TY - JOUR
T1 - Divergent plate motion drives rapid exhumation of (ultra)high pressure rocks
AU - Liao, Jie
AU - Malusà, Marco G.
AU - Zhao, Liang
AU - Baldwin, Suzanne L.
AU - Fitzgerald, Paul G.
AU - Gerya, Taras
N1 - Funding Information:
MM and LZ acknowledge colleagues of the CIFALPS working group for insightful discussions, and Yonghong Shi for illustrating Dabie geology in the field. Funding from the Swiss National Science Foundation – Swiss-AlpArray SINERGIA project CRSII2_154434/1 (to JL), the US National Science Foundation for projects 0208334 and 0709054 in PNG (to SLB and PGF), and the Thonis endowment (to SLB) is gratefully acknowledged. The manuscript benefited from constructive comments by the Editor Rebecca Bendick and two anonymous reviewers.
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - Exhumation of (ultra)high pressure [(U)HP] rocks by upper-plate divergent motion above an unbroken slab, first proposed in the Western Alps, has never been tested by numerical methods. We present 2D thermo-mechanical models incorporating subduction of a thinned continental margin beneath either a continental or oceanic upper plate, followed by upper-plate divergent motion away from the lower plate. Results demonstrate how divergent plate motion may trigger rapid exhumation of large volumes of (U)HP rocks directly to the Earth's surface, without the need for significant overburden removal by erosion. Model exhumation paths are fully consistent with natural examples for a wide range of upper-plate divergence rates. Exhumation rates are systematically higher than the divergent rate imposed to the upper plate, and the modeled size of exhumed (U)HP domes is invariant for different rates of upper-plate divergence. Major variations are instead predicted at depth for differing model scenarios, as larger amounts of divergent motion may allow mantle-wedge exhumation to shallow depth under the exhuming domes. The transient temperature increase, due to ascent of mantle-wedge material in the subduction channel, has a limited effect on exhumed continental (U)HP rocks already at the surface. We test two examples, the Cenozoic (U)HP terranes of the Western Alps (continental upper plate) and eastern Papua New Guinea (oceanic upper plate). The good fit between model predictions and the geologic record in these terranes encourages the application of these models globally to pre-Cenozoic (U)HP terranes where the geologic record of exhumation is only partly preserved.
AB - Exhumation of (ultra)high pressure [(U)HP] rocks by upper-plate divergent motion above an unbroken slab, first proposed in the Western Alps, has never been tested by numerical methods. We present 2D thermo-mechanical models incorporating subduction of a thinned continental margin beneath either a continental or oceanic upper plate, followed by upper-plate divergent motion away from the lower plate. Results demonstrate how divergent plate motion may trigger rapid exhumation of large volumes of (U)HP rocks directly to the Earth's surface, without the need for significant overburden removal by erosion. Model exhumation paths are fully consistent with natural examples for a wide range of upper-plate divergence rates. Exhumation rates are systematically higher than the divergent rate imposed to the upper plate, and the modeled size of exhumed (U)HP domes is invariant for different rates of upper-plate divergence. Major variations are instead predicted at depth for differing model scenarios, as larger amounts of divergent motion may allow mantle-wedge exhumation to shallow depth under the exhuming domes. The transient temperature increase, due to ascent of mantle-wedge material in the subduction channel, has a limited effect on exhumed continental (U)HP rocks already at the surface. We test two examples, the Cenozoic (U)HP terranes of the Western Alps (continental upper plate) and eastern Papua New Guinea (oceanic upper plate). The good fit between model predictions and the geologic record in these terranes encourages the application of these models globally to pre-Cenozoic (U)HP terranes where the geologic record of exhumation is only partly preserved.
KW - (U)HP rock exhumation
KW - Western Alps
KW - eastern Papua New Guinea
KW - mantle-wedge exhumation
KW - upper-plate divergent motion
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U2 - 10.1016/j.epsl.2018.03.024
DO - 10.1016/j.epsl.2018.03.024
M3 - Article
AN - SCOPUS:85044463238
SN - 0012-821X
VL - 491
SP - 67
EP - 80
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -