the kinematics of movements along the insubric line and the emplacement of the ivrea zone schmid sm zingg a and handy m 1987 the kinematics of movements along the insubric line and the emplacement of the ivrea zone in h j zwart m martens i van der molen c w passchier c spiers and r l m vissers editors tectonic and structural processes on a macro meso and micro scale tecta a hys 135 47 66 the insubric line west of locamo is characterized by a 1 km thick greenschist facies mylonite belt east of locamo these mylonites are overprinted by a discrete brittle fault the mylonites are derived from basement units of the central alps sesia zone and the southern alps ivrea zone as well as from the permo mesozoic cover of the southern alps canavese sense of shear criteria indicate that the mylonites accomm ated backt s g followed by dextral strike slip motion mylonitization during backtbrusting was synchronous with backfolding of the central alpine nappes under higher metamorphic conditions a horizontal temperature gradient resulted from the rapid juxtaposition of the warm central alpine block against the cold southern alpine block mylonites formed during the later dextral strike slip event are related to large transcurrent displacements in the central alps deduced from regional kinematic considerations thus both mylo t ation events are contempor eous with deformation to the north and south of the insubric line insubric phase extensively modifying the pre insubric crustal configuration of the alps the insubric phase post dates the bergell intrusion 30 m y the emplacement of the geophysical ivrea body is a combined effect of vertical uplift due to e w directed crustal thinning during the early jurassic and underplating by continental crust associated with late cretaceous compression a deep crustal normal fault pogallo line subsequently rotated during tertiary alpine orogenesis separates deeper parts of the southern alpine crust ivrea zone from intermediate crustal levels strona ceneri zone the rigid ivrea body localir ed large strains within the insubric mylonite belt and is responsible for the present curvature of the insubric line in uetion

metamorphic field gradients in the central alps metamorphic field gradients were determined across the entire amphibolite grade central alps c 50 100 km p t were calculated from 116 samples acquired from our own field work from samples provided to us by others and from rocks with mineral compositions described in the literature only fluid conserved equilibria were used to determine p t the use of an internally consistent thermodynamic database and mineral solid solution models makes the results robust and reduces relative errors the results are presented in contour maps temperature increases from 500 to 550 c along the limit of amphibolite grade metamorphism in the north and west to c 675 c toward the south at the insubric line near the town of bellinzona maximum recorded pressures of c 7 kbar are in a central region c 20 km north of the insubric line and decrease both to the north 5 5 kbar and south 4 5 kbar the p t results indicate that there is a relatively large area that reached conditions in the sillimanite stability field but developed neither sillimanite nor fibrolite this is interpreted as a result of kinetic constraints on nucleation and growth because of the small amounts of thermal overstep 40 c of the kyanite sillimanite phase boundary comparison of p t conditions with carbonate isograds in the region indicate that fluids present during metamorphism were not dominated by a homogeneous external source examination of the two dimensional distribution of pressure and temperature in the context of thermal and tectonic models indicates that two thermal pulses aected the central alps during the tertiary in the second heat aected only the southern parts of the area and overprinted the previously established p t gradients

alpine and pre alpine magmatism in the root zone of the western central alps the highest grade of metamorphism and associated structural elements in orogenic belts may be inherited from earlier orogenic events we illustrate this point using magmatic and metamorphic rocks from the southern steep belt of the lepontine gneiss dome central alps the u pb zircon ages from an anatectic granite at verampio and migmatites at corcapolo and lavertezzo yield 280 290 ma i e hercynian ages these ages indicate that the highest grade of metamorphism in several crystalline nappes of the lepontine gneiss dome is pre alpine alpine metamorphism reached sufficiently high grade to reset the rb sr and k ar systematics of mica and amphibole but generally did not result in crustal melting except in the steep belt to the north of the insubric line where numerous 29 to 26 ma old pegmatites and aplites had intruded syn and post kinematically into gneisses of the ductile simplon shear zone the emplacement age of these pegmatites gives a minimum estimate for the age of the alpine metamorphic peak in the monte rosa nappe the u pb titanite ages of 33 to 31 ma from felsic porphyritic veins represent a minimum age estimate for alpine metamorphism in the sesia zone a porphyric vein emplaced at 448 5 ma u pb monazite demonstrates that there existed a consolidated caledonian basement in the sesia zone

shear zone patterns and strain distribution at the scale of a penninic nappe the suretta nappe eastern swiss alps abstract shear zone patterns within the suretta nappe of the swiss alps are studied in order to understand finite strain and bulk tectonic displacements the suretta nappe is chosen for two main reasons the availability of late variscan granites deformed during alpine tectonics only and because of continuous outcrop from bottom to top of the nappe this alpine nappe recorded two major ductile deformation phases which developed under low grade metamorphic conditions the analysis of shear zone patterns in the roffna granite reveals that the first deformation is well developed in the entire nappe the second deformation however is more localized in the lower and upper parts the bulk asymmetry of the shear zone patterns confirms the kinematics recorded by other penninic nappes in this area first a stacking of the nappe towards the nw followed by the top to the e shearing during post thickening extensional tectonics the shear zone patterns and strain distribution allow us to deduce kinematics at the nappe scale

grustal shortening in the alpine orogen results from deep seismic reflection profiling in the eastern swiss alps line nfp 20 east the deep crustal seismic line nfp 20 east crosses almost the entire swiss alps despite the complex geometry of the well exposed nappe structure and the considerable axial plunge of some of the units the vibroseis survey yielded coherent reflections from several individually identifiable nappe contacts in the northern part of the survey the vibroseis data closely match the internal structure of the helvetic nappes and the underlying autochthonous parautochthonous mesozoic sediments on the northern flank of the aar massif an external basement uplift these mesozoic sediments seem to rise from a depth of approximately 7 8 km below sea level to the surface in a series of steps which is interpreted to represent crustal shortening achieved by a combination of folding and thrusting in the southern part of the survey it was possible to image a number of thin slivers of mesozoic carbonates pinched between slabs of penninic basement nappes as well as nappe contacts between lithologically contrasting units in addition it seems that the insubric fault zone which marks the contact between the penninic zone and the southern alps and which outcrops about 30 km to the south of the survey shows up as steeply north dipping reflections the lower european crust in the northern part of the survey is relatively transparent as opposed to the adriatic lower crust whose reflective nature may stem from shear zones associated with mesozoic crustal stretching the base of both the european and adriatic crust coincides with a 1 s thick band of laterally discontinuous reflections this reflection moho drops to greater depths going from the north toward the center of the alpine chain where it disappears with a steep southerly dip the moho reappears as a reflection band farther south this moho gap is situated above the lithospheric root and may be caused by perturbations related to subduction of lower crustal material the crustal scale structure obtained from the vibroseis data may be interpreted as a continent continent collision with wedge shaped indentation of a piece of adriatic crust into the european crust and vertical escape of the material in the core of the orogen along steeply dipping faults

cooling and uplift patterns in the lepontine alps south central switzerland and an age of vertical movement on the insubric fault line 96 new fission track ft apatite and zircon k ar and rb sr biotite and muscovite ages are presented for 19 samples mainly acid gneisses from a 40 km traverse through the lepontine alps in the maggia valley south central switzerland plotting measured mineral ages against assumed system closure temperatures yields cooling rates for each sample the entire profile shows a fairly uniform late neogene recent mean uplift rate of 0 5 mm a confirmed by a gradient of ft apatite age with elevation cooling from higher temperatures occurred earlier in the south where uplift rates of 2 2 mm a in the steep belt root zone indicate 9 km early miocene uplift of the northern pennine block this uplift started before 23 ma and is interpreted as resulting from a major phase of backthrusting along the insubric line and as dating the formation of the mylonite belt estimated cooling rates constrain the timing of lepontine mid tertiary metamorphism 3 schematic models are proposed which also consider published rb sr k ar mica and hornblende and u pb monazite ages slow cooling differential initial heating and subsequent cooling of different parts of the central alps and post 38 ma cooling with syntectonic metamorphism at 27 ma are postulated as alternative interpretations of isotopic data and geologic evidence from extrapolation between k ar and rb sr mica ages and apatite ft ages 240 50 c is proposed as the closure temperature for the retention of fission tracks in zircon

an integrated approach for the prediction of subsidence for coal mining basins abstract in this study land subsidence caused by underground mining activities was investigated by means of a new subsidence prediction approach isp tech which takes into account the most important parameters contributing subsidence development such as coal production methods depth mining sequence and other geomechanical characteristics of underground rock strata etc isp tech can be applied to operating mines to keep land subsidence under control as well as virgin coal sites to predict surface subsidence prior to mining activities in the method geological information gathered from the geographic information system gis and the mining information system mis are utilised to obtain geological cross sections which are used in finite element models for mesh building then a number of two dimensional finite element modelling analyses are carried out to determine land subsidence occurring due to mining operations finally land subsidence predicted from modelling studies is compared to the gps and or differential interferometry synthetic aperture radar din sar measurements if incompatibility of the results is detected finite element meshes should be optimised and then reanalysed to obtain more compatible results in the study two different case studies were given as examples of the application of isp tech results of the case studies showed that isp tech can successfully be applied to complex mine subsidence problems the proposed approach gives more accurate results than those obtained from other classical subsidence prediction methods

alpine and pre alpine subduction events in polycyclic basements of the swiss alps coupling macrostructural and microstructural observation with metamorphic petrology of polymetamorphic mafic rocks occurring in basement rocks of the central alps clearly provides evidence that some part of this basement underwent at least two different and independent events of high pressure metamorphism the older eclogitic event occurred at middle to high temperature and must have been pre alpine because late variscan plutons crosscut the high pressure structures the younger event occurred at high pressure and low temperature conditions and is tertiary in age the separation of alpine from pre alpine eclogite facies events is discussed for several alpine nappes

the height of fractured water conducting zone in undermined rock strata the height of fractured water conducting zone is of significant importance for the safety of underground mining because of the conspicuous discrepancy of the height of fractured water conducting zone in bulianta coal mine as predicted by the traditional method with those observed in practice a systematic research has been carried out the study indicates that two aspects should be taken into account firstly the traditionally proposed empirical formula in prediction of the height of fractured zone was based on the conditions of single slice mining where the mining height was less than 3 m and the total slice mining height was limited within 15 m in such a case it would not be suitable to predict the maximum fractured zone height for the conditions where a single mining height is larger than 3 m secondly the stratum structure such as the thick and strong rock layer termed as key stratum plays an important role in controlling of the height of movement in the overburden physical model tests by making use of a similar material illustrate that if the vertical distance from the primary key stratum to the coal seam is shorter than a certain value then the developing fracture zone will extend above the key stratum into the top of bedrock resulting in a larger height of water conducting zone than is calculated by the empirical method the outcome of the work presented will be helpful in practice to prevent the overburden aquifer inrush and to avoid mine water hazard

combined high precision chronometry and geochemical tracing using accessory minerals applied to the central alpine bergell intrusion central europe abstract the behaviour of nd u th and pb isotopes in granitic rocks is usually controlled by accessory minerals in this study an approach is adopted which uses the initial 143 nd 144 nd as a geochemical tracer together with high precision u th pb geochronology for accessory phases and their respective whole rock this combination of techniques is applied to zircon allanite sphene apatite and thorite from both a tonalite and a granodiorite from the tertiary alpine bergell intrusion inherited isotopic signatures have been identified in bulk zircon fractions by inverse discordance in the u pb system in the case of the granodiorite the initial nd in the zircon is 1 77 units lower than the bulk rock this result indicates that nd isotopes in zircon may serve as a useful tool for tracing crustal precursors in silicic rocks all other accessories yield an initial nd equal to their respective whole rock and u th pb ages equal to or lower than the respective intrusion ages this indicates either the absence of inherited cores or that such cores have exchanged their nd and pb in the case of apatite also sr by diffusion where available experimental mineral melt equilibria and diffusion models are consistent with this behaviour u pb geochronology of carefully selected core free zircons yields a precise intrusion age of 31 88 0 09 ma for the tonalite in contrast granodioritic zircons are partially reset due to radiation damage caused by high u concentrations however an alternative means of dating young intrusions is to use 232th 208pb ages of allanite in the case of allanite the presence of a large excess of 206pb derived from 230th indicates that no total pb loss has occurred since crystallization and the nd isotopes indicate the absence of inheritance using both the allanite age and a 238u 206pb age for sphene an intrusion age of 30 13 0 17 ma is indicated for the granodiorite taken together with an allanite th pb age for the tonalite these results strongly support the high closure temperatures for the allanites studied here 700 800 c at high post magmatic cooling rates all other accessory mineral ages are reset to values similar to hornblende 39ar 40ar ages and reflect the effect of post magmatic cooling superimposed on post metamorphic cooling

a modeling and experimental study of light nonaqueous phase liquid lnapl accumulation in wells and lnapl recovery from wells a formulation is presented for numerical modeling of light nonaqueous phase liquid lnapl accumulation in observation wells and lnapl removal from recovery wells the formulation includes fluid gravity segregation changing water and lnapl levels in the well and the corresponding changes in fluid storage in the well bore the method was added to a three dimensional finite difference model for hysteretic multiphase flow the model predictions are compared to three dimensional pilot scale experiments of lnapl infiltration and recovery model predictions matched experimental results well demonstrating the validity of the model formulation model results indicated that soil layering and lack of mechanical equilibrium had a significant influence on lnapl thicknesses in wells thus empirical approaches based on assumptions of soil homogeneity and mechanical equilibrium would not have been appropriate for prediction of lnapl volume from toluene thicknesses measured in wells

a ternary solid solution model for omphacite and its application to geothermobarometry of eclogites from the middle adula nappe central alps switzerland a ternary solid solution model for omphacite with the end members jadeite naalsi2o6 diopside camgsi2o6 and hedenbergite cafesi2o6 was derived from experimental data from the literature the subregular solution model fitted by linear programming is best suited to omphacites with very little aegirine component in common eclogites applying this solution model to the calculation of equilibrium phase diagrams of eclogites from the adula nappe central alps switzerland results in large stability fields for common eclogite assemblages garnet omphacite quartz h2o kyanite within this field the compositions of garnet and omphacite show very little variation a precise determination of the peak pressure and temperature is not possible the occurrence of amphibole overgrowing the peak pressure assemblage in fresh eclogite suggests retrograde re equilibration still under eclogite facies conditions the computation of isopleths for garnet and pyroxene end members allows the estimation of the pressure and temperature conditions of this re equilibration event 19 21 kbar c 700 c

dehydration melting and water saturated melting of basaltic and andesitic greenstones and amphibolites at 1 3 and 6 9 kb

an experimental and numerical investigation on the deformation of overlying coal seams above double seam extraction for controlling coal mine methane emissions abstract this study investigates the deformation and the resultant pressure relief of highly gassy coal seams where a double seam mining operation takes place at lower depths at the wulan coal mine china in order to predict the depressurization effect in the overlying coal seams we simulate the extraction process by constructing a scaled model in the laboratory using similar rock materials analyses of experimental results concluded that due to the mining induced stress redistribution the pressure within target coal seams which were 109 m above the mined seams could be fully relieved to attain the statutory approval for gas drainage in addition to scaled model studies computational modeling studies were conducted using udec universal distinct element code which showed that the features of deformation resulting from the double seam extraction were different from that of in the case of single seam extraction the results of the numerical studies revealed that in addition to the panel margin on the air return side areas near the intake entry could also be considered as borehole drilling positions besides it was found that the gob of the extracted seams below the gassy one provided a buffering effect for the would mined protective coal seam and that the depressurization effect was largely weakened the laboratorial findings are instructive to the field practice of methane drainage during the mining operation a displacement comparison method was adopted to measure the dilated amount of protected coal seams and as expected the maximum dilation percentage was much more than 0 2 the critical value upon which the target coal seam is appropriately depressurized to allow gas drainage to be safely and effectively implemented

physical modelling of subsidence from sequential extraction of partially overlapping longwall panels and study of substrata movement characteristics field examples of subsidence from sequential extraction of overlapping coal longwall panels have shown that complex and unexpected subsidence effects can occur physical models comprising sand and plaster obeying relevant similarity rules were used to investigate the subsidence mechanisms displacements within the models were measured using a combination of optical transducers photogrammetry and laser scanning the observed results were compared with finite element models the models demonstrate that the incremental subsidence and substrata movement profiles after lower seam extraction can be separated into three different zones these zones undergo different horizontal and vertical movement characteristics the zone of overlap of the two longwall panels undergoes greater total subsidence compared to a single seam of equivalent thickness the limit angle of the subsidence also differs at the two ends of the lower extraction as a result of the effects of the previously mined out area above

characterising the multi seam subsidence due to varying mining configuration insights from physical modelling abstract multi seam mining induced subsidence profile is observed to be different from that of single seam mining understanding the characteristics of multi seam subsidence is the first step in achieving reliable subsidence predictions characteristics of multi seam subsidence are investigated by means of several sand plaster physical models geological and site specific parameters are kept constant in all the models in order to compare the multi seam subsidence parameters for different mining configurations based on observations from the physical models it is concluded that the panel configurations of the two seams have significant impact on the multi seam subsidence development based on the relative location of the panels the multi seam mine area can be divided into different zones to which suitable subsidence characteristics can be assigned dividing the mine area into different zones enables characterisation of the strata movement and multi seam subsidence for various multi seam configurations the proposed characterisation of the multi seam subsidence can also be utilised in subsidence prediction methods in order to achieve reliable prediction results

basement cover relationships in the tambo nappe central alps switzerland geometry structure and kinematics in the pennine zone of the central alps the tambo nappe forms a thin crystalline sliver embedded in the mesozoic cover four tertiary alpine deformations are observed the d1 ductile deformation is linked to the progressive eocene stacking of the nappes towards the northwest during d1 basement deformation is governed by imbricate tectonics whereas cover is thin skinned and intensively folded these different structures reflect the original strong rheological contrast between basement and cover during the heterogeneous and ductile d2 deformation the behaviour of the basement and cover became similar the strong vertical d2 shortening associated with a top to the east shear led to the folding of the prior se dipping structures developing se vergent folds with axes close to the e w l2 stretching lineation d2 corresponds to post collisional crustal thinning following d2 crustal thickening the d3 and d4 deformations occurred under retrograde conditions and can be correlated with uplift and late dextral movement on the insubric line respectively

the tectonometamorphic history of the peridotitic chiavenna unit from mesozoic to tertiary tectonics a restoration controlled by melt polarity indicators eastern swiss alps abstract occurrences of mantle and lower crustal rocks are often preserved in mountain ranges when they occur in the internal part of collision belts their initial geometry and palaeogeography are sources of debate the mafic ultramafic chiavenna unit is one example in the pennine units located in the eastern swiss alps because of strong deformation and metamorphism during tertiary collision tectonics the pre collision geometry of this unit can only be restored using a qualitative geometrical analysis of the successive ductile deformation phases d1 d4 in situ melting and melt migration during the main alpine deformation phase d2 is a way up indicator and is of special importance to this restoration the restored prealpine geometry of the chiavenna unit indicates that a sub continental mantle close to a thinned continental margin becomes denuded during the mesozoic extension and subsequently covered by carbonate sediments taking into account the position of the chiavenna unit in the nappe pile and its pt path a northern brianconnais situation during mesozoic time becomes most probable

the metamorphic evolution of garnet cordierite sillimanite gneisses of the gruf complex eastern pennine alps metapelitic gneisses occuring as lenses and bands within the migmatites of the gruf complex in the eastern pennine alps contain various combinations of the minerals quartz biotite cordierite garnet sillimanite plagioclase k feldspar spinel orthopyroxene anthophyllite and muscovite the most common rock type is represented by a darkschistosebiotiterichcordierite garnet sillimanite gneiss a consistent pressure temperature range of 3 4 kb and 600 650 c has been calculated for the last metamorphic equilibration from six geological thermobarometers

partial melting of two amphibolites contrasting experimental results under fluid absent conditions a large portion of the lower continental crust may be amphibolitic in composition and without a free fluid phase as a consequence h2o undersaturated or fluid absent melting of amphibolites may be responsible for the formation of some granites and migmatites produced during major orogenic events in an attempt to determine the systematics of melting under fluid absent conditions a series of piston cylinder experiments was conducted on two natural amphibolites one a meta alkali basalt aba with a total water content of wt contained in hornblende and the other a meta island arc tholeiite iat which has 1 1 3 wt water contained in hornblende cummingtonite and biotite the experimentally determined melting ranges of the two amphibolites showed that the solidus temperatures and sta temperature interval over which amphibole was stable were controlled by the amphibolites different bulk compositions and their resulting metamorphic assemblages the volume of melt produced by melting of the two amphibolites were compared with estimated amounts based on burnham s 1979 water melt solubility model and the fluid absent melting model presented by clemens and vielzeuf 1987 the observed melt volumes were greater than estimated as the water content of melt largely detemines the volume of melt produced independent measurements of the water content of the glass formed during partial melting in the aba were made by thermogravimetric analyses the water content of the aba glass is 2 wt which is less than the assumed melt water content water content of the melt used in previous modeling of fluidabsent anatexis in mafic lithologies as a consequence more melt can be expected during fluid absent partial melting of mafic lower crust as is observed in the experiments a modification of the clemens and vielzeuf 1987 fluid absent melting model for mafic compositions has been made using the experimental data available on melting in basaltic systems and is presented here for pressures of 5 8 and 10 kbar tectonic scenarios in which the crust is thickened i e by collision then undergoes extension or where a previously thinned crust is later rethickened provide enough heat so that amphibolite melting under fluid absent conditions can become importan and hence responsible for some melts produced during post collisional magmatism the results may also have applications to melting in hydrated oceanic crust in subduction zones and in island arc terains

symmagmatic folding of the base of the bergell pluton central alps abstract evidence for magmatic submagmatic and solid state deformation in tonalite granodiorite and country rocks found at the deep seated floor 22 26 km of the bergell pluton demonstrates that final emplacement and crystallization occurred during regional deformation of the pluton and the underlying country rocks after northward emplacement over the country rocks but before complete crystallization the floor of the pluton was folded during simultaneous n s shortening and e w stretching this is evidenced by synmagmatic folds with e w striking nearly vertical axial planes and by regional east plunging stretching lineations in the country rocks which are parallel to the regional scale fold axes and the magmatic mineral lineations in the pluton opposite senses of shear from the well foliated occasionally mylonitic contact suggest that deformation was mostly accomplished by pure shear synmagmatic deformation is related to late stage n s shortening of the alpine orogen and shows that the still partially molten pluton responded to low differential stress very much like the country rocks deformed in the solid state at high temperatures post emplacement tilting associated with backthrusting along the insubric mylonites led to the exposure of the pluton s floor at its present day western margin

dislocation creep of dry quartz small scale shear zones within the permian truzzo meta granite developed during the alpine orogeny at amphibolite facies conditions in these shear zones magmatic quartz deformed by dislocation creep and recrystallized dynamically by grain boundary migration with minor subgrain rotation recrystallization to a grain size of around 250 750 m consistent with flow at low differential stresses fourier transform infrared ftir spectroscopy reveals very low water contents in the interior of recrystallized grains in the form of discrete oh peaks 20 h 10 6 si and very little broad band absorption 100 h 10 6 si the spectral characteristics are comparable to those of dry brazil quartz in ftir spectra magmatic quartz grains show a broad absorption band related with high water concentrations only in those areas where fluid inclusions are present while other areas are dry drainage of fluid inclusions and synkinematic growth of hydrous minerals indicates that a hydrous fluid has been available during deformation loss of intragranular water during grain boundary migration recrystallization did not result in a microstructure indicative of hardening these ftir measurements provide the first evidence that quartz with extremely low intragranular water contents can deform in nature by dislocation creep at low differential stresses low intragranular water contents in naturally deformed quartz may not be necessarily indicative of a high strength and the results are contrary to implications taken from deformation experiments where very high water contents are required to allow dislocation creep in quartz it is suggested that dislocation creep of quartz in the truzzo meta granite is possible to occur at low differential stresses because sufficient amounts of intergranular water ensure a high recovery rate by grain boundary migration while the absence of significant amounts of intragranular water is not crucial at natural conditions

observations from the floor of a granitoid pluton inferences on the driving force of final emplacement an east west profile across the tilted bergell pluton exposes a 10 km thick interval in terms of crustal depth consequently the floor as well as the root and side of the main intrusive body of the pluton crop out at the surface and a tentative three dimensional geometry is constructed at the highest crustal level the geometry and deformation features at the margin of the pluton indicate ballooning whereas the folded floor of the main intrusive body indicates synmagmatic shortening related to regional deformation these contrasting features are best explained by shortening of the base of the pluton which caused an expansion at a higher crustal level final emplacement of the pluton into higher crustal levels was therefore not driven primarily by buoyancy but rather by regional deformation within deeper levels of the crust

syn migmatization way up criteria abstract most geopetal way up structures are developed during primary formation or soon after in sedimentary or igneous rocks in migmatite terrains the possibly anomalous behaviour of rocks in which melt is present has often limited structural synthesis geopetal relationships may however be recognizable in at least some migmatites asymmetries in two structural relationships cauliflower structure and vein cluster involving neosome veins conformable with the main foliation of layered migmatites are interpreted as indicating the way up of these rocks when they were partially molten additional examples recognized in the literature suggest that similar structures can be seen in a wide range of geological environments these prove to be as reliable as sedimentary top and bottom features and suggest that the migmatites containing them were essentially sub horizontal while being strained and melted