New insights into the origin and depositional setting of the Haerdaban PbZn deposit, Chinese western Tianshan: Evidence from geology, chert geochemistry, and detrital zircon UPb geochronology
Jialin Wang , Xuexiang Gu , Jingchi Xu , Yongmei Zhang , Yiwei Peng , Liangtao Lu
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引用次数: 0
Abstract
The Haerdaban PbZn deposit (with an ore reserve of 10.93 Mt. at 1.0–25.65 % Zn and 0.7–12.29 % Pb) is hosted in weakly metamorphosed clastic‑carbonate rocks from the Proterozoic Haerdaban Group. It represents a significant addition of the sediment-hosted PbZn deposits in the Yili block, Chinese western Tianshan. Currently, there are ongoing debates regarding its genesis, with a particular focus on the crucial metallogenic mechanism (syngenetic sedimentary exhalation or epigenetic reworking) responsible for the primary sulfide mineralization. Mineralization at Haerdaban primarily occurs as banded to stratiform ore layers or lenses conformably sandwiched in their host rocks. Vein and stockwork ores occur locally below the stratiform ore layers. A syn-sedimentary fault trending SN was identified based on abrupt lateral changes in lithofacies and thickness of the stratigraphic units. The ore mineralogy is dominated by sphalerite, galena, quartz, and dolomite, with a small amount of pyrite, barite, and organic matter. Detrital zircon LA-ICP-MS UPb dating of the Haerdaban siltstones obtained a maximum depositional age of about 604 Ma. Their geochemical composition similar to the passive continental margin signatures, with rare earth element (REE) patterns enriched in LREE and negative Eu anomalies (Eu/Eu* = 0.50–1.14). Stratiform beds of chert that host disseminated ores have relatively high contents of hydrothermal components (e.g., Ba, Zn), with apparent positive Eu anomalies (Eu/Eu* = 7.38–49.34) and negligible negative Ce anomalies (Ce/Ce* = 0.85–0.98). They are thus interpreted to be hydrothermal sedimentary rocks (exhalites) deposited in a suboxic-anoxic environment proximal to the hydrothermal vents. Integrated geological and geochemical evidence indicates that the Haerdaban PbZn deposit is a typical vent-proximal sedimentary exhalative (SEDEX) deposit formed in a Neoproterozoic Sinian (Ediacaran) passive continental margin rift basin. Post-depositional metamorphism and deformation in the Paleozoic may have caused partial remobilization of primary ores but did not significantly alter the morphology of the orebodies. Furthermore, establishing a genetic model for the Haerdaban deposit has important implications for the exploration of similar deposits preserved in the equivalent stratigraphy within the Chinese western Tianshan region.
期刊介绍:
Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics.
Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to:
define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas.
analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation.
evaluate effects of historical mining activities on the surface environment.
trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices.
assess and quantify natural and technogenic radioactivity in the environment.
determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis.
assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches.
Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.