琼北地区北西方向长流-仙沟断裂带晚第四纪活动及与火山活动关系的讨论

琼北地区的火山活动以裂隙喷溢为主,晚更新世道堂期的射气岩浆喷发形成了众多的低平火山口,全新世雷虎岭期火山口主要分布于石山、永兴一带,沿NW向长流-仙沟断裂带分布。近2年在石山一带的射气岩浆喷发物中揭露出多条大规模的断裂,这些断裂带的单个断面虽然类似于地震活断层,但它们缺少断错地貌和断层方向的稳定性,一些断层组合成弧形。尽管这些断裂断面清晰,断距达4m,仍被认为是伴随火山喷发活动后期塌陷而形成的次级断层。此外,位于非火山岩分布区跨长流-仙沟断裂带的钻孔联合剖面探测表明,该断裂带在晚更新世晚期以来不活动。长流-仙沟断裂带晚更新世晚期以来的活动主要表现在作为深部岩浆的上涌通道。

Relationship Between the Activity of the Changliu-Xiangou Fault Zone in Late-Quaternary and Volcanic Activity in North Hainan Island

The volcanic eruption in North Hainan Island was mainly in the pattern of fissure eruption, until in the Late-Pleistocene Epoch many maars were caused by phreatomagmatic eruptions in the Daotang Group. The Holocene volcanic activity of the Leihuling Group are distributed mainly along the Changliu-Xiangou fault zone in the Shishan-Yongxing area Many large-scale faults are found in the base-surge deposits which are created by phreatomagmatic eruptions in Shishan area. Although the single profile of the fault zones seems to be earthquake active fault, they are in lack of the characteristics of dislocated geomorphology and the stability of fault trends. Some of fault trends show the characteristics of arc distribution, which are considered as the secondary faults caused by the volcanic rock collapse after eruption. The combined profile by borehole detection which lies in the region of non-volcanic area shows that the Changliu-Xiangou fault has not been active since the later period of Late-Pleistocene. The activity of Changliu-Xiangou fault zone are mainly in form of the magma channel since the later period of Late-Pleistocene.