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Rosenbaum, G.
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Rosenbaum, G.
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- PublicationRestrictedKinematics of slab tear faults during subduction segmentation and implications for Italian magmatism(2008)
; ; ; ; ; ;Rosenbaum, G.; School of Physical Sciences, University of Queensland, Brisbane, Queensland, Australia. ;Gasparon, M.; School of Physical Sciences, University of Queensland, Brisbane, Queensland, Australia. ;Lucente, F. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Peccerillo, A.; Dipartimento di Scienze della Terra, Universita` degli Studi di Perugia, Perugia, Italy. ;Miller, M. S.; Department of Earth Science, Rice University, Houston, Texas, USA.; ; ; ; Tectonic activity in convergent plate boundaries commonly involves backward migration (rollback) of narrow subducting slabs and segmentation of subduction zones through slab tearing. Here we investigate this process in the Italian region by integrating seismic tomography data with spatiotemporal analysis of magmatic rocks and kinematic reconstructions. Seismic tomography results show gaps within the subducting lithosphere,which are interpreted as deep (100–500 km) subvertical tear faults. The development of such tear faults is consistent with proposed kinematic reconstructions, inwhich different rates of subduction rollback affected different parts of the subduction zone. We further suggest a possible link between the development of tear faults and the occurrence of regional magmatic activity with transitional geochemical signatures between arc type and OIB type, associated with slab tearing and slab breakoff.We conclude that lithospheric-scale tear faults play a fundamental role in the destruction of subduction zones. As such, they should be incorporated into reconstructions of ancient convergent margins, where tear faults are possibly represented by continental lineaments linked with magmatism and mineralization.237 31 - PublicationRestrictedUnraveling the geometry of the New England oroclines (eastern Australia): Constraints from magnetic fabrics(2014-10-16)
; ; ; ; ;Mochales, T.; School of Earth Sciences, University of Queensland, Brisbane, Queensland, Australia ;Rosenbaum, G.; School of Earth Sciences, University of Queensland, Brisbane, Queensland, Australia ;Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pisarevsky, S. A.; School of Earth and Environment, University of Western Australia, Crawley, Western Australia; ; ; The southern New England Orogen (NEO) in eastern Australia is characterized by tight curvatures (oroclines), but the exact geometry of the oroclines and their kinematic evolution are controversial. Here we present new data on the anisotropy ofmagnetic susceptibility (AMS), which provide a petrofabric proxy for the finite strain associated with the oroclines. We focus on a series of preoroclinal Devonian-Carboniferous fore-arc basin rocks, which are aligned parallel to the oroclinal structure, and by examining structural domains, we test whether or not the magnetic fabric is consistent with the strain axes. AMS data show a first-order consistency with the shape of the oroclines, characterized, in most of structural domains, by subparallelism between magnetic lineations, “structural axis” and bedding. With the exception of the Gresford and west Hastings domains, our results are relatively consistent with the existence of the Manning and Nambucca (Hastings) Oroclines. Reconstruction of magnetic lineations to a prerotation (i.e., pre–late Carboniferous) stage, considering available paleomagnetic results, yields a consistent and rather rectilinear NE-SW predeformation fore-arc basin. This supports the validity of AMS as a strain proxy in complex orogens, such as the NEO. In the Hastings Block, magnetic lineations are suborthogonal to bedding, possibly indicating a different deformational history with respect to the rest of the NEO.321 97