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Paleomagnetic and Geochronologic Results of Latest Cretaceous Lava Flows From the Lhasa Terrane and Their Tectonic Implications
Author(s) -
Ma Yiming,
Yang Tianshui,
Bian Weiwei,
Jin Jingjie,
Wang Qiang,
Zhang Shihong,
Wu Huaichun,
Li Haiyan,
Cao Liwan,
Yuan Haifan,
Ding Jikai
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2017jb014743
Subject(s) - geology , paleomagnetism , terrane , lava , paleontology , cenozoic , fibrous joint , cretaceous , tectonics , petrography , volcano , structural basin , medicine , anatomy
To position the Asian southern margin before the India‐Asia collision, paleomagnetic and geochronologic studies were performed on the Dianzhong Formation lava flows from the Shiquanhe area of the westernmost Lhasa terrane (LT). Zircon U‐Pb analyses dated the lava flows to ~69.5 ± 2.5 Ma. The characteristic remanent magnetization directions contain antipodal polarities and pass fold tests, implying that they are primary magnetizations; this interpretation is supported by rock‐magnetic analyses and petrographic observations. Forty‐four site‐mean directions were divided into 17 statistically independent direction groups. The group‐mean direction after tilt correction is Ds = 43.3°, Is = 30.3°, k = 28.0, α 95 = 6.9°. The corresponding paleopole at 47.8°N, 181.4°E ( A 95 = 6.4°) yields a paleolatitude of 16.6° ± 6.4°N for the Shiquanhe area of westernmost Tibet (32.34°N, 80.12°E). Consistent paleolatitudes for the southern margin of the LT calculated from the western and central part of the LT indicate that the leading edge of the LT was aligned relatively W‐E. When compared with the reference pole at 70 Ma for Eurasia, this new paleopole suggests that crustal shortening between the Shiquanhe area and stable Asia was 1,500 ± 800 km. This is supported by the crustal shortening (600–1,000 km) absorbed by Cenozoic thrust and fold belts within this area, indicating that the magnitude of crustal shortening within Asia north of the India‐Asia suture zone was similar in the central and western part of the plateau.