Recognition of Yanshanian magmatic-hydrothermal gold and polymetallic gold mineralization in the Laowan gold metallogenic belt, Tongbai Mountains: New evidence from structural controls, geochronology and geochemistry

Identifying Geochemical Anomalies Associated with Gold Mineralization Using Factor Analysis and Spectrum–Area Multifractal Model in Laowan District, Qinling-Dabie Metallogenic Belt, Central China

“…From the center of the magmatic activity to the periphery, the element associations in the study area showed zonation patterns of Mo → Pb-Zn → Au-Ag. Combined with the age of the deposit (138 Ma) [55] versus the intrusions (127-139 Ma) [58,67] with the spatial distribution of element associations, the gold and polymetallic metallogenesis of the Laowan deposit had close spatial and temporal relationships with Yanshanian magmatism (especially the granite porphyry), which supported the magmatic-hydrothermal origin of the Laowan deposit. This study not only verified the previous views on the source of ore-formation and the genetic mechanism of the Laowan deposit, but also could be used as an independent statistical validation of the element zonation model proposed by the predecessors [58].…”

“…The Laowan ductile shear zone is the ore-controlling structure of the deposit, which has obvious deformation marks and various deformation fabrics. In addition, the fault is well-developed in the region, including the Laowan fault on the Northern side and the Songpa fault on the Southern sides, and several groups of brittle fault structures in the N-NW (North-northwest) and N-NE (Northhnortheast) directions [58]. The N-NW trending fault is the main ore-bearing structure in the area.…”

“…The main host rock of the Laowan deposit is a metamorphic rock series from the Guishan Formation of the middle Mesoproterozoic period, which has undergone many ductile and brittle shear activities ( Figure 2). The lithology is mainly mica-quartz schist and plagioclase-hornblende schist, and mylonitic silicified rocks [53,54,58,67]. The original rocks are basic volcano-clastic sedimentary [53].…”

“…Many studies in this area have focused on the geology of the Laowan gold deposit, ore-controlling structures, sources of ore-forming materials, and the relationship between Laowan granite and gold ore-formation: e.g., [53][54][55][56]. Some studies, such as [55][56][57][58], suggest that this deposit is of magmatic-hydrothermal origin and closely related to Yanshanian magmatism in time and space [58]. However, the ways of recognizing the geological process associated with gold mineralization and identifying geochemical anomalies are still the focus of the exploration of the deposit.In this study, factor analysis (FA) combined with the spectrum-area (S-A) multifractal model were used to process 15 element concentrations in the Laowan gold deposit.…”

“…The lithology is feldspar biotite granite. The granite porphyry dykes, with an age of 139 Ma [58], are mainly distributed along the Songpa fault. The edge of the dykes is highly fractured and formed gold, silver, and other polymetallic mineralization.…”