Variation of molybdenum isotopes in molybdenite from porphyry and vein Mo deposits in the Gangdese metallogenic belt, Tibetan plateau and its implications

Abstract

We present Mo isotopic ratios of molybdenite from five porphyry molybdenum deposits (Chagele, Sharang, Jiru, Qulong, and Zhuonuo) and one quartz-molybdenite vein-type deposit (Jigongcun) along the Gangdese metallogenic belt in the Tibetan Plateau. These deposits represent a sequence of consecutive events of the India-Asia collision at different periods. Additional molybdenite samples from the Henderson Mo deposit (USA), the oceanic subduction-related El Teniente (Chile), and Bingham (USA) porphyry Cu-(Mo) deposits were analyzed for better understanding the controls on the Mo isotope systematics of molybdenite. The results show that molybdenite from Sharang, Jiru, Qulong, and Zhuonuo deposits have similar δ 97 Mo (∼0‰), in agreement with the values of the Henderson Mo deposit (−0.10‰). In contrast, samples from the Changle and Jigongcun deposit have δ 97 Mo of 0.85‰ to 0.88‰ and −0.48 %, respectively. Molybdenite from the El Teniente and Bingham deposits yields intermediate δ 97 Mo of 0.27 and 0.46‰, respectively. The Mo isotopes, combined with Nd isotope data of the ore-bearing porphyries, indicate that source of the ore-related magmas has fundamental effects on the Mo isotopic compositions of molybdenite. Our study indicates that molybdenite related to crustal-, and mantle-derived magmas has positive or negative δ 97 Mo values, respectively, whereas molybdenite from porphyries formed by crust-mantle mixing has δ 97 Mo close to 0‰. It is concluded that the Mo isotope composition in the porphyry system is a huge source signature, without relation to the tectonic setting under which the porphyry deposits formed.

16 Good Golly, Why Moly? THE STABLE ISOTOPE GEOCHEMISTRY OF MOLYBDENUM

“…The starting Mo isotope composition of an ore-forming porphyry system can also influence the isotope compositions of molybdenites. Based on the comparison of Nd isotope data from magmatic rocks with Mo isotope data from molybdenites for a number of different deposits, Wang et al (2016) suggested that porphyry systems with crustal magma sources will precipitate molybdenites with generally higher δ 98 Mo compared with mantle-derived magmatic systems.…”

Validating the high-precision measurement of Mo isotopes at the 5 ng level using double spike MC-ICP-MS

“…22–24 Mo is also an essential but scarce micronutrient in biological systems. 25,26 Molybdenum isotopes hold great potential for deciphering Mo's biochemical reactions, displaying a wide range of Mo isotope fractionation concomitant with basic physicochemical processes. 27…”

“…[22][23][24] Mo is also an essential but scarce micronutrient in biological systems. 25,26 Molybdenum isotopes hold great potential for deciphering Mo's biochemical reactions, displaying a wide range of Mo isotope fractionation concomitant with basic physicochemical processes. 27 However, since Mo content in volcanic rocks such as the mid-ocean-ridge basalts (MORB), granites (<100 ng g À1 ), 28 and most plants (0.1-1 mg g À1 of dry weight) 29 is relatively lower, determining Mo isotopes in samples with low or ultra-low Mo contents is still challenging, which restricted the further applications of Mo isotopes in studying the biogeochemical cycle of Mo in the Earth's surface from the local to the global scale.…”

Machine Learning and EPCA Methods for Extracting Lithology–Alteration Multi-Source Geological Elements: A Case Study in the Mining Evaluation of Porphyry Copper Ores in the Gondwana Metallogenic Belt

“…The Gondwana metallogenic belt is located on the northern margin of the Tethys Ocean and is a vast metallogenic belt [18]. In this region, multiple tectonic deformations and magmatic activities occurred from the late Mesozoic to the early Cenozoic, resulting in complex rock compositions and structural patterns [19,20]. The metallogenic dynamic factors of the Gondwana metallogenic belt are closely related to the tectonic evolution of the region [21].…”