The ‘giant’ Tambogrande volcanogenic massive sulphide (VMS) deposits within the Cretaceous Lancones basin of northwestern Perú are some of the largest Cu-Zn-Au-Ag-bearing massive sulphide deposits known. Limited research has been done on these deposits, hence the ore forming setting in which they developed and the key criteria that permitted such anomalous accumulation of base-metal sulphides are not understood. Based on field relationships in the host volcanic rocks and U-Pb geochronology, the deposits formed during the early stages of arc development in the latest Early Cretaceous and were related to an extensional and arc-rift phase (~105-100 Ma, phase 1). During this time, bimodal, primitive basalt-dominant volcanic rocks were erupted in a relatively deep marginal basin. Phase 1 rhyolite is tholeiitic, M-type, and considered to have formed from relatively high temperature, small batch magmas. The high heat flow and extensional setting extant during the initial stages of arc development were essential components for forming a VMS hydrothermal system. The subsequent phase 2 (~99-91 Ma) volcanic sequence comprises more evolved mafic rocks and similar, but more depleted, felsic rocks erupted in a relatively shallow marine setting. Phase 2 is interpreted to represent late-stage arc volcanism during a waning extensional regime and marked the transition to contractional tectonism. The Tambogrande deposits are particularly unusual amongst the ‘giant’ class of VMS deposits in that deposition largely occurred as seafloor mound-type and not by replacement of existing strata. Paleomorphology of the local depositional setting was defined by seafloor depressions controlled by syn-volcanic faults and rhyolitic volcanism. The depressions were the main controls on distribution and geometry of the deposits and, due to inherently confined hydrothermal venting, enhanced the efficiency of sulphide deposition. Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget was sourced almost wholly from mafic volcanic strata. Therefore, unlike the implications of many conventional models, the felsic volcanic rocks at Tambogrande are interpreted to have only played a passive role in VMS formation.

The ‘giant’ Tambogrande volcanogenic massive sulphide (VMS) deposits within the Cretaceous Lancones basin of northwestern Perú are some of the largest Cu-Zn-Au-Ag-bearing massive sulphide deposits known. Limited research has been done on these deposits, hence the ore forming setting in which they developed and the key criteria that permitted such anomalous accumulation of base-metal sulphides are not understood. Based on field relationships in the host volcanic rocks and U-Pb geochronology, the deposits formed during the early stages of arc development in the latest Early Cretaceous and were related to an extensional and arc-rift phase (~105-100 Ma, phase 1). During this time, bimodal, primitive basalt-dominant volcanic rocks were erupted in a relatively deep marginal basin. Phase 1 rhyolite is tholeiitic, M-type, and considered to have formed from relatively high temperature, small batch magmas. The high heat flow and extensional setting extant during the initial stages of arc development were essential components for forming a VMS hydrothermal system. The subsequent phase 2 (~99-91 Ma) volcanic sequence comprises more evolved mafic rocks and similar, but more depleted, felsic rocks erupted in a relatively shallow marine setting. Phase 2 is interpreted to represent late-stage arc volcanism during a waning extensional regime and marked the transition to contractional tectonism. The Tambogrande deposits are particularly unusual amongst the ‘giant’ class of VMS deposits in that deposition largely occurred as seafloor mound-type and not by replacement of existing strata. Paleomorphology of the local depositional setting was defined by seafloor depressions controlled by syn-volcanic faults and rhyolitic volcanism. The depressions were the main controls on distribution and geometry of the deposits and, due to inherently confined hydrothermal venting, enhanced the efficiency of sulphide deposition. Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget was sourced almost wholly from mafic volcanic strata. Therefore, unlike the implications of many conventional models, the felsic volcanic rocks at Tambogrande are interpreted to have only played a passive role in VMS formation.

The ‘giant’ Tambogrande volcanogenic massive sulphide (VMS) deposits within the Cretaceous Lancones basin of northwestern Perú are some of the largest Cu-Zn-Au-Ag-bearing massive sulphide deposits known. Limited research has been done on these deposits, hence the ore forming setting in which they developed and the key criteria that permitted such anomalous accumulation of base-metal sulphides are not understood. Based on field relationships in the host volcanic rocks and U-Pb geochronology, the deposits formed during the early stages of arc development in the latest Early Cretaceous and were related to an extensional and arc-rift phase (~105-100 Ma, phase 1). During this time, bimodal, primitive basalt-dominant volcanic rocks were erupted in a relatively deep marginal basin. Phase 1 rhyolite is tholeiitic, M-type, and considered to have formed from relatively high temperature, small batch magmas. The high heat flow and extensional setting extant during the initial stages of arc development were essential components for forming a VMS hydrothermal system. The subsequent phase 2 (~99-91 Ma) volcanic sequence comprises more evolved mafic rocks and similar, but more depleted, felsic rocks erupted in a relatively shallow marine setting. Phase 2 is interpreted to represent late-stage arc volcanism during a waning extensional regime and marked the transition to contractional tectonism. The Tambogrande deposits are particularly unusual amongst the ‘giant’ class of VMS deposits in that deposition largely occurred as seafloor mound-type and not by replacement of existing strata. Paleomorphology of the local depositional setting was defined by seafloor depressions controlled by syn-volcanic faults and rhyolitic volcanism. The depressions were the main controls on distribution and geometry of the deposits and, due to inherently confined hydrothermal venting, enhanced the efficiency of sulphide deposition. Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget was sourced almost wholly from mafic volcanic strata. Therefore, unlike the implications of many conventional models, the felsic volcanic rocks at Tambogrande are interpreted to have only played a passive role in VMS formation. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

The Malaysian granitoids form the backbone of the Malay Peninsula and have long been recognized as composed of two distinct granitic provinces separated by the Bentong-Raub suture zone: <table><ol><li>Early Permian to Late Triassic Eastern Province (Indochina – East Malaya) with mainly “I-type” hornblende-bearing granitoids, associated with Cu-Au deposits, and subordinate hornblende-free pluton roof-zones hosting limited Sn-W deposits; and</li> <li>Late Triassic Main Range Province, western Malaysia (Sibumasu) with mainly “S-type” hornblende-free granitoids, associated with Sn-W deposits, and subordinate hornblende-bearing granitoids.</li></ol></table> Field observations and new geochemical data suggested that the division of the Eastern Province and Main Range granitoids using Chappell and White’s (1974) I-S classification could be problematic, as there is a large degree of overlap between the two granitic provinces in terms of lithology, mineralogy and metallogenic affinity. The Main Range granitoids are more fractionated than the hornblende-bearing Eastern Province. Although the two granitic provinces were emplaced into different continental terranes, both granitic provinces exhibit common trace element geochemistry in the enrichment of high field strength elements (HFSE) and rare earth elements (REE) compared to typical Cordilleran I-S granites. Such enrichment is interpreted as an inheritance signature from the protoliths. The Kontum massif (an analogue of Indochina lower continental crust) comprises intraplate ortho-amphibolites and para-gneisses, which could serve as two hypothetical source end-members for the Malaysian granitoids. The model suggests that the geneses of the parental magmas of the Eastern Province and the Main Range Province were related to hybridization of melts derived from protoliths, geochemically and isotopically similar to these two source end-members, but in differing proportions. The fact that the granites from the two granitic provinces are so similar compositionally and metallogenically, suggests that similar protoliths were involved in their source. The incorporation of sedimentary-sourced melt makes the Main Range granitoids transitional I/S-type in nature, but this is unlikely to be true for the less evolved Eastern Province fractionated I-type granitoids. The hybridization of igneous- and sedimentary-sourced melts, and granite fractionation promotes Sn metallogenesis in the Main Range granitic province. Previous ages were obtained using whole rock Rb-Sr and biotite K-Ar geochronology in the 1970s and 1980s, dating methods that almost certainly do not accurately represent the crystallization age of granites. New ion microprobe U-Pb zircon ages are presented that provide new temporal constraints for the Malaysian granitic magmatism. Eastern Province granitoids have U-Pb zircon ages that range from 289 to 220 Ma, while Main Range Province magmatism is constrained between 227 and 201 Ma. A progressive westward younging trend is apparent across the Eastern Province, but becomes less obvious in the Main Range Province. In addition, the U-Pb zircon analysis of the Malaysian granitoids suggests that both granitic provinces have Cambro-Ordovician and Mesoproterozoic inheritance signatures, which match the ages of the Kontum intraplate ortho-amphibolites and para-gneisses, the two source end-members of the suspected Indochina basement. Two different tectonic models have been suggested to explain the formation and the emplacement of the Malaysian granitoids. Both models involve an east-dipping subduction zone during the Early and Mid-Triassic with Palaeo-Tethys lithosphere rolling back along the Bentong-Raub suture zone to produce westward younging ages in the Eastern Province granitoids. The first model (modified after Searle et al. 2012) suggests the younger Main Range granitoids were produced by another Late Triassic – Cretaceous east-dipping (Neo-Tethyan) subduction to the west of Sibumasu, after the Sibumasu – East Malaya collision. The transitional I/S-type geochemistry of the Main Range granitoids was caused by the partial melting of the more heterogeneous Sibumasu basement. The second model (Oliver et al. 2014) suggests the younger Main Range granitoids were produced by the westward underthrusting of Indochina crust of East Malaya beneath Sibumasu along the Bentong-Raub suture zone after the continental collision. In this model, the source of the Main Range granitoids was the pre-collision I-type Eastern Province granitoids. The second model is less likely, as no geological evidence for such underthrust is found in the Malay Peninsula.

This study contributes to the understanding of major river evolution in Southeast Asia during the Cenozoic. In order to trace the evolution of a hypothesized palaeo-Yarlung Tsangpo-Irrawaddy River, this work undertakes the first systematic provenance study of detrital minerals from Cenozoic synorogenic fluvial and deltaic sedimentary rocks of the Central Burma Basin, employing a combination of high precision geochronology, thermochronology, and geochemistry analytical techniques on single grain detrital zircon and white mica. The dataset is compared to published isotopic data from potential source terranes in order to determine source provenance and exhumation history from source to sink. A Yarlung Tsangpo-Irrawaddy connection existed as far back as ca. 42 Ma and disconnection occurred at 18–20 Ma, based on provenance changes detected using a combination of U-Pb ages and εHf(t) values on detrital zircons, and ⁴ºAr/³⁹Ar dating on detrital micas. During the Eocene and Oligocene, units are dominated by U-Pb age and high positive εHf(t) values, characteristic of a southern Lhasa Gangdese magmatic arc source. An antecedent Yarlung Tsangpo-Irrawaddy River system formed the major river draining the eastern Himalaya at this time. A significant change in provenance is seen in the early Miocene, where detritus is predominantly derived from bedrock of the eastern Himalayan syntaxis, western Yunnan and Burma, a region drained by the modern Irrawaddy-Chindwin river system characterized by Cenozoic U-Pb ages and negative εHf(t) values. This is attributed to the disconnection of the Yarlung-Irrawaddy River and capture by the proto-Brahmaputra River, re-routing Tibetan Transhimalayan detritus to the eastern Himalayan foreland basin. Re-set zircon fission track ages of 14-8 Ma present in all units is used to infer post-depositional basin evolution related to changes in the stress regime accommodating the continued northward migration of India. The early Miocene initiation of the Jiali-Parlung-Gaoligong-Sagaing dextral shear zone and the continued northward movement of the coupled India-Burma plate aided in focusing deformation inside the syntaxis contributing to the disconnection of the Yarlung Tsangpo-Irrawaddy system, linking surface deformation and denudation with processes occurring at deeper crustal levels.

The studied area extends from the Ochtiná Unit in Western Carpathians to the Veitsch Nappe Eastern Alps. The thesis represents a complex multidisciplinary work that combines the structural analysis, petrology and geochronology. The three main objectives of this thesis: reevaluation of the structure, deformation and metamorphic records, and original position of the Ochtiná Unit, understanding the distinct metasomatic processes recorded along the contact of two major units of the Central Western Carpathians - in the Gemer-Vepor Contact Zone - and their relation to distinct tectono-metamorphic events, testing the possible links between the Ochtiná Unit in the Gemer-Vepor Contact Zone of the Western Carpathians and the Veitsch Nappe in the Greywacke Zone of the Easten Alps, both well known for the Lower Carboniferous shale/schist sequence accompanied by the abundant presence of magnesite ore bodies. Keywords: Central Western Carpathians, Greywacke Zone, Ochtiná Unit, Veitsch Nappe, U-Pb zircon dating, Phase equilibrium modelling

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