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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Emplacement and inflation of the Al-Halaq al Kabir lava flow field, central part of the Al Haruj Volcanic Province, Central Libya
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Emplacement and inflation of the Al-Halaq al Kabir lava flow field, central part of the Al Haruj Volcanic Province, Central Libya

机译：利比亚中部哈鲁吉火山省中部的Al-Halaq al Kabir熔岩流场的进位和膨胀

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Numerous of lava rise plateaus and tumuli developed in the medial and distal portions of the Al-Halaq al Kabir lava flow field during the last (Holocene) eruption in the central part of the Al Haruj Volcanic Province (AHVP). These inflation structures provide important data on the lava-emplacement mechanism in this part of the Al Haruj region where the widespread occurrence of tumuli and lava rise plateaus are good indicators of the mode of emplacement. We report the results of detailed measurements of the maximum and minimum diameters in plan-view of 551 lava-rise plateaus and 289 tumuli from the distal part of the Al-Halaq al Kabir lava field using ArcGIS and field observations. Tumuli and lava rise plateaus may be divided into subpopulations according to abrupt changes in the scaling exponents on log-log plots of their frequency versus diameter. Using the estimated stiffness (Young's modulus) of the basaltic rocks in the study area of 10-34 GPa, numerical and analytical results show that theoretical maximum tensile stresses in the inflated upper (solidified) crustal layers of the developing tumuli and lava rises at tens of mega-pascals (MPa). This theoretical stress is orders of magnitude higher than typical in-situ tensile strengths of rocks (0.5-9 MPa) and thus high enough to rupture the crustal layers of the lava rises and tumuli. The high tensile stresses are generated during crustal doming driven by a magmatic overpressure of only about 1 MPa. Our results partly explain the abundance of tension fractures at the surface of the Al-Halaq al Kabir lava flow field. Tumuli observed in the area are remarkably similar in morphology and aspect (height/width) ratios to the flow-lobe tumuli in Holocene lava flow fields in Iceland, suggesting an analogous mechanics of formation. There appears to be a coincidence between the age of an initial volcanism in the AHVP (7.9-53 Ma) and a local fauna and flora disappearance in the As-Sahabi area, NE Sirt Basin. during Messinian-Zanclean time (7-5 to 5 Ma). We speculate that the volcanism may have had a local negative environmental impact and contributed to the reported decline in the fauna and flora in the area. Crown Copyright (C) 2019 Published by Elsevier B.V. All rights reserved.
机译：在Al Haruj火山省（AHVP）的最后一次（全新世）喷发期间，在Al-Halaq al Kabir熔岩流场的中部和远端形成了许多熔岩上升高原和肿瘤。这些通货膨胀结构提供了有关Al Haruj地区这一地区熔岩侵入机制的重要数据，在这里，肿瘤和熔岩上升高原的广泛发生是该岩浆侵入模式的良好指标。我们使用ArcGIS和现场观测报告了从Al-Halaq al Kabir熔岩田的远侧部分到551个熔岩上升高原和289个古墓的平面图中最大和最小直径的详细测量结果。根据其频率与直径的对数对数图上缩放指数的突然变化，Tumuli和熔岩上升高原可分为亚群。利用研究范围为10-34 GPa的玄武岩的估计刚度（杨氏模量），数值和分析结果表明，发育中的动土和熔岩的膨胀的上（凝固）地壳层的理论最大拉应力在10时上升。兆帕（MPa）。该理论应力比典型的岩石原位抗拉强度（0.5-9 MPa）高几个数量级，因此足够高，足以使熔岩上升和生瘤的地壳层破裂。在地壳隆起期间，由于仅约1 MPa的岩浆超压而产生高拉伸应力。我们的结果部分解释了Al-Halaq al Kabir熔岩流场表面的大量张力裂缝。在该地区观察到的Tumuli与冰岛全新世熔岩流场中的流瓣肿瘤的形态和长宽比（高度/宽度）非常相似，表明形成机理相似。在AHVP（7.9-53 Ma）的初次火山爆发的年龄与NE Sirt盆地As-Sahabi地区的局部动植物消失之间似乎是巧合。在Messinian-Zanclean时间（7-5至5 Ma）期间。我们推测，火山活动可能会对当地环境造成负面影响，并导致该地区动植物数量下降。官方版权（C）2019由Elsevier B.V.保留所有权利。

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