Recurrence Rate and Magma Effusion Rate for the Latest Volcanism on Arsia Mons, Mars
Recurrence Rate and Magma Effusion Rate for the Latest Volcanism on Arsia Mons, Mars
复制标题
火星阿尔西亚山最新火山活动的复发率和岩浆喷发率
DOI：
10.1016/j.epsl.2016.10.040
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发表时间：
2017
影响因子：
5.3
通讯作者：
K. Kiyosugi
中科院分区：
文献类型：
--
作者：
J. Richardson;James Wilson;C. Connor;J. Bleacher;K. Kiyosugi
在整个火星历史上，岩浆作用和火山作用演变了火星岩石圈、地表和气候。限制地表岩浆产生的速度和火山活动的时间，可以澄清岩浆和火山活动塑造这些火星系统的方式。其他行星上熔岩流的年龄通常是使用撞击坑计数来估计的，假设单位面积上的撞击坑的数量和大小分布反映了熔岩流在地表上并暴露在潜在撞击中的时间。在这里，我们表明，通过添加在邻近熔岩相互毗邻的位置观察到的地层学信息，降低了撞击坑年龄模型的不确定性，并证明了这种年龄不确定性的降低对于理解火星Arsia Mons直径110公里的火山口中由29个喷口组成的火山场的历史具有重要意义。这个火山口内的每个喷口都产生了几到几十公里长的熔岩流；这些喷口可能是火星上最年轻的喷口之一，因为它们的熔岩流中没有直径大于1公里的撞击坑。首先，我们对每个喷口的年龄进行了建模，对其相应的熔岩流进行了撞击坑计数，发现单个喷口的年龄存在很大的年龄不确定性，通常跨越整个火山场的估计年龄。仅根据撞击坑计数得出的年龄模型是宽泛的和单峰的，估计该地区的峰值活动约为130 Ma。接下来，我们应用了我们的火山事件年龄模型(VEAM)，该模型使用地层关系的有向图和撞击坑年龄确定的随机抽样来创建替代的年龄模型。蒙特卡罗模拟被用来建立10,000个可能的喷口年龄集。对每个可能的年龄组计算火山活动的复发率，并将这些比率结合起来计算所有模拟的中位数复发率。将这种方法应用于29个火山口，火山活动可能在200-300 Ma左右开始，然后在150 Ma左右第一次达到顶峰，平均每Myr产生0.4个喷口。包括地层学数据在内的复发率估计具有明显的双峰性，在100 Ma左右出现第二个较低的活动峰值。火山作用随后减弱，直到产生10-90 Ma的最终喷口。在该模型的基础上，体积通量也是双峰的，在150 Ma时达到1-8km3Myr−1的峰值速率，并保持在这个速率的一半以上，直到90 Ma左右，之后体积通量急剧下降。200-150 Ma喷发火山作用的开始，可能是由于火山活动类型的转变，不再是火山活动的爆发式火山活动侵位在阿西蒙斯西侧，而150 Ma高峰后火山活动的减弱可能代表了与侧翼围裙熔岩侵位有关的阿西蒙火山活动的较大规模的减弱。
Magmatism and volcanism have evolved the Martian lithosphere, surface, and climate throughout the history of Mars. Constraining the rates of magma generation and timing of volcanism on the surface clarifies the ways in which magma and volcanic activity have shaped these Martian systems. The ages of lava flows on other planets are often estimated using impact crater counts, assuming that the number and size-distribution of impact craters per unit area reflect the time the lava flow has been on the surface and exposed to potential impacts. Here we show that impact crater age model uncertainty is reduced by adding stratigraphic information observed at locations where neighboring lavas abut each other, and demonstrate the significance of this reduction in age uncertainty for understanding the history of a volcanic field comprising 29 vents in the 110-km-diameter caldera of Arsia Mons, Mars. Each vent within this caldera produced lava flows several to tens of kilometers in length; these vents are likely among the youngest on Mars, since no impact craters in their lava flows are larger than 1 km in diameter. First, we modeled the age of each vent with impact crater counts performed on their corresponding lava flows and found very large age uncertainties for the ages of individual vents, often spanning the estimated age for the entire volcanic field. The age model derived from impact crater counts alone is broad and unimodal, with estimated peak activity in the field around 130 Ma. Next we applied our volcano event age model (VEAM), which uses a directed graph of stratigraphic relationships and random sampling of the impact crater age determinations to create alternative age models. Monte Carlo simulation was used to create 10,000 possible vent age sets. The recurrence rate of volcanism is calculated for each possible age set, and these rates are combined to calculate the median recurrence rate of all simulations. Applying this approach to the 29 volcanic vents, volcanism likely began around 200–300 Ma then first peaked around 150 Ma, with an average production rate of 0.4 vents per Myr. The recurrence rate estimated including stratigraphic data is distinctly bimodal, with a second, lower peak in activity around 100 Ma. Volcanism then waned until the final vents were produced 10–90 Ma. Based on this model, volume flux is also bimodal, reached a peak rate of 1–8 km3Myr−1by 150 Ma and remained above half this rate until about 90 Ma, after which the volume flux diminished greatly. The onset of effusive volcanism from 200–150 Ma might be due to a transition of volcanic style away from explosive volcanism that emplaced tephra on the western flank of Arsia Mons, while the waning of volcanism after the 150 Ma peak might represent a larger-scale diminishing of volcanic activity at Arsia Mons related to the emplacement of flank apron lavas.