An investigation was made into the factors governing plant distribution in two areas containing lead-zinc and in one case, copper, mineralisation in Northern Australia. The distribution of the major units within the savanna vegetation of the study-areas appears to be largely controlled by edaphic and drainage factors. Distinct plant assemblages are developed over the oredeposits. Although the assemblages are restricted to these environments, the individual species also occur in regions apparently devoid of mineralisation. In the area containing both lead-zinc and copper deposits, the same assemblage occurs on both types of mineralisation. The assemblage species are apparently better adapted to withstand higher concentrations of ore-metal in the substrate, and to absorb greater quantities of these metals, than the more widespread plants. Zinc, copper and lead occur in decreasing order of abundance in plants from un-mineralised localities. Plants growing over the ore-deposits can absorb large quantities of all three metals, but the distribution of metal within the aerial parts varies. In some species, an increased rate of absorption of lead and copper occurs when the plants are growing on soils rich in these metals compared with their rate of absorption elsewhere. This may be related to intra-specific variations within the plants.

Titanite is a calcium titanium silicate accessory mineral that serves as a sink for trace elements, especially the rare-earth elements and the high-field strength elements (Cerny and Rivadisa.L 1972; Groat, Carter et al. 1985; Enami, Suzuki et al. 1993; Perseil and Smith 1995; Della Ventura, Bellatreccia et al. 1999; Piccoli, Candela et al. 2000). It is also characterised by very sluggish diffusion of these elements, and as such it has the ability to resist most sub-solidus alteration. These characteristics make titanite a prime candidate for the ability to preserve a record of the petrogenetic processes which formed the igneous rocks in which it is found. In order to assess titanite’s ability to serve as a petrogenetic tool, a textural and geochemical study of titanite from different igneous environments was undertaken. The Ross of Mull Granite is an igneous complex located on the south west coast of the Isle of Mull, Scotland. It is a Caledonian age pluton that displays evidence of magma-mixing processes at depth and also contains notable amounts of titanite. Samples of different host granite and diorite enclave lithologies and relationships were documented and collected in order to asses the ability of titanite to retain evidence of magma-mixing processes within its compositional zoning. Titanite from the Ross of Mull Granite displays a large variety of textural features, both with respect to crystal shape and compositional zoning. The variation of the trace elements observed in titanite is a direct reflection of the compositional zoning pattern. Melts that are enriched in particular trace elements pass on that signature to the titanites. If melts of significantly contrasting chemistries mix or mingle, then titanite may record any significant instance of trace element diffusion between the melts. More importantly, there doesn’t need to be a transfer of trace elements between mingling/mixing melts for titanite to record evidence of the interaction. If the melts are of significantly different oxygen fugacities, then titanite may become destabilised and partially dissolve. This dissolution may only be temporary, but it may be difficult to tell if it was a product of increasing heat of the melt of if it was due to a change in oxygen fugacity. Titanite however, may record evidence of the cause of dissolution based on the nature of re-growth. As shown by some of the titanites within the Ross of Mull Granite, re-growth following a period of dissolution may be attributed to a change in oxygen fugacity if the new titanite growth is characterised by unusually low REE content. This is related to the nature of trace element incorporation in the titanite structure; REE are taken up due to coupled substitution mechanisms involving tetravalant Al and Fe. If a melt becomes reduced then the activity of ferric Fe will also be reduced, thus inhibiting the ability of titanite to take up REE by affecting the activity of the coupled substitution (Wones 1989; Piccoli, Candela et al. 2000). Titanite from the ROMG is largely characterised by compositional zoning that reflects the trace element chemistry of one of the end-member lithologies (host granite or dioritic enclaves), or has compositional zoning that reflects the changing conditions of the magmatic environment, namely: changes in melt composition, changes in temperature and pressure and changes in oxidation of the magma. In the case of the ROMG, all of these changes were wholly, or in part, brought about by magma mixing processes. Another way in which titanite reflects processes of petrogenesis is that it has been found to reflect the degree of homogenisation of the melt from which it has crystallised. To further asses the ability of titanite serve as a petrogenetic tool, a study was made of the characteristics of titanite from the volcanic environment. The Fish Canyon Tuff, from the San Juan volcanic field, Colorado, USA, was chosen as a suitable candidate for study due to its well documented nature; it is the largest known pyroclastic eruption to be documented. The Fish Canyon tuff also contains numerous phenocrysts of titanite. Eruption of the Fish Canyon Tuff is thought to have been brought about by the thermal rejuvenation of a batholith-sized magma chamber which had previously cooled to a rigid crystal mush (Bachmann and Bergantz 2003). The main conclusion from the study of titanites from the Fish Canyon Tuff and is that evidence for the thermal rejuvenation of the magma chamber by a mafic melt prior to eruption is preserved in the textural and chemical signature preserved in the compositional zoning of the titanites as dissolution and re-growth textures. This study illustrates that titanite is able to not only preserve evidence of magma mixing processes occurring at depth, but it is also able to preserve evidence of similar processes all the way through to the volcanic environment.

The origin of the southern Midland Valley Old Red Sandstone Conglomerates is reviewed with the specific aim of determining the nature and location of the source for the Old Red Sandstone Greywacke Conglomerate. The Silurian Midland Valley has been viewed as either i) a fore-arc basin with a rising trench-slope basin to the south (Leggett, 1980, Legget et al. 1983) or ii) an inter-arc basin with an arc in the Midland Valley and south in the location of the present day Southern Uplands (Bluck, 1983). The deposition of the Greywacke Conglomerate would thus record either the: i) culmination of a rising fore-arc and accretionary prism (Leeder et al. 1983), ii) time of emplacement between the northern section of the Southern Uplands and the Midland Valley (Thirlwall, 1988), or iii) age of the emplacement of the Southern Uplands over a missing fore-arc along a northward thrust, (Bluck, 1983). All of these models are dependent on the drainage basin for the Midland Valley within the present day Southern Uplands during Old Red Sandstone times. A re-appraisal of the sedimentology of the Greywacke Conglomerate has shown the sequence is characterised by vertically stacked small (2km) proximal alluvial fan sediments deposited in a series of separate N-S trending basins, each with one dominant fault controlled margin towards the east. The geometry and sedimentation pattern of these basins suggest the Southern Uplands Fault could not have controlled deposition of the Greywacke Conglomerate. The petrography and geochemistry of the greywacke clasts cannot be easily matched with a source in the Southern Uplands. The Southern Uplands sediments are characterised by petrographic consistency along strike. In contrast, there is a change in clast composition from the SW to the NE in the Midland Valley clasts, i.e. in the same general trend as the strike of the Southern Uplands. The evidence indicates that the source for the Greywacke Conglomerate was a basement cover of greywacke within the Midland Valley. This source may have been accreted to the Midland Valley during or prior to the obduction phase of the Ballantrae ophiolite. The source probably formed a series of highlands within the Midland Valley block since the Wenlock with major uplift of this source occuring in the uppermost Silurian-(?)Early Devonian.

The metabasites of the Arendal~Tvedestrand district were originally minor igneous intrusions, but are now characterised by wholly metamorphic mineral assemblages and textures, which are diagnostic of a prograde amphibolite-granulite facies transition. The main mineralogical changes with increasing grade of metamorphism (zone A to zone C) are decreases in modal hornblende and biotite, with increased pyroxenes. Major and trace element analyses for 176 metabasites are presented, and show the overall chemistry to be analogous to that of basaltic rocks. K and Rb vary systematically across the transition zone, declining in abundance with increased grade of metamorphism. In other respects, zones A and B are chemically homogeneous. Zone C (Tromloy) metabasites are characterised by low Ti02, K20, P205, H20, Zr, Ni, Sr, Ba, Rb, and high Na20, (MnO) , Zn, and oxidation ratios relative to the mainland suite. In part, these abundances are related to an original igneous fractionation in which a fairly strong iron-enrichment was accompanied by increased levels of Ti02, P205 and 'incompatible' elements, and decreases in transition trace elements. The relative absence of iron-rich differentiates in zone C accounts for the lower levels of P205 and Ti02 in this zone. Secondary fractionation accompanied the metamorphism, and resulted in K and Rb redistribution throughout the terrain and the Na20 enhancement in zone C. Ba, Sr and Zr appear to be depleted in this zone. These chemical changes are also noted in the acid- intermediate charn-ockitic suite of the transition zone, which is genetically distinct from the metabasites. 'Stable' element discrimination diagrams, ( when used with caution in view of these fractionation patterns) show the suite to be originally tholeiitic. Preliminary microprobe data support the concept of chemical equilibrium in the metabasites. Almandine-rich garnets are sporadically developed in the suite, and their growth is not directly related to the host-rock chemistry.

No description available.

The Matachewan Large Igneous Province (LIP) is interpreted to have formed during mantle plume-induced continental break-up during the early Proterozoic. When the Matachewan LIP is reconstructed to its original configuration, the dyke swarms,layered intrusions and flood basalt provinces emplaced over the lifetime of the province comprise one of the largest magmatic provinces recognised in the geological record. New geochemical data allow, for the first time, the Matachewan LIP to be treated as a single, coherent entity. The major and trace element data presented here show that Matachewan LIP suites share a common tholeiitic composition and trace element geochemistry characterised by enrichment in the most incompatible elements and depletion in the less incompatible elements. This signature, ubiquitous in early Proterozoic continental magmatic rocks, may indicate that the Matachewan LIP formed through contamination or mixing of its primary magmas with crustal material or that the early Proterozoic mantle had a fundamentally different composition to the modern mantle. Aside from the radiating geometry of the dyke swarms, a plume origin for the Matachewan LIP is implied by the geochemistry of some of the suites, used here to constrain the potential temperature of the magmatism. Comparison of these potential temperatures with the temperature of the early Proterozoic upper mantle, shows that the province is the product of anomalously hot magmatism as predicted by mantle plume theory. Geochemical data from coeval intrusions suggest that the plume head was compositionally heterogeneous and sampled material from both depleted and enriched mantle. Sr-Nd-Pb isotopic data show that this source heterogeneity dictates the Ni-Cu-PGE potential of the related intrusions. The enormity of the Matachewan LIP cannot be overstated and its potential impact on the early Proterozoic global environment was likely immense – it may even have been the trigger to the irreversible oxygenation of our planet.

No description available.

Upper Oligocene limestones up to c. 50 m thick form disconnected outcrops within a 20 km radius of Sciacca in southwest Sicily. Two facies are present: foraminiferal grainstone-packstones (dominatedby large benthonic foraminifera, particularly Lepidocyclines), and rhodolithic algal packstone-wackestones (in which eight species of coralline red algae are present). Petrology, fauna and flora indicate deposition in cool oxygenated waters of normal marine salinity at depths of 80-250 m in tropical subtropical latitudes; the two facies representing differences in local water depth and turbulence. Rare feldspars within the limestones are diagenetic, with a variable sodic oligoclase - calcic anorthoclase composition related to localised synchronous glauconitisation. The limestones rest disconformably on Cretaceous/Eocene carbonates, locally burrowed by Thalassinoid.es paradoxioa. A basal conglomerate contains both locally derived limestone cobbles and allochthonous phosphatised Eocene pebbles. All phosphate occurs as francolite re-placing limestone. Features of major, trace and Rare Earth elements clearly differentiate these phosphates from Lower Miocene phosphorites of both southeast Sicily and the Maltese islands, which have a very similar geochemistry. Lower Miocene limestones form similar outcrops generally to the north of the Upper Oligocene limestones and comprise a glauconitic limestone facies and a sandy limestone facies. Glauconite occurs as ubiquitous pellets, its geochemistry indicating formation by a gradational alteration of calcium carbonate. Petrology indicates deposition of the sediments in an outer shelf environment. Field relations of the two facies indicate that the Western Sicily Bridge (auot,) was a positive structural feature from basal Miocene times, acting as a barrier to the arenaceous Numidian Flysch facies derived from the west-southwest. Porosity of the Oligocene - Miocene limestones has been greatly reduced by compaction and by phases of both early submarine and latesubaerial diagenesis. Southward thrusting and associated folding post Lower Miocene times have slightly transported the sequences from their original (Saccense) carbonate platform and (Sicani) basin environments.

An imbricated Mesozoic to Palaeogene continental margin sequence is juxtaposed with ophiolitic rocks in the East Arm of Sulawesi, Indonesia. The two tectonic terranes are bounded by the Batui Thrust and Balantak Fault System, which are considered to be the surface expression of the collision zone between the Banggai-Sula Platform and the Eastern Sulawesi Ophiolite Belt. The collision complex contains three distinctive sedimentary sequences : 1) Triassic-Palaeogene continental margin sediments, ii) Cretaceous pelagic sediments and iii) Neogene coarse clastic sediments and volcanogenic turbidites. (i) Late Triassic Lemo Beds consisting largely of carbonate-slope deposits and subsidiary clastics including quartz-rich lithic sandstones and lensoidal pebbly mudstone and conglomeratic breccia. The hemipelagic limestones are rich in micro-fossils. Some beds of the limestone contain bivalves and ammonites, including Misolia, which typifies the Triassic-Jurassic sequence of eastern Indonesia. The Jurassic Kapali Beds are dominated by quartzose arenites containing significant amounts of plant remains and lumps of coal. The Late Jurassic sediments consist of neritic carbonate deposits (Nambo Beds and Sinsidik Beds) containing ammonites and belemnites, including Belemnopsis uhligi Stevens, of Late Jurassic age. The Jurassic sediments are overlain unconformably by Late Cretaceous Luok Beds which are predominantly calcilutite with chert nodules rich in microfossils. The Luok Beds are unconformably overlain by the Palaeogene Salodik Limestones which consist of carbonate platform sediments rich in both benthic and planktonic foraminifera of Eocene to Early Miocene age. These sediments were deposited on the continental margin of the Banggai-Sula Platform. (ii) Deep-sea sediments (Boba Beds) consist largely of chert and subsidiary calcilutite rich in radiolaria of Cretaceous age. These rocks are part of an ophiolite suite. (iii) Coarse clastic sediments (Kolo Beds and Biak Conglomerates) are typical post-orogenic clastic rocks deposited on top of the collision complex. They are composed of material derived from both the continental margin sequence and ophiolite suite. Volcanogenic Lonsuit Turbidites occur in the northern part of the East Arm in Poh Head and unconformably overlie the ophiolite suite. Late Miocene to Pliocene planktonic foraminifera occur in the intercalated marlstone and marly sandstone beds within these rocks. The collision zone is marked by the occurrence of Kolokolo Melange, which contain exotic fragments detached from both the ophiolite suite and the continental margin sequence and a matrix of calcareous mudstone and marlstone rich in planktonic foraminifera of late Middle Miocene to Pliocene age. The melange is believed to have been formed during and after the collision of the Banggai-Sula Platform with the Eastern Sulawesi Ophiolite Belt. Hence, the collision event took place in Middle Miocene time. The occurrence of at least three terraces of Quaternary coraline reefs on the south coast of the East Arm of Sulawesi testifies to the rapid uplift of the region. Seismic data suggest that the collision might still be in progress at the present time.

The Barmer Basin, western India, is a well-known and prospected petroleum system. However, the Lower Cretaceous Ghaggar-Hakra Formation has not been recognised as basin fill and not documented prior to this study. The formation outcrops in rotational fault blocks at the Sarnoo Hills and surrounding areas, on the eastern Barmer Basin margin. The thesis here describes and analyses the nature and evolution of the formation at both outcrop and within the subsurface, producing facies and depositional models. At outcrop, the deposits of the Ghaggar-Hakra Formation contain three dominant fluvial sandstone successions, known as the Darjaniyon-ki Dhani, Sarnoo and Nosar sandstones. The Darjaniyon-ki Dhani Sandstone is a gravel bedload dominated, low sinuosity fluvial system, the Sarnoo Sandstone represents a mixed-load, high sinuosity fluvial system and the Nosar Sandstone is highly erosive well-developed, bedload dominated, low sinuosity fluvial system. The intervening mudrocks represent floodplain deposits. The growth and development of the fluvial system between the Darjaniyon-ki Dhani and Sarnoo sandstones indicates that the climate and tectonics were stable at the time of deposition. However, the Nosar Sandstone represents rejuvenation of the fluvial system as it is suggested that this change in deposition style is due to the activation of the fault network forming the Barmer Basin and West Indian Rift System. The facies models derived from this work are applied to the subsurface to provide interpretations of the Cretaceous succession. This provides significant insights into the sedimentology, geometries of the sediment packages with the net to gross and the petrography, all indicating the reservoir quality of the Ghaggar-Hakra subsurface material.