Analysis For Amphibole Characteristics And Provennaces Of Typical Rivers In Northern China

Amphibole is widely distributed in the three main classes of rocks in earth’s crust, and itis also one kind of common heavy mineral in modern sediments, which can be found in thegulf, estuary littoral zone and continental shelf. The characteristics of amphibole can reflectthe feature of its original rock. Amphibole in mlastic sediment of the rivers is widely frommagmatic rock and metamorphic rock, eroded and transported through water. There are lots ofisomorphisms among different elements whose geochemical characteristics can play animportant role in revealing the environment of the rock, studying provenance and searchingfor the evolving path of ricer sand.Based on the reaserch we obtained46surface sediment samples in Yellow River Estuary,29samples in previous Yellow River Estuary in the northeast of Kenli County,45samples inLiaohe River, and35samples in the Yalvjiang River. According to the154field samplingconditions we carried out in the following laboratory processing.Firstly we acquired very fine sand which is easy for observation by means of water sieve,then obtained heavy mineral by CHBr₃and CHI₂,and finally got amphiboles which haveintegrated shape and weak weathering through optical microscope. After surveying the fieldof geological features, major elemental compositions of every amphibole separated from thesurface sediments in the Yellow River, Liao River and Yalvjiang River are all tested by meansof the electron microprobe analysis, and group chemical compositions of the amphiboles areanalyzed by ICP-MS and ICP-AES.The heavy mineral analysis shows that there are obvious difference in heavy mineralassemblage types and characters among the three rivers. Yellow River heavy mineralassemblage is hornblende+epidote+limonite; Liaohe River heavy mineral assemblage ishornblende+epidote+garnet; Yalvjiang River heavy mineral assemblage is hornblende+actinolite+biotite. The characteristic minerals of Yellow River are biotite and hydrobiotitewhose weathering are not strong; the characteristic mineral of Liaohe River is garnet withhigh content; while the characteristic minerals of Yalvjiang River are aegitite andoxyhornblende represented alkaline rock and volcanic rock. In the aspect of psephicity,Liaohe River is higher than the other river; Yalvjiang River is the lowest among the threerivers. We measured the major elements by electron microprobe including Si, Al, Ca, Mg, Fe,Mn,Na and K. Cation coefficients of the amphiboles are calculated on the basis of oxygenmeasurement. Limited by the stoichiometry, average coefficient of Fe³⁺,Fe²⁺and other relevantcation are estimated. We can draw the conclusions as follows: According to the cationcoefficients, we obtain the possible molecular formulas of the crystal structure andcorresponding crystal-chemical characteristics. Studies show that although the amphiboles ofthe three rivers have a large variation in the chemical composition, they are all characterizedby high silicon, calcium, magnesium and low alkalinity. According to crystallochemicalclassification, all of the amphiboles whose spices are relatively simple belong to thecalcium-amphibole. It contains10kinds of amphiboles, projected fixedly, including morethan50%of magnesiohornblende and small amount of edenite. The crystal-chemicalcharacteristics of the calcium-amphibole can provide identification basis for distinguishingthe Yellow River sediments form other basin. The crystallochemistry-genesis illustrationsdemonstrate that the amphiboles are mainly derived from the intermediate-acidic deposits,and then are metamorphic genesis deposits. And the magmatic origin type of amphiboles isoriginated from crust-mantle mixed source （mainly） and mantle source （secondly）, while themetamorphic genesis origin type comes form metamorphic environments below middlepressures and middle temperatures.In order to reflect the original state of the amphiboles, we made geochemical analysis onthe integrated amphiboles of every sample by ICP-AES and ICP-MS. With similar mainchemical components, the trace elements contents, ratios among elements and theireigenvalue of the three rivers vary slightly form each other. While discrepancy in the samplesof the new and old Yellow River is extremely little, which apparently shows the sedimentsoriginate from the same source. Moreover, some of the significant indexes of relativedeviation reaching up to20%indicate the sample of the three rivers distinguish greatly, andoriginate from different sources. Amphiboles in the Yellow River whose species and featuresare most common indicate that their original sources are universal and stable, and can be usedas standardized material in upper crustal terrigenous sediments in northern China.Altogether, geochemical characteristics of the amphibole groups indicate the REEcontents which have a feature of higher contents in HREE than in LREE are apparently higherthan Loess and whole-rock sediments of the Yellow River. Based on these differences we can offer a new and authentic technical means to discriminate different sediments. In addition,there are significant differences in trace elements such as Ba,Li,Rb,Cs,Ta,Tl,Pb,La,Ce,Pr,Nd,distinct differences in elements ratios such as La/Y, Sr/Rb, Zn/Cu,Gd/Cd,Li/Be,Rb/Cs, Sr/Ba,Hf/Ta,Pb/Bi, and differences in eigenvalue such as ΣREE,ΣLREE,ΣHREE,ΣLREE/ΣHREE,（La/Lu）_N,（La/Yb）_N,（La/Sm）_Namong the three rivers, which are all practicable indexes todistinguish them.