Re–Os geochronology of Cu and W–Mo deposits in the Balkhash metallogenic belt, Kazakhstan and its geological significance

Abstract

The Central Asian metallogenic domain (CAMD) is a multi-core metallogenic system controlled by boundary strike-slip fault systems. The Balkhash metallogenic belt in Kazakhstan, in which occur many large and super-large porphyritic CueMo deposits and some quartz vein-and greisen-type WeMo deposits, is a well-known porphyritic CueMo metallogenic belt in the CAMD. In this paper 11 molybdenite samples from the western segment of the Balkhash metallogenic belt are selected for ReeOs compositional analyses and ReeOs isotopic dating. Molybdenites from the Borly porphyry Cu deposit and the three quartz vein-greisen WeMo depositsdEast Kounrad, Akshatau and Zhanetdall have relatively high Re contents (2712e2772 mg/g for Borly and 2.267e31.50 mg/g for the other three W eMo deposits), and lower common Os contents ( 0.670e2.696 ng/g for Borly and 0.0051e0.056 ng/g for the other three). The molybdenites from the Borly porphyry CueMo deposit Geoscience Frontiers journal homepage: www.elsevier.com/locate/gsf Geoscience Frontiers (2010) 1, 115e124 and the East Kounrad, Zhanet, and Akshatau quartz vein-and greisen-type WeMo deposits give average model ReeOs ages of 315.9 Ma, 298.0 Ma, 295.0 Ma, and 289.3 Ma respectively. Meanwhile, molybdenites from the East Kounrad, Zhanet, and Akshatau WeMo deposits give a ReeOs isochron age of 297.9 Ma, with an MSWD value of 0.97. ReeOs dating of the molybdenites indicates that CueWeMo metallogenesis in the western Balkhash metallogenic belt occurred during Late Carboniferous to Early Permian (315.9e289.3 Ma), while the porphyry CueMo deposits formed at w316 Ma, and the quartz vein-greisen WeMo deposits formed at w298 Ma. The ReeOs model and isochron ages thus suggest that Late Carboniferous porphyry granitoid and pegmatite magmatism took place during the late Hercynian movement. Compared to the Junggar-East Tianshan porphyry Cu metallogenic belt in northwestern China, the formation of the CueMo metallogenesis in the Balkhash metallogenic belt occurred between that of the Tuwu-Yandong in East Tianshan and the Baogutu porphyry Cu deposits in West Junggar. Collectively, the large-scale Late Carboniferous porphyry CueMo metallogenesis in the Central Asian metallogenic domain is related to Hercynian tectono-magmatic activities. ª

Late-Paleozoic emplacement and Meso-Cenozoic reactivation of the southern Kazakhstan granitoid basement

“…A Carboniferous (328-312 Ma) porphyry Cu metallogenic event is related to calc-alkaline arc magmatism whilst early Permian (306-289 Ma) greisen W-Mo metallogenic deposits are associated with alkaline magmatism in a collisional to post-collisional context (Shen et al, 2013a). Also Chen et al (2010Chen et al ( , 2014 confirmed that late Paleozoic felsic magmatism occurred mainly during the late Carboniferous to earliest early Permian in that region. Generally, Carboniferous arc magmatism can be related to the subduction of the Junggar-Balkhash Ocean, which resulted in the formation of the Balkhash-Ili (BY) magmatic belt in SE Kazakhstan (Heinhorst et al, 2000;Korobkin and Buslov, 2011;Levashova et al, 2012;Xiao et al, 2010) (Fig.…”

SHRIMP U–Pb, Ar–Ar and fission-track geochronology of W–Mo deposits in the Balkhash Metallogenic Belt (Kazakhstan), Central Asia, and the geological implications

“…2), at an elevation of 432 m. It is an underground, post-magmatic W-Mo deposit formed at the front of the volcano-intrusive zone of the Late Paleozoic continental margin. The ore deposit occurs in endo-and exocontact zones of syenogranite (alkaline granite; see Tables 1 and 2 for compositions), with reserves of 0.2-0.25 Mt Mo at an average grade of 0.056% (Chen et al, 2010;Cao et al, 2011).…”

“…The best-known ore deposits in the BMB are the super-large Kounrad and Aktogai porphyry Cu-Mo deposits, the large-scale Borly porphyry Cu-Mo deposit, the large-scale Sayak skarn Cu-polymetallic ore-field, and a series of large-scale quartz vein-type W-Mo deposits such as the East Kounrad, the Akshatau, and the Zhanet. The West Junggar metallogenic belt in northern Xinjiang, China is the eastward extension of the BMB (Chen et al, 2010;Shen and Shen, 2010;Shen et al, 2012Shen et al, , 2013.…”

A review of the geological characteristics and geodynamic setting of Late Paleozoic porphyry copper deposits in the Junggar region, Xinjiang Uygur Autonomous Region, Northwest China

“…Molybdenite of Tsagaan Suvarga porphyry Cu-Mo deposit, Mongolia, yielded Re-Os isochron ages of 370 ± 0.8 Ma, and zircon SHRIMP U-Pb dating of the monzogranite porphyry yielded weighted average age of (365.7 ± 3.6) Ma, suggesting that mineralization took place in Late Devonian, coeval with that of the monzogranite porphyry (Watanabe and Stein, 2000;Hou et al, 2010). In the western segment, the mineralization ages in the Balkhash region of Kazakhstan range from 330 to 316 Ma; for example, the age of the Aktogai deposit is $320 Ma and that of the Kounrad copper deposit is 330 Ma (Seltmann and Porter, 2005), and that of the Borly copper deposit is 315.9 Ma (Chen et al, 2010). The age of the Mengxi copper-molybdenum deposit is similar to that the age of the early-stage mineralization of the Oyu Tolgoi copper-gold deposit and the age of the Yelekenhalasu and Halasu deposits are close to that the age of the main-stage mineralization of the Oyu Tolgoi deposit, and the age of the Baogutu copper deposit is close to that of porphyry copper deposits in the Balkhash region.…”