DETRITAL MINERAL COMPOSITION OF THE SEDIMENTS FROM HUANGHE AND ITS HYDRODYNAMIC ENVIRONMENTAL CONSTRAINTS

The composition of detrital minerals of the sediments from Huanghe mainstream and major tributaries are similar in general,albeit certain variation between different rivers.The main assemblages of heavy minerals are opaque minerals-garnet-epidote-carbonate and altered minerals.It is difficult to delineate the source area by using the source index of light minerals.The maturity index of light minerals also shows very complicated variations between different river samples,reflecting the combined controls of the sediment sources and sorting process during transportation and deposition.It is lower in the middle mainstream than in the upper and the lower reaches.The variations of garnet,opaque minerals and hornblende contents obviously suggest the differentiation of suspended loads and hydrodynamics changes of rivers.The regional distribution of ZTR index well corresponds to the provenance of the river sediments.A differentiation index was proposed in this study to reveal the differentiation of characteristic minerals caused by regional hydrodynamic sorting.The index can be used as a good indicator for study of sedimentary hydrodynamic environment and differentiation of detrital minerals.As a whole,the mineral compositions are not only controlled by their sources,but also constrained by seasonal hydrodynamic intensity of the river and the mineral gravity differentiation induced by sedimentary environment changes.It should be careful to identify sediment sources in the marginal sea just based on the mineral assemblages of the river,such as Huanghe.