菲尔德斯半岛火山构造及其时空演化

菲尔德斯半岛火山活动有两个高峰期,相应分为两个亚族回.火山机构有二类,一类以火山颈相岩柱为标志,另一类发育着火口相、近火口相集块岩、集块熔岩.据形成时间又可分为早期和晚期火山机构.火山活动明显受区域构造控制,为典型的裂隙中心式喷发,形成本区NW向、间距约为2km的火山喷发带.早期活动遍及全区,具有自SW向NE迁移的总体演化趋势;晚期沿火山喷发带自NW向SE局部性迁移.

VOLCANIC STRUCTURES AND THEIR TEMPORAL AND SPATICAL EVOLUTION ON FILDES PENINSULA, ANTARCTICA

The volcanic sequence on Fildes Peninsula is named the Fildes Cycle. It may be divided into two subcycles. The first subcycle includes the Jasper Hill Member (Eb) and the Agate Beach Member (Em). Eb occurs in the southern part of the Peninsula while Em crops out over much of Fildes Peninsula. The second subcycle is composed of the Fossil Hill Member (Eh) and the Block Hill Member (Ey) which crop out mostly over the eastern Fildes Peninsula. There are two main kinds of volcanic edifices in the area. One is the positive edifice characterized by volcanic neck facies pillar and radiating dikes, such as Horatio Stump, Gemel Mt. and Shanhaiguan Peak. The other is the negative edifice with agglomerates (lava), agglomerate breccias (lava) of crater facies and near crater facies, showing negative topography, such as volcanic edifices in Windstorm Cove and Norma Cove. Cenozoic volcanic activities in the area were controlled by regional tectonics and have some trends in time-space distribution. From the south to the north, four eruptive zones, spaced about 2km apart, were recognized, they are Flat Top-Shanhaiguan Peak volcanic eruption zone, Gemel Mt. -Ardley Island zone, Windstorm Cove-Suffield Point zone, and Great Wall Rock zone, corresponding to four major NW-trending structural zones. The structures controlling the eruptive zones are extentional faults, related to subduction of the Pacific plate beneath the Antarctic Peninsula. Early eruption occurred almost all over Fildes Peninsula, and had a progressive north easterly migration, consistent with that of whole South Shetland Islands; late eruption had a south easterly migration, showing local characteristics.