长江水系沉积物碎屑矿物组成及其示踪意义  

Detrital Mineral Compositions of the Changjiang River Sediments and Their Tracing Implications

作　　者：王中波[1] 杨守业[2] 李萍[2] 李从先[2] 蔡进功[2] 

机构地区：[1]青岛海洋地质研究所,山东青岛266071 [2]同济大学海洋地质国家重点实验室,上海200092

出　　处：《沉积学报》2006年第4期570-578,共9页Acta Sedimentologica Sinica

基　　金：国家自然科学基金(批准号:40206008;40476029);上海青年科技启明星计划(04QMX1430)资助

摘　　要：长江碎屑矿物组成研究表明,轻矿物以石英、长石和岩屑为主,不同支流轻矿物组成特征不同,成熟度指数平均是2.0,一般干流高于支流,成熟度随沉积物搬运距离增加而增大。QFL及QtFL三角图解显示长江沉积物主要来自再旋回造山带物源区,流域风化剥蚀速度较快,不同支流物质汇入干流,使得干流轻矿物组成复杂多变而难以和支流区别。重矿物含量从长江上游至下游呈递减趋势,其主要组合是磁铁矿—普通角闪石—普通辉石—石榴子石—绿帘石—褐铁矿—钛铁矿。红柱石和磷灰石是金沙江沉积物的特征矿物组合;蓝晶石是岷江流域的特征矿物;涪江的特征矿物是榍石;汉江的特征矿物组合是磷灰石、紫苏辉石和硅镁石;锆石是湘江的特征矿物。不同流域的特征矿物指示其源岩性质。上游的雅砻江、大渡河以及岷江等支流沉积物对中、下游干流沉积物的贡献较弱。涪陵以上长江流域风化作用强烈,母岩主要是沉积岩类(碎屑岩、泥岩);其下流域沉积物中近源弱风化物质明显增加,其源岩类型体现为岩浆岩和变质岩类;而金沙江攀枝花地区及湘江、沅江沉积物则更多来自流域内广泛分布的大片变质岩类。The study of the detrital minerals of Changjiang sediments indicates that the light minerals mainly consist of quartz, feldspar and lithic fragment. The light mineral assemblages are different between the tributaries, and the mature index increases downstream with an average of 2. 0. The diagrams of QFL and QtFL show that the Changjiang sediments are primarily sourced from recycled orogenic provenance due to stronger tectonic erosion and weathering in the river basin. The main assemblages of heavy minerals include magnetite, common hornblende, augite, garnet, epidote, limonite and ilmenite. Among which, andalusite and apatite are characteristic minerals of the Jinshajiang, cyanite is typical in the Minjiang, sphene and zircon abound in the Fujiang and Xiangjiang respectively, while the Hanjiang is relatively rich in apatite, hypersthene and humite. The distributions of characteristic minerals in the tributaries are obviously controlled by source rock types in the drainage basins. The sediments from the Yalongjiang, Daduhe and Minjiang contribute little to the middle-lower Changjiang reaches. The indexes of heavy minerals indicate that the heavy minerals in the river upstream Fuling are mainly provided by sedimentary rocks whereas the river sediments downstream Fuling are mixed by different source rocks with a large contribution form local magmatic and metamorphic rocks. In contrast, the sediments from the Xiangjiang and Yuanjiang are largely provided from low-and medium-grade metamorphic rocks.

关 键 词：长江 沉积物 物源 碎屑矿物 

分 类 号：P512.2[天文地球—地质学]