U–Pb zircon and Rb–Sr whole-rock analyses from various gneisses and plutonie rocks of the Moldanubian and Moravo-Silesian zones and the stable foreland of the Hercynian (Variscan) orogenic belt indicate that most of the crust in Central Europe was first formed during the Cadomian orogeny which straddles the Precambrian–Cambrian boundary. Zircons, however, have a memory of older ages which correspond with those of events known in Fennoscandia. The new radiometrie data are consistent with the stratigraphie record in that they do not provide any evidence for a major early Palaeozoic tectonothermal event between the Cadomian and Hercynian orogenies.

Granulites from two localities in the Moldanubian zone yield U–Pb zircon ages of 345 ± 5 Ma; discordant zircon data points indicate that the granulite facies metamorphism was not of long duration. Tectonic units containing these high grade rocks were emplaced amongst amphibolite facies rocks during an event of widespread shearing which has been dated at 341 ± 4 Ma on the basis of a lower U–Pb zircon intercept age from one of the sheared gneisses and 338 ± 3 Ma U–Pb ages from monazites. Rb–Sr muscovite ages of 331 ± 5 Ma from pegmatites axial planar to asymmetrical folds date the last stage of SE-directed simple shear. A Rb–Sr whole-rock isochron of 331 ± 4 Ma from a principal magmatic type of the Central Bohemian pluton confirms the field evidence that the large NE-trending plutons of the Moldanubian zone were emplaced during a late stage of the deformation. The strong disturbance of the U–Pb zircon isotopic system in the sheared gneisses suggests U loss while a high U/Th ratio in monazite from one of these tectonised rocks suggests the simultaneous passage of hydrothermal fluids. Thus a crustal source is indicated for the uranium deposits of the Moldanubian zone.

Critical to any plate tectonic model for the development of the Middle European Hercynides was the existence of an ocean in Early Devonian times which separated a North European continent from a South European continent(s). The northward movement of the South European continent over a shallowly-dipping subduction zone and subsequent continental collision can explain the high T–low P metamorphism and the imbricated tectonic style of the Moldanubian zone and adjacent Moravo-Silesian zone along the southeastern Hercynian foreland. The temporal separation of granulites and granites implies distinct conditions of formation and it has been suggested that the plutonism, following on from the imbrication of the Cadomian crust, was initiated by the subduction of wet oceanic sediments.

Records of the low field magnetic susceptibility at three sites in the Chinese Loess Plateau, each with sediments covering the last 2·5 Ma, were averaged and combined into a single stacked file whose dating is independent of astronomic chronology. The stack reveals orbital frequencies, which are in general agreement with the astronomically tuned oxygen isotope deep sea chronology in the upper part of the Brunhes epoch, but disagree prior to 0·5 Ma ago.

This study attempts to ascertain whether the differing provenance sources and plate tectonic settings of deposition of clastic sediments and rocks can be identified by chemical means, thus opening the increased use of these rocks and their metamorphosed derivatives in plate tectonic modelling. Mineralogically immature feldspathic and mafic sands, muds, sandstones and shales from Mesozoic, Cenozoic and Holocene clastic deposits in California, Oregon, Alaska and Colorado have been both modally and chemically analysed providing a valuable data base (217 samples; 216 samples chemically analysed, many for 28 elements).

There is significant upward chemical variation in the Great Valley sequence of California which mimics previously described petrographic variation and in turn reflects provenance changes with igneous episodes and erosional stripping of the Sierra Nevada in late Mesozoic time. Differing sandstone petrofacies result in varying chemical signatures and while the provenances of monomict sediments are easiest to identify, polymict sources involving granitoid or ophiolitic material can often be identified by potassium feldspar or Cr contents. The distinction of K which is derived from detrital potassium feldspar from K derived from detrital illite, micas or other sheet minerals, is best made by a Niggli al–alk plot against k. Mafic sandstones derived from mafic volcanic or plutonic rocks preserve essentially mafic igneous chemistry and could be possible parent sources of some amphibolites which grade into metasediments. The lithified erosion products of the Sierra Nevada calc-alkaline igneous rocks have higher Niggli al–alk and higher average Niggli si at any given mg value than the fresh igneous rocks enabling meta-arkoses to be distinguished from meta-igneous rocks.

Applying previously published chemical criteria gives the actual plate tectonic setting of deposition of most of the sandstones studied. This suggests that the chemical composition of sandstones can yield much more information about the provenance and plate tectonic setting than hitherto recognised.

Grain size characteristics of the sediment and the flow stage characteristics of the river are the two most important factors influencing sedimentation in the channel zone. Climate is important in its influence on floodplain (overbank) sediment.

Supra-bar platform (upper) parts of mature bars from a wide range of climatic conditions consistently show a sequence in the development of contained sedimentary structures which is related to the flow stage. At high stage, in rivers where the bed materials are quite mobile, the bar form is not thought to be present: the form develops on the falling stage, and the bar is dissected on the lowest stage. The various bar forms have a related diagnostic structure which determined from the nature and distribution of the stratification types, and the manner of their deposition on the falling flow stage. The exposed (supra-platform) parts of lateral bars have a side and longitudinally filled inner channel which comprises fine sediment. Medial bars have converging cross-strata in sands which are overlain partly by gravels in an upward coarsening sequence.

Lateral migration of the channel zone, brought about by the preferential bar accretions to one side, results in building of a lithosome, the facies structure of which is partly determined by the nature of the bar accretions. As the channel migrates the abandoned bars may be covered with fine sediments so as to build up an upward fining sequence. The nature of the fine overbank part of the braided stream cycle is as complex as the coarse lower, so that a highly variable vertical sequence of lithological types is likely to be constructed.

Upward fining cycles are also built by some fine braided streams but they are the product of a single flood rather than lateral channel migration. Braided stream deposits are distinguishable from those of small, coarse meandering stream deposits by the presence of inner accretionary banks in the latter, and inner channels in the former.

There can be no reasonable doubt that a relation exists between the physiological action of a substance and its chemical composition and constitution, understanding by the latter term the mutual relations of the atoms in the substance. There are numerous indications of such a relation, and attempts have been made to express it formally in certain cases. Thus it has been long observed, that the salts of the same base have a common physiological action, and it has been pointed out by Mr Blake that, with some exceptions, the salts of isomorphous bases have a similar action. A corresponding likeness in physiological action may be traced in salts having the same acid, but beyond these generalisations we are not aware that any approach has been made to the statement of a law connecting the physiological action of a substance with its chemical constitution.

The ore-element associations of granite-related ore deposits in the eastern Australian Palaeozoic fold belts can be related to the inferred relative oxidation state, halogen content and degree of fractional crystallisation within the associated granite suites. Sn mineralisation is associated with both S- and I-type granites that are reduced and have undergone fractional crystallisation. Cu and Au are associated with magnetite- and/or sphene-bearing, oxidised, intermediate I-type suites. Mo is associated with similar granites that are more fractionated and oxidised. W is associated with a variety of granite types and shows little dependence on inferred magma redox state. The observed ore deposit-granite type distribution in eastern Australia, and the behaviour of ore elements during fractionation, is consistent with models of ore element sequestering by sulphides and Fe-Ti phases (e.g. pyrrhotite, ilmenite, sphene, magnetite) whose stability is nominally fO2-dependent. Fractional crystallisation acts to amplify this process through the progressive removal of compatible elements and the concentration of incompatible elements into decreasing melt volumes. The halogen content is also important. S-type granites are poorer in Cl than I-types. Cl decreases and F increases in both S- and I-type granites with fractional crystallisation. Low Cl contents combined with low magma fO2 in themselves seem to provide an adequate explanation for the rarity of Mo, Cu, Pb and Zn type mineralisation with S-type granites. Although such properties of granite suites seem adequately to predict the associated ore-element assemblage to be expected in associated mineral deposits, additional factors determine whether or not there is associated economic mineralisation.

The paradox of Lachlan Fold Belt (LFB) granitoids is that although contrasted chemical types (S- and I-types) imply melting of distinct crustal sources, the simple Nd–Sr–Pb–O isotopic arrays indicate a continuum, suggesting mixing of magmatic components. The paradox is resolved by the recognition that the previously inferred, isotopically primitive end-member is itself a crust-mantle mix, so that three general source components, mantle, lower crust and middle crust, comprise the granitoids. Based on Nd isotopic evidence, mantle-derived basaltic magmas melted and mixed with Neoproterozoic-Cambrian, arc-backarc-type material to produce primitive I-type, parental granitoid magmas in the lower–middle crust. Ordovician metasediment, locally underthrust to mid-crustal levels, was remobilised under the elevated geotherms and is most clearly recognised as diatexite in the Cooma complex, but it also exists as gneissic enclaves in S-type granites. The diatexite mixed with the hybrid I-type magmas to produce the parental S-type magmas. Unique parent magma compositions of individual granite suites reflect variations within any or all of the three major source components, or between the mixing proportions. For example, chemical tie-lines between Cooma diatexite and mafic I-type Jindabyne suite magma encompass almost all mafic S-type granites of the vast Bullenbalong supersuite, consistently in the proportion Jindabyne: Cooma, 30:70. The modelling shows that LFB S-type magmas are heavily contaminated I-type magmas, produced by large-scale mixing of hot I-type material with lower temperature diatexite in the middle crust. The model implies a genetic link between migmatite and pluton-scale, crustally derived (S-type) granites.

Given the chemical and isotopic contrasts of the crustally derived source components, and their typically unequal proportions in the magmas, it is not surprising that the LFB granitoids are so distinctive and have been categorised as S- and I-type. The sublinear chemical trends of the granitoid suites are considered to be secondary effects associated with crystal fractionation of unique parental magmas that were formed by three-component mixing. The model obviates the necessity for multiple underplating events and Proterozoic continental basement, in accordance with the observed tectonostratigraphy of the Lachlan Fold Belt.

The Peninsular Ranges Batholith of southern and Baja California is the largest segment of a Cretaceous magmatic arc that was once continuous from northern California to southern Baja California. In this batholith, the emplacement of igneous rocks took place during a single sequence of magmatic activity, unlike many of the other components of the Cordilleran batholiths which formed during successive separate magmatic episodes. Detailed radiometric dating has shown that it is a composite of two batholiths. A western batholith, which was more heterogeneous in composition, formed as a static magmatic arc between 140 and 105 Ma and was intrusive in part into related volcanic rocks. The eastern batholith formed as a laterally transgressing arc which moved away from those older rocks between 105 and 80 Ma, intruding metasedimentary rocks. Rocks of the batholith range from undersaturated gabbros through to felsic granites, but tonalite is the most abundant rock throughout. Perhaps better than elsewhere in the Cordillera, the batholith shows beautifully developed asymmetries in chemical and isotopic properties. The main gradients in chemical composition from W to E are found among the trace elements, with Ba, Sr, Nb and the light rare earth elements increasing by more than a factor of two, and P, Rb, Pb, Th, Zn and Ga showing smaller increases. Mg and the transition metals decrease strongly towards the E, with Sc, V and Cu falling to less than half of their value in the most westerly rocks. Oxygen becomes very systematically more enriched in18O from W to E and the Sr, Nd and Pb isotopic systems change progressively from mantle values in the W to a more evolved character on the eastern side of the batholith. In detail the petrogenesis of the Peninsular Ranges Batholith is not completely understood, but many general aspects of the origin are clear. The exposed rocks, particularly in the western batholith, closely resemble those of present day island arcs, although the most typical and average tonalitic composition is distinctly more felsic than the mean quartz diorite or mafic andesite composition of arcs. Chemical and isotopic properties of the western part of the batholith indicate that it formed as the root of a primitive island arc on oceanic lithosphere at a convergent plate margin. Further E, the plutonic rocks appear to have been derived by partial melting from deeper sources of broadly basaltic composition at subcrustal levels. The compositional systematics of the batholith do not reflect a simple mixing of various end-members but are a reflection of the differing character of the source regions laterally and vertically away from the pre-Cretaceous continental margin.

The chert of the Muir of Rhynie, containing plant-remains, was discovered by Dr W. Mackie of Elgin while investigating the sedimentary and volcanic rocks of Craigbeg and Ord Hill which occur in that area. The original discovery was made on loose specimens, built into the dykes or scattered over the fields, especially those lying to the north of the road which runs from Rhynie to Cabrach, and east and west of the right-of-way that here connects Windyfield Farm with the public road.

Garnetiferous peridotite masses which occur among gneisses in the Tafjord district of Norway are cold intrusions emplaced as crystalline rocks late in the metamorphic history of the region. No relationship other than similarity of mineral facies can be established between the peridotites and the eclogite bodies in the surrounding gneiss. Chemical analyses of twelve olivines, fourteen orthopyroxenes, nine chrome diopsides, nine garnets, three amphiboles and two rocks are presented, representing material from the Tafjord and Almklovdalen districts of Norway, a garnetiferous peridotite mass near Bellinzona, Switzerland, and the garnet-peridotite inclusions in the kimberlite pipes of South Africa. Optical and X-ray data for the analyzed and some unanalyzed assemblages are also presented. The mineral assemblages of these rocks are compared with each other, and with data from the peridotites of layered tholeiitic intrusions, alpine-type peridotites and the peridotite nodules in basalts. The garnet-peridotites of Norway, Switzerland and South Africa are believed to be little altered fragments of the mantle, whereas the peridotite nodules in basalts and the alpine-type peridotites are believed to be of igneous origin. Examination of the distribution of cations between the coexisting phases suggests that there are too many variables to permit a reliable interpretation of the results.

The orthopyroxenes from the garnetiferous peridotites are not rich in A1203, contrary to expectations based upon recent experimental work.

1. The mathematical work of the present paper has been performed to illustrate the hypothesis, that space is continuously occupied by an incompressible frictionless liquid acted on by no force, and that material phenomena of every kind depend solely on motions created in this liquid. But I take, in the first place, as subject of investigation, a finite mass of incompressible frictionless fluid completely enclosed in a rigid fixed boundary.

S-type granites have properties that are a result of their derivation from sedimentary source rocks. Slightly more than half of the granites exposed in the Lachlan Fold Belt of southeastern Australia are of this type. These S-type rocks occur in all environments ranging from an association with migmatites and high grade regional metamorphic rocks, through an occurrence as large batholiths, to those occurring as related volcanic rocks. The association with high grade metamorphic rocks is uncommon. Most of the S-type granites were derived from deeper parts of the crust and emplaced at higher levels; hence their study provides insights into the nature of that deeper crust. Only source rocks that contain enough of the granite-forming elements (Si, Al, Na and K) to provide substantial quantities of melt can produce magmas and there is therefore a fertile window in the composition of these sedimentary rocks corresponding to feldspathic greywacke, from which granite magmas may be formed.

In this paper, three contrasting S-type granite suites of the Lachlan Fold Belt are discussed. Firstly, the Cooma Granodiorite occurs within a regional metamorphic complex and is associated with migmatites. It has isotopic and chemical features matching those of the widespread Ordovician sediments that occur in the fold belt. Secondly, the S-type granites of the Bullenbalong Suite are found as voluminous contact-aureole and subvolcanic granites, with volcanic equivalents. These granites are all cordierite-bearing and have low Na2O, CaO and Sr, high Ni, strongly negative εNd and high 87Sr/86Sr, all indicative of S-type character. However, the values of these parameters are not as extreme as for the Cooma Granodiorite. Evidence is discussed to show that these granites were derived from a less mature, unexposed, deeper and older sedimentary source. Other hypotheses such as basalt mixing are discussed and can be ruled out. The Strathbogie Suite granites are more felsic but all are cordierite-bearing and have chemical and other features indicative of an immature sedimentary source. They are closely associated with cordierite-bearing volcanic rocks. The more felsic nature of the suite results in part from crystal fractionation. It is suggested that the magma may have entered this “crystal fractionation” stage of evolution because it was a slightly higher temperature magma produced from an even less mature sediment than the Bullenbalong Suite. The production of these S-type magmas is discussed in terms of vapour-absent melting of metagreywackes involving both muscovite and biotite. The production of a magma in this way is consistent with the low H2O contents and geological setting of S-type granites and volcanic rocks in the Lachlan Fold Belt.

Conventional rock classification diagrams do not distinguish the variety of peraluminous rock series. Moreover, peraluminous granite types have not been clearly discriminated in recent revisions. The study of several peraluminous series in different intracontinental orogenic belts reveals that four distinct groups can be defined. Using an A-B diagram, these four groups are: (1) highly peraluminous granitoids (hP) characterised by high A values and typified by an increase in peraluminosity toward the most mafic varieties; (2) moderately peraluminous granitoids (mP) which occupy the intermediate field and generally show increasing peraluminosity towards the most felsic varieties; (3) low peraluminous granitoids (IP) which plot in the lowest part of the peraluminous field defining negative slope trends; (4) highly felsic peraluminous granites (fP) with poorly defined variation trends.

In intracontinental orogenic belts, the genesis of peraluminous granitic series is favoured by the abundance of fertile crustal protoliths, mainly metapelites, metaigneous rocks and metagreywackes. The difficulty of attaining temperatures in excess of 950°C at lower crustal levels during the tectonothermal evolution of thickened crust, inhibits the partial melting of more basic sources. Although the physical parameters of the melting process influence their chemical and mineralogical characteristics, source rock composition ultimately determines the degree of peraluminosity of the granitic series.

Fossil assemblages can give quantitative estimates of palaeotemperatures, by comparison with modern biota, only in the recent geological past. Oxygen isotopic palaeotemperatures on calcareous or phosphatic fossils are potentially available for the whole Phanerozoic. Their reliability is limited by physiological effects (generally believed minor), preservation (for which criteria are available), and by uncertainty in the isotopic composition of ancient seawater. The latter is greatly affected by glaciation. In the Cenozoic, the relative contribution of ice-volume change and temperature change in producing isotopic variations can largely be resolved by analysing planktonic and benthic foraminifera in deep-sea cores. For earlier times only continental shelf deposits are available. In the Mesozoic, reasonable assumptions about ocean isotopic composition lead to palaeotemperature estimates that suggest generally higher temperatures than at present, particularly for mid- to high latitudes. This agrees with estimates based on biotic distributions. Late Palaeozoic glaciation is reflected in variable isotopic compositions in high palaeolatitude areas. In the earlier Palaeozoic, well-preserved fossils indicate either oceans enriched in 16O compared to today's or generally higher temperatures; controversy continues about the relative importance of the two effects.

Foraminiferal studies have been used in palaeo-environmental reconstructions of the marine Cretaceous succession (upper Aptian to Maastrichtian) of the Sergipe Basin, in northeastern Brazil. The foraminiferal assemblages show broadly three types of response to changes in environment: (1) variations in morphotypes of the taxa present; (2) changes in specific and generic diversity; and (3) changes in relative abundance.

Twelve palaeocommunities, characterised by the relative dominance of the major foraminiferal groups, can be recognised in the succession. Their palaeoenvironmental distribution is proposed as a model with reference to the Sergipe Cretaceous sequence.

An intimate relationship is inferred among foraminiferal association distribution patterns, trophic structures (community feeding strategy, dwelling habits, substrate niche patterns) and water-mass conditions (depth-related in part). It is suggested that the distribution patterns may be a direct response of the functional adaptive morphology of the foraminiferal tests to individual characteristics of behavioural structure (preferential dwelling microhabitat and trophic strategy versus environment). The approach is a simple, yet very powerful tool, for the interpretation of foraminiferal palaeocommunities and palaeoceanographic research. It may also permit interpretation of palaeocommunity strategies in terms of adaptation rate and selection response (i.e. “r-selection” versus “k-selection”) to variable environmental conditions.

Well preserved material of the crossopterygian fish Eusthenopteron enables fresh reconstructions and interpretations of its postcranial skeleton to be given. Comparisons throughout with other bony fishes show that it may be primitive in many features. Similarities with early amphibians such as the screw-shaped glenoid, the form of the humerus (on which an attempt to restore the pectoral musculature is based), the dorsal bicipital ribs and the possibility of a sacral attachment, throw much light on the origin of the tetrapod postcranial skeleton, particularly of the cheiropterygium. A functional analysis of the skeleton of Ensthenopteron is attempted, suggesting that it resembled the pike (Esox) in its mode of life and that it may have been capable of short journeys “walking” overland. The possible selective factors stimulating the evolution of such a fish, and further evolution to the tetrapod stage are discussed.

The object of the following communication is to describe a method by which every variety of visible colour may be exhibited to the eye in such a form as to admit of accurate comparison; to show how experiments so made may be registered numerically; and to deduce from these numerical results certain laws of vision.

The different tints are produced by means of a combination of discs of paper, painted with the pigments commonly used in the arts, and arranged round an axis, so that a sector of any required angular magnitude of each colour may be exposed. When this system of discs is set in rapid rotation, the sectors of the different colours become indistinguishable, and the whole appears of one uniform tint. The resultant tints of two different combinations of colours may be compared by using a second set of discs of a smaller size, and placing these over the centre of the first set, so as to leave the outer portion of the larger discs exposed. The resultant tint of the first combination will then appear in a ring round that of the second, and may be very carefully compared with it.

A global review of new and existing data on the distribution of uppermost Ordovician (Hirnantian) brachiopods indicates the existence of at least three biogeographically distinct faunas. The typical Hirnantia fauna characterised subtropical and temperate latitudes and comprised a variety of ecological associations; the fauna reached its acme during the bohemicus and uniformis zones. Atypical Hirnantia faunas, developed marginal to Gondwana, are of low diversity and have few species in common with the typical Hirnantia fauna; their spatial distribution probably marked the margin of the polar ice sheets. The extinction of the Hirnantia fauna occurred in response to changes in sea level. Diverse and quite different faunas, including those from the Midcontinent of North America, Kolyma, the Oslo Region and probably Anticosti Island, occupied equatorial latitudes during the latest Ordovician. The Holorhynchus fauna, on evidence to date, predates the Hirnantia fauna.

Since the classical work of Sir Thomas Holland at the beginning of this century on the charnockite series in Peninsular India there have appeared numerous papers describing rocks from all over the world which have been claimed to belong to this series. The rocks from the type area around Madras have now been re-examined, with particular reference to their chemistry and chemical mineralogy, to provide further evidence for their mode of origin.

Following petrographic descriptions, fifteen new analyses of these rocks are presented together with trace element determinations, and these are shown to produce smooth curves on a variation diagram. For several rocks all the constituent minerals have been analysed, and it has thus been possible to discuss the mineralogical location of the various major and trace elements in these rocks. Trace element determinations are presented for the 43 minerals analysed together with those for a further 35 minerals not chemically analysed, and their variation within the mineral species is discussed.

The possible modes of origin of these rocks are considered, and from the evidence obtained they are held to represent a plutonic igneous rock series which has undergone recrystallization in the solid state on being subjected to plutonic metamorphism.

The pursuit of a comprehensive theory for the origin and evolution of granitoids is hindered by our incomplete understanding of the nature of the source and the mechanisms by which the magma is segregated and transported. This paper is a collection of three largely independent and necessarily incomplete perspectives on these outstanding issues. Lower to mid-crustal regions, which contain the principal source material for granitoid magmas, are highly heterogeneous. Consideration of available transfer mechanisms suggests that (1) this heterogeneity survives all foreseeable lower crustal processes; (2) closure is on very different scales for different chemical systems (e.g. Pb, Nd, Sr and O isotopes); in almost all cases, however, closure scale is much smaller than the scale of magma extraction zones for plutons; and (3) pluton-wide homogenisation of magmas by diffusion is precluded by low diffusivities in felsic melts. Thus, granitoid magmas begin life as aggregates of small, isolated chemical domains; homogenisation occurs only through (and on the scale of) effective stirring by convection. Because of variability in local conditions as well as in bulk composition, crustal regions undergoing anatexis must be patchworks with variable melt fractions and melt compositions. The way in which magma is extracted from and coalesces with this patchwork exerts a critical influence on the nature of granitoid magmas. Decoupling and unusual coupling of compositional parameters and isotopic heterogeneity within plutons are to be expected in crust-derived granitoids and do not require contamination. Granites image their sources, but these sources are ill-defined and do not correspond to simple, easily-recognised materials. Extent and patterns of heterogeneity remaining in crystallised plutons may be effective indicators of the ascent process.

The efforts of materials scientists in characterising the nature and evolution of solid-phase interconnectivity in partially-molten materials may offer some insights into crustal magmatic processes. In particular, the rheological properties of partially-molten crustal rocks are probably strongly affected by the contiguity of the solid grains in the system (i.e. the fraction of their surface area that is shared with other grains). Theory and experimental data for simple alloy systems reveal that contiguity depends principally upon melt fraction and upon the characteristic wetting angle (θ) of the system. Measured θ's in granitoids (∼50° on average) imply contiguities as high as ∼0·2 for melt fractions of 0·5 or greater. This value in turn suggests that, at least under static conditions, a continuous skeleton of solid grains is maintained to quite high degrees of melting in the crust. Consequently, regions consisting of 50% or more of melt can, in principle, maintain not only high yield strength, but also high viscosity (provided the strain rate is sufficiently low to avoid disrupting contiguity).

Despite the fact that on some time scale the continuous solid skeleton of a partially-molten region resists deformation, it is itself subject to textural evolution that could lead to the upward migration of melt. Occasional detachment of grains from the skeleton and subsequent “microsettling” within the partially-molten column may lead eventually to compaction of the solid (without plastic deformation) and net upward displacement of melt.

Proposed granite transport mechanisms are discussed, although several are viewed as having historical interest only. In the absence of tectonic transport, diapirism appears to be the most compelling of these processes. However, considerable diversity exists in the literature regarding a pivotal requirement for this mechanism. Structural studies have tended to conclude that the granite diapir must be highly crystallised in order to ascend, whereas results of physical modelling yield contradictory results. For ascent to occur in these models, the magmas must be sufficiently fluid to allow convective circulation. Indeed, heat loss associated with diapirism is so efficient as to be a significant restriction on overall ascent. The resolution of these contrasting views appears to be that they reflect different phases of the ascent/emplacement continuum. Understanding the emplacement history of a southeastern Australian pluton allows assessment, via the diapir model, of the flow properties of the rock within the deformation aureole. Results suggest rock viscosities about an order of magnitude lower than those predicted by laboratory experiments, perhaps reflecting difficulties in reproducing natural conditions in the laboratory.