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[Display omitted] • The Mengku dacites, Lincang granites and diorites are spatially and temporally related. • The Triassic Mengku dacites is characterized by rejuvenation of the Lincang crystal mush. • The thermal input was supplied by mafic magma represented by the Lincang diorites. • Magmatic evolution was related to mantle upwelling in the post-collisional setting. The tectono-magmatic event of the Changning-Menglian Paleo-Tethys orogen is an important process for understanding the tectonic evolution of the SE Tibetan Plateau. This orogen is composed of Changning-Menglian suture, Lancang group, Lincang batholith, and Yunxian volcanics. The Lincang batholith and its volcanic counterparts are part of Triassic magmatism in this orogen. The botholith is composed of biotite monzogranite, granodiorite and diorite. The Middle to Late Triassic volcanics include Manghuai rhyolite, Xiaodingxi basalt and Mengku dacite. The Mengku dacite is volcanic dome in west of the batholith. Lincang biotite monzogranite and Mengku dacite have similar geochemistry and are characterized by negative ε Hf (t) values (–13.2 to –5.2) and ε Nd (t) values (–14.7 to –8.8), whereas diorite dikes within the Lincang batholith have slightly high ε Hf (t) values (–8.3 to –4.9) and ε Nd (t) values (–6.9 to –6.7). Manifestations of resorption textures in quartz and reverse compositional zoning in feldspars are recognized from Mengku dacite. We consider that Mengku dacites resemble the erupted Lincang biotite monzogranite as they occur in the same tectonic settings and have similar geochemical features and mineral assemblages dominated by plagioclase, alkali-feldspar, quartz, and biotite. The evolution of the Mengku dacite magma is characterized by the rejuvenation of crystal mush represented by the Lincang batholith. The required thermal input was supplied by mafic magma, represented by diorite dikes and enclaves within the Lincang batholith. The Middle to Late Triassic magmatic event in this orogen likely resulted from lithospheric delamination and upwelling of the asthenosphere in a post-collisional environment. [ABSTRACT FROM AUTHOR]

Granitoids, as a major component of the Earth's crust, have large K isotopic variations (δ41K = −1.0‰ to 0.4‰), but K isotope fractionation during granite differentiation is poorly constrained. Here, we examined K isotopic compositions of a suite of well-characterized crustal igneous rocks (quartz diorite, granodiorite and monzogranite) from the Tagong pluton, northeastern Tibetan Plateau. The rocks display increasing δ41K in the following order: quartz diorite (δ41K = −0.798‰ to −0.538‰) < granodiorite (δ41K = −0.520‰ to −0.378‰) < monzonite granite (δ41K = −0.439‰ and − 0.436‰). The δ41K values are positively correlated with SiO 2 and K 2 O contents and negatively with MgO and Al 2 O 3 contents, indicating up to ∼0.42‰ fractionation during magmatic differentiation. Taking into account mineral assemblage, fractional crystallization of K-rich phases (mica and K-feldspar) likely plays a dominant role in K isotopic variation. In addition, mafic microgranular enclaves (MMEs) commonly occurring in granitoid rocks show comparable δ41K values (−0.489‰ to −0.416‰) to their corresponding host rocks, implying their schlieren origin. These features demonstrate that K isotope heterogeneity of the crust could have been induced by magma differentiation in addition to source control. • K isotope fractionation during granite differentiation. • Fractional crystallization probably controlled fractionation of K isotopes. • Schlieren origin of mafic microgranular enclaves from perspective of K isotopes. • Contribution of magma differentiation to K isotopic heterogeneity of the crust. [ABSTRACT FROM AUTHOR]