Monazite chemistry and timing of mineralization at Paramanahalli, Chitradurga Greenstone Belt, Dharwar Craton, India: Implications for gold exploration

IF 3.4 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS Journal of Geochemical Exploration Pub Date : 2025-01-30 DOI:10.1016/j.gexplo.2025.107688
Manju Sati , Rajagopal Krishnamurthi , Sakthi Saravanan Chinnasamy
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Abstract

Paramanahalli gold deposit, Chitradurga greenstone belt in the Western Dharwar Craton, is a shear zone-hosted/ structurally controlled, mineralization confined to carbonated metabasalt and Banded Iron Formation. Chlorite (Fe-rich) + quartz + ankerite + rutile + monazite ± pyrite ± gold is the mineral association found in the mineralized zone. Monazite from carbonated metabasalt (intensely altered rocks; proximal alteration zone) is interpreted as hydrothermal in origin, based on its mode of occurrence, texture, and chemical composition, particularly its low ThO2 content, whereas monazite grains from schistose metabasalt (least altered rocks; distal alteration zone), found to be metamorphic. Hydrothermal monazite from the mineralized zone is enriched in light rare earth elements LREEs (La2O3 + Ce2O3 > 51 wt%) and exhibits low ThO2 concentrations (<1.5 wt%) classified as anomalous values, in contrast to metamorphic monazite, contain lower LREEs (La2O3 + Ce2O3 < 45 wt%) and higher ThO2 (> 1.5 wt%) identified as background values. The ratios such as Ce/Pr, La/Nd, La/Pr, along with REE trends, serve as diagnostic tools to target and exploration of orogenic gold deposits. This study highlights the utility of monazite as a geochemical tool to unravel mineralized zones, thereby enhancing exploration strategies for orogenic-type gold mineralization in the Dharwar Craton and similar terranes. Notably, we are the first to report the timing of a hydrothermal event related to gold mineralization at Paramanahalli by estimating the chemical ages (CHIME) of monazites through Electron Probe Micro Analysis. The study reveals two distinct ages: 2622 ± 08 Ma (older) and 2510 ± 12 Ma (younger), corresponding to metamorphism and syn-ore hydrothermal alteration/mineralization events, respectively. The Neoarchean mineralization event at Paramanahalli (2510 ± 12 Ma) aligns closely with ages estimated for gold mineralization in Ajjanahalli (2520 ± 9 Ma) and Gadag (2522 ± 6 Ma) within the Western Dharwar Craton. Our findings indicate that gold mineralization across the WDC is attributed to a regional tectono-thermal event around 2520 Ma, characterized by extensive fluid flux into the crust.
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来源期刊
Journal of Geochemical Exploration
Journal of Geochemical Exploration 地学-地球化学与地球物理
CiteScore
7.40
自引率
7.70%
发文量
148
审稿时长
8.1 months
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.
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