Palaeomagnetic re-investigation of early permian rift basalts from the Baoshan block, SW China: Constraints on the site-of-origin of the gondwana-derived eastern cimmerian terranes

A palaeomagnetic investigation was carried out on a series of rift basalts (Woniusi Formation) that accumulated on the Baoshan block (SW China) in the Early Permian, the aim being to provide quantitative palaeogeographical information on the eastern Cimmerian terrane as it detached from eastern Gondwana. Reliable data were obtained from four locations/28 individual cooling units, and when combined with the findings of an earlier study (three locations/19 sites) indicate that breakup occurred at 41.9°S (with errors, 34.2-51.2°S). Using this information, we fit Baoshan against Gondwana within a narrow longitudinal belt close to where northeast Greater India and northwest Australia were once in close proximity. Furthermore, we suggest that Sibumasu (Simao-Burma-Malyasia-Sumatra; the largest of the eastern Cimmerian blocks) lay directly to the east, offshore of Australia; Qiangtang and Lhasa almost certainly sat to the west (off northern Greater India-SE Arabia), but we are uncertain as to their exact configuration. Our findings are compared with several rather different models that have been published in recent years. The new palaeomagnetic constraint highlights the flexibility authors currently have in reconstructing the region, principally because of the overall lack of similar high-quality data from the various blocks. We explain how new data could resolve these ambiguities, thereby offering more robust explanations for eastern Gondwana's late Palaeozoic development

The Common Assessment Framework (CAF) and the evaluation of Quality in a Public Service: Case Study of Academic Services of the University of Évora, Portugal

Society is more and more demanding on professional terms. Therefore, in order to achieve Excellence we need to go though processes of continuous improvement and we need to measure and to evaluate Quality which is increasingly seen as a competitive and distinguishing factor between institutions. And institutions from Public Sector like Universities are no exception. It’s urgent to evaluate their quality. But a question remains: how do we evaluate them? Why is it important? Should we evaluate the graduate and post-graduate degrees, the services that support all the University,…What? In Portugal it is compulsory to evaluate the quality of the degrees taught on a Higher Education Institution. For that purpose a set of legislation has been approved: Law n.º38/94 of 21st November, Decree-law n.º205/98 of 11th July and Law n.º1/2003 of 6th January. But if this is a compulsory procedure, shouldn’t the structures that support all the life of a Higher Education Institution also be evaluated? What happens if, for instance, the Academic Services don’t work properly or collapse? This service is considered as essential and fundamental on Higher Education Institutions

Comment on “Trans‐Hudson Orogen of North America and Himalaya‐Karakoram‐Tibetan Orogen of Asia: Structural and thermal characteristics of the lower and upper plates” by MR St‐Onge et al.

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Detrital heavy minerals constraints on the Triassic tectonic evolution of the West Qinling terrane, NW China: implications for understanding subduction of the Paleotethyan Ocean

We have examined the Triassic sediments in the west Qinling terrane, northeastern Tibet. These sediments consist mainly of flysch and shallow-sea and fluvial deposits with abundant lithic and heavy mineral detritus, sandwiched between and overlying Late Paleozoic and Early-Middle Triassic ophiolitic mélanges. Volcanic and metamorphic detritus dominates the lithic component of Lower Triassic sandstones accompanied by high Cr-spinel, pyroxene, and magnetite contents, indicating a mixed ophiolite and metamorphic source. Detrital mineral geochemistry further suggests that ophiolitic, high-grade metamorphic, basic, and intermediate-acidic igneous rocks must have been exposed and deeply eroded in their source area. Abundances of zircon, rutile, garnet, tourmaline, and epidote are greater in the Middle Triassic samples, and granitic and volcanic sources are the major contributors of detrital clasts. Considering these new observations on sedimentary petrography and detrital heavy mineral geochemistry, along with published data on paleocurrents, detrital zircon U-Pb ages, sedimentary facies, and regional magmatism, we suggest that these Triassic sediments represent the sedimentary fill of a forearc basin that overlies a late Paleozoic ophiolitic complex. A south-facing Andean-type convergent continental margin system developed along the southern margin of the North China block during the Triassic, in response to northward subduction of the Paleotethyan Ocean

A single Dras‐Kohistan‐Ladakh arc revealed by volcaniclastic records

Tectonic interpretations of arc remnants in the Himalayan orogen remain uncertain, despite their important implications for the overall convergence history between India and Eurasia. Provenance results from deep‐water volcaniclastic rocks of the Indus Suture Zone in Ladakh provide new constraints on the Mesozoic tectonic evolution of the Dras and Kohistan‐Ladakh arcs. Detrital zircon (DZ) U‐Pb ages and whole‐rock geochemistry of the fault‐bounded Upper Cretaceous Nindam and Paleocene Jurutze formations present age patterns and compositions that are consistent with those of the Dras and Kohistan‐Ladakh arcs, respectively. The combination of DZs of the Nindam and Jurutze formations with the igneous zircons of the Dras and Kohistan‐Ladakh arcs shows similar age distributions that support a Late Jurassic to Paleocene tectonic connection between all these units. We argue that the secular trends in geochemical composition of DZs and volcaniclastic material are consistent with the magmatic evolution of one convergent margin, which shifted from a primitive to a mature stage during the Late Cretaceous. The recognition of a single Dras‐Kohistan‐Ladakh arc sets the stage for reevaluating competing scenarios of the Mesozoic evolution of the India–Eurasia convergent system. We find that the most likely scenario is that of a Jurassic arc formed above a south‐dipping intraoceanic subduction zone and accreted to Eurasia during the Early Cretaceous, after which it evolved above a north‐dipping subduction zone

Paleozoic ocean plate stratigraphy unraveled by calcite U-Pb dating of basalt and biostratigraphy

Oceanic mafic volcanic rocks preserve unique information regarding the nature and evolution of tectonic plates. However, constraining their age is commonly challenging because of their lack of datable minerals and high degrees of alteration. We present in situ laser ablation–inductively coupled plasma–mass spectrometry U-Pb dating of calcite phases in altered basalts in a Paleozoic subduction complex (eastern Australia). Calcite enclosed in amygdules and filled in fractures yielded two distinctive ages with contrasting geochemical signatures. These results, combined with new biostratigraphic and whole-rock geochemical data, suggest that oceanic islands formed in the Panthalassa Ocean at about 365 million years ago, accreted to eastern Gondwana at about 330 million years ago, and underwent brittle deformation at about 305 million years ago. Calcite U-Pb geochronology is valuable to help constrain minimum formation ages of volcanic rocks and their deformation history, ultimately improving ability to unravel the geological record of accretionary complexes, and more generally ancient underwater volcanic systems

A importância das artes num projecto autárquico de turismo cultural

As artes são uma mais-valia em qualquer projecto de Turismo Cultural. Faz todo o sentido a comunhão da estética, da ética, memórias, usos e costumes, tradições e conhecimento, que nos afecta, melhorando a visão do mundo que nos rodeia e fazendo de nós turistas ou não, pessoas abertas às diferenças e às mudanças dum mundo, que se altera a cada moment

δ13Corg and n-alkane evidence for changing wetland conditions during a stable mid-late Holocene climate in the central Tibetan Plateau

This study has examined bulk and compound specific organic carbon isotopes (δC) and lipid n-alkanes of modern plants and a wetland sediment sequence from the central Tibetan Plateau and explores the usefulness of these two methods for palaeoenvironmental reconstructions. Results show that a combination of δC values and n-alkane indices can help differentiate organic matter from C3 terrestrial plant, C4 terrestrial plant and submerged macrophytes, the three main sources of organic matter in the study area. The analyses of total organic carbon, δC values and n-alkane indices for the sediment sequence imply that a wetland habitat was established about 8000years ago, and the wetland conditions were largely stable with dominantly C3 wetland herbs covering the wetland. However, small fluctuations in the dominant organic matter supply between vascular and aquatic plants are revealed, suggesting short duration changes in the extent of open water area within the wetland or variations in the productivity of submerged macrophytes and aquatic plants within the wetland ecosystem, which reflects variations in the strength of precipitation and evaporation

Lajishankou Ophiolite Complex: Implications for Paleozoic Multiple Accretionary and Collisional Events in the South Qilian Belt

The Lajishan ophiolite complex in the Qilian Orogen is one of several ophiolites situated between the Qaidam and North China blocks that record episodic closure of the Proto-Tethyan Ocean. Detailed field relations and geochemical and geochronological studies are critical to unraveling the tectonic processes responsible for an extensive period of intraoceanic subduction that produced juvenile ophiolite/island arc terranes, which were obducted onto continental margins during ocean closure. The Lajishankou ophiolite complex crops out along the northern margin of the South Qilian belt and was thrust over a Neoproterozoic-Ordovician passive margin sequence that was deposited upon the Proterozoic Central Qilian block. The mafic rocks in Lajishankou ophiolite complex are the most abundant slices and can be categorized into three distinct groups based on petrological, geochemical, and geochronological characteristics: massive island arc tholeiites, 509-Ma back-arc dolerite dykes, and 491-Ma pillow basaltic and dolerite slices that are of seamount origin in a back-arc basin. These results, together with spatial relationships, indicate that the Cambrian island arc rocks, ophiolite complex, and accretionary complex developed between 530 and 480 Ma as a single, intraoceanic arc-basin system as a result of south directed subduction of the Proto-Tethyan Ocean prior to Early Ordovician obduction of this system onto the Central Qilian block. Final continental amalgamation involved continental collision of the Central Qilian block with the Qaidam block during the Late Ordovician. This model solves the long-lasting discussion on the emplacement of the Lajishan ophiolite and contributes to an improved understanding of multiple accretionary and collisional processes in the Qilian Orogen