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Lower Cretaceous Xigaze ophiolites formed in the Gangdese forearc: Evidence from paleomagnetism, sediment provenance, and stratigraphy

  • The India-Asia suture zone of southern Tibet exposes Lower Cretaceous Xigaze ophiolites and radiolarian cherts, and time-equivalent Asian-derived clastic forearc sedimentary rocks (Xigaze Group). These ophiolites have been interpreted to have formed in the forearc of the north-dipping subduction zone below Tibet that produced the Gangdese magmatic arc around 15-20 degrees N, or in the forearc of a subequatorial intra-oceanic subduction zone. To better constrain the latitude of the ophiolites, we carried out an integrated paleomagnetic, geochronologic and stratigraphical study on epi-ophiolitic radiolarites (Chongdui and Bainang sections), and Xigaze Group turbiditic sandstones unconformably overlying the ophiolite's mantle units (Sangsang section). Detrital zircon U-Pb geochronology of tuffaceous layers from the Chongdui section and sandstones of the Xigaze Group at the Sangsang section provides maximum depositional ages of 116.5 +/- 3.1 Ma and 128.8 +/- 3.4 Ma, respectively, for the Chongdui section and an Asian provenance signatureThe India-Asia suture zone of southern Tibet exposes Lower Cretaceous Xigaze ophiolites and radiolarian cherts, and time-equivalent Asian-derived clastic forearc sedimentary rocks (Xigaze Group). These ophiolites have been interpreted to have formed in the forearc of the north-dipping subduction zone below Tibet that produced the Gangdese magmatic arc around 15-20 degrees N, or in the forearc of a subequatorial intra-oceanic subduction zone. To better constrain the latitude of the ophiolites, we carried out an integrated paleomagnetic, geochronologic and stratigraphical study on epi-ophiolitic radiolarites (Chongdui and Bainang sections), and Xigaze Group turbiditic sandstones unconformably overlying the ophiolite's mantle units (Sangsang section). Detrital zircon U-Pb geochronology of tuffaceous layers from the Chongdui section and sandstones of the Xigaze Group at the Sangsang section provides maximum depositional ages of 116.5 +/- 3.1 Ma and 128.8 +/- 3.4 Ma, respectively, for the Chongdui section and an Asian provenance signature for the Xigaze Group. Paleomagnetic analyses, integrated with rock magnetic experiments, indicate significant compaction-related inclination 'shallowing' of the remanence within the studied rocks. Two independent methods are applied for the inclination shallowing correction of the paleomagnetic directions from the Sangsang section, yielding consistent mean paleolatitudes of 16.2 degrees N 113 degrees N, 20.9 degrees N] and 16.8 degrees N [11.1 degrees N, 23.3 degrees N], respectively. These results are indistinguishable from recent paleolatitude estimates for the Gangdese arc in southern Tibet. Radiolarites from the Chongdui and Bainang sections yield low paleomagnetic inclinations that would suggest a sub-equatorial paleolatitude, but the distribution of the paleomagnetic directions in these rocks strongly suggests a low inclination bias by compaction. Our data indicate that spreading of the Xigaze ophiolite occurred in the Gangdese forearc, and formed the basement of the forearc strata. (C) 2015 Elsevier B.V. All rights reserved.show moreshow less

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Author:Wentao Huang, Douwe J. J. van Hinsbergen, Marco Maffione, Devon A. Orme, Guillaume Dupont-Nivet, Carl Guilmette, Lin Ding, Zhaojie Guo, Paul Kapp
DOI:https://doi.org/10.1016/j.epsl.2015.01.032
ISSN:0012-821X (print)
ISSN:1385-013X (online)
Parent Title (English):Earth & planetary science letters
Publisher:Elsevier
Place of publication:Amsterdam
Document Type:Article
Language:English
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
Tag:Xigaze ophiolite; inclination shallowing; paleomagnetism and rock magnetism; sedimentary contact
Volume:415
Pagenumber:12
First Page:142
Last Page:153
Funder:U.S. NSF [EAR-1008527]; Netherlands Organisation for Scientific Research (NWO) VIDI; European Research Council (ERC) [306810]; Alexander von Humboldt Foundation; Cai Yuanpei program of the French Ministry of Foreign Affairs; Ministry of Higher Education and Research; Ministry of
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Erd- und Umweltwissenschaften
Peer Review:Referiert