关键词: 西南极;纳尔逊岛;火山岩;地层;岩石化学

Abstract:

The Stansbury Peninsula of the Nelson Island, a neighbor of Fildes Peninsula, on which the Chinese Great Wall Station is located, is covered with basaltic, basalt-andesi-tic lavas and breccias as well as fossiliferous volcanic-sedimentary clastic rocks. Based on the stratigraphical relationship and the rock's association the author considers that the stratigraphical division of volcanic rocks on Stansbury Penins ula is much similar to that in Fildes Peninsula. The volcanic rocks and volcanic-sedimentary clastic rocks are the products of two stages of volcanism and can be stratigraphically subdivided into three members. The breccias, interbedding basaltic, basaltandesitic lavas and breccias formed successively, which are comparable with that of Jasper Hill plus Agate Beach Members in Fildes Peninsula. Before the end of this stage some subvolcanic intrusives appeared. The flira-bear-ing volcanic sedimentary clastic rocks belonging to Fossil Hill Member as found on Fildes Peninsula represent a long time break of volcanic activities on the peninsula. A lots of agglomeratic lavas and breccia on the volcanic sediments near the east coast of peninsula are comparable with those of Block Hill Member on the Great Wall Station area and showes that the centre of volcanic activities of the second stage had migrated eastwards. The similar development of volcanic strata and the discovery of plant fossils provided an evidence for such a suggestion that the volcanic rocks on Stansbury Peninsula and on Fildes Peninsula resulted from the same regional volcanism in the Early Tertiary. The faults on the peninsula parallel to the Fildes Strait Fault are the main structure and control the distribution of subvolcanic intrusives in the Peninsula. The petrological characteristics of the volcanic rocks from the Stansbury Peninsula suggest that the lavas and subvolcanic intrusives are basicaly basaltic and basalt andesi-tic. The phenocrystals of rocks include plagioclase and clinopyroxene. The Al2O3, CaO,MgO and tatol iron contents of the chemical compositions of rocks gradualy decrease and the alkali increase with the decreasing SiO2 from basaltic through basalt an-desitic to andesitic rocks. The petrochemical evoluting trend of rocks is similar to that from the Fildes Peninsula, that is, belongs to the clac-alkaline series with some high-Als and low-K features. Rare Eaith Element and other Trace Element concentration and chondrite-normalized patterns show that the volcanic rock association is probably resulted from the same magma sourse and the similar fractional crystallization of plagio-clase and pyroxene as discussed on the volcanic rock from the Fildes Peninsula.