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• Southwest Madagascar is comprised of five tectonic domains. • These domains record c. 500 million years of accretionary tectonics prior to the formation of Gondwana. • Vohibory, Graphite and Androyen domains formed on the western side of the pre-Gondwana Mozambique Ocean. • Ikalamavony and Anosyen domains formed on the eastern side of the pre-Gondwana Mozambique Ocean. • Ediacaran-Cambrian orogenesis is common to all terranes and marks the collision and suturing of Gondwana. Southern and western Madagascar is comprised of five tectonic provinces that, from northeast to southwest, are defined by the: (i) Ikalamavony, (ii) Anosyen, (iii) Androyen, (iv) Graphite and (v) Vohibory Domains. The Ikalamavony, Graphite and Vohibory Domains all have intermediate and felsic igneous protoliths of tonalite-trondhjemite-granodiorite-granite composition, with positive εNd, and low Sr and Pb isotopic ratios. All three domains are interpreted to be the products of intra-oceanic island arc magmatism. The protoliths of the Ikalamavony and Graphite Domains formed repectively between c. 1080–980 Ma and 1000–920 Ma, whereas those of the Vohibory Domain are younger and date to between c. 670–630 Ma. Different post-formation geologic histories tie the Vohibory-Graphite and Ikalamavony Domains to opposite sides of the pre-Gondwana Mozambique Ocean. By contrast, the Androyen and Anosyen Domains record long crustal histories. Intermediate to felsic igneous protoliths in the Androyen Domain are of Palaeoproterozoic age (c. 2200–1800 Ma), of tonalite-trondhjemite-granodiorite-granite composition, and show negative εNd, moderate to high 87Sr/86Sr and variable Pb isotopic compositions. The felsic igneous protoliths of the Anosyen Domain are of granitic composition and, when compared to felsic gneisses of the Androyen Domain, show consistently lower Sr/Y and markedly higher Sr and Pb isotope ratios. Like the Vohibory and Graphite Domains, the Androyen Domain can be linked to the western side of the Mozambique Ocean, while the Anosyen Domain shares magmatic and detrital zircon commonalities with the Ikalamavony Domain. It is consequently linked to the opposing eastern side of this ocean. The first common event observed in all domains dates to c. 580–520 Ma and marks the closure of the Mozambique Ocean. The trace of this suture lies along the boundary between the Androyen and Anosyen Domains and is defined by the Beraketa high-strain zone. [ABSTRACT FROM AUTHOR]

Detrital zircon U-Pb age data collected from the argillitic sedimentary rocks of the Timorese Aileu Complex and Gondwana Sequence indicate that both units were derived from a common source containing 200–600 Ma, 900–1250 Ma and 1450–1900 Ma zircon. The modally most significant age population within this range of ages dates to c. 260 Ma. The observed spectrum of ages can be traced to the eastern active margin of Pangaea and its immediate foreland, which today is best exposed along the northeast coast of Australia. Compared to the relative homogeneity of the detrital zircon age data, geochemical and Nd isotopic data show that the mudstones of the Aileu Complex are on average more siliceous, have higher K 2 O/Na 2 O, Rb/Sr, Th/Sc and yield notably older Nd T DM model ages when compared to those from the Gondwana Sequence. These data are interpreted to suggest that, although both sequences share a common east Pangaea provenance, they were eroded from different sections of this active margin and deposited in spatially separated basins. The present proximity of these units is a result of their tectonic juxtaposition during the Pliocene to Recent collision between the northern edge of the Indo–Australia plate and the Banda Arc. [ABSTRACT FROM AUTHOR]

Highlights: [•] Similar detrital zircon spectra are present in most post-Archaean sedimentary rocks. [•] Regional cross-cutting relationships date these rocks to the Tonian and Cryogenian. [•] Intercalated volcanic rocks argue for a similar depositional age. [•] Described strata were deposited along the western margin of the Indo-Antarctic plate. [•] The tectonic domains of Madagascar acquired their current configuration in the Tonian. [ABSTRACT FROM AUTHOR]

Abstract: Ion microprobe U–Pb dating of detrital zircons from the Chiquitania and San Ignacio groups of Eastern Bolivia show that these rocks were derived mostly from a 1765Ma source and were deposited after 1690Ma. The emplacement of the Lomas Maneches granitoid suit, dated at 1690–1660Ma, accompanied the deposition of these metasediments. These rocks, which collectively define the basement of Eastern Bolivia, were subsequently deformed and metamorphosed during two discrete periods of orogenesis. The oldest of these events, the San Ignacio Orogeny, deformed the terrane through three successive phases of deformation and was accompanied by voluminous syn-tectonic granite intrusion and migmatisation of the 1690Ma sediments and intrusions. U–Pb age data from igneous and metamorphic zircon constrain the San Ignacio Orogeny to between 1340 and 1320Ma, while the orientation of structures suggests deformation was the result of W–NW directed shortening. A 300 million years hiatus, during which the overlying Sunsas Group was deposited, separated the San Ignacio Orogeny from the Sunsas Orogeny. Shortening during Sunsas orogenesis resulted in an intense NW trending structural overprint in the southern and western extremes of the study area. The intensity of deformation decreased toward the northeast such that in the San Ignacio region, Sunsas tectonism resulted in distinct dome and basin fold interference patterns. Late syn- to post-tectonic granites were emplaced in the region of highest Sunsas strain. One of these intrusions, the Taperas granite, yielded an age of ca. 1075Ma. When taken collectively, these new data highlight a number of important points: (1) The deposition of the Chiquitania and San Ignacio groups, and the synchronous emplacement of the Lomas Maneches granitoid suite (1690–1660Ma) have no temporal equivalents in the either the Rondônia and Mato Grosso regions of Brazil to the north or east, or the Proterozoic pre-Andean inliers to the west; (2) the trend of the structures attributed to the San Ignacio Orogeny are oriented at a high-angle to the NW trending pre-Sunsas margin of Amazonia and; (3) the Sunsas Orogeny represents the only geological event with a common age and direction of crustal shortening recorded in both the Amazon Craton and the rocks of Eastern Bolivia. These data are interpreted to suggest that the rocks of Eastern Bolivia represent a geologically distinct microcontinent (the Paragua Craton) that was accreted to the southern margin of Amazon Craton during the Sunsas Orogeny. [Copyright &y& Elsevier]

A review of U–Pb age data from intrusive and volcanic rocks for Antarctica and Australia has highlighted the remarkable synchronicity in the shift from passive margin or continental arc tectonism, to convergent orogenesis along the Pacific margin of Gondwana. This event, the Ross–Delamerian Orogeny, marks a distinct and rapid shift in the style of deformation, rate of uplift, volume of magmatism and syn-orogenic sedimentation along the entire 4000+ km length of the orogen. The Ross–Delamerian Orogeny is constrained to have begun at 515±5 Ma, an interval that also encompasses the youngest collisional events that lead to the suturing of Gondwana. We propose that these geographically separate events are intimately linked and represent the cause and effect of a major tectonic reorganisation in the motion of the Earth’s plates. We suggest the mechanism controlling this Early to Middle Cambrian plate reorganisation was the rapid reduction in relative motion, driven by continental collision, between the final two components of Gondwana. Due to the need to maintain a zero sum for all plate motions, the change in the rate of convergence at this boundary resulted in compensatory changes elsewhere in the global plate circuit. One such change was an increase in the rate and perhaps direction of convergence along the Pacific margin of Gondwana. [Copyright &y& Elsevier]

The Lambert Glacier–Amery Ice Shelf occupies a narrow NNE–SSW-orientated fault-bound depression referred to as the Lambert Graben. Deep faults associated with this structure are recognised geophysically, and are interpreted to extend at least 700 km inland from the Antarctic coast. Kinematic and palaeostress data from quartz- and calcite-bearing faults, inferred to represent the surface expression of these deeper structures, suggest that a single faulting event occurred in response to NW–SE-directed extension, oblique to the axis of the graben. The bulk of the movement along these faults was dextral strike slip, accommodating components of both normal and reverse offset. In the northern Prince Charles Mountains, these faults disrupt the Permo-Triassic Amery Group and juxtapose it against Proterozoic basement. Equivalent strike-slip faults in the southern Prince Charles Mountains produce dextrally offset tectonic boundaries and metamorphic isogrades across the Lambert Glacier. The similarity in orientation between the palaeostress field calculated for these faults and the Cretaceous divergence vector between India and Antarctica strongly supports the inference that faulting was of Cretaceous age, and related to the break-up of Gondwana. [Copyright &y& Elsevier]

New structural and metamorphic data coupled with U–Pb SHRIMP zircon and Rb–Sr step-leach biotite ages help constrain a period of Early Palaeozoic (Pan-African) deformation recognised in the northern Prince Charles Mountains, east Antarctica. This period of deformation is accommodated along discrete northeast trending mylonites that preserve up-dip reverse kinematics with dominantly southeast over northwest vergence. Ambient P–T conditions of 524±20°C and 7.6±4 kbar accompanied deformation. This phase of deformation post-dated the intrusion of planar felsic dykes that yield ages of c. 550 Ma and pre-dated Rb–Sr biotite ages of c. 475 Ma that record cooling of the terrane below c. 300°C. These mylonites are identical in age to continental collisional events recognised in the southern Prince Charles Mountains and Prydz Bay, which lie to the south and east of the northern Prince Charles Mountains, and similar in age to orogenesis recognised to the west in Lu¨tzow-Holm Bay. These belts represent sutures between the component lithospheric blocks of east and west Gondwana. The northern Prince Charles Mountains lie between these sutures. Consequently, the mylonites we report here are interpreted to have formed in an intraplate setting and developed in response to stresses applied along the plated margins as a consequence of continental collision during the amalgamation of Gondwana. [Copyright &y& Elsevier]

Examines the Paleozoic tectonism within the East Antartic craton. Definition of lithospheric block margins; Suturation of the Indo-Antartic continent with west Gondwana; Existence of a laterally continuous orogenic belt.