IS THE SOUTH CHINA BLOCK AN ACCRETIONARY OROGENY? INSIGHTS FROM RECENT GEOLOGICAL AND GEOCHRONOLOGICAL DATA AND LESSONS FROM THE APPALACHIAN-CALEDONIAN OROGENY

2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014) (2014)

Changqing Yin

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Orogeny

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Geological and Geochemical Analysis

earthquake and tectonic studies

Geological Studies and Exploration

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Palaeomagnetic constraints on the evolution of the Caledonian-Appalachian orogen

Geological Society London Special Publications (1988)

J. C. Briden Dennis V. Kent P. L. Lapointe J. Roy Roy Livermore

Summary Late Proterozoic and Palaeozoic (pre-Permian) palaeomagnetic data from all regions involved in, or adjacent to, the Caledonian-Appalachian orogenic belt are reviewed. Between about 1100 and about 800 Ma the Laurentian and Baltic shields were close together, prior to the opening phase of the Caledonian-Appalachian Wilson cycle. The problems of tectonic interpretation of Palaeozoic palaeomagnetic data from within and around the belt derive mostly from differences of typically 10°–20° between the pole positions. These can variously be interpreted in terms of (i) relative displacements between different continents or terranes, (ii) differences in ages of remanence and (iii) aberrations due to inadequacy of data or geomagnetic complexity, and it is not always easy to discriminate between these alternatives. If the Pangaea A2 reassembly of continents around the northern and central Atlantic is taken as the end-product of Caledonian-Appalachian orogenesis, the following conclusions can be drawn. 1 Lower Palaeozoic palaeolatitude differences between the N American and British-Scandinavian margins of the Caledonides are small; hence any convergence must have been mainly E-W. 2 There are additional differences which could be due to major pre-Carboniferous strike-slip (more than 1000 km), although later strike-slip on this scale is no longer considered likely. 3 The Lower Palaeozoic apparent polar wander paths for Northern Scotland and N America disagree on face value, but must be reconciled if their conventionally assumed geographic relation is correct. 4 Lower Old Red Sandstone data from Britain and Norway disagree, but this is more likely to be due to magnetic overprinting in the Norwegian rocks than to remnant oceans between the regions of Old Red Sandstone facies. 5 Armorica seems to have been far to the S, adjacent to Gondwana, in Ordovician time. The latest view is that it collided with Euramerica in early Devonian time to form the Old Red Continent. 6 The timing of Gondwana’s collision with the Old Red Continent is controversial; it is within either the late Devonian or the Carboniferous. If it occurred early in that time range, much of Hercynian-Alleghanian orogeny post-dated it.

10.1144/gsl.sp.1988.038.01.03

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Investigating the secular geochemical and geodynamic evolution of accretionary orogens with zircon petrochronology: A case study from West Antarctica

D. A. Nelson

Author(s): Nelson, Demian Alan | Advisor(s): Cottle, John M | Abstract: ABSTRACTInvestigating the secular geochemical and geodynamic evolution of accretionary orogens with zircon petrochronology: A case study from West AntarcticabyDemian Alan Nelson Subduction-related processes in accretionary orogens modulate Earth’s geochemistry. Uncovering the secular geodynamic evolution of accretionary orogens, therefore, is the key to Earth’s geochemical history. A record of the secular geodynamic evolution of accretionary orogens is preserved in the tempo, geochemistry, and distribution of subduction-related magmatism. Zircon is ubiquitous in subduction-related magmas and provides a valuable time integrated geochemical proxy for the secular geodynamic evolution of accretionary orogens via U-Pb geochronology, Hf isotopes, and trace-elements (i.e., zircon petrochronology). The paleo-Pacific margin of Gondwana, including South America, eastern Australia, and West Antarctica, provides an ideal opportunity to investigate the secular geodynamic evolution of accretionary orogens with zircon petrochronology because it contains the most long-lived and best-preserved record of accretionary orogenesis on Earth. This dissertation represents the first comprehensive zircon petrochronologic study of Phanerozoic subduction and accretionary orogenesis in West Antarctica and combines the results with existing data from adjacent regions in eastern Australia and South America to refine our understanding of the secular evolution of accretionary orogens. Chapter 1 investigates volcaniclastic sedimentary rocks in the central Transantarctic Mountains and documents episodic isotopically depleted magmatism along the Antarctic margin of Gondwana. Comparisons of these data from the central Transantarctic Mountains demonstrate a shared tectonic history between Antarctica, Zealandia, and Australia that contrasts with that of South America. Chapter 2 applies zircon petrochronology to the plutonic rocks in eastern Marie Byrd Land and Thurston Island. These new data combined with existing data from the Antarctic Peninsula, western Marie Byrd Land, and central Transantarctic Mountains provides an ~450 million year geochemical and geodynamic history for the Antarctic margin of Gondwana. This record is then compared with compilations from South America and Australia to determine similarities and differences in geochemical and geodynamic evolution along the Gondwana margin. Chapter 3 traces the source of Permian volcanic deposits in central Antarctica to a voluminous volcanic province in South America, the Choiyoi Province, which may have contributed to Permian climate change and environmental degradation.

Geochronology

Accretionary wedge

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Paleozoic transpressional tectonics in the Beishan orogenic collage, Northwest China: Evolution of the Hongliuhe suture zone

Nathan Cleven

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S-52 New Geologic Aspects in the Korean Peninsula and Implications for East Asian Tectonics : Prolonged Permo-Triassic Orogeny((6) Accretionary Orogen update: Japan, Asia and mid-contients)

日本地質学会学術大会講演要旨 (2006)