Island-arc geochemical signatures of Cenozoic alkali-rich intrusive rocks from western Yunnan and their implication

Spatial–temporal framework for the closure of the Junggar Ocean in central Asia: New SIMS zircon U–Pb ages of the ophiolitic mélange and collisional igneous rocks in the Zhifang area, East Junggar

“…This indicates that the 330-310 Ma intrusions were obviously not formed at a pre-collisional island arc setting, because igneous rocks formed at oceanic island arc generally have a great amount of tholeiite rocks, and are enrichment of Th, P and Sr and depletion of Nb, Zr, Hf and Ti (Bailey, 1981;Ellam and Hawkesworth, 1988;Winter, 2001), and oxidized (Carmichael, 1991;Tomkins et al, 2012). The 330-310 Ma intrusions with arc geochemical signatures may be possibly formed at a post-collisional setting by underthrusting of the remained oceanic slab or partial melting of an older island arc, similar to the large number Tertiary porphyries in Western Sichuan and Yunnan Provinces (Guo et al, 2005;Wu et al, 2005;Xu et al, 2007), and Jurassic porphyries in the Dexing porphyry copper deposit . Similarly, adakitic rocks may be formed by partial melting of mafic lower crust at post-collisional setting as well (Hou et al, 2004;Topuz et al, 2005Topuz et al, , 2011Guo et al, 2007;Ghadami et al, 2008;Ding et al, 2011).…”

Geochemistry Characteristics of Cenozioc Alkaline-Rich Intrusions and its Forming Tectonic Setting in Jiudingshan Porphyry Cu-Mo Polymetallic Deposit, West Yunnan

“…The alkaline-rich intrusive rocks, proposed by refer with [1], occur in the special geological tectonic setting and be characterized by high alkali abundance (K 2 O+Na 2 O> 8%), potassium-enrichment (mostly K 2 O/Na 2 O>1) and common lack of hydrated minerals (i.e. biotite, hornblende, etc) refer to [2]. The rocks, mostly including being alkaline rocks, syenite and high-alkali alkali-feldspar granite, be formed in a post-collisional rift environment environment [3,4] and be common associated with mantle-derived magmation [3,5].…”