Forearc hyperextension dismembered the south Tibetan ophiolites

Suprasubduction zone ophiolites are relics of oceanic upper plate forearcs and are typically preserved as discontinuous belts with discrete massifs along suture zones. Ophiolites usually contain an incomplete condensed section compared to average modern oceanic lithosphere. The incompleteness and discontinuity of ophiolites are frequently attributed to dismemberment, but tectonic causes remain poorly constrained. Here we show new paleomagnetic and field geological evidence for the preservation of extensional detachment faults that thinned and dismembered the south Tibetan ophiolite belt during the Early Cretaceous. Similar to those documented in modern slow- and ultraslow-spreading ridges, these detachments exhumed lithospheric mantle, and subophiolitic melange, to the seafloor, which became unconformably covered by Asia-derived forearc strata. We call this mechanism forearc hyperextension, whereby widespread detachment faults accommodate upper plate extension above a subduction zone. We propose that hyperextension is the key mechanism responsible for dismemberment of the south Tibetan ophiolitic belt shortly after its magmatic accretion.

[1]  Huaichun Wu,et al.  New insights into the India–Asia collision process from Cretaceous paleomagnetic and geochronologic results in the Lhasa terrane , 2015 .

[2]  L. Ding,et al.  Lower Cretaceous Xigaze ophiolites formed in the Gangdese forearc : Evidence from paleomagnetism, sediment provenance, and stratigraphy , 2015 .

[3]  P. Robinson,et al.  Origin of podiform chromitite, a new model based on the Luobusa ophiolite, Tibet , 2015 .

[4]  P. Robinson,et al.  Origin of ultrahigh pressure and highly reduced minerals in podiform chromitites and associated mantle peridotites of the Luobusa ophiolite, Tibet , 2015 .

[5]  Fu-Yuan Wu,et al.  Formation of gabbronorites in the Purang ophiolite (SW Tibet) through melting of hydrothermally altered mantle along a detachment fault , 2014 .

[6]  M. Anderson,et al.  Recognizing detachment-mode seafloor spreading in the deep geological past , 2013, Scientific Reports.

[7]  Chengshan Wang,et al.  Rapid forearc spreading between 130 and 120 Ma: Evidence from geochronology and geochemistry of the Xigaze ophiolite, southern Tibet , 2013 .

[8]  Chengshan Wang,et al.  The Indus–Yarlung Zangbo ophiolites from Nanga Parbat to Namche Barwa syntaxes, southern Tibet: First synthesis of petrology, geochemistry, and geochronology with incidences on geodynamic reconstructions of Neo-Tethys , 2012 .

[9]  Chengshan Wang,et al.  Revision of the Cretaceous–Paleogene stratigraphic framework, facies architecture and provenance of the Xigaze forearc basin along the Yarlung Zangbo suture zone , 2012 .

[10]  Chengshan Wang,et al.  Discovery of a dismembered metamorphic sole in the Saga ophiolitic mélange, South Tibet: Assessing an Early Cretaceous disruption of the Neo-Tethyan supra-subduction zone and consequences on basin closing , 2012 .

[11]  M. Reagan,et al.  The timescales of subduction initiation and subsequent evolution of an oceanic island arc , 2011 .

[12]  J. Escartín,et al.  Quantitative constraint on footwall rotations at the 15°45′N oceanic core complex, Mid‐Atlantic Ridge: Implications for oceanic detachment fault processes , 2011 .

[13]  G. Lesage,et al.  Petrology and geochemistry of the Saga and Sangsang ophiolitic massifs, Yarlung Zangbo Suture Zone, Southern Tibet: Evidence for an arc-back-arc origin , 2009 .

[14]  J. Gee,et al.  Footwall rotation in an oceanic core complex quantified using reoriented Integrated Ocean Drilling Program core samples , 2009 .

[15]  J. Gee,et al.  Paleomagnetic evidence of large footwall rotations associated with low-angle faults at the Mid-Atlantic Ridge , 2007 .

[16]  Deborah K. Smith,et al.  Widespread active detachment faulting and core complex formation near 13° N on the Mid-Atlantic Ridge , 2006, Nature.

[17]  J. Escartín,et al.  Constraints on deformation conditions and the origin of oceanic detachments: The Mid‐Atlantic Ridge core complex at 15°45′N , 2003 .

[18]  J. Aitchison,et al.  Precise radiolarian age constraints on the timing of ophiolite generation and sedimentation in the Dazhuqu terrane, Yarlung–Tsangpo suture zone, Tibet , 2003, Journal of the Geological Society.

[19]  S. Edwards,et al.  Geochemistry and tectonic significance of peridotites from the South Sandwich arc–basin system, South Atlantic , 2000 .

[20]  An Yin,et al.  Geologic Evolution of the Himalayan-Tibetan Orogen , 2000 .

[21]  R. Mccaffrey.  Slip vectors and stretching of the Sumatran fore arc , 1991 .

[22]  R. L. Fisher,et al.  Petrology and Geochemistry of Igneous Rocks from the Tonga Trench: A Non-Accreting Plate Boundary , 1987, The Journal of Geology.

[23]  J. Girardeau,et al.  Origin of the Xigaze ophiolite, Yarlung Zangbo suture zone, southern Tibet , 1985 .

[24]  J. Burg,et al.  Tectonics and structural zonation of southern Tibet, China , 1984, Nature.

[25]  E. Moores.  origin and emplacement of ophiolites , 1982 .

[26]  B. Dupré,et al.  The Xigaze ophiolite (Tibet): a peculiar oceanic lithosphere , 1981, Nature.

[27]  John Malpas,et al.  Geochemical and geochronological constraints on the origin and emplacement of the Yarlung Zangbo ophiolites, Southern Tibet , 2003, Geological Society, London, Special Publications.

[28]  Julian A. Pearce,et al.  Characteristics and tectonic significance of supra-subduction zone ophiolites , 1984, Geological Society, London, Special Publications.

[29]  B. P. Kokelaar,et al.  Marginal basin geology : volcanic and associated sedimentary and tectonic processes in modern and ancient marginal basins , 1984 .