The Cretaceous stationary Lhasa terrane constrained by the paleolatitude of 103 Ma volcanic rocks from the Nima area.
The Cretaceous stationary Lhasa terrane constrained by the paleolatitude of 103 Ma volcanic rocks from the Nima area.
复制标题
白垩纪静止的拉萨地体受尼玛地区103Ma火山岩古纬度的限制。
DOI：
10.1016/j.gloplacha.2022.103998
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发表时间：
2023
影响因子：
3.9
通讯作者：
Shihong Zhang
中科院分区：
文献类型：
--
作者：
Chao Niu;Yiming Ma;Huapei Wang;Tianshui Yang;Haiyan Li;Fei Han;Chang Xu;Junxiang Miao;Zongyong Yang;Hongzhu Cai;Wenpin Gong;Shihong Zhang
为确定拉萨地区白垩纪的古纬度演化和方向，对拉萨地区中部尼玛县附近的曲申拉组火山岩进行了古地磁研究。岩石磁学和磁性岩相学研究表明，初始冷却过程中形成的磁铁矿和赤铁矿是主要的磁性载体。分离出了温度在1500 °C至1680 °C之间的高温组分。在99%的置信水平下，位点平均方向通过了折叠检验，在倾斜校正后，18个位点的平均倾角为35.4°。这些结果表明，火山岩记录了一次原始剩余磁化强度，表明拉萨火山南缘参考点（29.0°N，87.5°E）的古纬度在10103 Ma时为17.9°N。结合前人的古地磁结果，我们的研究结果表明，在白垩纪期间，在北纬16.7 -19°N，稳定的拉萨古地磁场经历了NW-ESE向的延伸。拉萨-羌塘地区侏罗纪-白垩纪的古纬度演化表明，拉萨-羌塘碰撞发生在距今155-132 Ma之间。
To constrain the paleolatitude evolution and orientation of the Lhasa terrane in the Cretaceous, we performed a paleomagnetic study on the Qushenla Formation volcanic rocks dated to ∼103 Ma near Nima County in the central part of the Lhasa terrane. Rock magnetism and magnetic petrography indicate that the primary magnetic carriers are magnetite and hematite that formed during initial cooling. A high-temperature component was isolated between ∼500 °C and ∼680 °C. The site-mean direction passes the fold tests at a 99% confidence level, yielding a mean inclination of 35.4° for 18 sites after tilt correction. These results suggest that the volcanic rocks recorded a primary remnant magnetization, revealing a paleolatitude of ∼17.9°N at ∼103 Ma for the reference point (29.0°N, 87.5°E) at the southern margin of the Lhasa terrane. Together with previous paleomagnetic results from the Lhasa terrane, our results indicate WNW–ESE elongation of the stationary Lhasa terrane at ∼6.7–19°N during the Cretaceous. The paleolatitude evolution of the Lhasa terrane during the Jurassic–Cretaceous suggests that the Lhasa–Qiangtang collision occured at ∼155–132 Ma.