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特提斯喜马拉雅位于大印度最北端,其构造演化是理解印度-亚洲大陆碰撞过程的关键之一.为了更好地限定特提斯喜马拉雅中生代以来的古地理位置及其漂移历史,本文对藏南江孜床得剖面侏罗系下热组、维美组和白垩系床得组开展了古地磁研究.古地磁样品取自39个采样点,其中下热组5个,岩性为青灰色安山岩;维美组25个,岩性为粉砂岩和砂岩;床得组9个,岩性为灰岩.对118个古地磁柱状样品进行的逐步热退磁和交变退磁结果显示,下热组和维美组样品未能分离出稳定的特征剩磁;床得组样品分离出了稳定的特征剩磁(Ch RM),且具有正反极性,并通过了倒转检验.结合沉积学和岩石磁学结果,床得组样品的特征剩磁很可能为原生剩磁,其年龄为86.3~74.0 Ma.床得组样品特征剩磁的平均方向为Ds=152.0°,Is=?52.9°,?=18.0,?95=5.9°.该数据表明,特提斯喜马拉雅江孜地区在晚白垩世(80.1±6.2 Ma)所处的古纬度为南纬33.1°±5.6°,与印度板块北缘同时代所处的古纬度一致(参考点28.0°N,88.5°E),说明二者至少在晚白垩世之前从运动学意义上仍然是一个块体,缺乏大洋分隔的证据.这为理解印度-亚洲大陆碰撞方式提供了新的古地磁约束.
The Tethyan Himalayas are located in the northernmost tip of Greater India and their tectonic evolution is one of the keys to understand the Indian-Asian continent collision process.In order to better define the Paleo-Himalayan Mesozoic paleogeographic location and its drift history, Paleomagnetism studies were carried out in the Jurassic Lower Cretaceous, the Weimei Formation and the Cretaceous Bedde Formation in the Gyangde section. The paleomagnetic samples were collected from 39 sampling sites, of which 5 were in the lower heat group with lithic andesite; There are 25 Vimet groups with lithology of siltstone and sandstone, 9 beds with lithology of limestone, and the gradual thermal demagnetization and alternating demagnetization of 118 paleomagnetism samples show that the lower heat group and the dimension The stable sample remanent magnetism could not be separated from the samples of the US group, and the stable characteristic residual magnetism (Ch RM) was isolated from the sample of the bed group, with positive and negative polarities, and passed the inversion test. Combined with sedimentology and rock magnetism As a result, the remanent remanence of the bed group samples is likely to be native remanence with an age of 86.3-74.0 Ma. The average remanent magnetization direction of the bed group samples is Ds = 152.0 °, Is =? 52.9 °,? = 18.0 , 95 = 5.9 °. The data show that the Tethyan Himalayas in the Gyantse region were in the Late Cretaceous (80.1 ± 6. 2 Ma) is located at 33.1 ° ± 5.6 ° South latitude, which coincides with the paleo-latitudinal latitudes of the northern margin of Indian Plate (reference point 28.0 ° N, 88.5 ° E), indicating that at least during the Late Cretaceous Previously, it was still a block in terms of kinematics, lacking evidence of oceanic separation, which provided a new paleomagnetic constraint for understanding the collision pattern of India-Asia continent.