Calderas on Mars: characteristics, structure, and associated flank deformation
Calderas on Mars: characteristics, structure, and associated flank deformation
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火星上的火山口：特征、结构和相关的侧面变形
DOI：
10.1144/gsl.sp.1996.110.01.24
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
J. Aubele
中科院分区：
文献类型：
--
作者：
L. Crumpler;J. Head;J. Aubele
火星火山的火山口和侧翼结构使我们能够洞察火山结构演化的一般问题，以及在侵蚀最小的环境中的地下岩浆室。通过详细的地质填图，我们记录了每个火星建筑物建造期间的构造、相关的火山学特征，以及侧翼结构和破火山口事件之间的地层关系。火星上发现了两种完全不同的破火山口类型(奥林匹斯型和阿西亚型)，它们可能代表了岩浆室大小和深度的末端成员的差异。许多毗邻破火山口边缘的侧翼结构与岩浆室膨胀和通货紧缩的预测结果一致，后者对许多火山的结构发展产生了重大影响。较大的火星火山上翼的大规模梯田和陡峭可能起源于岩浆室膨胀和径向逆冲。因此，由累积的岩浆室增长导致的火山增长的内生成分可能是显着的。许多最深的火山口与侧翼其他地方和贯穿裂缝的大规模喷发有关，似乎主要是由于岩浆室的疏散和泄气，而没有广泛的前兆膨胀。在这些情况下，岩浆以长达数百公里的浅岩墙的形式横向传播，以及相关的线性裂缝的形成，可能有助于岩浆室的排出。嵌套的破火山口序列、相关的侧面坑、大规模的坍塌、梯田和扇形结构经常以线性模式排列，是穿透喷发线或数百公里长的裂缝的一部分，这些都是几个火星盾形火山的特征。如此长的裂缝被解释为从浅层岩浆室向外传播的岩墙，这些岩浆室遵循了最小区域应力方向。将观测到的破火山口构造的形状和方向与侧面变形的方位和样式进行了比较，并与理论预测进行了比较，表明区域应力可能对火星火山的破火山口和侧面构造有重要影响。最小区域应力方向可能主要受与Tharsis地区和极乐地区有关的区域斜坡控制，对于Tyrrhena Patera来说，与希腊盆地有关的预先存在的放射状裂缝可能控制着最小区域应力方向。
Abstract Calderas and flank structures of martian volcanoes yield insight into general questions of volcano structural evolution and the underlying magma chambers in an environment where erosion is minimal. We have documented, through detailed geological mapping, the structures, associated volcanological features, and the stratigraphical relationships between the flank structures and caldera events during the building of each martian edifice. Two fundamentally different types of calderas are identified on Mars (the Olympus type and the Arsia type) that may represent end member variations in the size and depth of magma chambers. Many of the flank structures adjacent to caldera rims are consistent with the predicted effects of magma chamber inflation as well as deflation that exert significant influences in the structural development of many volcanoes. Large-scale terracing and steepening of the upper flanks of the larger martian volcanoes may originate from magma chamber inflation and radial thrusting. Thus the endogenous component of volcano growth resulting from accumulated magma chamber growth may be significant. Many of the deepest calderas are associated with evidence for voluminous eruptions elsewhere on the flanks and along through-going fissures and appear to result largely from evacuation and deflation of magma chambers without extensive precursor inflation. Draining of the magma chamber in these cases may be aided by the lateral propagation of magma in the form of shallow dykes up to several hundred kilometres in length and the associated formation of linear fissures. Nested caldera sequences, related flank pits, large-scale slumping, terracing, and sector structure are frequently arranged in linear patterns and are part of through-going eruptive lines or fissures several hundred kilometres in length that characterize several martian shield volcanoes. Fissures this long are interpreted to be dykes propagated outward from shallow magma chambers that have followed a minimum regional stress orientation. Comparison of the observed shape and orientation of caldera structures with orientation and style of flank deformation, and with the predictions from theory, indicate that regional stresses have probably been an important influence on the caldera and flank structures of martian volcanoes. The minimum regional stress orientation may be controlled largely by regional slopes associated with the Tharsis region and Elysium regions, and, in the case of Tyrrhena Patera, pre-existing radial fractures associated with the Hellas basin.