The Mariana Trough, a relatively simple intra-oceanic back-arc basin, is ideal for investigating magmatic processes and mantle- crust interaction in a subduction setting. We present new major- and trace element compositions for 31 basaltic lava and glass samples from the Mariana Trough back-arc spreading center. The studied lavas include phenocrysts of plagioclase, olivine and pyroxene. Major element compositions show that these lavas range from tholeiitic basalt to basaltic andesite, and belong to a sub- alkali tholeiitic series produced by fluid-influenced fractional crystallization of primary basaltic melts. Trace element composi- tions show that these lavas are transitional between typical normal mid-ocean ridge basalts (MORB) and island arc basalt (IAB), and are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs). Trace element ratios, e.g., Ba/Th, Pb/Ce, Th/Nd, La/Sm, Th/Nb, Ba/Nb and Th/Nb, indicate that the mantle from which these lavas were derived underwent modification resulting from the addition of multiple subduction components. Some typical trace element ratios (e.g., Ba/Nb- total subduction component, Ba/Th- shallow subduction, and Th/Nb-deep subduction component) from our new data and the literature suggest that a latitudinal variation exists in addition to subduction components, and indicates a more complex and heterogeneous distribution of subduction components in the Mariana back-arc region. We suggest that, (1) compared to back-arc locations at 18° N and 15.5° N, lavas from back-arc locations at 17° N indicate higher levels of modification by hydrous fluid released from the subducted slab, and (2) compared to back-arc locations at 17° N and 15.5° N, petrogenesis of lavas from back-arc locations at 18° N indicates a greater influence of sediment melt.

The Malay Peninsula is characterised by three north-south belts, the Western, Central, and Eastern belts based on distinct differences in stratigraphy, structure, magmatism, geophysical signatures and geological evolution. The Western Belt forms part of the Sibumasu Terrane, derived from the NW Australian Gondwana margin in the late Early Permian. The Central and Eastern Belts represent the Sukhothai Arc constructed in the Late Carboniferous-Early Permian on the margin of the Indochina Block (derived from the Gondwana margin in the Early Devonian). This arc was then separated from Indochina by back-arc spreading in the Permian. The Bentong-Raub suture zone forms the boundary between the Sibumasu Terrane (Western Belt) and Sukhothai Arc (Central and Eastern Belts) and preserves remnants of the Devonian-Permian main Palaeo-Tethys ocean basin destroyed by subduction beneath the Indochina Block/Sukhothai Arc, which produced the Permian-Triassic andesitic volcanism and I-Type granitoids observed in the Central and Eastern Belts of the Malay Peninsula. The collision between Sibumasu and the Sukhothai Arc began in Early Triassic times and was completed by the Late Triassic. Triassic cherts, turbidites and conglomerates of the Semanggol "Formation" were deposited in a fore-deep basin constructed on the leading edge of Sibumasu and the uplifted accretionary complex. Collisional crustal thickening, coupled with slab break off and rising hot asthenosphere produced the Main Range Late Triassic-earliest Jurassic S-Type granitoids that intrude the Western Belt and Bentong-Raub suture zone. The Sukhothai back-arc basin opened in the Early Permian and collapsed and closed in the Middle-Late Triassic. Marine sedimentation ceased in the Late Triassic in the Malay Peninsula due to tectonic and isostatic uplift, and Jurassic-Cretaceous continental red beds form a cover sequence. A significant Late Cretaceous tectono-thermal event affected the Peninsula with major faulting, granitoid intrusion and re-setting of palaeomagnetic signatures.

The chronostratigraphic framework of the Sydney, Gunnedah and Bowen basins using CA-IDTIMS geochronology is enhancing correlation of stratigraphic units and providing a better understanding of local and regional sedimentation patterns. Ages range from 271.45 Ma (Rowan Formation) to 247.71 Ma (Garie Formation). Two examples demonstrate these studies. Firstly, depositional rates in coal sequences are demonstrated. In the Ulan Coal (Sydney Basin), both the C Ply (256.05 Ma) and the F Ply (257.03 Ma) tuffs have been dated and are separated by about 5 m, giving a depositional rate of about 5.1 m/my. In the Yebna 1 well (Bowen Basin) tuff beds from the top and bottom of a coal interval of the Kaloola Member of the Bandanna Formation, separated by 8.9 m, were dated as 252.49 Ma and 252.97 Ma indicating a depositional rate of 18.6 m/my. The Trinkey Formation (Gunnedah Basin), with 2 thin coal beds, has a maximum thickness of 258 m. Tuff beds near the top and bottom have ages of 253.27 Ma (Blackville 1) and 255.57 Ma (Brawboy 1), a depositional rate of 255 m/my. Secondly, precise local and regional stratigraphic correlation can be demonstrated. Examples are the Awaba Tuff and the Nalleen Tuff; the Hoskinsons Formation of the Gunnedah Basin with the Ulan Coal of the Western Sydney Basin and the Woonona Coal Member of the Wilton Formation of the Southern Sydney Basin. A previously suggested correlation that we can demonstrate as incorrect is that of the Watermark Formation with the Nowra Sandstone.

Twenty-eight new high-precision Chemical Abrasion Isotope Dilution Thermal Ionisation Mass Spectrometry U-Pb zircon dates for tuffs in the Sydney and Bowen Basins are reported. Based on these new dates, the Guadalupian-Lopingian/Capitanian-Wuchiapingian boundary is tentatively placed at the level of the Thirroul Sandstone in the lower part of the Illawarra Coal Measures in the Sydney Basin. The Wuchiapingian-Changhsingian boundary is at or close to the Kembla Sandstone horizon in the Illawarra Coal Measures, southern Sydney Basin, in the middle part of the Newcastle Coal Measures in the northern Sydney Basin, and in the middle of the Black Alley Shale in the southern Bowen Basin. The end-Permian mass extinction is recognised at the base of the Coal Cliff Sandstone in the southern Sydney Basin, at the top of the Newcastle Coal Measures in the northern Sydney Basin, and close to the base of the Rewan Group in the Bowen Basin and is dated at c. 252.2 Ma. The end-Permian mass extinction is interpreted to be synchronous globally in both marine and terrestrial environments, and in high and low latitudes (resolution <0.5 my). The GSSP-defined Permian-Triassic boundary is interpreted to be approximately at the level of the Scarborough Sandstone in the lower Narrabeen Group, Sydney Basin, and in the lower Rewan Group, Bowen Basin. Newdates presented here suggest that the P3 and P4 glacial episodes in the Permian of eastern Australia are early Roadian to early Capitanian, and late Capitanian to mid Wuchiapingian in age respectively. The greenhouse crisis in the uppermost Pebbly Beach and Rowan Formations of the Sydney Basin is interpreted as early mid Roadian, a mid-Capitanian age for the crisis at the base of the Illawarra/Whittingham Coal Measures is confirmed. Greenhouse crises in the upper Illawarra/ Newcastle Coal Measures and lower Narrabeen Group of the Sydney Basin are dated as upper Changhsingian-Induan, and in the upper Narrabeen Group/lower Hawksbury Sandstone as upper Olenekian.

A Permo-Triassic volcanic arc system, the Sukhothai Arc, is recognised between the Indochina and Sibumasu continental blocks. The Chanthaburi terrane is here interpreted as a fault-detached, highly disrupted southern segment of the Sukhothai Arc, occupying part of southeastern Thailand and extending into Cambodia. The Klaeng tectonic line is defined as the boundary between the Chanthaburi terrane and Sibumasu block. The stratigraphy of the Chanthaburi terrane is compared with that of the Sukhothai terrane in Northern Thailand. The Late Palaeozoic-Mesozoic sequences of these two volcanic arc terranes in the Sukhothai Zone share important similarities, but show marked contrasts to those of the Sibumasu and Indochina blocks, where the Late Permian-Triassic is largely absent due to the Indosinian I unconformity (western Indochina) or is dominantly carbonates with little terrigenous clastic input (Sibumasu). There is no clear evidence of pre-Carboniferous sedimentary rocks for either the Sukhothai or Chanthaburi terranes. Late Permian lyttoniid brachiopod shale near Klaeng in the Chanthaburi terrane was revisited. The brachiopod, previously reported as 'Leptodus', is re-identified to 'Oldhamina', the genus previously known, elsewhere in Southeast Asia, only in the Huai Tak Formation of the Sukhothai terrane. 'Oldhamina' in Thailand is confined to the Sukhothai Arc. The marine stratigraphy of the Sukhothai Arc is represented by a Permian-Triassic lithological succession of mixed carbonates and siliciclastics, with common volcanic material. The Late Permian and Triassic litho- and biostratigraphy of the Chanthaburi terrane are comparable with the upper Ngao and Lampang groups of the Sukhothai terrane; in particular, they share similar successions from 'Oldhamina' brachiopod bearing shale to 'Palaeofusulina-Colaniella' foraminifer bearing limestone in the latest Permian. Marine depositional conditions were terminated on the Sukhothai Arc by end-Triassic times, later than on the Indochina block (Late Permian) but earlier than on the Sibumasu block (Jurassic/Cretaceous).

SE Asian continental crust comprises a heterogeneous collage of continental blocks, derived from the India-west Australian margin of eastern Gondwana, and subduction related volcanic arcs assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones containing ophiolites and accretionary complexes. The continental core, Sundaland, comprises a western Sibumasu block and an eastern Indochina-East Malaya block with an island arc terrane, the Sukhothai Island Arc System, sandwiched between. This island arc formed on the margin of Indochina-East Malaya, and then separated by back-arc spreading in the Permian. The Jinghong, Nan-Uttaradit and Sra Kaeo Sutures represent this closed back-arc basin. The Palaeo Tethys is represented to the west by the Changning-Menglian, Chiang Mai/Inthanon and Bentong-Raub Suture Zones. The Cathaysian West Sumatra and West Burma blocks, rifted and separated from Gondwana, along with Indochina and East Malaya in the Devonian and were accreted to the Sundaland core in the Triassic. South West Borneo and East Java-West Sulawesi are now identified as the missing Banda and "Argoland" blocks which must have separated from NW Australia in the Jurassic by opening of the Ceno-Tethys and accreted to SE Sundaland by subduction of the Meso-Tethys in the Cretaceous. Palaeogeographic reconstructions illustrating long-term subduction and terrane accretion orogenesis in SE Asia and adjacent regions are presented.

The Guadalupian-Lopingian-Boundary (GLB) is currently placed at ~260 Ma and defined by the first occurrence of the conodont species 'Clarkina postbitteri postbitteri'. Near the end of the Guadalupian stage, in the mid-Capitanian a major biotic crisis occurred, which affected both terrestrial and marine organisms. Globally this event is recognised by changes in C and Sr isotope signatures and sea-level regression. However, a detailed chronology of this major event is not fully established. We performed high-precision U-Pb geochronology on zircons from ash layers in eastern Australian basins to place the GLB and the extinction horizon in eastern Australia. Drill core and outcrop samples were collected from the Sydney and Gunnedah Basins. Zircons were analysed by chemical abrasion ID-TIMS, which has an age resolution at the sub-permil level. In the Sydney Basin the boundary interval occurs between the Broughton Formation (263.4 Ma) and the Fairford Formation (257.3 Ma). In the Gunnedah Basin the GLB is above the Watermark Formation (262.4 Ma) and below the Pamboola Formation (255.9 Ma). Further ongoing studies of additional ash layers in core and outcrop sections will hopefully allow us to better constrain the GLB in the eastern Australian basins.

The Early Triassic Induan-Olenekian Stage boundary (Dienerian-Smithian sub-stage boundary) has been identified at a depth of 2719.25 m in the petroleum exploration well Senecio-1 located in the northern Perth Basin, Western Australia. Conodont faunas represent three conodont zones in ascending order, the 'Neospathodus dieneri' Zone, the 'Neospathodus waageni eowaageni' Zone and the 'Neospathodus waageni waageni' Zone. The Induan-Olenekian (Dienerian-Smithian) boundary is placed at the base of the 'Neospathodus waageni eowaageni' Zone equivalent to the first appearance of 'Neospathodus ex. gr. waageni' utilised elsewhere and adopted by the IUGS ICS Triassic Subcommission to define the base of the Olenekian. Bulk kerogen δ13C carbon isotopes define a positive peak of c. 4 per mille that essentially coincides with the Induan-Olenekian boundary as seen in proposed Global Stratotype Sections and Points (GSSPs) in South China and Spiti, India demonstrating the global utility of this level for correlation. An anoxic zone is recognised in the lower part of the Senecio-1 core and the upper limit of this zone is dated as late Induan (late Dienerian). Temporal and spatial mapping of marine anoxia and dysoxia globally demonstrates that pulses of dysoxia/anoxia affected shallow-marine zones at different times in different locations. Dysoxia/anoxia in the shallow-marine environment appeared in the latest Permian at the extinction level, later than in the deep-marine environment, and appears to be largely restricted to the Induan (Griesbachian and Dienerian) and early Olenekian (Smithian). Temporally and geographically restricted upwelling of an oxygen minimum zone into the ocean surface layer due to environmental perturbations including extreme global warming, increased terrestrial chemical weathering intensity and continental erosion, sea level rise, and changes in marine nutrient inventories and productivity rates, is interpreted as a likely cause of observed variation in shallow-marine dysoxia/anoxia in the Early Triassic.

The Late Paleozoic Ice Age involved several pulses of glaciation from the early Carboniferous through mid-Permian in southern Gondwana. In eastern Australia, biostratigraphy suggested the final pulse to be c. 265 Ma. New U-Pb zircon ages from volcanic layers revise the age of latest glacigenic deposits to c. 255 Ma, making the late stage of the LPIA broadly synchronous with emplacement of the Emeishan large igneous province (ELIP) of China. Recent zircon U-Pb ages indicate rapid emplacement of the intrusive phase of the ELIP, from 260-257 Ma. New zircon U-Pb ages from volcanics overlying the youngest basalts indicate a short-lived effusive component, ending by 258 Ma. Emeishan volcanism has been linked with the end-Mid-Permian mass extinction, though radioisotopic ages from sedimentary units that record the extinction are limited. The ELIP is smaller than other magmatic provinces that have been associated with mass extinctions, though in terms of devolatilization reactions that can affect climate, volume is less significant than eruption rate and composition of the host rock. An important test of the impact of the ELIP on climate is the stable isotopic record of ocean sediments. Initial stable Ca isotope data from marine carbonates indicate the change in ocean chemistry in the Mid- to Late Permian was smaller than that associated with the end-Permian extinction, but suggest ocean anoxia. Efforts are ongoing to establish a robust chronology for the end-Mid-Permian extinction.

South-east Asia is a giant 'jigsaw puzzle' of allochthonous continental lithospheric blocks and fragments (terranes) and that are bounded by suture zones (remnants of Palaeo-Tethys, Meso-Tethys and Ceno-Tethys oceans and back-arc basins). 400 million years of geological evolution have resulted in major collisional orogenic belts, magmatic belts and volcanic arcs. Tectonic evolution in the region has produced significant oil and gas reserves and mineral deposits, and underpins major biogeographic divides (e.g. Wallace's Line), biodiversity and diversity hotspots in the region.