucogranites at 321 ma simultaneously extensional subhorizontal shear zones were preferentially developed over layers of the migmatite series that owing to their elevated heat production and fertility had the highest melt fraction shearing provoked further anatexis and contributed significantly to the in situ production of high melt fraction granodiorites and adamellites from the migmatites this process occurred from 325 to 305 ma with a maximum at 309 ma marking the peak of the variscan extensional collapse in central iberia after c 305 ma the melt fraction decreased quickly so that the production of new zircons was insignificant at 300 ma and had stopped completely by 297 ma

a geochemical and experimental study of the role of k feldspar during water undersaturated melting of metapelites abstract the production of s type granites has been related to the extraction of melts during water undersaturated melting of metasediments in the lower continental crust if this mechanism is of widespread applicability a chemically distinctive granulitic restite must be left behind with a positive eu anomaly and depleted incompatible element concentrations however little geochemical evidence has been found in support of this hypothesis the rare earth element geochemistry of lower crustal granulites and associated melts will depend on the behaviour of the phases in which ree and trace elements are concentrated i e zircon monazite and k rich feldspar new experimental data on synthetic metapelites show that k feldspar can be a product or a reactant during water undersaturated melting of biotite depending on the h2o k2o of the melt relative to biotite past confusion over the role of k feldspar during melting is due to the reaction being close to degeneracy and changing its stoichiometry in response to only small changes in bulk composition coherent interpretation of the role of k feldspar in different experimental studies requires a better knowledge of phase water contents than has commonly been available the leucosomes formed in some antarctic granulite facies migmatites are likely to have had low h2o k2o ratios which suggests that k feldspar would have been a reactant during melting this could cause the positive eu anomalies observed in the leucosomes through the disequilibrium melting of k feldspar during water undersaturated melting the undersaturation of trace elements and ree in the leucosomes strongly suggests that disequilibrium melting took place caused by the incomplete dissolution of accessory phases monazite and zircon these phenomena give the melts a distinctive geochemical character which has also been seen in the other granulite facies leucosomes analysed to date this geochemical character contrasts with that of s type granites and therefore the production of granulites in the lower crust may not necessarily be associated with this type of magmatism if lower crustal granulite facies migmatites are the source region for peraluminous s type granites then the melts generated must undergo considerable modification during ascent

distinguishing tsunami and storm deposits an example from martinhal sw portugal abstract geological identification of past tsunamis is important for risk assessment studies especially in areas where the historical record is limited or absent the main problem when using the geological evidence is to distinguish between tsunami and storm deposits both are high energy events that may leave marine traces in coastal stratigraphic sequences at martinhal sw portugal both storm surge and tsunami deposits are present at the same site within a single stratigraphic sequence which makes it suitable to study the differences between them excluding variations caused by local factors the tsunami associated with the lisbon earthquake of november 1st 1755 ad had a major impact on the geomorphology and sedimentology of martinhal it breached the barrier and laid down an extensive sheet of sand as described in eyewitness reports besides the tsunami deposit the stratigraphy of martinhal also displays evidence for storm surges that have breached and overtopped the barrier flooding the lowland and leaving sand layers both marine derived flood deposits show similar grain size characteristics and distinctive marine foraminifera the most important differences are the rip up clasts and boulders exclusively found in the tsunami deposit and the landward extent of the tsunami deposit that everywhere exceeds that of the storm deposits identification of both depositional units was only possible using a collection of different data and extensive stratigraphical information from cores as well as trenches

kinetics of crystallization of igneous rocks the geochemistry of igneous rocks is discussed with the primary objectives of bringing together the theories underlying the kinetics of crystallization of igneous rocks and illustrating the use of these theories in understanding experimental and observational data the primary purpose of the chapter is to introduce current thinking about the kinetics of igneous rocks and to provide a basis for understanding other work a basic assumption made in the discussion is that the rate of any chemical reaction including the crystallization of igneous rocks is zero at equilibrium and proceeds at a finite rate only at a finite deviation from equilibrium as such an understanding of the processes operating in igneous rocks requires an understanding of how deviation from equilibrium affects the rates and mechanisms of the processes occurring during crystallization these processes are detailed with special emphasis given to nucleation and crystal growth jmt

origin and evolution of a migmatite the development of a stromatic migmatite exposed east and southeast of arvika western sweden is described in four stages beginning with the country rock and following evolution through three areas characterized by low medium and high amounts of leucosomes areas l m and h respectively

water saturated and undersaturated melting of metaluminous and peraluminous crustal compositions at 10 kb evidence for the origin of silicic magmas in the taupo volcanic zone new zealand and other occurrences

formation and evolution of granite magmas during crustal reworking the significance of diatexites taylor mclennan 1985 the physical processes ina continuous section through reworked archaean crust records the volved particularly how granite magma is formed remain generation of granitic magma and its subsequent development in the controversial miller et al 1988 white chappell opatica subprovince in the canadian shield there the transition 1990 a partially melted source can form a granitic from palaeosome to granite was a closed system process through magma only if large volumes of melt are separated from intermediate stages of patch migmatite and diatexite the average most of their residuum understanding this process is degree of partial melting was less than 30 but the melt crucial to determining how crustal recycling and differfraction was redistributed within individual diatexite layers during entiation occurs for example melt residuum separation deformation regions that lost melt became residual diatexites could be a nearly perfect single stage process at the enriched in tio2 feot mgo cao sc cr co sr rare earth site of partial melting as described for leucosomes in elements ree and high field strength elements hsfe melt metatexite migmatites wickham 1987a sawyer 1991 accumulated to create diatexite magmas enriched in large ion 1994 brown et al 1995 alternatively the separation lithophile elements lile but contaminated with residuum macould be an imperfect multi stage process that yields a terial such diatexite magmas are parental to granites found at magma with a large residual component as is observed higher crustal levels in the terrane flow of the diatexite magma in in diatexite migmatites bea 1991 greenfield et al response to deformation separated some of its residuum into schlieren 1996 sawyer 1996 the metatexite model necessarily parautochthonous plutons were created where ascending granitic produces leucocratic residuum free granites such as magma locally ponded below impermeable layers and structures those described by le fort 1981 and montel et al magma left the anatectic region in dykes and lost its remaining residuum as it crystallized consequently the allochthonous granite 1991 and maximizes the geochemical signature of magmas that rose through 20 km of crust to feed the highest level crustal differentiation in contrast the diatexite model plutons in this region are highly fractionated and essentially free of can produce residuum rich granites and so reduce the residuum geochemical effect of crustal differentiation as chappell 1996 noted how anatectic magmas formed in the deeper crust evolve to the granitic magmas emplaced in the upper crust is also poorly known because few crustal sections

constraints on melting and magma production in the crust major intrusions of granitic rocks are found in several tectonic settings and in all cases crustal melts may contribute to the volumes of granitic magma high grade metamorphism and partial melting of the crust take place predominantly under fluid absent conditions we present a model for calculating the amounts of melt that may be formed by fluid absent breakdown of micas and amphiboles in common crustal rock types pelitic quartzofeldspathic intermediate and mafic melt proportions depend mainly on the kind of source rock the pressure at which melting takes place the temperature and the hydrous mineral h2o content of the source as a consequence of the pressure dependence of water solubility in silicate melts any given source rock will produce more melt by a given fluid absent reaction at lower pressure at a given pressure higher temperature reactions can produce more melt from a given source rock based on a survey of the compositions of common rock types we show that the amounts of melt can vary from 50vol thus crustal rocks vary widely in their fertility as magma sources depending on the types and amounts of hydrous phases they contain in general muscovite breakdown in pelites will yield only small quantities of melt and lead to migmatite formation biotite breakdown in pelites occurs at higher temperature and because most high grade pelites below granulite grade are biotite rich can yield up to about 50 vol of granitoid melt rocks of intermediate composition and hornblende rich mafic rocks are potentially highly fertile magma sources also provided that the high temperatures necessary for biotite and hornblende breakdown are realized pyroxene rich mafic rocks and quartzofeldspathic rocks are much less potentially fertile data suggest that mechanisms exist for the efficient segregation of melt and restite in systems with 30and probably 20vol melt the pressure temperature history of a region can greatly influence crustal source fertility through its control over the occurrence of subsolidus dehydration and melting equilibria

a routine high precision method for lu hf isotope geochemistry and chronology a method for chemical separation of lu and hf from rock meteorite and mineral samples is described together with a much improved mass spectrometric running technique for hf this allows i geo and cosmochronology using the176lu 176hf decay scheme and ii geochemical studies of planetary processes in the earth and moon chemical yields for the three stage ion exchange column procedure average 90 for hf chemical blanks are 0 2 ng for lu and hf from 1 g of hf a total ion current of 0 5 10 11 ampere can be maintained for 3 5 h yielding 0 01 0 03 precision on the ratio176hf 177hf normalisation to179hf 177hf 0 7325 is used extensive results for the johnson matthey hf standard jmc 475 are presented and this sample is urged as an international mass spectrometric standard suitable aliquots prepared from a single batch of jmc 475 are available from denver lu hf analyses of the standard rocks bcr 1 and jb 1 are given the potential of the lu hf method in isotope geochemistry is assessed

an interpretation of trends in grain size measures abstract the mean grain size sorting and skewness of a sedimentary deposit are dependent on the sediment grain size distribution of its source and the sedimentary processes of i winnowing erosion ii selective deposition of the grain size distribution in transport and iii total deposition of the sediment in transport if a source sediment undergoes erosion and the resultant sediment in transport is deposited completely the deposit must be finer better sorted and more negatively skewed than the source this trend is referred to as case i the lag remaining after erosion on the other hand must be coarser better sorted and more positively skewed case ii if sediment in transport undergoes selective deposition the resultant deposit can either be finer case iiia or coarser cas iiib than the source but the sorting will be better and the skew more positive although exceptions to these trends may occur they suggest that comparison of one sediment must be made with another for the proper identification of the sedimentary process and therefore it is not possible for a single grain size distribution to identify the depositional environment the trends also suggest that the skewness of a grain size distribution has been widely misinterpreted and implies neither the truncation of one of the tails nor the mixing of more than one mode rather a skewed sediment is the natural result of the sedimentary process in a system of related environments these trends can be used to identify both the probable source and the probable deposit and by inference the net sediment transport paths among sedimentary deposits such an analysis provides a rapid understanding of the sedimentary processes identifies patterns of erosion and accretion and may suggest transport processes

behaviour of trace elements during magmatic processes in the crust application to acidic volcanic rocks of tuscany italy abstract plio quaternary acidic rock suites from three volcanic centres of tuscany italy san vincenzo roccastrada and monte amiata are composed predominantly of rhyolitic and rhyodacitic ignimbrites the rocks are characterized by distinct enrichments particularly of k and rb and display considerable compositional differences among the various volcanic centres the volcanic rocks of roccastrada and most of s vincenzo were probably generated by partial melting of metapelitic rocks from the paleozoic basement of tuscany leaving a residue composed of biotite cordierite and quartz and sometimes plagioclase or garnet the enrichment of k and related elements can be attributed to selective contamination by fluids the other volcanic rocks including trachytes of mt amiata have also been affected by interaction with an upper mantle component probably k rich basaltic rocks a similar petrogenetic model can be applied to the granodiorite pluton of mt capanne elba which belongs to the same magmatic cycle since the variation trends observed in the tuscany volcanic rocks are similar to those reported from many acidic plutons it appears that crustal anatexis accompanied by interaction with upper mantle components has frequently played an important role in the genesis of the granitic rocks

importance of melt fraction and source rock composition in crustal genesis the example of two granitic suites of northern portugal in the montalegre area northern portugal two varieties of syn to late tectonic hercynian aluminous granitoids are distinguished 1 1 muscovite rich two mica granites forming many successively emplaced bodies with little chemical variation the chemical characteristics of these units suggest partial melting of various crustal rocks under distinct p t and water saturation conditions there has been no homogenization between the different melt batches the rocks contain very few restitic minerals segregation processes may have operated either in the source rock or in an early magmatic stage 2 2 a cordierite biotite and muscovite bearing granitic body its mineralogical composition is extremely heterogeneous and it contains many xenoliths the genesis of this granite results essentially from partial melting of peraluminous orthogneisses the melt fraction was higher than the rheological critical melt percentage rcmp during anatexis the rigid framework of the source rock broke down leading to migration of both melt and residual minerals towards upper crustal levels the heterogeneity of the resulting granite is mostly related to an incomplete separation of residual crystals and melt the existence of biotite and cordierite rich samples is the result of accumulation of residual minerals during the magma emplacement this study emphasizes the role of the source rock composition which controls the degree of partial melting at given p t and water saturation conditions during crustal melting the strong geochemical differences between the two kinds of granitoids are related to the near absence of residual minerals in the muscovite rich granites and to the presence of residual minerals in the cordierite bearing granite it is suggested that the muscovite rich granites are mostly low melt fraction rcmp the presence of many residual crystals alkali feldspars and plagioclases as well as dark minerals in the cordierite granite implies a high viscosity of the melts and therefore water undersaturated melting conditions

petrological and geochemical variations of a turbidite like metasedimentary sequence over the metatexite to diatexite transition within the pampean orogen argentina large masses of turbidite systems have been metamorphosed in orogenic systems during earth s history under granulite facies conditions the transformation of turbidite sedimentary successions into metasedimentary sequences drives intracrustal differentiation by anatexis and melt residuum separation we report on a migmatite terrane developing from turbidite successions that were buried into the deep crust during the neoproterozoic to early cambrian pampean orogeny in central argentina at the exposed middle crustal paleodepths migmatites occur on the regional scale but lithological zones are characterized by 1 bedded migmatites 2 metatexite and 3 diatexite bedded migmatites are the low temperature part of the migmatite terrane where the alternating metapelite and metagreywacke layers are traceable among migmatites of different protoliths the temperature 790 c was sufficient high for melting the metapelite but not for melting the metagreywacke the majority of the migmatite terrane consists of stromatic metatexites in which the limit among different progenitors is either faint or erased by migmatization metatexite zone acts as melt transfer in the migmatite terrane in the stromatic migmatites the major oxide composition of leucosomes and tabular bodies of leucogranite resembles those of the glasses of experimental petrology however leucosomes and leucogranites are crystallized melts that have low zr th and lree contents and positive eu anomalies resulting from accessory mineral retention in melting residues the transformation of metatexite into diatexite is gradational over tens of metres and related to an accumulated melt fraction that dismembers the stromatic fabric the most abundant diatexite is mesocratic and has little or lacks k feldspar a subordinate proportion of diatexites is leucocratic contains k feldspar phenocrysts and shows igneous like textures leucogranites and leucocratic diatexites are the potential carriers of an anatectic melt rich component from granulite facies migmatite sequences toward shallow crustal levels turbidite successions are fertile protoliths that undergo widespread melting under low granulite facies temperature 850 c and the development of large diatexite massifs makes them suitable sources of granitic magmatism

distribution of partial melt in a felsic system the importance of surface energy the texture distribution and infiltration tendency of a quartz albite melt in equilibrium with a synthetic texturally equilibrated quartzite was examined in a series of distribution and infiltration experiments at 1 250 c and 8 kbar hydrostatic pressure wetting angle measurements from melt distribution experiments show a dihedral angle of 60 degrees implying a quartz quartz interfacial energy approximately 1 7 times the quartz melt value because of this specific relationship between interfacial energies the system can achieve its lowest surface free energy state with the melt either in pools or along grain edge intersections possibly forming some interconnected channels stability of melt in pockets and along grain edge intersections was observed in a fourteen day dispersed melt experiment yet melt pools failed to disperse into the quartzite during infiltration experiments comparison of the observed dihedral angle with previously measured surface energy values for the melt and quartz shows excellent agreement and also demonstrates that an aggregate of randomly orientated anisotropic grains acts approximately isotropically

influence of macrobenthos meretrix meretrix linnaeus on erosion accretion processes in intertidal flats a case study from a cultivation zone fil shi benwei tongji university republica de china east china normal university republica de china

behaviour of boron in the generation of an anatectic complex the pen a negra complex central spain abstract the pe na negra anatectic complex central spain was formed from a pelitic protolith low in boron 3 80 ppm by dehydration reactions melting and fluid loss which expelled much of the boron residual b is present in sillimanite and muscovite migmatite melanosomes and restites sillimanite biotite ilmenite are relatively richer in b mean 29 ppm while the leucosomes are poorer 13 ppm late shears fractures and zones of retrograde alteration have permitted some reintroduction of b experiments demonstrated that b cannot be removed from these rocks by heating or by leaching indicating that very little is present in superficial adsorption and that the element occurs in mineral structures

palynology a tool to identify abrupt events an example from chabahar bay southern iran tsunami storm and flood events are destructive agents that have the potential to cause much damage and cost lives the coastal regions around the north western arabian sea are prone to these natural disasters with recent events including the storm and flood of ad 1842 the makran tsunami of 1945 and cyclone gonu in 2007 despite their severity the paucity of reliable historical records does not allow us to answer pertinent questions concerning their frequency intensity and impact palaeo event analysis from the geological record allows us to extend and test the historical record here we have dated and examined a 92 cm long sediment core from the tectonically active cyclone and storm prone chabahar bay area southern iran our appraisal directly tests conventional proxies for identifying abrupt events e g grain size geochemical data which we supplement with a novel palynological pollen and dinocyst approach both sedimentological and palynological approaches suggest a large event which was dated at ad 1808 41 whereas geochemical approaches remain inconclusive the increase of continentally derived pollen pinaceae salix betula and typha sparganium increases in brigantedinium sp and s ramosus as well as decreases in lingulodinium machaerophorum suggest enhanced fluvial delivery in association with a flood this investigation provides evidence of a major flash flood affecting the chabahar bay region at ad 1808 41 which we infer is the geological expression of the storm and associated flash flood of ad 1842 moreover our study demonstrates the utility of palynology in identifying and understanding the causes of abrupt events to complement more widely applied techniques

tsunami and palaeotsunami depositional signatures and their potential value in understanding the late holocene tsunami record in recent years much research on modern and palaeotsunami deposits has been published from these studies a range of signature types has been identified identifying and dating such deposits is an important element in understanding late holocene tsunami hazard and risk however important questions such as do modern and palaeotsunami leave similar or dissimilar traces do tsunami leave the same signatures all around the world or are there significant variations and what is the actual record of tsunami in different parts of the world still remain answering these questions is not an easy task but examining megatsunami flood deposits should shed some light on these questions because such high magnitude events should leave very clear and detailed traces within the coastal landscape the coast of se australia is reported to have been affected by numerous palaeomegatsunami in the late holocene as such the coast of new south wales offers an important natural laboratory to examine in detail deposits associated with such events here we summarize the published characteristics of modern and palaeotsunami deposits globally and within australia we briefly outline the tsunami risk to australia before examining a site called minnamurra point on the coastline of se australia south of sydney that has previously been described as containing evidence for a palaeomegatsunami of an unknown age we describe the results of a detailed coastal survey field stratigraphic investigation and various standard laboratory analyses surprisingly we are unable to replicate the previously reported findings of tsunami deposits whilst we prefer the interpretation that the sequence is an in situ soil the sediment sequence examined contains none of the usually reported lines of evidence to demonstrate tsunami provenance we recognize and discuss the significance and difficulty of identifying tsunami deposits in the field and consider the implications of our findings to the wider debate about the preservation of tsunami deposited sediments

velocity distribution in the roughness layer of rough bed flows several models for the vertical distribution of the double averaged in time and in the plane parallel to the mean bed longitudinal velocity in the flow region between roughness troughs and roughness tops are suggested we found that the same model for velocity distribution may be applicable to a range of flow conditions and roughness types which share some common features the suggested models for velocity distribution in the near bed region are 1 constant velocity 2 exponential velocity distribution and 3 linear velocity distribution the measured velocity distributions may be approximated by a single model or by a combination of models depending on roughness geometry and flow conditions the validity of these models for velocity distribution is supported by laboratory data

a method for modelling mass balance in partial melting and anatectic leucosome segregation a method is proposed for adjusting the mass balance to characterize quantitatively the behaviour of minerals in anatexis the method is based on an unconstrained simple mixing model that can be expressed as where b a0 and a1 n are compositional vectors of segregate source rock and source minerals respectively the most important concepts are 1 degree of partial fusion fmm 1 a0 2 mineral fractionation index and 3 plagioclase differentiation index for a given mineral the mfi values have the following meaning a mfi mfi mfi 1 preferential incorporation into the segregate and e mfi a0 external contribution to the anatectic system defined by a0a0 to test the method and illustrate its use it was applied to two real problems of partial melting in the pena negra anatectic complex central spain the first is a very simple case of segregation of a diktyonitic neosome from an orthogneiss through partial melting located in vertical shear zones this process is characterized by 1 fmm 0 51 2 active incorporation of k feldspar plagioclase and biotite into the segregate 3 disequilibrium melting of plagioclase 4 residual behaviour of quartz and ilmenite the second case concerns the formation of a cordierite bearing granite from granodioritoid diatexites through an anatectic process whose most salient characteristics are 1 fmm 0 45 2 incongruent melting of biotite 3 residual behaviour of plagioclase which melted with a pdi of 1 22 4 preferential incorporation of quartz into the segregate 5 total extraction of k feldspar from the residue

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

late holocene vegetation and ocean variability in the gulf of oman fossil pollen and dinocyst records in marine sequences are frequently combined to reveal the response of vegetation and ocean conditions to changes in both regional and global climate in this study we analysed pollen and dinocysts within a clearly laminated sediment core off the iranian coast in the gulf of oman an extremely data poor area to reconstruct climatic change during the late holocene last 1900 years the vegetation record from southern iran indicates a replacement of savannah by desert formations at c 910 ce shortly after the islamic invasion and the subsequent collapse of the sassanid empire from c 910 to 1145 ce during the medieval climate anomaly mca the vegetation was heavily dominated by desert formations such as amaranthaceae caryophyllaceae asteraceae centaurea and calligonum in parallel in the gulf of oman the presence of impagidinium paradoxum indicates a lack of freshwater discharge into the ocean around this time the desert taxa of the mca were subsequently replaced by savannah formations at c 1145 ce comprised mainly of poaceae and cyperaceae corresponding to the little ice age lia indicating generally wetter climatic conditions a sudden increase in spiniferites ramosus 1 63 at c 1440 ce suggests an increase in the strength of the sw summer monsoon with increased freshwater discharge into the ocean at this time our data indicate that over the past two millennia the nw arabian sea region has alternated between contrasting climatic conditions with firstly a humid phase equivalent to the cultural period of the sassanid empire a significantly drier climate during the mca and a relatively wetter climate during the lia the mechanisms resulting in dry conditions during the mca in the middle east associated with the northward shift of the itcz and the intensification of the indian summer monsoon may be similar to those causing the dry conditions which dominated the early holocene in the near east our palaeoenvironmental proxy data support current observations that a globally anthropogenically induced warmer climate is likely to lead to increased drought severity in the middle east putting additional stress on governments already struggling with poverty and social tensions

primary crustal melt compositions insights into the controls mechanisms and timing of generation from kinetics experiments and melt inclusions abstract we explore the controls mechanisms and timing of generation of primary melts and their compositions and show that the novel studies of melt inclusions in migmatites can provide important insights into the processes of crustal anatexis of a particular rock partial melting in the source region of granites is dependent on five main processes i supply of heat ii mineral melt interface reactions associated with the detachment and supply of mineral components to the melt iii diffusion in the melt iv diffusion in minerals and v recrystallization of minerals as the kinetics of these several processes vary over several orders of magnitude it is essential to evaluate in nature which of these processes control the rate of melting the composition of melts and the extent to which residue melt chemical equilibrium is attained under different circumstances to shed light on these issues we combine data from experimental and melt inclusion studies first data from an extensive experimental program on the kinetics of melting of crustal protoliths and diffusion in granite melt are used to set up the necessary framework that describes how primary melt compositions are established during crustal anatexis then we use this reference frame and compare compositional trends from experiments with the composition of melt inclusions analyzed in particular migmatites we show that for the case of el hoyazo anatectic enclaves in lavas the composition of glassy melt inclusions provides important information on the nature and mechanisms of anatexis during the prograde suprasolidus history of these rocks including melting temperatures and reactions and extent of melt interconnection melt homogenization and melt residue equilibrium compositional trends in several of the rehomogenized melt inclusions in garnet from migmatites granulites in anatectic terranes are consistent with diffusion in melt controlled melting though trace element compositions of melt inclusions and coexisting minerals are necessary to provide further clues on the nature of anatexis in these particular rocks

genesis of alkaline and peralkaline syenite granite series the kharitonovo pluton transbaikalia russia the kharitonovo pluton is located in the central part of the large mongolian transbaikalian province of late paleozoic alkaline syenites and granites the province stretches for a distance of almost 2000 km and contains over 350 plutons the kharitonovo pluton occupies an area of 230 km 2 it is made up of a type granitoids forming two successive alkaline and peralkaline syenite granite series syenites largely predominate over granites rocks of both series are characterized by abundant mesoperthitic feldspar about 90 vol in syenites more than 60 in granites while plagioclase is almost absent in the peralkaline series mafic minerals are riebeckite arfvedsonite kataphorite and aegirine with secondary annitic biotite in the alkaline series edenite and iron rich biotite are the major mafic minerals in the alkaline series coeval mafic rocks commonly occur in the form of synplutonic composite dikes they indicate at least two stages of mafic magma injection into the silicic magma chamber major

partition coefficients for rare earth elements in mafic minerals of high silica rhyolites the importance of accessory mineral inclusions abstract ree concentrations of mafic mineral separates from high silica rhyolites measured by inaa are high and variable compared to electron microprobe analyses of the minerals themselves the mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element ree rich minerals optical and electron microscopic observation revealed discrete grains of chevkinite rare earth titano silicate included within clinopyroxenes from the sierra la primavera mexico rhyolite and monazite grains adhering to ortho and clinopyroxenes from the bishop tuff california during hand picking of mineral separates inclusions are only partly removed as a result the magnitude and variability of true mineral melt partition coefficients for light ree have been overestimated the true ree partition coefficients of la primavera and bishop tuff pyroxenes obtained by microprobe are only slightly higher than they are in lower silica rhyolites and are not as variable as previously thought the partitioning slope is positive as in less silicic systems the relative partitioning behavior of ree in high silica rhyolites is dominated by crystal chemical controls and not by liquid structural effects when a partition coefficient is used for crystallization calculations adhering phases and inclusions should be retained or the minor phases must be accounted for separately alternatively a bulk distribution coefficient can be calculated using whole rock and glass compositions and the glass mode

a tsunami ca 6300 years bp and other holocene environmental changes northern hawke s bay new zealand abstract sediment cores collected in a coastal lagoon a few kilometres east of wairoa northern hawke s bay new zealand were examined using sedimentological geochemical palynological and micropaleontological analyses a distinct short lived catastrophic saltwater inundation csi about 6300 years bp and possibly other minor marine incursions are preserved in the coastal estuarine to lagoonal freshwater sedimentary sequences which have been deposited in the last 6500 years the csi is characterised by a gravel unit that thins landward and decreases in particle size to sand within a sequence consisting mainly of brackish estuarine muds diatom assemblages indicate a marked change from the shallow brackish estuarine muds to marine gravels and sands to brackish estuarine muds the marine influence in the gravel and sand is also shown by the presence of marine dinoflagellates and a peak in na rb sedimentological chemical and paleontological in particular diatoms evidence indicates it is a csi we conclude that this was a tsunami and propose the most likely propagating mechanisms marine influence decreases upcore and totally freshwater conditions are evident in the upper section of the cores the geochemistry of the sediments mainly reflects the change in stratigraphy with distinct signatures for tephra na fe cr organic rich and peat units as br and the coarse gravel sand csi unit na rb cr fe but it is also indicative of changes in depositional environment the change in chemistry na rb in the csi event is indicative of a saltwater influence whereas a marked change in s content suggests a sudden change from brackish to freshwater conditions shortly after 4800 years bp another peak in s and br content about 3200 years bp may indicate another temporary change to brackish conditions

evaluating the controls on tourmaline formation in granitic systems a case study on peraluminous granites from the central iberian zone ciz western spain

causes of geochemical diversity in peraluminous granitic plutons the jalama pluton central iberian zone spain and portugal abstract the jalama pluton jp is one of the best examples of the late hercynian two mica granites of the central iberian zone ciz of the hesperian massif spain and portugal this pluton is a multiphase intrusion that consists of three intrusive units 1 the external unit eu comprises three main facies a two mica coarse grained porphyritic granite pg a two mica coarse grained equigranular granite eg and a tourmaline bearing muscovite leucogranite tl which define both vertical and horizontal zonation the main petrographic and compositional characteristics of the eu can be explained by a fractional crystallization process that takes place in independent magma batches generated from heterogeneous source rocks 2 the sillimanite monzogranite sm is distinguished by the presence of micaceous aggregates composed of biotite muscovite and sillimanite based on major and trace element data the compositional variability within the sm has been ascribed to inheritance from compositionally heterogeneous source rocks 3 the late leucogranites ll appear mainly as dykes intruded in the pg from a comparison with this pg it can be deduced that the ll represent derivative liquids segregated after important fractionation from magmas equivalent to pg magmas but at deeper levels the most important implication of our study is that the jalama granites were generated by partial melting of high grade metamorphic peraluminous rocks that were compositionally heterogeneous on different scales during this small scale intracrustal melting event temperature was the limiting factor for the degree of melting