| Ore-field structure analysis plays an important role in the studying the tectonic evolutions of the ore-field, determining the different types of ore-control tectonic frameworks and establishing structural ore-controlling models in the area. This study focuses on the analysis of construction system in joint structure and fault structure in Laochang ore-field in Gejiu city which is based on the theories guidances of structural geology, ore-field tectonics and ore-field in geomechanics. Combined with the existing results, we divided the distribution and analysed the evolutionary characteristics of ore-field structural systems, the tectonic system is established. This paper has made the following achievements and knowledges:1. Development of fault tectonics in the Laochang ore-field have the characteristics of multi-stage activity, which can be divided into 4 faults:East-West, North-East, North-West and North-South, that respectively showed different characteristics of geometric, kinematic, tectonic and dynamic. After studying, we supposed that principal stress σ1 in the ore-field has experienced nearly South-Northâ†'North-West —South-Eastâ†'North-East—South-Westâ†'East-West in the transformation process since Mesozoic.2. Development of joint in the Laochang ore-field is dominated by shear joint with steep dip angle, which directions mainly concentrates in NW(300°～330°), NE(30°～60°), EW(80°～100°) and SN(350°～10°), also secondary zones are exist with the directions of NWW(280°～300°), NEE(60°～80°), NNW(330°～350°) and NNE(10°～30°). Maximum principal stress orientation in the ore-field has four main groups:SN(2°～11°), NW-SE(308°～324°), NE-SW (34°～48°) and EW (75°～109°). After studying on structure of typical faults and joints and supporting research in stages, we supposed that Laochang ore-field has experienced 4 stages of tectonic stress, the stages of the formation in σ1 of the order are:SN(2°～11°) in first period, NW-SE(308°～324°) in second period, NE-SW(34°～48°) in third period and EW(75°～109°) in fourth period.3. After analysising and researching, the tectonic system in the Laochang ore-field can be divided into 4 groups of structures:the directions of East-West, North-East, North-West and South-North.4. After further studying, we supposed that the northeastern tectonic zone should mainly tectonic system. The framework of the distribution of basic rocks of ore-controlling structure is formed by early tectonic zone in East-Weat direction, while North-West and South-North tectonic zone formed the latter metallogenic tectonic system. |
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