Abstract
The Yidun arc, located in the southeastern Tibetan Plateau, was formed by the westward subduction of the Ganze-Litang Paleo-Tethys ocean in Late Triassic. It is well-known for the formation of numerous Mesozoic porphyry-skarn Cu-Mo-(Au) deposits in the arc. To date, more than 20 Cu-Mo-(Au) deposits (>10 million tonnes Cu resources) have been discovered in the southern Eastern Yidun arc. However, few Cu-Mo deposits have been discovered in the northern Eastern Yidun arc. In recent years, some Cu-Mo deposits or occurrence are successively discovered in the northern Eastern Yidun arc, but their ore-forming ages are not well constrained. It remains unclear whether such Cu-Mo mineralization formed by similar metallogenic event and geodynamic setting as the Cu-Mo-(Au) mineralization in the south. In order to determine the metallogenic age and shed light on potential links between Cu-Mo mineralization and regional magmatic events, we present molybdenite Re-Os and zircon U-Pb ages to constrain the timing of two types of Cu-Mo mineralization in the northern Eastern Yidun arc (type I and type II). Molybdenite ICP-MS Re-Os dating results show that type I mineralization was formed at 217.7 ± 3.6 Ma, which is highly consistent with the formation ages of the host granite (218.1 ± 1.5 Ma, 2σ, n = 15, MSWD = 0.92) and aplite dyke (217.3 ± 1.3 Ma, 2σ, n = 16, MSWD = 0.50) within error. While the type II mineralization has a relatively younger formation age of 211.8 ± 4.7 Ma than the host granite (217.1 ± 1.5 Ma, 2σ, n = 14, MSWD = 0.96) and type I Cu-Mo mineralization. These data indicate that the Cu-Mo mineralization in the northern Eastern Yidun arc was temporally and spatially related to the Late Triassic magmatism in the region. Rhenium (Re) concentrations in the molybdenite from type I mineralization, ranging from 12.77 to 111.1 ppm (typically > 100 ppm), indicate that the ore-forming metals were derived mainly from a mantle source. However, Re contents in molybdenite from the type II mineralization, ranging from 7.983 to 10.40 ppm, indicate that the ore-forming metals were derived from a mixed mantle and crustal source with a predominantly crustal component. This study confirms that the northern Eastern Yidun arc exists Late Triassic Cu-Mo metallogenesis, and thus much attention should be paid on this region to find more Late Triassic Cu-Mo resources.
Highlights
The Yidun arc is one of the largest volcanic island arcs in the Sanjiang Tethyan Metallogenic Domain of the southeastern Tibetan Plateau (Figure 1a) [1,2]
This study confirms that the northern Eastern Yidun arc exists Late Triassic Cu-Mo metallogenesis, and much attention should be paid on this region to find more Late Triassic Cu-Mo resources
All analyses are concordant within analytical errors and yield a concordia age of 217.3 ± 1.4 Ma (MSWD = 0.22, n = 16), with a weighted mean age of 217.3 ± 1.3 Ma (MSWD = 0.50, n = 16) (Figure 6a,b), representing the formation age of the granitic aplite
Summary
The Yidun arc is one of the largest volcanic island arcs in the Sanjiang Tethyan Metallogenic Domain of the southeastern Tibetan Plateau (Figure 1a) [1,2]. More than 20 porphyry, skarn, and quartz-vein type Cu-Mo-(Au-W) polymetallic deposits of various sizes have been discovered and explored (Figure 1b) [5,6,7,8,9,10,11]. The porphyry Cu-Mo-Au deposits include the giant Pulang Cu-Au deposit, the large Xuejiping Cu-Au deposit, and several medium to small Cu deposits (e.g., Lannitang, Chundu, Songnuo) (Figure 1b) [6,12,13]. The quartz-vein type W-Mo deposits include the Relin and Xiuwacu W-Mo deposits with medium scale (Figure 1b) [5,14,15]. These deposits are exclusively clustered in the Southern Eastern Yidun
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