Internal Geology and Evolution of the Redondo Dome, Valles Caldera, New Mexico
Internal Geology and Evolution of the Redondo Dome, Valles Caldera, New Mexico
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新墨西哥州火山口火山口雷东多圆顶的内部地质和演化
DOI：
10.1029/jb089ib10p08695
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发表时间：
1984
影响因子：
--
通讯作者：
J. Hulen
中科院分区：
文献类型：
--
作者：
D. Nielson;J. Hulen
在复兴的雷东多圆顶的山谷破火山口的深层地热钻探，使我们能够定义一个一致的火山口内地层序列，在许多方面不同于时间上等同的序列外的破火山口。在深度侵蚀的上新世Paliza峡谷地层之上，长英质灰流和圆顶区域的沉积物形成了一个复杂的序列，其年龄未定，我们称之为下凝灰岩。侵蚀间隔将这些岩石与上覆的Otowi Member（140万年）分开。班德利尔凝灰岩另一个侵蚀期，在此期间沉积了凝灰质砂岩，将Otowi与上覆的Tshirege Member（110万年）分开。关于Bandelier Otowi和Tshirege成员的最大厚度分别为833和1155米，在破火山口内比外面厚得多，表明同时沉积和坩埚沉降。两者都主要是密集焊接与独特的内部带的花岗斑岩结晶。在Tshirege段就位后，恢复性隆起开始形成，这一点可通过冷却单元上部在上覆单元沉积之前的侵蚀得到证明。在这一侵蚀时期沉积的砂岩的等厚图显示，流排水隆起的圆顶是本地化沿着目前雷东多河趋势。随后的火山活动导致形成至少三个额外的灰流凝灰岩冷却单位之前，火山口填充和雷东多溪成员的山谷流纹岩喷发的沉积。应用于Redondo圆顶形成的数值模型表明，成因岩浆体的顶部位于圆顶中最深的地热井底部以下约4700 m，1458 m的深度。没有任何威尔斯井穿透过可能与岩浆有关的侵入体。我们认为，边界顶端地堑的圆顶断层的位置的影响，与东北走向Jemez线性构造的老故障。这些断层在穹丘隆起历史的早期活动，并解释了假设的穹丘发展与现实之间的许多结构差异。
Deep geothermal drilling in the resurgent Redondo dome of the Valles caldera has allowed us to define a consistent intracaldera stratigraphic sequence that differs in a number of respects from the temporally equivalent sequence outside the caldera. Above the deeply eroded, Pliocene Paliza Canyon Formation, felsic ash flows and sediments in the dome area form a complex sequence of undetermined age that we call the Lower Tuffs. An erosional interval separates these rocks from the overlying Otowi Member (1.4 m.y.) of the Bandelier Tuff. Another period of erosion, during which a tuffaceous sandstone was deposited, separates the Otowi from the overlying Tshirege Member (1.1 m.y.) of the Bandelier. Both the Otowi and Tshirege members, with maximum thicknesses of 833 and 1155 m, respectively, are substantially thicker within the caldera than outside, indicating simultaneous deposition and cauldron subsidence. Both are predominantly densely welded with distinctive interior zones of granophyric crystallization. Resurgent doming was initiated after emplacement of the Tshirege Member as evidenced by erosion of the upper portions of the cooling unit prior to deposition of overlying units. An isopach map of the sandstone deposited during this erosional period shows that streams draining the uplifting dome were localized along the present Redondo Creek trend. Subsequent volcanic activity resulted in the formation of at least three additional ash flow tuff cooling units prior to deposition of caldera fill and eruption of the Redondo Creek Member of the Valles Rhyolite. A numerical model applied to formation of the Redondo dome suggests that the top of the causative magma body is located at a depth of about 4700 m, 1458 m beneath the bottom of the deepest geothermal well in the dome. No wells have penetrated intrusives that could be related to this magma. We suggest that the locations of faults bounding the apical graben of the dome were influenced by older faults associated with the northeast trending Jemez lineament. These faults were active early in the uplift history of the dome and account for many of the structural differences between hypothetical dome development and reality.