The crystallochemistry characteristics and genetic analysis of amphibole in the sediments of the Huanghe River

The chemical composition of amphibole in the surface sediments of the Huanghe River is studied by means of the electron microprobe analysis.The cation coefficients of the 69 amphibole are calculated on the basis of oxygen measurement. Limited by the stoichiometry,the average coefficients of Fe³⁺, Fe²⁺ and other relevant cation are estimated. According to the cation coefficients, the possible molecular formulas of the crystal structure and corresponding crystal-chemical characteristics are obtained. The results show that although the amphiboles of the Huanghe River have a large variation in the chemical composition, they are all characterized by high content’s silicon, calcium, magnesium and low alkalinity. According to crystallochemical classification, the 69 amphiboles whose spices are relatively simple all belong to the calcic-amphibole. It contains ten kinds of hornblende; the projected spots are concentrating in the graphics of classification of the calatic amphiboles, including more than 50% of magnesiohornblende and small amount of edenite. The characteristics of crystallochemistry of these can provide identification basis for distinguishing the Huanghe River sediments form other sedimentary body. The crystallochemistry-genesis illustration demonstrates that the 69 hornblendes are mainly derived from the intermediate-acidic magmatites, and then are metamorphic origin rocks. And the magmatic origin type of amphiboles is originated from a crust-mantle mixed source (mainly) and a mantle source (secondly), while the metamorphic genesis origin type comes in metamorphic environments below middle pressures and middle temperatures. Amphibole in the Huanghe River whose species and features are most common indicate that their original sources are universal and stable, and can be used as standardized material in the upper crustal terrigenous sediments in northern China.