Structures and Implications for Fluid Migration in the Jiadi Carlin‐Type Gold Deposit, Guizhou Province, Southwest China

Abstract

The Jiadi gold deposit is a newly discovered Carlin-type gold deposit in the Guizhou Province, Southwest China. This deposit is structurally controlled by a shallow fold-fault superimposed system along the Lianhuashan trend. Field geological investigations, structural analysis, and mathematical research are conducted to study its structures and hydrothermal fluid flow process. Geological investigations (i.e. sections, stope, and drill hole) indicate that the structures are dominated by NE-trending folds, NWW-trending folds, and faults. A trend-surface analysis of the low interformational fracture zone suggests that the overall distribution of the Lianhuashan trend is controlled by the NE-trending Lianhuashan anticline. Nearly all primary Carlin-type gold deposits are distributed along the southeastern flank where the fold axis changes from NE to EW. Gold orebodies are hosted by the interformational fracture zones and primarily situated at the transitions from the high-value areas to the low-value areas of the interformational fracture zones. A stress analysis on the hydrothermal veins indicates that they are of tenso-shear properties. The ore-forming elements (Au, As, Sb, Hg, and Tl) of the hydrothermal veins from the interformational fracture zones and intrusive breccia body present strong positive anomalies compared with those from the adjacent wall rocks. According to the development patterns of the ore-forming elements and hydrothermal veins, a migration process of the ore-forming fluids is proposed: the deeply sourced ore-forming fluids migrated vertically to shallow crust along an intrusive breccia body, subsequently flowed horizontally along the interformational fracture zones accompanied by gold precipitation in the early stage, and finally migrated outward along steep microfractures during following stages.

Structure–Fluid–Mineralization System of Jiadi Gold Deposit in Southwestern Guizhou, China

“…The NS-trending F201 fault is distributed in the west of the mining area, which is a regional deep large fault. It is a high-angle normal fault with a dip angle of more than 70 • , a width of 50~300 m, a length of more than 3.5 km, and a fault displacement of more than 200 m. It is regarded as the preexisting fault structure in the area, and it was formed before the Permian [14]. Conjugate joints can be seen in tuff near the fault (Figure 5l), and the direction of the maximum primary stress is NE-trending (Figure 6k).…”

“…The F2 fold hinge in Jiadi is NE-trending, which is consistent with the strike of the Lianhuashan anticline and is the main tectonic age of the regional interformational sliding (Figure 5a). According to the fold (Figure 6b) and fault (Figure 6e,f,h,i) inversion tectonic stress field, the Lianhuashan area is mainly characterized by the reverse movement of the Shizong-Mile fault, which formed the NE-trending Lianhuashan anticline (F2) and the NE-trending fault structure (S2), thus corresponding to the regional compression stress of NW-SE in the early Yanshanian [14].…”

“…It was the strongest tectonic movement in Southwest Guizhou since the Paleozoic. In addition, the Yanshanian magmatic rock intrusion was also formed in this region [14]. In the late Yanshanian period, with the acceleration of the northward movement of the Indian plate, a regional tectonic stress field compressed from SSW to NNE and was formed in China [36].…”

“…It is the largest primary basalt-hosted gold deposit in Guizhou Province [4]. Previous studies have focused on the geological characteristics, mineral assemblage, and hydrothermal alteration of the deposit [13,14]; in addition, there have been certain studies conducted on the fluid geochemistry, mineralogy, chronology, gold occurrence regularity of gold, etc. [15][16][17][18].…”