黄海中北部和渤海东部表层沉积物轻矿物特征及其指示意义

对采自黄海中北部和渤海东部的233个表层沉积物样品的轻矿物含量、分布特征和矿物组合等进行了分析，对其指示意义进行了讨论。结果表明，轻矿物组成主要是现代黄河物质与海区周边近源物质相互叠加的结果，黄、渤海潮流系统对轻矿物的分布具有重要影响。现代黄河物质主要分布于渤海南部、环山东半岛泥质区、北黄海西部泥质区和南黄海中部泥质区，以高含量的云母为典型特征。辽东半岛东南侧近海一带的高成熟度细砂质沉积则可能为全新世海侵所形成的残留沉积。钾长石是近源花岗岩等酸性岩浆岩的敏感指标。云母分异指数可用来指示云母类矿物的搬运路径，表征云母类矿物之间的水动力分异程度。以云母为示踪剂，本文揭示了两条黄河悬浮物质的运移路径：大多数云母主要沿山东半岛北侧，绕经成山角，向南黄海输送；另有少部分在北黄海西部冷涡环流的驱动下，从山东半岛北侧近海向北黄海西部泥质区搬运，然后再沿黄海暖流的路径向渤海东部输送。

CHARACTERISTICS OF LIGHT MINERALS IN THE SURFICIAL SEDIMENTS AND THEIR IMPLICATIONS IN THE NORTH CENTRAL YELLOW AND EASTERN BOHAI SEAS

Light minerals were identified in 233 surficial sediment samples collected from the north central Yellow and eastern Bohai Seas, China(36°~40°N, 120.0°~124.5°E). The grain-size compositions were also measured to help distinguish depositional environment. Cluster analysis and sensitive mineral indices associated with non-linear mapping were used as unbiased multivariate statistical tools to identify sediment provenance, to discriminate light mineral province and to explain the distribution patterns observed. Results show that the composition of light minerals is a combination of adjacent terrigenous minerals and the modern Yellow River derived materials. The tidal current system of the Yellow and Bohai Seas plays an important role in their distributions. The light mineral suite is characterized by plagioclase, quartz, and orthoclase in most area, mainly representing the rock-forming mineralogy of the metamorphic crystalline basement complex~amphibolite and greenschist facies of adjacent drainage basins as well as widespread outcrops of magmatic rocks mainly including granites and granitic diorites. The Yellow River derived sediments, characterized by high concentrations of mica, are dominant in the southern Bohai Sea, the Shandong subaqueous mud wedge, the western North Yellow Sea mud deposit, and the central South Yellow Sea mud deposit, where the light mineral suite contains plagioclase, quartz, mica, and lithic fragment. A typical belt of fine-sand deposit is present along the coast of the southeastern Liaodong Peninsula with high maturities, which is interpreted as relict deposit formed during Holocene transgression. Orthoclase is sensitive to granites and indicative of transport routes and dispersal systems of the adjacent source-area weathering materials from medium-acidic igneous rocks. It tends to concentrate along the northern coast of the Shandong Peninsula and in a narrow zone off the southern Liaodong Peninsula westward till the eastern Bohai Sea. Its distribution pattern shows a clear response to the coastal current flowing eastward and the residual Yellow Sea Warm Current westward in the North Yellow Sea. The cross-shore dispersion of orthoclase is impeded by shearing of the residual Yellow Sea Warm Current and the north Shandong coastal current in winter and by the presence of stationary front between the North Yellow Sea cold water mass and the coastal current in summer, resulting in orthoclase deficiency in the central zone of the North Yellow Sea. The mica differential index is effective for indicating transport route of micas and distinguishing the fractionation degree of muscovite against biotite, while integrated with mica distribution. Two routes of transport for Yellow River derived matter are revealed in terms of mica. Most of them are delivered along the north side of the Shandong Peninsula and turn toward the South Yellow Sea after passing through Cape Chengshanjiao. On the other subordinate route, some of them are forced by a local circulating current from the north side of the Shandong Peninsula northward to the mud deposit of the western North Yellow Sea, and then they are merged with the residual Yellow Sea Warm Current backward to the eastern Bohai Sea.