We present a revised global plate motion model with continuously closing plate boundaries ranging from the Triassic at 230 Ma to the present day, assess differences among alternative absolute plate motion models, and review global tectonic events. Relatively high mean absolute plate motion rates of approximately 9–10 cm yr−1 between 140 and 120 Ma may be related to transient plate motion accelerations driven by the successive emplacement of a sequence of large igneous provinces during that time. An event at ∼100 Ma is most clearly expressed in the Indian Ocean and may reflect the initiation of Andean-style subduction along southern continental Eurasia, whereas an acceleration at ∼80 Ma of mean rates from 6 to 8 cm yr−1 reflects the initial northward acceleration of India and simultaneous speedups of plates in the Pacific. An event at ∼50 Ma expressed in relative, and some absolute, plate motion changes around the globe and in a reduction of global mean plate speeds from about 6 to 4–5 cm yr−1 indicates that an increase in collisional forces (such as the India–Eurasia collision) and ridge subduction events in the Pacific (such as the Izanagi–Pacific Ridge) play a significant role in modulating plate velocities.

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[1] Uncommonly long-lived subduction and variable plate geometry along the South American Andean Plate margin resulted in diverse relationships between magmatic flux and extensional and contractional deformation, as recorded by the overriding continental plate. Convergence velocities, absolute overriding plate velocities, and subducting slab ages were resolved along the trench from 170 Ma to the present using a recently developed kinematic global plate model to identify any relationship between subduction conditions, deformation style, and magmatic features in the overriding plate. Key correlations reflect the dependence of macroscopic crustal strain style on subduction mechanism and relative plate vectors. Extensional back-arc basins involving mafic/oceanic crust developed only when the overriding plate velocity of South America was directed away from the trench and the modeled age of the subducting slab was older than 50 Myr. The development of fold and thrust belts, and uplift of major plateaus, was accompanied by trench normal convergence velocities in excess of 4 cm/yr. Parameters investigated in this study revealed no correlation with the timing of major magmatic events, nor was any correlation observed with the structural style of fold and thrust belts.

The Cordillera Darwin metamorphic complex is unique in the Andes in exposing kyanite-staurolite schist north of the Beagle Channel in southern Patagonia. Garnet in amphibolite facies pelitic schists from Bahı´a Pia has patchy textures whereby some grains consist of clear, grossular-rich garnet with fine-grained S1 inclusion trails truncated by regions of turbid spessartine-pyrope-rich garnet with biotite, muscovite, plagioclase and quartz inclusions. Micron-scale aqueous inclusions in turbid garnet are consistent with recrystallization facilitated by fluid ingress; S2 inclusion trails indicate this was broadly contemporary with the growth of kyanite and staurolite in the matrix. Pseudosection modelling in Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O-TiO 2 -Fe 2 O 3 (NCKFMASHTO) is used to infer a P-T path dominated by decompression from 12 to 9 kbar at T 620°C, coupled with garnet mode decreasing from 5% to <1%. U-Th-Pb in situ dating of S2 monazite indicates that staurolite and kyanite growth and thus exhumation was underway before 72.6 ± 1.1 Ma. Contact aureoles developed adjacent to late granite intrusions include sillimanite-bearing migmatites formed at P 6 kbar after 72 Ma. Metamorphism of southern Cordillera Darwin induced by continental underthrusting beneath the arc, related to closure of the Rocas Verdes back-arc basin, was terminated by thrusting-controlled exhumation, with the rocks at P 9 kbar by c. 73 Ma and 6 kbar by c. 70 Ma.

Rosemary O'Donnell works with the Academic Services division of the University of Sydney Library. She supports teaching and research through the delivery of pedagogically informed online learning experiences and information / digital literacy services. Rosemary completed a Certificate in Further Education Teaching at Thames Polytechnic London and holds a PhD in Social Anthropology from the