Integrated Geophysical Interpretation Of3D Geological Structure Of Benxi-Ji’an Metallogenic Belt

Benxi-Ji’an metallogenic belt is among19key metallogenic belts selectedby China Geological Survey. There are two different geological units in the area，one is Archean ancient continental nucleus，which is composed of Archeanmetamorphic rocks and is important to the area of the Ore, major minerals,including iron, copper (zinc), gold, pyrite. The other one is Proterozoic Liaojiancient rift zone, which is very rich in mineral resources, such as magnesite, talc,lead, zinc, boron, cobalt, iron, gold, uranium, etc. Many large or very largedeposit are formed. Benxi-Linjiang Region is located in the Precambriantectonic domain, the ancient Asian tectonic and domain-Pacific tectonic domainsuperimposed parts, geological history is complex and long， geological structureis also complex，experienced Archean continental nucleus formation and theformation of Proterozoic platform Paleozoic stable stage evolution andMesozoic-Cenozoic continental margin activities stage. Formation of ancientmetamorphosed Archean-Paleoproterozoic crystalline basement, especially sincethe Late Triassic Jurassic-Early Cretaceous superimposed on a large-scalestructure magmatic activity.The three dimensional geological mapping of Benxi-Ji’an metallogenic belthas an important signification for deep ore deposit prospecting. Thethree-dimensional geological mapping is an important practice for the geologicalwork change from the traditional to the modern, from a single means to anintegrated resort, from two-dimensional to three-dimensional development and itis becoming a powerful force to promote the development of geological science.Through Benxi-Ji’an metallogenic belt with three-dimensional geologicalmapping，we can understand Archean ore-bearing, the Paleoproterozoic Liaojipaleorift with space spread morphology and its constraints on mineral relationship from the three-dimensional dimensional and predict the deep geologyvision. At the same time, through three-dimensional geological mapping, wecould summarize working methods of three-dimensional geological mapping,technical processes in the metallogenic belt, to provide experience anddemonstration for other parts of the three-dimensional geological mapping.This thesis processes the5profiles of the measured gravity and magneticand electricity data and analyzes the measured physical properties of specimendata overall. The integrated geophysical profiles were inversed with advancedgravity and magnetic fitting software GM-SYS and magnetotelluric soundingsoftware SCS2D. Combined with existing geological, geophysical and otherdata of5profiles in the area, we executed a comprehensive geological andgeophysical interpretation and got the preliminary three-dimensional geologicalstructure of the study area, and the following conclusions:1. The depth of Longgang Block Archean basement from north to southgradually deepened，Liaoji rift basement mainly are granite.2. In the northern margin of the slopes，the western basement are NeoarcheanDasu River gneissic complex，the eastern are the Xinbin Neoarchaean gneissiccomplex. Rock magnetic and density of the former are bigger than the latter．3. The low gravity area within Liaoji rift are mostly the intrusive granite orMesozoic basins. The intrusive activities within rift are strong，even in the presenceof the local Archean，size and thickness are not very big. Proterozoic granite inLiaoji are most surrounded by the late intrusive rock， and Indosinian andYanshanian granites may exist inheritance relationship with rift.4. The polymetallic deposits within the Liaoji rift are mainly distributed in thetransition zone of high gravity and low gravity，that is distributed close to thecontact zone of the residual stratigraphic and intrusive granite，which is related toIndosinian and Yanshanian intrusions and specific strata. Iron ore mainlycorresponded to the Anshan Group strata high magnetic anomalies. The boron,magnesite are related to special layer of Proterozoic.5. According to the measurements of the gravity and magnetic and electricity，and the physical properties of the inversion，we can infer the shape and nature of thesubsurface geological body.