Paleomagnetism of the structurally deformed Latir volcanic field, northern New Mexico: Relations to formation of the Questa caldera and development of the Rio Grande rift
Paleomagnetism of the structurally deformed Latir volcanic field, northern New Mexico: Relations to formation of the Questa caldera and development of the Rio Grande rift
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新墨西哥州北部结构变形的拉提尔火山场的古地磁学：与奎斯塔火山口形成和里奥格兰德裂谷发展的关系
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发表时间：
1986
期刊：
影响因子：
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通讯作者：
P. Lipman
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作者：
J. Hagstrum;P. Lipman
渐新世-中新世的奎斯塔破火山口和相关的岩石在沿着新墨西哥州北方的格兰德河裂谷的东侧出露。这些岩石的年龄大约为25-26百万年，是该地区伸展构造的开始。前早期阶段的扩展的特点是目前低角度的正断层，造成火山单位，特别是在奎斯塔破火山口的陡峭倾斜。古地磁测量的侵入和喷出岩石从阿马尔领域表明，倾斜突然开始后，爆发的阿马利亚凝灰岩和随后形成的奎斯塔破火山口26百万年。前特别是，大部分倾斜发生在火山口内熔结凝灰岩和次火山口岩浆房的最上部冷却并磁化之后，但在随后复活的岩体就位并充分冷却以磁化约1百万年之前。后该地区的差异隆起暴露了南部同样具有非倾斜磁化作用的类似年龄的次火山深成岩。当晚期的深成岩被磁化时，倾斜已经完全停止了，至少在破火山口结构内部和南部是这样。较年轻的裂谷相关沉积岩和层间玄武岩流（15百万年）旧）表明倾斜继续向北部的破火山口过去的这个时候。然而，古地磁证据表明，附近的700万至1100万年。古老的流纹岩穹丘可能是不倾斜的，这表明该地区的显著倾斜在这个时候已经结束。伸展的最新阶段以高角度深穿透正断层为特征，这是该地区目前观察到的高构造起伏的原因。
The Oligocene-Miocene Questa caldera and related rocks of the Latir volcanic field are exposed along the eastern flank of the Rio Grande rift in northern New Mexico. These rocks bracket in age the beginning of extensional tectonics in the region approximately 25–26 m.y. ago. The early phase of extension is characterized by currently low-angle normal faults that caused steep tilting of volcanogenic units, particularly within the Questa caldera. Paleomagnetic measurements on intrusive and extrusive rocks from the Latir field show that tilting began abruptly after the eruption of the Amalia Tuff and subsequent formation of the Questa caldera 26 m.y. ago. Specifically, most of the tilting occurred after the intracaldera welded tuff and uppermost portion of the subcaldera magma chamber had cooled and become magnetized, but before the subsequent resurgent plutons had been emplaced and cooled sufficiently to also become magnetized about 1 m.y. later. Differential uplift of the region exposes similarly aged subvolcanic plutonic rocks to the south that also have untilted magnetizations. Tilting had ceased altogether by the time the late-stage plutons were magnetized, at least within the caldera structure and to the south. Younger rift-related sedimentary rocks and interbedded basalt flows (15 m.y. old) show that tilting continued to the north of the caldera past this time. However, paleomagnetic evidence indicates that a nearby 7- to 11-m.y.-old rhyolite dome is probably untilted, suggesting that significant tilting in the region had ended by this time. The latest phase of extension is characterized by high-angle deeply penetrating normal faults, which are responsible for the high structural relief presently observed in the region.