Explore the vast range of titles available.

The Jinshan gold deposit, located on the southern flank of the Keguqin Mountains in the western Tianshan orogen, is a typical low-grade, large to super-large epithermal system within a continental volcanic terrain. Although its genesis is linked to Late Palaeozoic volcanic-intrusive activity, controversies over ore-controlling structures have constrained deep and peripheral exploration. Through detailed field and outcrop observations, this study identifies multiple Carboniferous palaeo-volcanic edifices (pipes, depressions, necks), overprinted by NS-trending normal faults and conjugate NNW- and NE-trending strike-slip faults. Mineralisation is shown to be jointly controlled by these volcanic edifices, regional fault systems and the unconformity between Ordovician limestone and Carboniferous volcanic-clastic rocks – termed the ‘silica-calcite interface’. A corresponding ore-controlling model highlights favourable exploration targets at this unconformity within structural intersections of subsidiary vents and regional/ring/radial fractures. Subsequent drilling not only confirmed high-grade, thick orebodies (e.g. 6 m @ 3.56 g/t, peak 56.3 g/t) in predicted areas but also revealed anticipated mineralisation types in unexplored zones south of the mine. The study provides a validated structural model for epithermal exploration in similar volcanic terrains worldwide.

In Central Asia, the Carboniferous is a crucial period in the formation of the Tianshan Belt and associated bending of the Kazakhstan tectonic collage. In order to reveal Carboniferous magmatic events of the region and their tectonic implications, we conducted field investigations, zircon U–Pb dating, whole-rock geochemical and Sr–Nd isotopic studies on the Early Carboniferous Dahalajunshan Formation and Late Carboniferous Yishijilike Formation volcanic rocks of the Wusun Mountain Range (southern Yili-Central Tianshan Block). Volcanic rocks of the Dahalajunshan Formation consist of calc-alkaline basalt, andesite and dacite, yielding new zircon U–Pb ages of ~ 350 Ma. They have positive whole-rock εNd(t) values (+ 0.5 to + 1.6). In contrast, the Yishijilike Formation volcanic rocks dominantly comprise alkaline and calc-alkaline bimodal suites that erupted at ~ 337 Ma to 313 Ma and have higher whole-rock εNd(t) values (+ 2.3 to + 4.3). These two episodes of Carboniferous magmatism were correlated with partial melting of depleted mantle that metasomatized by slab-derived fluids. The late Carboniferous Wusun Mountain magmatic belt shows characteristics of a back-arc system that evolved due to trench retreat relative to the southern margin of the Yili-Central Tianshan Block. This mechanism induced an extensional regime with gradually depleting magma sources. The asymmetric retreat of the paleo-subduction zones of the South Tianshan Ocean and Junggar Ocean relative to the Yili-Central Tianshan Block was hence a vital driving force for the bending of the Kazakhstan Orocline.

Rutile is a common Ti-bearing accessory mineral in high pressure (HP) metamorphic rocks of the western Tianshan. Distribution of rutile in the HP rocks varies from 0.5% in the greenschist to 30% in the rutile-bearing vein. Rutile can be subdivided into three groups based on the variation of trace elements: The first group has an averaged Zr content of 18 ppm–44 ppm and Hf content of 0.8 ppm–2.4 ppm, which correspond to occurrence of rutile from vein; the second group Zr of 59 ppm–63 ppm, Hf of 3.5 ppm–3.7 ppm; and the third group Zr of 150 ppm–160 ppm and Hf of 3.9 ppm, corresponding to rutile in the matrix of blueschist and eclogite, respectively. Rutile has been retrograded to ilmenite and titanite partly or completely, reducing the value of the ore. But rutile of HP rocks in the western Tianshan usually has the lowest content of uranium (<1 ppm U), which might become an attractive raw material for the Ti industry. Therefore, rutile-bearing HP rocks in the western Tianshan as a mineral resource will be the focus of considerable attention.