南设得兰群岛西海域S_(11)岩芯沉积物中碎屑矿物及沉积作用的探讨

本文对南设得兰群岛西海域S_(11)钻孔岩芯中的重、轻矿物作了描述,按矿物在垂直方向上的变化和优势矿物种确定矿物组合类型,并将晚更新世到全新世的341cm沉积地层划分为四层:1.上火山碎屑矿物沉积层,2.中火山碎屑矿物沉积层,3.火成碎屑矿物沉积层(深海砂层),4.下火山碎屑矿物沉积层。本文还讨论了物质来源和深海砂层的可能成因。

DETRITAL MINERALS IN THE SEDIMENTS OF CORE S_11 AND SEDIMENTATION IN SEA AREA WEST OF SOUTH SHETLAND ISLANDS

There are more than thirty of detrital minerals in sediments of core S11. Analysis of heavy mineral assemblages reveals that pyroxene and amphibole are the dominant heavy minerals in the sediments. The feldspar and quartz are the dominant light minerals. According to the characteristics of the detrital mineral assemblages in the vertical direction, four types of heavy mineral assemblages can be found: 1) Pyroxene-amphibole-epidote-garnet, 2) Pyroxene-amphiple-epidote-authigenic pyrite, 3) Amphibole-pyroxene-epidote-sheet minerals, 4) Pyoxene-amphibole-epidote-sheet minerals-authigenic pyrtite.And two light mineral assemblges: 1) feldspar-quartz-volcanic glass fragment, and 2) feldspar-quartz were defined.The mineralogical characteristics of sediments show their specific source rocks. On the basis of the different mineral assemblages, the sediments in core S11 consist of four layers from the uppermost part to the lower part as follow:1) Upper layer of pyroclastic minerals, 0-125cm;2) Middle layer of pyroclastic minerals, 125-255cm;3) The layer of pyroclastic minerals (pelagic sands), 255-282cm;4) Lower layer of pyroclastic minerals, 282-341cm.The source of the pelagic sands was discussed in this paper. The materials of layers 1,2 and 4 have possibly come from intermediate-basic volcanic rocks and volcanic eruptions on the South Shetland Islands. The sediments of layer 3 mainly come from intermediate-acidic igneous rocks on Antarctic Peninsala. Thus they might be formed by turbidite sedimentation.