Late Triassic Au-Mo mineralization in the Xiaoqinling region and a genetic connection to carbonatitic magmatism

• The southern margin of the North China craton hosts a number of quartz vein-style deposits of the unusual AuMo ore spectrum, including the Dahu deposit in the Xiaoqinling region. Pristine euhedral monazite and rutile crystals from the Dahu Au-Mo mineralized veins yield LA-ICP-MS weighted mean 206Pb/238U ages of 212.1 +/- 1.7 Ma (1 s, MSWD = 1.13) and 209.7 +/- 2.7 Ma (2 s, MSWD = 1.7), respectively. These ages point to a Late Triassic gold mineralization event in the Xiaoqinling region, aside from the regionally well-recognized Early Cretaceous gold mineralization event. Tectonic setting, mineral association, elemental and isotopic signatures, and fluid characteristics of the Dahu deposit suggest that the Late Triassic Au-Mo mineralization represents a carbonatiteassociated hydrothermal system, with ore fluids exsolved from a late-stage carbonatite system. Mineralogically, the Dahu deposit is enriched in hydrothermal minerals common to carbonatite systems, such as carbonates, sulfates, and REE minerals. Trace element and isotope compositions of vein minerals also show similarities to those of carbonatites. Monazite displays a pronounced LREE-enriched and smooth pattern (no Eu anomaly), with epsilon Nd(t) values ranging from -14.9 to -13.3. Rutile is characterized by high Nb concentrations (6 to 18 wt%) and extremely high Nb/Ta ratios of 236 to 2044. Fluid inclusions in the Dahu Au-Mo mineralized veins and the regionally distributed coeval carbonatites are all dominated by low to moderate salinity H2O-CO2 fluids that contain sulfates as trapped solids/daughter minerals. Our study suggests that the southern margin of the North China craton has potential for the exploration of polymetallic hydrothermal mineralization related to hidden carbonatites.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

Late Triassic

Carbonatitic magmatism

Gold

Molybdenum

Xiaoqinling

mesozoic molybdenum deposits

north china craton

u-pb monazite

re-os

qinling orogen

gold deposits

quartz-vein

isotopic composition

niobian rutile

solid-solution

Geology

Mineralogy

Mining & Mineral Processing

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