山东半岛南部近岸海域碎屑矿物对中小河流的物源响应

    PROVENANCE RESPONSE OF DETRITAL MINERALS FROM MEDIUM AND SMALL RIVERS IN OFFSHORE SOUTHERN SHANDONG PENINSULA

    • 摘要: 对山东半岛南部近岸海域的106个表层沉积物样品及大沽河、五龙河和乳山河的94个表层沉积物样品进行碎屑矿物分析,系统地研究了碎屑矿物的分布特征及物源指示。研究区共鉴定出40种重矿物和13种轻矿物,重矿物以普通角闪石、绿帘石、黑云母和自生黄铁矿为主,轻矿物以石英、斜长石、钾长石和风化云母为主。根据碎屑矿物组合特征,将研究区分为4个矿物区:Ⅰ区为胶州湾口至崂山头的附近海域;Ⅱ1亚区为丁字湾和鳌山湾附近水深约15 m以浅的海域,Ⅱ2亚区为研究区东南部水深>20 m的远岸区;Ⅲ区处于Ⅱ区和Ⅳ区的过渡带;Ⅳ区为乳山口西南部近岸海域。Ⅰ区和Ⅱ区的矿物组合均为普通角闪石-绿帘石-石英-长石,Ⅰ区和Ⅱ1亚区受大沽河、五龙河和乳山河输入的物质及沿岸基岩、岛屿风化碎屑的影响较大,Ⅱ2亚区主要为晚更新世低海平面时形成的陆架残留沉积。Ⅲ区矿物组合为普通角闪石-石英-长石-片状矿物,Ⅳ区矿物组合为云母类-自生黄铁矿-普通角闪石-石英,Ⅲ区、Ⅳ区物源多样,黄河物质对两区贡献显著。

       

      Abstract: 106 surface sediment samples from the coastal waters off the southern Shandong Peninsula plus 94 samples from the Dagu, Wulong and Rushan Rivers are collected and analyzed for detrital minerals. The distribution pattern and provenances of the detrital minerals are systematically studied and a total of 40 heavy minerals and 13 light minerals recognized. Heavy minerals are dominated by hornblende, epidote, biotite and authigenic pyrite, whereas light minerals consist mainly of quartz, plagioclase, potassium feldspar and weathered mica. There are four mineral zones in the study area. The Zone Ⅰ is the offshore area from Jiaozhou Bay mouth to Lushantou. The Zone Ⅱ may be further divided into 2 sub-areas. The Zone Ⅱ1 is a shallow water area near the T-Shaped Bay and Aoshan Bay about 15 m deep. The Ⅱ2 is far in the southeast of the study area in a water depth of more than 20 m. The Zone Ⅲ is in the transitional zone between Zone Ⅱ and Ⅳ. The Zone Ⅳ is the coastal water in the southwestern part of Rushankou. The mineral assemblage of Zone I and Zone Ⅱ is commonly consisting of hornblende, epidote, quartz and feldspar. The Zone Ⅰ and the Sub-zone Ⅱ1 are greatly affected by the materials from the Dagu, Wulong and Rushan Rivers, as well as the coastal bedrock and island weathering debris. The Sub-zone Ⅱ2 is mainly covered by the shelf relict sediments deposited during the Late Pleistocene low sea level. The mineral assemblage in the Zone Ⅲ is dominated by hornblende, quartz, feldspar and flaky minerals. The mineral assemblage in the Zone Ⅳ is dominated by flaky minerals, authigenic pyrite, hornblende and quartz. The material sources of the Zones Ⅲ and Ⅳ are diverse, and the Yellow River contributes significantly.

       

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