钱塘江河口区重矿物特征及其与动力环境的关系

本文研究钱塘江河口区的重矿物组成、组合类型、重矿物的分区及其与水动力的关系,同时探讨其物质的来源。钱塘江河口区已鉴定的重矿物有25种,分为四种组合类型,同时存在与其相适应的四个重矿物区,近口段重矿物区、河口段重矿物区,杭州湾重矿物区与金山深槽重矿物区。钱塘江河口区在不同的区段其沉积物来源不一样。近口段主要来自钱塘江流域,口外海滨主要来自长江口,河口段则两者兼有,而金山深槽主要来自槽下被冲刷出来的全新世的沉积物。

Characteristics of Minerals in Qiantang-jiang Estuary and Its Relationship with Hydrodynamic Environment

This article deals with the composition and combination of heavy minerals in Qiantang-jiang estuarine region; with the regionalization of these heavy minerals and their relationship with hydrodynamic conditions; and at the same time,makes some inquiries about their sources. The identified 25 different kinds of heavy minerals in Qiantang-jiang estuarine region fall into 4 combination types,distributed over their corresponding heavy mineral zones,namely:1,the heavy mineral zone near river mouth,where runoff action predominates and the contents of magnetite,hematite,epidote,and zircon are higher; 2,the Hangzhou Bay heavy mineral zone,where tidal current action prevails,and hornblende and epidote preponderates; 3,the heavy mineral zone of river mouth section,where interaction between tidal current and runoff is evident,and the contents of hornblende,epidote,and hematite are higher; 4,the Jinshan deep-trough heavy mineral zone,where underwater strata are exposed by tidal current erosion,and there are high contents of hornblende and epidote,while pyrite and micaceous minerals richly gathered at some scattered spots. Sediments in different sections of Qiantang-jiang estuarine rigion come from different sources.In the near-mouth section,sediment comes chiefly from Qiantangjiang vally; in offshore section away from the mouth,the matcrial comes from Chang-jiang estuary; while the river-mouth section receives deposits from both.The Jinshan deep-trough zone gets Holocene sediment from erosion under the trough.