Conjugate Interpretation Method Of Magnetic Anomaly

Such prospecting propositions as crisis mines, deep side of mines, searching for deep deposit and undetected mines proposes much higher requirement for spatialization of mineral target. Therefore, under the subsidization of resource crisis mine prospecting fund project replaced by Yaogangxian tungsten deposit of Hunan province, Machangjing-Xiaolongtan Cu-Mo ore of Yunnan province overall geological exploration fund project and Baoshan-Pingding Lead-Zinc polymetallic ore zone of Guangdong province geophysical exploration comprehensive research enterprise funded project, this thesis conducts the study of interpretation method with conjugate element of magnetic anomaly and completes the conjugate element interpretation method system, which is provided with significant meaning both in theory and practice.The interpretation on magnetic anomaly is the key link which transforms the magnetic anomaly as the geological cognition, which also is the hotspot and difficult point on study for magnetic exploration. The past studies mainly start from mathematical model, and the inversion method which takes its starting point as anomaly characteristics is rare, however, there is prevalent presence of "incongruous problem" which influences anomaly interpretation due to difference in magnetization direction in reality and relevant achievements cannot be seen yet, which is a blank field in interpretation problem of magnetic anomaly.The conjugate element interpretation on magnetic anomaly is an innovative interpretation method of magnetic anomaly combined with many interpretation methods and based on magnetic anomaly characteristics, it is provided with a relatively independent and complete method system. This thesis has conducted rather systematic research for method systems of theoretical basis, basic principle and interpretation of this method and has also carried out the model study for typical geological body and geological structure, and finally, in combination with production of practical magnetic detection, the thesis elaborates the technology of realizing the complex magnetic anomaly interpretation by making use of conjugate element interpretation and introduces the verification results of drill hole.The innovativeness of study in the thesis is mainly reflected in the following aspects:(1) The thesis studies the thin plate magnetic anomaly forward formula which is published in1965by Grant F.S., revises problems in treatment of angle in the formula, comes up with corrected formula (Formula2-1) and performs the repeated check computations for the corrected formula via setting different parameters and different geographic environments. And the results show that the corrected thin plate formula can be used as thin plate magnetic anomaly computational formula.(2) According to "Addition" principle of magnetic anomaly, the magnetic anomaly forward formula for arbitrary body will be deduced according to the specific rules and based on thin plate magnetic anomaly forward formula (formula2-1) to provide the new way for magnetic anomaly forward formula of complex body, so as to avoid the complex integration and matrix operation and puts forward a series of mathematical model with unified foundational model, which is close to geological structure body. These relatively simple forward formulas are also applicable to such problems as nonuniform magnetization and remanence.(3) The interpretation problem for magnetic anomaly under circumstances of magnetic superposition from different magnetization directions and different trends on an arbitrary profile or on the same profile of single or superposed geologic body model is called "Incongruous Problem". Relevant achievements have not been seen yet in the existing inversion methods for magnetic anomaly; the thesis puts forward interpretation method for dyssymmetry, and further proposes dyssymmetry discipline through introducing the concepts of profile declination, profile displacement, which realizes the solving of "incongruous problem" successfully to fill the blank of "incongruous problem" in magnetic anomaly inversion field.(4) The thesis comes up with and develops study of "Deepened Focus" for magnetic anomaly, and puts forward Deepened Focus discipline, realizes the focus separately for magnetic in different depths by utilizing interpretation anomaly of step length of focusing, to acquire the focus interpretation results of the same interpretation precision; and the focus interpretation results provide the theoretical foundation for achieving the interpretation with high precision in deep space with large scale;(5) This thesis establishes the graphics transformation function and conjugate ratio function for magnetic anomaly conjugate triangles and propose the magnetic anomaly graphics transformation theory. This lays the theoretical foundation for interpretation of graphic domain of magnetic anomaly. Considering that the conjugate triangle has concentrated integral information of magnetic anomaly and conjugate element as well as its function has simplified relation between anomaly and parameters of magnetic, so that it is possible for solving in subsections of magnetic anomaly and also creates the conditions for avoidance of solution for complex linear simultaneous equations during inversion of magnetic anomaly, complex matrix operation and simplified interpretation process as well as accurate solution.(6) This thesis studies the graphics transformation technique, namely it is to change the conjugate triangle by applying the law variable model parameter, gradually searching and limitlessly approaching the conjugate point to realize the subsection solution of model parameter through carrying the similar conjugate element of inversion model parameter, which is the key technology of conjugate interpretation. It constitutes basic process of conjugate interpretation together with equal ratio conversion and Planar Rectification, and is a new inversion method for magnetic anomaly which is totally different from the existing interpretation methods. In fact, the process of obtaining parameters for different models separately on the divided stages is the solving process in subsections for complicated function, which is an important advantage of conjugate interpretation relative to normal interpretation. Because of integration of profile features and plane features of magnetic anomaly in the interpretation process, the interpretation results possess a higher reliability.(7) Aiming at magnetic anomaly under complicated topographical environment, the thesis proposes the difference curve to plane interpretation method for magnetic anomaly, which has built independent method and theory for interpretation of magnetic anomaly under accidented relief and also provided a brand new thinking for curve to plane treatment of magnetic anomaly. For typical complex magnetic and magnetic anomaly, it puts forward the corresponding interpretation methods, such as variable magnetism interpretation, lateral trending interpretation, thick plate interpretation, trend interpretation and gradient interpretation. On one hand, proposals of these methods provide the specific methods for conjugate interpretation in handling the common complicated magnetic anomaly, on the other hand, they offer thinking for conjugate interpretation in further treatment of other complicated magnetic anomaly.(8)The article also discussed some skills for the perfect conjugate interpretation. such as magnetic field leveling, good-neighborly decomposition, conjugate Rectification, etc, It provides technical support that conjugate interpretation result came close the production more actual.