Research Of Regional Geochemical Units: Concept, Methods And Applications

There are more than 55.4 million initial geochemical data had beencollected from ca. 6.5 million km~2 area since the execution of "The Project ofGeochemical Exploring of China" in 1978. These data mainly had beenanalyzed for prospecting and mining rather than geological, agricultural,environmental or ecological applications. Therefore, it appears important toextract more geological or geochemical information contained in these data.In present thesis, the concept, methods and associated applications ofGeochemical Units have been addressed. The concept of Geochemical Unitshas been proposed for the first time, depended upon the controls of elements'affinity and activity. This concept suggests that a regional geochemical unit,formed during the geological history, is a geologic unit marked by certainelemental combination that can be explored objectively, pertinently in multi-entity and level.The present thesis focus the identification of geochemical units where areunmonitored under either the factors classification or multiplicative index.The identification mainly base on multi-leveled regional geochemical data andelemental compositions, droved from the spatial self-correlation of specimensand the corresponding correlationship between specimens and space.Furthermore, the concept and principle are supported by serials of appliedresolutions in which the quality-and quantity-geochemical appear being unified.Moreover, the identification of two types of monitored geochemical units isproposed, which seems reinforcing the unmonitored ones. Two methods ofsystematic error correction, method of least squares and method of addition, aregiven in order to solve the systematic error among different maps or differentsamples.The concept and principle as mentioned above are applied in 1:200,000Mapping of Tahe and Siziwangqi separately, and 1:50,000 Mapping ofDuobaoshan Copper Mine. These applications appear well resulted in manyfacets, such as the identification of stratigraphy, lithology, deducing the faults,and mineral resources prediction. The author has made her achievements inthe present study in the following aspects:1. The concept and associated methods have been proposed for the firsttime, which greatly keep abreast of current theory and development ofexploring geochemistry, and new ideas in extracting regional geochemical data.2. The regional geochemical unit is corresponding to affinity and activityof elements' (combination), which can be explored objectively, pertinently inmulti-entity and level. A certain geological and geochemical signification of aregional geochemical unit should be impact, based upon different research aimsvia endowing with different variables.3. In order to solve the question of systematic error in the identification ofregional geochemical unit, two methods of systematic error correction, methodof least squares and method of addition, are given and can be used to cancel theeffect of the systematic error among different maps and different samples. Thenew method and path are provided to improve the comparable capability ofregional geochemical data.4. The methods and techniques of regional geochemical unit have beendeductively discussed to solve the problems of great samples' classification andseparate contributions in one map in which the geochemical data are consisted.This comprehensive map is benefit for extracting the geochemical data andexploring information as a whole.5. The maps drove from regional geochemical analysis can clearly deliverinfluent of information of the quality-and quantity-geochemistry, which arebenefit for correlating among several geological methods.6. After the applications of regional geochemical units, followinggeological questions have been discussed:① Stratigraphical correlation: in the present study, strata in Tahe andSiziwangqi areas have been correlated, which also appears helped in sedimentalenvironment analysis.② identification of the instrusive body: the type of lithology and thelithologic distribution in Tahe, Siziwangqi and Duobaoshan areas. The rockbodies identifying from geochemical units analysis are well corresponding tothose of initial geological maps. Moreover, many suggestions have beenproposed for revising the initial geological maps, but some of them need to bevalidated in further field geologic survey.③ deducing the conceal rock body: several conceal rock bodies have beendeduced in the present study, Among them, one conceal rock body inDuobaoshan Copper Mine has been validated by relevant geophysicalexploration.④ deducing fault structures: some of the faults identified from regionalgeochemical units analysis well match the geological map.⑤ regional geochemical abnormal and rock body zone: The space zoningcharacteristics of regional geochemical unit in Duobaoshan Copper Mineembodies the axial zoning characteristics of primary halo of mineral deposit.The geochemical units in Siziwangqi identified the zoning of the stage andphase belt of a intrusive rock and reflected the forming and evolving history.⑥ delineation of the prospecting target area: some metallogenicprospective areas of noble metal and poly-metal are presented in Tahe andSiziwangqi. And in Duobaoshan Copper Mine, the known deposit andmineralized point are identified well and the prospecting target areas aredelineated based on the study of better regional metallogenic condition.