a spectrum of potentially diamondiferous lamproites and minettes from the jharia coalfield eastern india abstract abundant cretaceous 110 ma lamprophyric sills in the gondwana coalfields show a comagmatic continuum from olivine lamproites to lamproites and minettes four sills in the jharia coalfield have exotic mineralogy dominated by olivine fo 85 92 and phlogopite 5 10 tio 2 5 13 al 2 o 3 with subordinate potassium titanian richterite and or arfvedsonite and spectacularly zoned sr rich apatite up to 20 sro accessory to minor phases include clinopyroxene titanian diopside to aegirine augite k feldspar or 96 variable spinel up to 47 cr 2 o 3 perovskite niobian ilmenite niobian rutile sphene and ba poor priderite complex primary carbonate assemblages involve breunnerite ferroan dolomite witherite alstonite and strontianite the whole rocks show low al 2 o 3 5 7 combined with high k 2 o 4 5 mgo up to 30 and cr up to 1500 ppm plus extreme tio 2 up to 8 5 sr zr up to 6000 ppm each ba up to 8000 ppm and lree ce up to 3000 ppm in many rocks k al molecular 0 7 na k al 1 and k na k 0 6 radiogenic isotopes sr 7 to 21 and nd 1 5 to 3 1 imply derivation from a metasomatized lithosphere mantle source with time integrated rb sr and sm nd slightly higher than bulk earth intensive carbonation up to 14 co 2 in some rocks may reflect fluids derived from the magmas themselves from carbonatite like fluids and perhaps from coking of the invaded coal seams minor crystal fractionation within sills as little as 2 5 m thick has yielded complementary olivine lamproites and feldspathic lamproites the latter grade ultimately into minettes via increase of al 2 o 3 and decrease of mgo positive indicators of diamond potential in these rocks include their bulk compositional similarity to diamondiferous olivine lamproites elsewhere e g argyle their cr rich spinels and perhaps their tectonic position negative factors include their quiet emplacement the noted differentiation and the associated coking of the coal seams

structural and chemical variations in phlogopite from lamproitic rocks of the central mediterranean region abstract micas from mafic ultrapotassic rocks with lamproitic affinity from several localities of the central mediterranean region were studied through single crystal x ray diffraction sc xrd electron microprobe analysis empa and secondary ion mass spectrometry sims mossbauer spectroscopy mos when feasible was also applied to minimise the number of unknown variables and uncertainties analysed lamproitic samples cover the most important central mediterranean type localities from plan d albard western alps to sisco corsica montecatini val di cecina and orciatico tuscany italy and torre alfina northern latium italy the studied crystals show distinctive chemical and structural features all of them belong to the phlogopite annite join and crystallise in the 1 m polytype except for micas from torre alfina where both 1 m and 2 m 1 polytypes were found studied micas have variable but generally high f and ti contents with mg mg fe ranging from 0 5 to 0 9 2 m 1 crystals from torre alfina radically differ in chemical composition showing high contents of ti and fe as well as of al in both tetrahedra and octahedra leading to distinctive structural distortions especially in tetrahedral sites sims data indicate that studied micas are generally dehydrogenated with oh contents ranging from 0 2 apfu atoms per formula unit for orciatico and torre alfina to 1 4 for plan d albard crystals this feature is also testified by the length of the c parameter which decreases with the loss of hydrogen and or the increase of the f oh substitution chemical and structural data suggest that the entry of high charge octahedral cations is mainly balanced by an oxy mechanism and to a lesser extent by a m 3 4 tschermak substitution our data confirm that ti preferentially partitions into the m2 site and that different ti and f contents as well as different k al values are both dependant upon f h2o and the composition of magma rather than controlled by p and t crystallisation conditions the obtained data help to discriminate among lamproite like rocks formed within a complex geodynamic framework but still related to a destructive tectonic margin and evidence different trends for micas from the youngest torre alfina northern latium lamproites referred to the apennine orogeny and those of the older lamproites from orciatico montecatini val di cecina tuscany western alps and corsica the latter referred to the alpine orogeny phlogopite crystals from the older lamproites fall within the compositional and structural field of worldwide phlogopites from both within plate and subduction related settings phlogopite from the plio pleistocene lamproite like occurrence in tuscany and northern latium despite crystals with low mg of the torre alfina rock plot well within the general field of the other crystals in less evolved samples follows a different evolution trend similar to that of shoshonites from tuscany and northern latium on this basis we argue that the observed differences are inherited by slight differences in the magma compositions that are related to different genetic and evolution pathways

intraplate extension prior to continental extrusion along the ailao shan red river shear zone left lateral movement of the ailao shan red river shear zone lends support to the hypothesis of continental extrusion resulting from the collision of india with asia our new observations from northwestern yunnan china and northwestern vietnam on different sides of the shear zone demonstrate that the sinistral offset was 600 km according to correlations of permian triassic flood basalt successions and late paleogene highly potassic mafic magmas we conclude that the shear was propagating on the south china continental margin and does not correspond to a suture between south china and indochina furthermore the highly potassic magmas were emplaced from ca 40 to 30 ma before the shear movement which was caused by the late oligocene to early miocene ca 27 22 ma extrusion activity this suggests that a late eocene to early oligocene intraplate extension possibly induced by delamination of thickened continental lithosphere took place in northwestern yunnan or eastern tibet as a response to the india asia collision this extension and sea floor spreading of the south china sea that began ca 30 ma could have accounted for the initiation of the ailao shan red river shear zone

contrasting exhumation histories along a crustal scale strike slip fault zone the eocene to miocene ailao shan red river shear zone in southeastern tibet abstract four metamorphic massifs in southeastern tibet the xuelong shan xls diancang shan dcs ailao shan als and day nui con voi dncv have been suggested to constitute coherent parts of the ailao shan red river asrr shear zone this study details the cooling exhumation histories of the crustal scale shear zone by determining the cooling paths of the als massif and comparing these paths to those of the dcs massif we show that the different parts of the als massif have experienced two stages of diachronous cooling histories the two cooling stages of the als massif i e an early rapid cooling of ca 45 715 c myr and a late slow cooling of 10 17 c myr differ significantly from the cooling of the dcs massif along the same shear zone which featured an early slow cooling of 11 17 c myr and a late rapid cooling of 30 140 c myr this study confirms that differing cooling exhumation histories exist along the same crustal scale shear zone from the contrasting cooling exhumation histories we would argue that the als and dcs massifs are isolated units with different tectono thermal histories during the oligo miocene tectonic evolution of southeastern tibet

mineralogy of mafic xenoliths and their reaction zones in the olivine lamproite from prairie creek arkansas and the paragenesis of haggertyite ba fe6ti5mg o19 the recently discovered mineral haggertyite which belongs to the magnetoplumbite family occurs in the prairie creek lamproite exclusively in a reaction zone at the contact between the olivine lamproite and serpentized xenoliths compositional characteristics of the lamproite are an extreme enrichment in elements such as k ba and ti associated with very low al2o3 based on textural evidence it appears that the xenoliths represent a quenched very mafic magma possibly komatiitic an absence of perovskite in the reaction zone is the consequence of si diffusion from the xenolith iron available in the xenolith may be the controlling factor for the crystallization of haggertyite and other fe and ti oxides involved in the reaction other elements k ti and ba diffused from the lamproite toward the xenolith zone but only the outermost edge of the xenoliths reacted the crystallization of haggertyite appears to have resulted from a local chemical environment created by element diffusion between the two significantly contrasting lithologies

numerical analysis of boulder transport by the 2004 indian ocean tsunami at pakarang cape thailand at pakarang cape thailand we conducted field observations and numerical modeling of the spatial and grain size distributions and sources of boulders deposited by the 2004 indian ocean tsunami the boulders are a very rare example of boulders for which a tsunami origin is well confirmed numerical modeling of the tsunami s boulder transport revealed that the grain size and spatial distributions of boulders are explainable by the initial distribution of boulders at the source and the tsunami s local behavior which is controlled strongly by the tsunami hydrodynamic features and local topography soon after the bore front reached at the beach the tsunami s hydraulic force on the tidal bench decreased suddenly below the critical force necessary to displace the boulder because of the seaward propagation of the reflected wave that had been generated at the beach slope consequently all boulders were deposited below the high tide line and subsequently concentrated at the western coast of the cape absence of boulders that had been originally deposited deeper than 10 m water depth is also explained by this reflected wave because the wave passed over boulders that had been originally deposited at 10 m water depth before the boulder crossed the reef edge our well tuned model elucidates how the tsunami was able to deposit large boulders on the tidal bench at the cape the results demonstrate that theoretically up to 250 tons of boulders might have been emplaced on the tidal bench by the 2004 indian ocean tsunami at the cape approximately 7 m wave height the calculated maximum weight is of comparable order to that of boulders around the world that are inferred to be of tsunami origin although we infer that the weight is determined based on the sensitive balance of the local topography hydrodynamic features of the tsunami and the initial distribution of boulders at the source

the red river fault system in the tonkin gulf vietnam abstract the red river fault system in the tonkin gulf offshore haiphong was studied using seismic profiles calibrated by deep wells well characterised left lateral strike slip occurred continuously within a narrow 30 km wide zone southwest of the vinh minh fault between 30 ma and 5 5 ma however the corresponding amount of offset probably does not exceed a few tens of kilometres no sign of post 5 5 ma right lateral motion can be detected prior to 30 ma there is a widespread extension in a wider 100 km wide zone which could be related to a significant amount of left lateral motion the motion of the fault splays to the northeast of the vinh minh fault prior to 30 ma was absorbed in the rifting of the gulf of beibu a 15 5 ma unconformity separates the transtensional regime from a later transpresional regime this 15 5 ma date coincides with the cessation of sea floor spreading in the south china sea

geodynamics and tectonic evolution of the panxi rift abstract this paper gives a report on the geophysical geological and geochemical studies of the panxi rift the results of wide scale gravity measurements deep seismic soundings aeromagnetic geomagnetic geothermal and seismicity investigations which have been carried out by the institute of geophysics of the academia sinica are presented and analysed thereby the results from geotraverse i are discussed in detail the following rift associated features have been found an intracrustal low velocity and resistivity layer lower than normal velocities of 7 6 7 9 km s and low resistivity of 250 m in the upper mantle elevated velocities and resistivities in the central region doming as analysed from the gravity and seismicity data n s rift oriented positive magnetic anomalies in the central region n s striking faults and n s oriented distribution of basic and ultrabasic proterozoic rocks and grabens it is shown that the region containing the panxi rift was subjected to extensional and compressional tectonics which started in the late proterozoic and found their climax in the late palaeozoic the recent compressional tectonics are considered to relate to the collision of the indian and eurasian plates rifting and igneous processes during the tectonic evolution of the panxi rift are compared with the major continental rifts and conceptual models for the various rifting episodes are presented

petrogenesis of calc alkaline shoshonitic and associated ultrapotassic oligocene volcanic rocks from the northwestern alps italy along the western alps there is geological evidence of late alpine oligocene magmatic activity which clearly postdates the lepontine eocene early oligocene metamorphism and related deformation of the alpine nappe pile this magmatic activity was notably delayed in relation to the most important convergent processes and may be related to buoyancy of lithosphere tensional tectonics and thermal updoming subsequent to the collision between the eurasian and african plates the geochemical features of the rocks and the geophysical characteristics of the alpine chain suggest that a shoshonitic and calcalkaline melts may have been generated by partial melting of metasomatized peridotitic material and subsequent fractional crystallization and crustal contamination silicic andesites and latites however could have been also derived from metasomatized eclogite or deep continental crust material b the ultrapotassic lamprophyres with high k p lree th zr u and high 87sr 86sr ratios were generated by partial melting of strongly metasomatized mantle the varied sr isotopic ratios may partially also reflect additional radiogenic component from the continental crust following magma segregation from the source

timing of tibetan uplift constrained by analysis of volcanic rocks the tibetan plateau has had a central role in the development of recent models for the mechanics of mountain belts1 2 and cenozoic global climate change3 the present elevation and extensional deformation of the plateau probably result from uplift owing to convective thinning of the underlying lithospheric mantle1 2 an age for the uplift would provide a valuable constraint on these models but because recently proposed indicators of uplift are all climate dependent they are equivocal possibly reflecting global cooling rather than regional uplift4 here we present new geochemical data on post mid miocene lavas from the plateau which show that the lavas were derived from the lithospheric mantle simple thermal arguments indicate that the generation of such magmas also necessitates thinning of the lithospheric mantle thus volcanism is coincident with uplift providing a climate independent means of dating the onset of uplift dating by the laser 40ar 39ar technique places the beginning of this volcanism and therefore the time of uplift of the tibetan plateau at 13 myr ago

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

numerical study of wave interaction with a composite breakwater located on permeable bed abstract the response of a composite breakwater against wave load is numerically investigated using smoothed particle hydrodynamic sph model permeability of the stone layer beneath the caisson is implemented in the model and a new scheme free of any tuning parameter is introduced to estimate the dynamic friction forces transitionally applied to the moving caisson to overcome pressure noises inside the porous medium a treatment based on sph scheme is utilized and its performance is verified by modeling a simple hydrostatic condition inside a homogeneous porous medium the model ability in simulating fluid flow through porous media is approved by modeling dam break flow through a porous block in addition a caisson breakwater with an impermeable bed is modeled and the results are compared with experimental and other numerical results to validate the performance of the introduced friction coefficient then the same caisson but with a permeable bed is simulated against the incident waves and the horizontal forces as well as sliding displacements are calculated good agreements with the experimental data show the acceptable performance of the developed model as well as the importance level of the permeable bed on the caisson response based on the results neglecting the flow through the porous bed of the caisson may result in an overestimated wave force and an underestimated caisson sliding finally the caisson responses to different wave conditions are studied and it is shown that the peak load on the caisson increases as the wave height or wave period rises

structural petrological and thermal evolution of a tertiary ductile strike slip shear zone diancang shan yunnan the diancang shan a horst massif within the red river fault zone in yunnan people s republic of china preserves a structural petrological and thermal record of two distinct phases of tectonic activity a left lateral ductile shear that terminated between 20 and 17 ma and a ductile to brittle phase of normal faulting which began at 4 7 ma and remains active mylonitic rocks in the core of the range display an early steep high temperature ht schistosity and a horizontal stretching lineation that are both parallel to the trend of the belt kinematic indicators indicate that shear was left lateral the complex shape of the ht schistosity at the southern termination of the massif likely results from a large scale oblique left lateral c shear plane that dismembered the shear zone and separated the ailao shan and the diancang shan as left lateral deformation terminated thermochronological and thermobarometric results suggest that the gneisses were partially unroofed during this event along the eastern edge of the diancang shan the ht fabrics were overprinted by low temperature structures during activation of east dipping normal faults cooling associated with this normal right lateral faulting along the diancang shan and perhaps activation of the right lateral normal movement on the range front fault farther south along the ailao shan began at 4 7 0 1 ma these results tend to support the view that extrusion of indochina occurred along the left lateral red river shear zone between 35 and 19 17 ma initiation of right lateral normal slip during the late miocene may relate to eastward extensional collapse of the thickened tibetan crust or more probably to initiation of the second phase of extrusion

a lower crust origin of some flood basalts of the emeishan large igneous province sw china abstract high seismic velocity layers within the lower crust i e 40 km of the yangtze block are interpreted as mafic underplated rocks derived from the late permian emeishan mantle plume however the region experienced a previous magmatic event during the neoproterozoic 800 ma that produced the kangdian basalts and associated mafic intrusions and therefore the lower crust seismic velocity layers may represent a mixture of two different magmatic episodes the identification of inherited neoproterozoic i e 750 to 850 ma zircons within emeishan magmatic rocks indicates either assimilation of older material during emplacement or that the rocks could be derived from a mafic neoproterozoic precursor equilibrium partial melt modeling of neoproterozoic kangdian basalts can produce compositions similar to emeishan basalt at a pressure of 1 2 gpa i e 40 km depth it is suggested that the injection of high temperature picritic magmas into the lower crust of the yangtze block could be sufficient to induce high degrees of melting of the lower crust and produce magmas that are similar in composition to some emeishan mafic rocks and or produce melts that could contaminate pristine emieshan magmas

convective removal of thermal boundary layer of thickened continental lithosphere a brief summary of causes and consequences with special reference to the cenozoic tectonics of the tibetan plateau and surrounding regions england p 1993 convective removal of thermal boundary layer of thickened continental lithosphere a brief summary of causes and consequences with special reference to the cenozoic tectonics of the tibetan plateau and surrounding regions in m j r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 67 73 the tectonics of tibet and its surroundings underwent marked changes at about 8 ma normal faulting of the plateau appears to have initiated at about this time widespread highly potassic volcanism interpreted as the result of rapid heating of the mechanical boundary layer began about 12 8 ma such rapid heating could be the consequence of convective removal of the lower lithosphere and its replacement by asthenosphere this process would have raised the surface height of the plateau and could have provided the driving force for extension the diffuse deformation in the indian ocean probably began at about 8 ma analysis of the buckling of a plastic lithosphere implies that the horizontal force per unit length required to drive this deformation is consistent with uplift of the tibetan plateau by 1 3 km the indian monsoon intensified at about 8 ma this intensification is consistent with the rapid passage of the surface height of the plateau across a threshold required to disrupt the pre existing atmospheric circulation of the region taken together these observations imply that the surface height of the tibetan plateau rose by between 1 and 3 km in a few million years around 8 ma such a rapid increase in surface height affecting an area the size of the tibetan plateau could not be achieved by crustal thickness changes but could have been caused by the convective removal of a substantial thickness of lower continental lithosphere of the region

non linear wave attenuation quantification model improves the estimation of wave attenuation efficiency of mangroves abstract the wave attenuation function of mangroves follows the dalrymple model but changes nonlinearly with vegetation structure in various places which has not been fully addressed here taking the da guan sha of beihai city china as a case study the landscape metrics characterizing mangrove structures including the diameter at breast height dbh crown breadth crown density and rhizome and stem systems were obtained through remote sensing and field measurements then the nonlinear spatiotemporal pattern of the wave attenuation function decreasing rate of wave height was explored and revealed among six 20 200 m parallel transects passing through mangroves along the direction of the current the results showed the following 1 the dbh and crown breadth first increased and then decreased from the seaward to landward side of each transect showing a nonlinear inverted u pattern of distribution 2 the wave attenuation function of mangroves was dominated by the canopy at high tide but significantly affected by the structure of the rhizome or stem system at low tide the wave height during a specific storm surge could decrease by nearly 97 among the six transects at high tide but by only 87 at low tide on average if the wave crossed through the mangroves over a distance of 100 m from the seaward side of the mangroves edge 3 the wet surface width of a major part of mangrove trees with wave attenuation functions would change with the distribution of the dbh crown breadth and tree height along the transects which would also change with the dynamics of the water level the wave attenuation of mangroves ranged from 85 to 90 at low tide and from 96 to 97 at high tide if the wave crossed through mangroves at a distance of 100 m from the seaward side of the mangrove edge 4 the predicted practical decreasing rate of wave height based on the forward differencing method a method that considered the varied vegetation structure along transects in the model during the calculation of wave attenuation which would be close to reality would be 12 and 9 higher at low and high tide respectively than those estimated by the simplified calculation method a method of taking the average value of the vegetation structure of each transect to calculate wave attenuation if the wave crossed through mangroves at a distance of 200 m from the seaward side of the mangrove edge the integration of mangrove structures into the established empirical models improves our understanding of the nonlinear wave attenuation function of mangroves and may provide decision makers with more valuable information on restoring mangrove ecosystems to protect against storm surges

lamproites in north vietnam a re examination of cocites the term cocite was coined by lacroix for rocks that share with lamproites a number of characteristics among them the presence of k rich minerals and high mgo and k 2 o a re examination of the type specimens indicates the absence of ti rich oxides and k richterite but the presence of ti rich phlogopites in addition to previously recognized olivine clinopyroxene sanidine analcime and chromite magnetite a phase absent from typical lamproites is also present the compositions of constituent phases the mineral assemblage and the trace element contents are all unlike those of lamproites and indicate that cocites are close to but not typical lamproites

distribution origin and transport process of boulders deposited by the 2004 indian ocean tsunami at pakarang cape thailand abstract the tsunami of 2004 in the indian ocean transported thousands of meters long boulders shoreward at pakarang cape thailand we investigated size position and long axis orientation of 467 boulders at the cape most of boulders found at the cape are well rounded ellipsoid in shape without sharp broken edges they were fragments of reef rocks and their sizes were estimated to be 3 22 7t the distribution pattern and orientation of long axis of boulders reflect the inundation pattern and behavior of the tsunami waves it was found that there is no clear evidence indicating monotonous fine coarse shoreward trends of these boulders along each transect line on the other hand the large boulders were deposited repeatedly along the three arcuate lines at the intertidal zone with a spacing of approximately 136m interval this distribution pattern may suggest that long lasting oscillatory flows might have repositioned the boulders and separated the big ones from small no boulders were found on land indicating that the hydraulic force of the tsunami wave rapidly dissipated on reaching the land due to the higher bottom friction and the presence of a steep slope we further conducted numerical calculation of tsunami inundation at pakarang cape according to the calculation the sea receded and the major part of the tidal bench area with boulders at present was exposed above the sea surface before the arrival of the first tsunami wave the first tsunami wave arrived at the cape from west to east at approximately 130min after the tsunami generation and then inundated inlands our calculation shows that tsunami wave was focused around the offshore by a small cove at the reef edge and spread afterwards in a fan like shape on the tidal bench the critical wave velocities necessary to move the largest and average size boulders by sliding can be estimated to be approximately 3 2 and 2 0m s respectively the numerical result indicates that the maximum current velocity of the first tsunami wave was estimated to be from 8 to 15m s between the reef edge and approximately 500m further offshore this range is large enough for moving even the largest boulder shoreward these suggest that the tsunami waves that were directed eastward struck the reef rocks and coral colonies originally located on the shallow sea bottom near the reef edge and detached and transported the boulders shoreward

geochemistry and mineralogy of the minette lamproite association from the indian gondwanas abstract in northeast india early cretaceous lamprophyres intrude both the gondwana permian lower cretaceous sedimentary sequence and older cratonic blocks spessartite is the typical lamprophyre of the proterozoic meghalaya craton whereas a minette lamproite suite intrudes the gondwana coal bearing sequence cores from exploration boreholes and rocks from deep coal mines have provided excellent fresh samples the petrography mineral chemistry geochemistry and isotope geochemistry of such samples have been examined essential characteristics of the minette lamproite suite are a depletion in ca al and na b enrichment in k ti and other incompatible elements and c presence of phlogopite megacrysts of possible mantle origin preliminary sr pb and nd isotopic data demonstrate significant differences between the minette lamproite suite and the spessartites it is concluded that the minette lamproite suite evolved from a primary magma generated by the partial melting of a carbonate bearing harzburgite that had been extensively metasomatised

timing of left lateral shearing along the ailao shan red river shear zone constraints from zircon u pb ages from granitic rocks in the shear zone along the ailao shan range western yunnan china as the boundary between the indochina and the south china blocks the ailao shan red river asrr shear zone underwent a sinistral strike slip shearing which is characterized by ductile deformation structures along the ailao shan range the timing issue of left lateral shearing along the asrr shear zone is of first order importance in constraining the nature and regional significance of the shear zone it has been therefore focused on by many previous studies but debates still exist on the age of initiation and termination of shearing along the shear zone in this paper we dated 5 samples of granitic plutons dykes along the ailao shan shear zone zircon u pb ages of four sheared or partly sheared granitic rocks give ages of 30 9 0 7 36 6 0 1 25 9 1 0 and 27 2 0 2 ma respectively an undeformed granitic dyke intruding mylonitic foliation gives crystallization age of 21 8 1 ma the th u ratios of zircon grains from these rocks fall into two populations 0 17 1 01 and 0 07 0 08 reflecting magmatic and metamorphic origins of the zircons detailed structural and microstructural analysis reveals that the granitic intrusions are ascribed to pre syn and post shearing magmatisms the zircon u pb ages of these granites provide constraints on timing of the initiation later than 31 ma from pre shearing granitic plutons but earlier than 27 ma from syn shearing granitic dykes and termination ca 21 ma from the post shearing granitic dykes of strong ductile left lateral shearing which is consistent with previous results on the diancang shan and day nui con voi massifs in the literature we also conclude that the left lateral shearing along the asrr shear zone is the result of southeastward extrusion of the indochina block during the indian eurasian plate collision furthermore the left lateral shearing was accompanied by the ridge jump postdating the opening of the south china sea

geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy abstract serri g innocenti f and manetti p 1993 geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy in m j r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 117 147 the neogene quaternary magmatism of the northern apenninic arc took place in four phases separated in space and time which become progressively younger from west to east phase i 14 ma phase ii 7 3 6 0 ma phase iii 5 1 2 2 ma phase iv 1 3 0 1 ma this magmatism is the result of the activation of three physically separate sources 1 the adriatic continental crust extracted from the mantle in the late proterozoic 2 a strongly refractory recently k enriched harzburgitic mantle located in the mechanical boundary layer mbl of the lithosphere and 3 a recently metasomatized cpx rich mantle compositionally variable from iherzolite to wehrlite clinopyroxenite interpreted as an ephemerally k enriched asthenosphere the adriatic continental crust is the dominant source of the acid plutonic and volcanic rocks of the tuscan region the acid magmatism is mostly found inside an ellipsoidal area about 150 300 km centred on giglio island here defined as the tuscan crustal dome within this area mantle derived magmas unaffected by important crustal contamination processes and mixing with crustal anatectic melts have so far not been found pure crustal magmas are rare but are represented for example by some of the san vincenzo and roccastrada rhyolites virtually all the tuscan acid centres show evidence of mixing with potassic mantle derived magmas major and trace elements as well as 87 sr 86 sr and 143 nd 144 nd data on primitive rocks mg 65 reveal two groups of mantle derived magmas these define two distinct mantle enrichment trends both essentially due to the additions of k rich components which metasomatized separate compositionally diverse upper mantle sectors in both cases the most remarkable mineralogical effect of these enrichment processes is the production of variable amount of phlogopite through reaction between fluids and or melts with the mantle the rocks of group i ol hy and q normative lamproites ultrapotassic high mg latites ultrapotassic shoshonites and shoshonites saturated trend are considered to be derived by partial melting at low pressure 87 sr 86 sr 0 717 ce sr 0 3 and k 2 o na 2 o 6 7 and low ratios of 143 nd 144 nd 0 5121 0 5120 and ba la 87 sr 86 sr 0 712 and k 2 o na 2 o 8 9 values and low 143 nd 144 nd ba la 0 10 ratios these constraints do not allow to exclude a complete identity between the k rich components which metasomatized the mantle sources of the saturated and undersaturated trend magmas the geochemical and isotopic features of the components that metasomatized the mantle sources of the northern apenninic arc magmatism can be explained by a geodynamic process which causes a large amount of crustal materials to be incorporated within the upper mantle we propose that the delamination and subduction of the adriatic continental lithosphere related to the still ongoing northern apennine continental collision provide a viable mechanism to explain the genesis and eastward discontinuous migration of the magmatism in central italy the subduction of delaminated lithospheric mantle with lower crustal slivers would have exposed uppermost mantle adriatic mbl and crustal units previously imbricated in the apennine chain to the heating advected by the upwelling of a recently and ephemerally k enriched asthenospheric mantle wedge and by the underplating of magmas derived from it we consider that the diapiric uprising of a hot crustally contaminated asthenosphere occurs in the wake left above the sinking of the adriatic delaminated subducting continental lithosphere the delamination subduction process of the adriatic lithosphere has probably started in the early middle miocene but earlier than 15 14 ma ago as indicated by the age and petrologic characteristics of the first magmatic episode sisco lamproite of the northern apennine orogenesis

mineralogy and petrogenesis of a ba ti zr rich peralkaline dyke from sebkovice czech republic recognition of the most lamproitic variscan intrusion abstract a peralkaline ultrapotassic dyke found at sebkovice t ebic district western moravia is a mineralogically extreme member of a dyke swarm occurring along the south eastern border of the moldanubian region of the bohemian massif the dyke shows a simple zoning with a very fine grained marginal zone grading into a medium grained central zone it has a primary mineral assemblage of microcline and potassic amphiboles with accessory apatite and altered phlogopite the microcline exhibits an unusual red luminescence colour and pronounced substitution of fe3 for al with measured contents of fe2o3 up to 8 5 wt 0 31 apfu fe3 amphiboles have very high k up to 0 99 apfu and si contents their compositions follow an alkaline fractionation trend from potassic richterite to potassic magnesio arfvedsonite characterized by an increase of na k and a decrease of ca mg fe2 and ti via heterovalent substitutions b ca c mg fe2 b na c fe3 and ti mg 2fe3 the most evolved apatite is significantly enriched in sro up to 9 7 wt 0 49 apfu sr the core of the dyke and late veinlets contain unique late to post magmatic ba ti zr bearing mineral assemblages of baotite henrymeyerite titanite rutile benitoite and bazirite anhedral baotite fills interstices distributed inhomogeneously in the dyke centre it is locally replaced by a ba bearing titanite henrymeyerite rutile quartz assemblage henrymeyerite the second record in a lamproite shows variable fe ti ratios and represents a solid solution of the hepta and hexatitanate components euhedral crystals of benitoite and bazirite are enclosed in the late stage quartz titanite apatite veinlets in the fine grained margin of the intrusion in terms of a mineralogical genetic classification the sebkovice dyke can be considered as a new high silica 57 wt sio2 variety of lamproite variety sebkovice and represents a unique expression of post collisional potassic magmatism on the south eastern border of the bohemian massif the peralkaline dykes from this area show mineralogical and geochemical features similar to those of silica rich orogenic lamproites emplaced at destructive plate margins in terms of the modern classification of lamproites the sebkovice dyke is the first lamproite recognised in the variscan orogenic belt

orthopyroxene minettes and lamproites their status and genetic significance orthopyroxene is a normal if rare constituent of some minettes and lamproites it is sometimes partly xenocrystic but mostly authigenic i e separated directly from lamprophyric magmas as can be shown when orthopyroxene lamprophyres are compared with the experimental phase diagrams of appropriate systems the orthopyroxene bearing lamprophyres represent modified mantle derived magmas characterized by a high mgo high sio2 speciation which was acquired in different ways in individual regions the crystallization of orthopyroxene lamprophyres was not controlled by particular pressure temperature conditions compared with clinopyroxene potassic lamprophyres the orthopyroxene lamprophyres represent more primitive magmas orthopyroxene minettes can also be altered by a post magmatic hydrothermal inflow which occasionally increases their cao content to the level normal in clinopyroxene minettes if this had happened before magma consolidation clinopyroxene instead of orthopyroxene would have crystallized orthopyroxene minettes are well defined mineralogically and chemically and may be related to other types in the minette series

carbonatite near the loch borralan intrusion assynt a suite of intrusive carbonate rocks some containing xenoliths of nepheline syenite and durness group dolomite has been discovered near the shore of loch urigill assynt scotland c 400m outside the contact of the strongly alkaline loch borralan intrusion four varieties occur porphyritic white sovite phlogopite sovite sovite breccia and foliated silicocarbonatite initially only the white sovite was found in situ intrusive into durness dolomites but excavation has revealed all types except the silicocarbonatite in place the rocks are largely sr rich calcite often enclosing phlogopite poikilitically together with fluorapatite rosettes fluorite titanite pyrrhotite pyrite chalcopyrite and ilmenite also occur diopside potassic richterite and chondrodite are found in the silicocarbonatite and in the vicinity of xenoliths of silicate rock and dolomite in the other carbonatite types the carbonate rocks have the high sr rb and ba rare earth element patterns and carbon and oxygen isotopic ratios characteristic of carbonatites from a mantle source region and are chemically distinct from the durness dolomites even when the latter are sampled as xenoliths in nepheline syenite although the absence of nb and the lack of significant fenitization of accompanying silicate rocks are somewhat uncharacteristic we conclude that the rocks at loch urigill are true carbonatites related to the loch borralan complex the strongly alkaline loch borralan intrusion and its associated carbonatite represent the most westerly expression of caledonian magmatism in britain which supports the view that they represent the products of small scale partial melting in old cold lithospheric mantle on the flanks of the orogen

petrology and petrogenesis of mesoproterozoic lamproites from the ramadugu field nw margin of the cuddapah basin eastern dharwar craton southern india abstract petrography mineral chemistry and major and trace element data are presented for the newly discovered mesoproterozoic 1 33 1 43 ga lamproites from the ramadugu field rlf at the nw margin of the paleo mesoproterozoic cuddapah basin in the eastern dharwar craton edc southern india rlf lamproites are emplaced as dykes have a nw se trend and their petrography reveal the effects of low temperature alteration however their textural features mineralogy and geochemistry are closely similar to other well characterised lamproites worldwide including examples from the eastern dharwar craton leucite hills west kimberley smoky butte and labrador the rlf magmas have undergone varying degrees of olivine clinopyroxene fractionation yet their compatible and incompatible trace element concentrations are sufficiently high to signal a primitive character incompatible element ratios suggest limited contamination by continental crust geochemical evidence indicates the derivation of rlf magmas from metasomatised harzburgite within the garnet stability field rare earth element inversion modelling further highlights substantial involvement of the sub continental lithospheric mantle in their genesis the rlf lamproites are geochemically similar to the well known extension related ultrapotassic lavas from eastern virunga and western anatolia and exclude an affinity with orogenic lamproites such as those from the mediterranean region bulk rock geochemical models recently developed to infer diamond potential reveals that rlf lamproites are non prospective lamproites of the rlf together with those from the krishna lamproite field and cuddapah basin are interpreted as an expression of extensional events in the eastern dharwar craton possibly related to the break up of the supercontinent of columbia between 1 5 and 1 3 ga

cenozoic plate reconstruction of southeast asia abstract the india eurasia collision alone set up a series of chain reactions and caused the formation and destruction of sedimentary basins within the domain of the collision belt changes in the rate and angle of convergence between the india and eurasia plates reflect different stages of tectonic development in southeast asia for example extrusion of the indochina block induced the consumption of the pre existing proto south china sea along northeastern kalimantan and led to the eventual opening of the south china sea along the south china margin subsequent motions of the sino burma thailand malay peninsula sumatra and kalimantan blocks have produced a succession of basins stretching from north sumatra to central thailand and on to the natuna area we present reconstructions of the southeast asia region at 60 ma 50 ma 40 ma 30 ma 20 ma 15 ma 10 ma and 5 ma it is clear from the reconstructions that the impact between greater india and southeast asia took place in the northwestern part of southeast asia the duration for the impact was probably from the middle eocene to early miocene this timing is in good agreement with the dating of the main red river fault motion wu et al 1989 scharer et al 1990 since the impact between greater india and southeast asia was basically west of the burma block there is no reason to assume that the sumatra malay peninsula and kalimantan should extrude to the southeast first along the left laterally displaced mae ping and three pagodas fault zones as suggested by peltzer and tapponnier 1988 if the opening of the central thailand basins the gulf of thailand and the malay basin are taken into consideration a dextral megashear zone is required to compensate the relative motion between indochina and the malay peninsula this dextral megashear zone might even extend into western kalimantan and serve as a boundary between the indochina block and kalimantan

design and construction of caisson breakwaters the japanese experience abstract the history of breakwater construction in japan is reviewed and present design methods of vertical breakwaters are discussed in terms of wave forces and breakwater stability current design techniques of vertical breakwaters in japan are the culmination of many years of experiences and practical research in this field the goda formula which accurately predicts the design wave forces under most conditions of vertical breakwaters is an excellent aid in the design of the breakwaters under certain conditions excessive impulsive forces due to the action of breaking waves are exerted on the upright section such conditions must be minimized in the design of vertical breakwaters and the adoption of vertical breakwaters covered with wave dissipating concrete blocks or the wave dissipating caisson breakwaters offer potential solutions of this problem the bearing capacity of rubble mound foundation and the stability of armor units are also discussed

onset timing of left lateral movement along the ailao shan red river shear zone 40ar 39ar dating constraint from the nam dinh area northeastern vietnam left lateral motion along the ailao shan red river asrr shear zone has been widely advocated to be the result of the collision between the indian and eurasian plates and to account for sea floor spreading in the south china sea our new 40 ar 39 ar data on the south easternmost outcrop of the day nui con voi metamorphic massif northern vietnam suggest that the exhumation of metamorphic massif by shearing along the asrr zone began 027 ma and lasted until 022 ma a perfect correlation between location and cooling path for the samples along the shear zone suggests that the transtensional deformation may have propagated northwestward at a rate of 0 6c m y 1 such a good correlation also indicates that the onset of the leftlateral movement of the shear zone may have occurred later than 027 5 ma this conclusion is consistent with our previous interpretation that collision induced southeastward extrusion of indochina along the asrr shear zone postdates the opening of the south china sea and that extrusion tectonics in se china may not be responsible for the opening of the south china sea 2000 elsevier science ltd all rights reserved

intraplate tectonics in asia a precise age for large scale miocene movement along the ailao shan red river shear zone china tertiary left lateral movement along the 1000 km long ailao shan red river shear zone appears to have played an important role in absorbing post collisional northward penetration of india into asia crustal strike slip shear along this zone caused the formation of a gneiss belt metamorphosed to amphibolite grade including anatectic melting both metamorphism and melting were induced by ductile deformation yielding the possibility to date the major tectonometamorphic event that shaped the ailao shan red river belt 17 u pb isotope analyses were performed on small size fractions of zircon monazite and xenotime extracted from two different leucogranitic layers the two samples are located about 50 km apart in the central segment of ailao shan in structurally well controlled settings where the melts crystallized within the strongly foliated gneisses during late stages of deformation all mineral u pb analyses had to be corrected for excess or deficit amounts of radiogenic 206 pb originating from initial 230 th disequilibrium in the 238 u decay series in monazite such disequilibrium 206 pb reaches 20 of total radiogenic 206 pb the corrected u pb ages of monazite and xenotime lie between 22 1 and 23 9 ma whereas zircon yields significantly discordant u pb ages between 30 5 and 33 9 ma pointing to precambrian material in the magma source region inherited components could also be detected in monazite the set of u pb data shows that monazite and xenotime formed simultaneously in both localities substantiating an early miocene age of 23 0 0 2ma for late kinematic crystallization of anatectic melts in the metamorphic belt of the ailao shan red river shear zone

evidence for a mid holocene tsunami deposit along the andaman coast of thailand preserved in a mangrove environment abstract klong thap lamu a large mangrove fringed tidal channel along the northern andaman coast of thailand provides an ideal location to test the hypothesis that a paleotsunami record can be preserved in the sediments of a mangrove forest the 2004 indian ocean tsunami destroyed local swaths of mangrove forest with highly variable widths up to 300 m left in the wake of the tsunami is a thin mantling of laterally discontinuous sand macerated shells and localized coral rubble that is being mixed rapidly into the underlying mangrove peat transects across the channel s tsunami modified shore show that the sand layer thins abruptly at the border of the undisturbed mangroves suggesting that the energy of the wave dissipated quickly as it entered the forest the distribution and sedimentology of the 2004 tsunami deposit unit ti suggest that any paleotsunami deposit within this mangrove environment should be spatially restricted and thoroughly bioturbated sediment cores collected from within the 2004 tsunami zone penetrate a buried coral shell peat unit unit tiii that tapers inland unit tiii is strikingly similar to unit ti except for unit tiii s diffuse sedimentology which we attribute to extensive bioturbation unit tiii also cross cuts an identified facies boundary that is traceable across the width of the 2004 tsunami zone rather than a facies boundary associated with the regional early to late holocene sea level regression stratigraphic correlations suggest that unit tiii represents an event horizon i e tsunami ams 14 c dates on material from within unit tiii combined with an upper bracketing age suggest that the tsunami event occurred sometime between 2720 and 4290 cy bp if correct this tsunami predates the 3 4 tsunami events recognized to the north at koh phra thong unit tiii is however a potential far field equivalent of a recently recognized paleotsunami deposit on the southwestern indian coast ca 3 710 years before present nair et al 2010

an early miocene transition in deformation regime within the red river fault zone yunnan and its significance for indo asian tectonics recent work has tended to support the view that lateral extrusion of indochina along the red river fault zone was a significant factor in accommodating the convergence of india with asia to better understand the nature and timing of this feature 40ar 39 ar age spectrum analyses were undertaken on minerals from the ailao shan red river metamorphic belt in southern yunnan china interpreted using diffusion domain theory these results yield thermal histories in the temperature range 550 150 c discontinuities in cooling rates observed from these results suggest a transition in deformation style in the shear zone during the early miocene at least in the vicinity of our samples left lateral strike slip ductile deformation appears to have ceased by about 20 ma the mylonitic gneisses in the shear zone were subsequently obliquely unroofed probably due to a component of normal faulting along the eastern edge of the shear zone causing a brief locally 100 c m y cooling episode this transition may have resulted from a component of northeast southwest extension attributable to greater clockwise rotation of indochina relative to south china after 20 ma than that consistent with pure strike slip along the fault k ar ages on clay minerals from gouge within the normal faults bounding the ailao shan and diancang shan yield a range of ages between 20 and 185 ma but show a significant clustering at 20 25 ma these results suggest that early miocene movement on a precursor to the range front normal fault in the ailao shan caused oblique unroofing of the shear zone this early miocene event corresponds in time with a transition from low to very high denudation rates throughout the himalaya and southern tibet this coincidence may reflect that once left lateral strike slip motion on the red river fault zone slowed or was terminated accommodation of much of the continued northward convergence of india occurred on the main central thrust resulting in rapid uplift in the tethyan himalaya and gangdese belt

kimberlite from rajmahal magmatic province sr nd pb isotopic evidence for kerguelen plume derived magmas 1 previous studies showed that the rajmahal sylhet bengal rsb flood basalt province 117 2 ma in eastern india was spatially close to the active kerguelen hotspot about 118 ma ago yet it could not be unequivocally correlated to this hotspot due to wide variation in isotopic compositions of both the rsb and kerguelen plateau basalts however we report sr nd pb isotopic compositions 87sr 86sri 0 70535 to 0 70561 end t 2 6 to 3 2 206pb 204pbi 17 88 to 18 07 of a co eval 116 2 ma group ii kimberlite from this flood basalt province that is identical to recently identified pristine kerguelen plume basalts from the kerguelen plateau archipelago and broken ridge this suggests that the kerguelen hotspot could indeed be responsible for the 117 ma magmatic activity in eastern india

duration of strike slip movements in large shear zones the red river belt china abstract sixty four size fractions of zircon monazite xenotime and titanite were dated by the u pb method to temporally and spatially constrain left lateral movements in the red river shear zone between the depths of 15 and 20 km the shearing led to the formation of the high grade metamorphic gneisses that form the bulk of the 4200 m high diancang shan and 3100 m high ailao shan mountain ranges the omnipresence of melt layers and pockets in these gneisses shows that temperatures associated with tectonometamorphism lie at and above the solidus of continental crust and deformation patterns are very homogeneous over the entire length of the belt north of the gneisses subvolcanic bodies intrude unmetamorphosed cover rocks in particular eocene red beds along the projected trend of the red river shear zone for a leucogranitic layer in the diancang shan gneisses an age of 24 2 0 2 ma 2 is obtained for monazite and 22 4 0 2 ma is obtained for xenotime whereas zircon formed through two growth stages at 24 23 ma these ages record solidification of the anatectic melts over a period of at least 1 8 0 4 ma during which left lateral shear was continuously active in the ailao shan gneisses zircon and titanite ages are 26 3 0 3 and 26 1 0 2 ma for two monzonitic bodies and 24 1 0 2 and 22 4 0 2 ma for two pegmatitic layers that occur within the monzonitic intrusions these results show that zircon monazite titanite and probably also xenotime are closed systems for u and pb under melting conditions 650 c therefore the ages date mineral formation in the melt rather than cooling below certain closure temperatures a significantly older age of 35 0 0 1 ma is obtained for a monzonitic subvolcanic intrusion north of the diancang shan gneisses because these intrusions follow the trend of the shear zone they most likely represent the surface expression of early activity along that zone indicating that strike slip movement had already occurred in latest eocene time the total set of u pb ages shows that magmatic and metamorphic activity occurred from 35 to 20 ma strengthening the idea that the red river shear zone absorbed most of the intraplate movements required to compensate the opening of the south china sea between 32 and 16 ma the existence of monzonitic syenitic intrusions along the red river zone implies that melting affected source rocks other than the diancang shan and ailao shan gneiss protoliths potential sources to produce such rocks lie in the deep crust possibly including melts from the mantle consequently the red river shear zone must be a deep rooted structure along which melts migrated to the surface moreover the contemporaneity of shear motion and magma generation suggests that melting occurred in direct relation to strike slip activity

paleomagnetic results from the upper permian of the eastern qiangtang terrane of tibet and their tectonic implications abstract paleomagnetic samples were collected from red intercalations within the upper permian tuoba formation from the eastern qiangtang terrane of tibet progressive thermal demagnetization has revealed a prefolding possibly primary characteristic remanent magnetization chrm which yields a tilt corrected mean direction ofd i 25 2 6 7 95 8 6 the equatorial paleolatitude for the qiangtang terrane indicated by this result and the similarity of late permian fauna and flora shared by the qiangtang terrane and south china block scb suggest that the two terranes were in close proximity during the late permian a late permian paleogeographic reconstruction involving the major terranes of the present day east asia is constructed in which the songpan garze sea is surrounded by laurasia the north china block ncb the scb and the qiangtang terrane the permian development of the songpan garze sea appears to be related to the rifting of the qiangtang terrane off the scb its triassic evolution may resemble that of the solomon sea today in the southwestern pacific

violent breaking wave impacts part 2 modelling the effect of air when an ocean wave breaks against a steep fronted breakwater sea wall or a similar marine structure its impact on the structure can be very violent this paper describes the theoretical studies that together with field and laboratory investigations have been carried out in order to gain a better understanding of the processes involved the wave s approach towards a structure is modelled with classical irrotational flow to obtain the different types of impact profiles that may or may not lead to air entrapment the subsequent impact is modelled with a novel compressible flow model for a homogeneous mixture of incompressible liquid and ideal gas this enables a numerical description of both trapped air pockets and the propagation of pressure shock waves through the aerated water an exact riemann solver is developed to permit a finite volume solution to the flow model with smallest possible local error the high pressures measured during wave impacts on a breakwater are reproduced and it is shown that trapped air can be compressed to a pressure of several atmospheres pressure shock waves reflected off nearby surfaces such as the seabed can lead to pressures comparable with those of the impact typical examples of pressure time histories force and impulse are presented and discussed in terms of their practical implications the numerical model proposed is relevant for a variety of flows where air effects are important further applications including extended studies of wave impacts are discussed 2009 cambridge university press

geochemistry mineralogy and petrology of a new find of ultramafic lamprophyres from bulljah pool nabberu basin yilgarn craton western australia abstract four variously pipe or sill like carboniferous 305 ma bodies have been located near the ne edge of the archaean yilgarn craton the rocks comprise ba ti bearing tetraferriphlogopite tetraferriannite low al ti diopside calcite perovskite and groundmass titanomagnetite chromite up to 41 3 cr2o3 with minor apatite mg mn ilmenite rare earth phosphate k ba feldspar up to 17 bao baryte and an unidentified ba zr silicate the last three reflect very high whole rock ba up to 5 652 ppm aegirine rich pyroxenes occur in fenitic alteration assemblages together with high si al and low mg ca whole rock geochemistry these features are diagnostic of ultramafic lamprophyres damkjernites and aillikites although the rocks also show some affinities with classical kimberlites mineral concentrates from loam samples yield an array of minerals of mantle origin including garnets dawson and stephens groups g1 3 5 9 and 10 chromian diopsides up to 6 2 cr2o3 magnesiochromites up to 20 mgo 70 cr2o3 and four compositional groups of ilmenites low mn picroilmenites mn rich mg poor and two moderate mn mg compositions actual spinel lherzolite nodules are common in one body and the presence of spinel and or garnet lherzolites can be inferred in the others from the concentrates the bulljah bodies are therefore of deep mantle origin as confirmed by the recovery of a single microdiamond they thus extend the field of potentially if not necessarily economically diamondiferous rocks beyond kimberlites and lamproites when added to other recent lamprophyre finds the bulljah discoveries suggest that the yilgarn craton could like many other ancient cratons be ringed and or dotted by a diverse array of alkaline and lamprophyric rocks of varying ages which remain to be discovered

an unmetasomatized source for the malaitan alnoite solomon islands petrogenesis involving zone refining megacryst fractionation and assimilation of oceanic lithosphere the ma tan alnijite contains a rich and varied megacryst suite of unprecedented compositional range we have undertaken trace element and isotope modeling in order to formulate a petrogenetic scheme which links the host alniiite to its entrained megacrysts this requires that a proto alntiite magma is the product of zone refining initiated by diapiric upwelling where the initial melt passes through 200 times its volume of mantle isotopic evidence indicates the source of the proto alniiite contains a time integrated lree depleted signature 143nd 44nd 0 51274 impingement upon the rigid lithosphere halts or dramatically slows the upward progress of the mantle diapir at this point the magma cools and megacryst fractionation begins with augites crystallizingjirst followed by subcalcic diopsides and finally phlogopites garnet probably crystallizes over the entire range of clinopyroxene fractionation estimated proportions of fractionating phases are 30 augite 24 5 subcalcic diopside 27 garnet 12 9 phlogopite 5 bronzite 0 5 ilmenite and 0 1 zircon as this proto alnoite magma crystallizes it assimilates a subducted component of seawater altered basalt which underplates the ontong java plateau this is witnessed in the isotopic composition of the megacrysts and alnoite

the reduction effects of mangrove forest on a tsunami based on field surveys at pakarang cape thailand and numerical analysis abstract using an integrated approach including satellite imagery analysis field measurements and numerical modeling we investigated the damage to mangroves caused by the 2004 indian ocean tsunami at pakarang cape in pang nga province thailand comparing pre and post tsunami satellite imagery of the study area we found that approximately 70 of the mangrove forest was destroyed by the tsunami based on field observations we found that the survival rate of mangroves increased with increasing stem diameter specifically we found that 72 of rhizophora trees with a 25 30 cm stem diameter survived the tsunami impact whereas only 19 with a 15 20 cm stem diameter survived we simulated the 2004 indian ocean tsunami using the nonlinear shallow water wave theory to reproduce the tsunami inundation flow and investigated the bending moment acting on the mangrove trees results of the numerical model showed that the tsunami inundated areas along the mangrove creeks and its current velocity reached 5 0 m s 1 based on the field measurements and numerical results we proposed a fragility function for mangroves which is the relationship between the probability of damage and the bending stress caused by the maximum bending moment we refined the numerical model to include the damage probability of mangrove forests using the obtained fragility function to investigate the tsunami reduction effect of mangrove forest under simple numerical conditions related to the mangrove forest ground level and incident wave the model showed that a mangrove forest of rhizophora sp with a density of 0 2 trees m 2 and a stem diameter of 15 cm in a 400 m wide area can reduce the tsunami inundation depth by 30 when the incident wave is assumed to have a 3 0 m inundation depth and a wave period of 30 min at the shoreline however 50 of the mangrove forest is destroyed by a 4 5 m tsunami inundation depth and most of the mangrove forest is destroyed by a tsunami inundation depth greater than 6 m the reduction effect of tsunami inundation depth decreased when the tsunami inundation depth exceeded 3 m and was mostly lost when the tsunami inundation depth exceeded 6 m

new mineral names the following new minerals are discussed in this issue langbanshyttanite pseudolyonsite and yangzhumingite these new minerals have been described in the european journal of mineralogy and are reported here n v chukanov i v pekov e jonsson n v zubkova y e filinchuk d i belakovskiy and d yu pushcharovsky 2011 langbanshyttanite a new low temperature arsenate mineral with a novel structure from langban sweden eur j mineral 23 675 681 the new mineral langbanshyttanite was discovered in a specimen from the langban mine filipstad district varmland county bergslagen ore province sweden the carbonate hosted langban deposit 59 86 n 14 27 e is together with related occurrences in the western part of the palaeoproterozoic bergslagen ore province in south central sweden characterized by anomalously pb as ba be sb rich metamorphosed stratabound fe and mn oxide ores with associated skarn units sulfide assemblages as well as abundant vein and fissure hosted mineral assemblages the name is for langbanshyttan which is the old name of both the mine mining village and smelter that in more recent times has been known plainly as langban langbanshyttan actually means langban s smelter or langban s furnace langbanshyttanite occurs as a very late low temperature species in the deposit it crystallized during the last stage of hydrothermal activity involving metal remobilization in the langban system post dating regional metamorphism of the volcanic hydrothermal ores and their host rocks based on existing evidence these minerals formed at very low temperature and pressure in this case most likely below 70 c the mineral formed in fractures and corrosion veinlets post dating calcite in a mn oxide bearing mn silicate rich rock associated late stage minerals are calcite antigorite sparse euhedral trigonite and a few microscopic aggregates of a so far unidentified as bearing mineral typically both calcite and antigorite exhibit evidence of being partly corroded away prior to langbanshyttanite formation trigonite coeval with langbanshyttanite occurs as sparse euhedral crystals the groundmass to the veinlets or fractures mainly consists

15 n enriched gondwana lamproites eastern india crustal n in the mantle source abstract a comagmatic suite of lamproites ultramafic lamprophyres and minettes was intruded at 100 ma into thick siliciclastic sequences deposited in five intracratonic basins which developed during gondwana rifting in eastern india lamproites are dominated by microphenocrysts of ti rich phlogopite and olivine pseudomorphed by serpentine and talc with variable modal abundances of aegirine amphibole apatite carbonates cr spinel fluorite perovskite priderite and titanomagnetite compositionally lamproites are characterized by extremely high contents of tio2 4 2 10 wt k2o and p2o5 over a range of mg from 80 to 75 in keeping with lamproites worldwide they have high abundances of ba th u and ree 1019 5400 ppm with pronounced fractionation of ree where la smcn 3 5 5 6 and gd ybcn 7 3 18 consistent with residual garnet in the mantle source nitrogen isotope compositions range from 1 6 to 8 7 with an average of 3 8 and n contents average 107 ppm mantle 15n averages 5 with a n content of 2 ppm whereas continental crust varies from 2 to 6 with 30 90 ppm n atmospheric n2 is sequestered by n fixing microorganisms and stored as kerogen with an average 15n of 3 in sedimentary rocks some of the organic n is converted to nh4 which substitutes for k in crustal k silicates the 15n enriched lamproites are interpreted to have formed from partial melting of enriched harzburgitic mantle lithosphere by decompressional melting accompanying extension enrichment resulted from subduction erosion of continental crust or subduction of sediments low degree partial melting hybridization of the melts with mantle lithosphere and incubation prior to decompressional melting consequently some crustal n is recycled to the mantle

a simplified method to downscale wave dynamics on vertical breakwaters abstract a coastal structure is usually designed with the final objective to guarantee its functionality and stability throughout its life cycle regarding stability the three main failure modes are sliding overturning and failure of the foundations to accomplish the design objectives a design sea state is usually used when calculating the loads and scour around the structure this design sea state corresponds to a certain sea state with specific return period values of a significant wave height however the combination of different simultaneous sea state parameters can produce other critical situations compromising the stability of the structure which then require the calculation of long time series of wave forces corresponding to long term historical wave situations moreover a design force associated to a certain return period can be defined from the time series of the stability parameters the most accurate techniques which can be used to estimate structure stability are based on numerical and physical models but these are very time consuming and the calculation of long time series is therefore unfeasible here we propose a hybrid methodology to transform wave conditions into wave forces acting upon vertical structures and scour around it the methodology consists of a selection of a subset of sea states representative of wave climate at the structure location using a maximum dissimilarity algorithm the wave forces acting upon the structure and scour around it for the wave situations selected are then estimated as is the reconstruction of the calculated parameters corresponding to historical sea states using an interpolation technique based on radial basis function the validation of the results through a direct comparison between reconstructed series and analytically semi empirical formulations calculated ones confirms the ability of the developed methodology to reconstruct time series of stability parameters on vertical breakwaters this methodology allows its application to numerical and physical models

2004 indian ocean tsunami flow velocity measurements from survivor videos 1 the tsunami of 26th december 2004 severely affected banda aceh along the north tip of sumatra indonesia at a distance of 250 km from the epicenter of the magnitude 9 0 earthquake this tsunami flow velocity analysis focused on two survivor videos recorded within banda aceh more than 3 km from the open ocean the exact locations of the tsunami eyewitness video recordings were revisited by the survey team between february 22 and 25 2005 to record camera calibration ground control points the motion of the camera during the recordings was determined the individual video images were rectified with a direct linear transformation dlt assuming a planar water surface at the level finally a cross correlation based particle image velocimetry piv analysis was applied to the rectified video images to determine instantaneous tsunami flow velocity fields the measured tsunami flow velocities were within the range of 2 to 5 m s

comment on borgia a mazzoldi a brunori c a allocca c delcroix c micheli l vercellino a grieco g 2014 volcanic spreading forcing and feedback in geothermal reservoir development amiata volcano italia j volc geoth res 284 16 31 abstract borgia et al 2014 illustrated an active volcanic spreading model for the amiata volcanic area southern tuscany italy although at first glance the model may appear appealing this is not fully supported by the available data and the paper does not take into account their discussion accordingly the supposed negative consequences of the borgia et al 2014 model on both contamination of shallow water and geothermal exploitation can likely be regarded as speculative

u pb zircon geochronology and geochemistry from ne vietnam a tectonically disputed territory between the indochina and south china blocks volcanoplutonic complexes in ne vietnam have recently been interpreted as intraplate products of the emeishan plume alternatively mafic ultramafic rocks have been considered as dismembered palaeotethyan ophiolites juxtaposed along a tectonic melange zone new u pb zircon geochronological and geochemical datasets presented here suggest a complex geological history that records collision between the indochina south china blocks mafic ultramafic rocks exposed within a tectonic melange song hien tectonic zone include sub alkaline pillow basalts that define two geochemically distinct ophiolitic suites sh 1 n morb like sh 2 transitional e morb like both suites have geochemical signatures suggestive of crustal contamination compatible with a volcanic passive margin rift setting we suggest that sh 1 basalts may correlate with the devonian carboniferous jinshajiang ailaoshan song ma branch of the palaeotethys and form part of the associated dian qiong belt whereas sh 2 basalts are co magmatic with middle late permian mafic ultramafic intrusive rocks dolerites gabbros peridotites that developed in a rift basin most likely on the margin of the down going south china plate during west vergent subduction beneath indochina during continental orogenesis and thrust stacking these ophiolitic rocks were juxtaposed with other lithotectonic blocks within the song hien tectonic zone post collisional relaxation led to the development of a rift basin song hien rift comprising late permian triassic volcano sedimentary strata including 270 265 ma terrigenous sandstones 252 ma mudstones and c 254 248 ma felsic effusives granites and granodiorites were emplaced across ne vietnam between c 252 and 245 ma in a syn to post collisional setting the late permian early triassic felsic magmatic rocks best correlate with coeval rocks in sw guangxi and the central and western ailaoshan fold belts china and the truong son fold belt vietnam together they signal the final to post collisional stages of indochina south china collision we demonstrate that the analysed magmatic rocks in the lo gam song hien domains of ne vietnam are not genetically linked to the emeishan large igneous province in the yangtze block of south china as has been previously widely proposed

tsunami earthquake can occur elsewhere along the japan trench historical and geological evidence for the 1677 earthquake and tsunami since the 11 march 2011 tohoku earthquake the mechanisms of large earthquakes along the japan trench have been intensely investigated however characteristics of tsunami earthquakes which trigger unusually large tsunami remain unknown the earthquake of 4 november 1677 was a tsunami earthquake striking the southern part of the japan trench its source mechanism remains unclear this study elucidates the fault slip and moment magnitude of the 1677 earthquake and tsunami based on integrated analyses of historical documents tsunami deposits and numerical simulation geological survey results the analytical results of thickness and grain size distributions and diatoms revealed that tsunami deposits in a small pond at 11 m elevation were probably formed by the 1677 event this finding and historical descriptions are useful as important constraint conditions to estimate unusually large fault slips and moment magnitude of the 1677 earthquake numerical simulation results reveal that 8 34 8 63 moment magnitude with the large 11 16 m slip area is necessary to satisfy the constraint conditions this fault slip and magnitude are equivalent to those of the 1896 sanriku earthquake a well known tsunami earthquake in the northern part of the japan trench we therefore conclude that a tsunami earthquake of moment magnitude 8 3 8 6 with unusually large slip can occur elsewhere along the japan trench this point should be considered for future tsunami risk assessment along the japan trench and along any trench having similar tectonic settings to those of the japan trench

crustal thickening versus lateral expulsion in the indian asian continental collision since the beginning of the continental collision between india and asia there has been about 2500 km of convergence and the northward movement of india has been accommodated by major internal deformation of the asian lithosphere the crustal thickening in and around the tibetan plateau is clearly a direct consequence of this collision but there is considerable debate as to whether a large fraction of the indentation has been accommodated by eastward motion of the lithospheric blocks of southeastern asia and southern china numerical experiments described here test this hypothesis for a range of indentation geometries and rheological models of the lithosphere we employ a thin viscous sheet model of the lithosphere with a depth averaged nonlinear viscous rheology described by a stress strain rate exponent n and including gravitational buoyancy forces scaled by the dimensionless argand number ar the eastern boundary for the collision region is described as a lithostatic boundary the precollision normal stress is determined by static balance and that constant stress is applied throughout the collision the experiments show that during collision the eastern boundary is smoothly displaced to the east at a rate about 1 4 of the indentation rate with only minor variation due to geometry or rheology crustal thickening rates in the region of the plateau are reduced by between 10 and 25 of the corresponding rates determined for similar experiments with a rigid eastern boundary to generalize from the results of these experiments the total north south shortening strain produced by the collision is partitioned between crustal thickening and eastward displacement in the ratio of at least 3 1 and more probably 4 1

wave loads on rubble mound breakwater crown walls abstract crown walls are primarily built to reduce wave overtopping of mound breakwaters several methods have been proposed to calculate wave loads on the crown wall e g iribarren and nogales iribarren r nogales c 1964 obras maritimas dossat ed madrid 376 pp jensen jensen o j 1984 a monograph on rubble mound breakwaters danish hydraulic institute and gunbak and gokce gunbak a r gokce t 1984 wave screen stability of rubble mound breakwaters international symposium of maritime structures in the mediterranean sea athens greece pp 2 99 2 112 in this paper a new method based on those previous results and on further experimental work using monochromatic waves is presented the application of the new method requires waves breaking on the armour layer i e only broken waves will reach the crown wall the method is extended to irregular waves via the hypothesis of equivalence introduced by saville saville t 1962 an approximation of the wave run up frequency distribution proc 8th international conference on coastal engineering mexico city and is applied to the crown walls of gijon and bilbao breakwaters in spain the comparison of the probability force distributions obtained by the present method to that measured by burcharth et al burcharth h f frigaard p berenguer j m gonzalez b uzcanga j villanueva j 1995 design of the ciervana breakwater bilbao in t telford ed proc 4th coastal structures and breakwaters chap 3 institution of civil engineers and jensen 1984 is relatively good

petrology of an unusual orthopyroxene bearing minette suite from southeastern peru eastern andean cordillera al rich lamproites contaminated by peraluminous granites abstract the puno minettes eastern andean cordillera southern peru are phlogopite phyric rocks with a groundmass consisting mainly of phlogopite alkali feldspar and apatite microphenocrysts and or microlites they display the strong large ion lithophile element enrichments that characterize potassic to ultrapotassic rocks of the lamprophyre clan rb ba sr up to 103 primordial mantle ree up to 6 102 ci chondrites in addition to their close association with granitoids the rocks of this series show many features of minettes occurring in arc related collisional zones i e absence of mantle xenoliths up to 30 vol felsic xenocrysts and strong negative nb and ti anomalies however they are distinguished by unusual phenocryst phases whole rock compositions and groundmass mineralogy some minettes contain only a few per cent of biotite quartz plagioclase xenocrysts immersed in a typical minette groundmass whereas those richer in xenocrysts display the complete liquidus paragenesis of the coexisting peraluminous granite biotite quartz plagioclase alkali feldspar cordierite zircon pyrite in a high k latitic to trachydacitic groundmass field relations radiometric ages whole rock data and felsic xenocrysts all indicate that the puno minettes result from a mixing process involving al rich lamproites and peraluminous monzogranites the most common phenocryst assemblage highly magnesian phlogopite olivine titanian cr spinel ca rich enstatite magnesian ilmenite al and ti poor diopside is similar to that reported in al rich phlogopite lamproites from southeastern spain likewise the host rocks have diagnostic features of spanish phlogopite lamproites e g k2o al2o3 ratios 9 cao contents

reduction effect of tsunami sediment transport by a coastal forest numerical simulation of the 2011 tohoku tsunami on the sendai plain japan abstract we examined the effect of the coastal forest on tsunami sediment movement on the sendai plain japan during the 2011 tohoku tsunami using a numerical simulation of sediment transport to account for the variable roughness coefficient in the coastal forest a composite equivalent roughness coefficient was adopted the simulated mean concentration of suspended sediment wave height flow velocity and inundation limit were significantly reduced by the coastal forest for fine to medium sand the volumes of maximum deposition and erosion were reduced to 57 83 of those in the simulation without the coastal forest these reductions were particularly notable for fine sand the maximum extent and thickness of the sand layer were also reduced the simulated sediment thickness and extent with the coastal forest for finer grain sizes roughly agreed with the observations while the simulated results for coarser sand underestimated the observations the reduction of sediment transport due to the coastal forest suggests that land use conditions and the vegetation environment at the time of a tsunami should be considered when studying historical and paleo tsunamis using the geological evidence

experimental study of barium partitioning between phlogopite and silicate liquid at upper mantle pressure and temperature barium partition coefficients for phlogopite crystallized from a natural lamproite at 10 30 kbar and 900 1150 c show a three fold decrease in partition coefficient d with increasing pressure from 10 to 30 kbar e g from 0 75 to 0 23 and 35 50 increase in d with increasing temperature from 1000 to 1100 c at 10 and 15 kbar e g from 0 51 to 0 75 the variation with temperature is contrary to most recorded variations of d and is attributed to a compositional control in the phlogopite d correlates with substitution of titanium in the phlogopite thus as the titanium content increases with increasing temperature the barium content and hence d increases application of partitioning data for barium in models for lamproite genesis suggests that phlogopite of metasomatic origin and possibly some barium rich accessory phases are present in the source rocks for lamproite and phlogopite plays a major role in the generation of lamproitic magma

k richterite olivine phlogopite diopside sanidine lamproites from the afyon volcanic province turkey middle miocene volcanic activity in the afyon volcanic province eastern part of western anatolia is characterized by multistage potassic and ultrapotassic alkaline volcanic successions the volcanism is generally related to the northward subduction of the african plate beneath the eurasian plate in afyon the middle miocene volcanic products consist of melilite leucitite tephriphonolite trachyte basaltic trachyandesite phonolite phonotephrite tephriphonolite and lamproite rocks near surface emplacement and relatively quiescent subaerial eruptions of lamproitic magma produced different emplacement forms such as dome plug shaped bodies and lava flows showing variation in volume and texture the mineralogical constituents of the lamproites are sanidine olivine 77 mg no 81 phlogopite 74 mg no 78 k richterite clinopyroxene 74 mg no 78 with accessory apatite calcite and opaque minerals afyon lamproites resemble mediterranean type si rich lamproites their compositional range is 50 52 wt sio2 4 8 wt mgo and they display a typical lamproitic affinity chondrite normalized ree patterns exhibit enrichment in lree relative to hree la yb cn 15 3 17 0 they show extreme enrichment in lile relative to primitive mantle values and troughs of nb and ti the lamproites give a range of high initial 87sr 86sr ratios and low 143nd 144nd ratios the geochemical and isotopic characteristics suggest that lamproitic magma is derived from highly metasomatized mantle the enrichment history may include metasomatic events related to subduction as in other active orogenic areas of the mediterranean

melting and dynamic metasomatism of mixed harzburgite glimmerite mantle source implications for the genesis of orogenic potassic magmas abstract tectonically young orogenic settings are commonly the sites of post collisional silica rich ultrapotassic magmas with extreme k2o contents of up to 9 wt and k2o na2o 2 many experimental studies investigating the generation of these melts have concentrated on melting of homogenous phlogopite bearing peridotites whereas geochemical signatures indicate the involvement of at least two types of source rocks ultra depleted and k and trace elements enriched ones we report the results of melting experiments at 1 2 gpa of mixed glimmerite and harzburgite in which these rock types make up two halves each capsule melting begins in the glimmerite and its metasomatic effects on the harzburgite are apparent at 1100 c even before melt pools are visible the first melts are na rich seen in zoning of olivines and as growth of clinopyroxene in the harzburgite but change at higher degrees of melting to produce a typical lamproite like melt with k2o 10 wt a major advantage of this study is the preservation of distinct melts in different parts of the capsule which reflect a process of dynamic metasomatism within the harzburgite matrix the infiltrating melt derived from melting of the glimmerite changes consistently with the distance of travel through the harzburgite enabling quantification of the metasomatic effects as an increase in sio2 and k2o this results principally from assimilation of orthopyroxene which increases the ol opx ratio of the residual harzburgite the effects of quench olivine growth are recognizable and can be quantified due to a step change in composition at the glimmerite harzburgite border the large total surface area of olivine and small melt fraction mean that the amount of quench olivine is high within the harzburgite but negligible in the almost completely molten glimmerite melts of the glimmerite contain up to 8 10 wt k2o and 53 wt sio2 which increase to 55 56 wt after interaction with the harzburgite mediterranean lamproites resemble melts of glimmerite whereas melts that have interacted with harzburgite are more similar to less potassic but more sio2 rich shoshonites of the mediterranean region

tsunami impact computed from offshore modeling and coastal amplification laws insights from the 2004 indian ocean tsunami the 2004 indian ocean tsunami gave the opportunity to gather unprecedented tsunami observation databases for various coastlines we present here an analysis of such databases gathered for 3 coastlines among the most impacted in 2004 in the intermediate and far field thailand myanmar se india sri lanka and se madagascar non linear shallow water tsunami modeling performed on a single 4 coarse bathymetric grid is compared to these observations in order to check to which extent a simple approach based on the usual energy conservation laws either green s or synolakis laws can explain the data the idea is to fit tsunami data with numerical modeling carried out without any refined coastal bathymetry topography to this end several parameters are discussed namely the bathymetric depth to which model results must be extrapolated using the green s law or the mean bathymetric slope to consider near the studied coast when using the synolakis law using extrapolation depths from 1 to 10 m generally allows a good fit however a 0 1 m is required for some others especially in the far field madagascar possibly due to enhanced numerical dispersion such a method also allows describing the tsunami impact variability along a given coastline then using a series of scenarios we propose a preliminary statistical assessment of tsunami impact for a given earthquake magnitude along the indonesian subduction conversely the sources mostly contributing to a specific hazard can also be mapped onto the sources providing a first order definition of which sources are threatening the 3 studied coastlines

the mlindi ring structure an example of an ultrapotassic pyroxenite to syenite differentiated complex the mlindi ring complex in southern malawi dated at 495 ma is intrusive in the proterozoic migmatite basement composed mainly of hornblende and biotite bearing paragneiss and dolomitic marble three main lithologic facies have been distinguished 1 syenite which crops out in the outer part of the complex as an oval shaped ring dike 7 km 9 km and as a rim of massive bodies cutting the mafic rocks of the central part 2 two types of diopside biotite gabbro syenogabbro and gabbronorite and 3 a banded phlogopite pyroxenite cumulate intruded by the diopside biotite gabbro

comment on onset timing of left lateral movement along the ailao shan red river shear zone 40ar 39ar dating constraint from the nam dinh area northeastern vietnam by wang et al 2000 journal of asian earth sciences 18 281 292

geochemistry and petrogenesis of lamproites late cretaceous age woodson county kansas u s a abstract lamproite sills and their associated sedimentary and contact metamorphic rocks from woodson county kansas have been analyzed for major elements selected trace elements and strontium isotopic composition these lamproites like lamproites elsewhere are alkalic molecular k 2 o na 2 o al 2 o 3 1 6 2 6 are ultrapotassic k 2 o na 2 o 9 6 150 are enriched in incompatible elements lree or light rare earth elements ba th hf ta sr rb and have moderate to high initial strontium isotopic compositions 0 7042 and 0 7102 the silica saturated magma olivine hypersthene normative of the silver city lamproite could have formed by about 2 percent melting of a phlogopite garnet lherzolite under high h 2 o co 2 ratios in which the iherzolite was enriched before melting in the incompatible elements by metasomatism the rose dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain significant fractional crystallization of phases that occur as phenocrysts diopside olivine k richterite and phlogopite in the silver city magma and that concentrate co cr and sc are precluded as the magma moved from the source toward the surface due to the high abundances of co cr and sc in the magma similar to that predicted by direct melting of the metasomatized iherzolite ba and to a lesser extent k and rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone the silver city lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected