Hot and Dry Deep Crustal Xenoliths from Tibet

Hacker, Bradley R.; Gnos, Edwin; Ratschbacher, Lothar; Grove, Marty; McWilliams, Michael; Sobolev, S. V.; Wan, Jiafu; Wu, Zhenhan

doi:10.1126/science.287.5462.2463

Cited by 286 publications

(251 citation statements)

References 37 publications

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“…Fig. 8a shows a number of estimates of P, T from such nodules, from Hacker et al (2000Hacker et al ( , 2005, Ducea et al (2003), Jolivet et al (2003), Ding et al (2007), Chan et al, (2009), andGordon et al (2012). In agreement with Fig.…”

Section: Craton Formationsupporting

confidence: 71%

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Speculations on the formation of cratons and cratonic basins

McKenzie

2016

Earth and Planetary Science Letters

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Section: Craton Formationsupporting

confidence: 71%

“…The estimates are from the metamorphic xenolith locations shown in Fig. 2b, marked with the same three letter codes, from Hacker et al (2000Hacker et al ( , 2005, Ducea et al (2003), Jolivet et al (2003), Ding et al (2007), Chan et al, (2009), andGordon et al (2012). (b) shows the same curves for shortening occurring 3 Ga ago.…”

Section: Discussionmentioning

confidence: 99%

Speculations on the formation of cratons and cratonic basins

McKenzie

2016

Earth and Planetary Science Letters

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“…Peak P-T conditions in the Antananarivo Domain of central Madagascar were lower grade (0.4-0.6 GPa and 650-820°C; Key et al, 2011) and al- Figure 6. P-T paths for the southern East African Orogen (sources cited in text) compared with P-T estimates for Tibetan xenoliths (Hacker et al, 2000) and facies fields (Fig. 1).…”

Section: Metamorphism Between the Suturesmentioning

confidence: 99%

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

Fitzsimons

2016

Journal of Mineralogical and Petrological Sciences

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Granulites of the southern East African Orogen formed by continental collision during Gondwana assembly. The highest metamorphic gradients of 25-50°C km −1 were attained at 0.58-0.53 Ga in a microcontinental block that was sandwiched between two collisional sutures and is now exposed in Madagascar and southern India. The 50 Myr duration of extreme pressure-temperature (P-T) conditions and lack of coeval mantle magmatism suggest that metamorphism was driven by radiogenic heat accumulation beneath a long-lived orogenic plateau. Bounding sutures most likely record transfer of this microcontinent across the Neoproterozoic Mozambique Ocean, analogous to Gondwanan terranes that crossed Tethys before final India-Asia collision and, like Tibet, these sutures mark the edges of a plateau that formed following terminal ocean closure and collision. Both sutures record moderate metamorphic gradients of 15-25°C km −1 but with quite different ages. Metamorphism along the western suture at 0.65-0.61 Ga followed the end of magmatism in an adjacent 0.85-0.65 Ga ocean-arc terrane. It has an anti-clockwise P-T path that reflects preferential thickening of the hot arc during early stages of collision, and dates ocean closure at the western suture. Metamorphism along the eastern suture at 0.53-0.51 Ga has a clockwise P-T path and is widely assumed to date terminal collision in the East African Orogen. However, this event was coeval with rapid exhumation of granulites in the adjacent plateau and is more likely to reflect reactivation of a much older eastern suture during plateau collapse. Great care should be taken when using metamorphism to date ocean closure in ancient orogens. Rocks with hot metamorphic gradients give poor age constraints on initial collision because peak T is attained >50 Myr after ocean closure if radioactivity is a major part of the heat budget. Suture zone rocks with moderate metamorphic gradients can provide more reliable estimates for the time of ocean closure but are also prone to later reactivation in orogens with protracted histories.

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“…The composition of the lower crust and upper mantle can directly be known only from xenoliths entrained in ultrapotassic or potassic (shoshonitic) volcanic rocks that have sampled the lower crust on their way up to the surface (e.g. Hacker et al 2000Hacker et al , 2005Ducea et al 2003;Chan et al 2009). …”

mentioning

confidence: 99%

Crustal–lithospheric structure and continental extrusion of Tibet

Searle

Elliott

Phillips

et al. 2011

JGS

230

153

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Crustal shortening and thickening to c. 70-85 km in the Tibetan Plateau occurred both before and mainly after the c. 50 Ma India-Asia collision. Potassic-ultrapotassic shoshonitic and adakitic lavas erupted across the Qiangtang (c. 50-29 Ma) and Lhasa blocks (c. 30-10 Ma) indicate a hot mantle, thick crust and eclogitic root during that period. The progressive northward underthrusting of cold, Indian mantle lithosphere since collision shut off the source in the Lhasa block at c. 10 Ma. Late Miocene-Pleistocene shoshonitic volcanic rocks in northern Tibet require hot mantle. We review the major tectonic processes proposed for Tibet including 'rigid-block', continuum and crustal flow as well as the geological history of the major strikeslip faults. We examine controversies concerning the cumulative geological offsets and the discrepancies between geological, Quaternary and geodetic slip rates. Low present-day slip rates measured from global positioning system and InSAR along the Karakoram and Altyn Tagh Faults in addition to slow long-term geological rates can only account for limited eastward extrusion of Tibet since Mid-Miocene time. We conclude that despite being prominent geomorphological features sometimes with wide mylonite zones, the faults cut earlier formed metamorphic and igneous rocks and show limited offsets. Concentrated strain at the surface is dissipated deeper into wide ductile shear zones.

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Hot and Dry Deep Crustal Xenoliths from Tibet

Cited by 286 publications

References 37 publications

Speculations on the formation of cratons and cratonic basins

Speculations on the formation of cratons and cratonic basins

Pan–African granulites of Madagascar and southern India: Gondwana assembly and parallels with modern Tibet

Crustal–lithospheric structure and continental extrusion of Tibet

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