Abstract
An integrated zircon geochronological, elemental geochemical, and Sr–Nd–Hf isotopic investigation was carried out on a suite of dioritic–granitic rocks at Zalute in the southern Great Xing’an Range (SGXR), NE China, in order to probe the source and petrogenesis of these granitoid rocks and further constrain the geodynamical setting of early Early Cretaceous magmatism. The results of Sensitive High-Resolution Ion Micro Probe (SHRIMP) zircon U–Pb dating reveal that the Zalute dioritic–granitic rocks have a consistent crystallization age of ca. 137–136 Ma, consisting of quartz diorite (136 ± 1.4 Ma), monzogranite (136 ± 0.8 Ma), and granite porphyry (137 ± 1.3 Ma), which record an early Early Cretaceous magmatic intrusion. Geochemically, the quartz diorites, monzogranites, and granite porphyries are mostly high-K calc-alkaline and show features of typical I-type affinity. They possess uniform and depleted Sr–Nd–Hf isotopic compositions (e.g., initial 87Sr/86Sr ratios of 0.7035 to 0.7049, εNd(t) of −0.02 to +2.61, and εHf(t) of +6.8 to +9.6), reflecting a common source, whose parental magma is best explained as resulting from the partial melting of juvenile source rocks in the lower crust produced by underplating of mantle-derived mafic magma, with minor involvement of ancient crustal components. Evidence from their close spatio–temporal relationship, common source, and the compositional trend is consistent with a magmatic differentiation model of the intermediate-felsic intrusive suite, with continued fractional crystallization from quartz diorites, towards monzogranites, then to granite porphyries. Combined with previously published data in the SGXR, our new results indicate that the Zalute intermediate-felsic intrusive suite was formed during the post-collisional extension related to the closure of the Mongol–Okhotsk Ocean and subsequent slab break-off.
Highlights
Granitoid rocks are widely considered to be one of the most important components of the continental crust, which are mainly generated by a massive transfer of heat and/or mantle materials to the crust in the various geodynamical settings [1,2,3,4,5]
Several models have been proposed to decipher the origin and geodynamics of the Early Cretaceous granitoids in the southern Great Xing’an Range (SGXR), including (1) the “extreme fractional crystallization model of mantle-derived magma” which emphasizes evolved mantle-derived basaltic magma associated with the continental rifting [4]; (2) the “slab window model” advocates partial melting of subducting oceanic crust near the Mongol–Okhotsk ridge, accompanied with extension in the overlying lithosphere [20]; (3) the “mixing model” stresses on crust–mantle magma mixing, which is related to a post-collisional extensional setting [13,21,22]; (4) the “delamination model” proposes the gravitational collapse of thickened continental crust related to closure of the Mongol–Okhotsk Ocean [5,11,23,24] or subduction of the
We report new Sensitive High-Resolution Ion Micro Probe (SHRIMP) U–Pb zircon ages, major and trace elements, zircon Hf isotopic and whole-rock Sr–Nd isotopic data for quartz diorite, monzogranite, and granite porphyry at Zalute in the SGXR
Summary
Granitoid rocks are widely considered to be one of the most important components of the continental crust, which are mainly generated by a massive transfer of heat and/or mantle materials to the crust in the various geodynamical settings [1,2,3,4,5]. Several models have been proposed to decipher the origin and geodynamics of the Early Cretaceous granitoids in the SGXR, including (1) the “extreme fractional crystallization model of mantle-derived magma” which emphasizes evolved mantle-derived basaltic magma associated with the continental rifting [4]; (2) the “slab window model” advocates partial melting of subducting oceanic crust near the Mongol–Okhotsk ridge, accompanied with extension in the overlying lithosphere [20]; (3) the “mixing model” stresses on crust–mantle magma mixing, which is related to a post-collisional extensional setting [13,21,22]; (4) the “delamination model” proposes the gravitational collapse of thickened continental crust related to closure of the Mongol–Okhotsk Ocean [5,11,23,24] or subduction of the. The purpose of this study is to (1) constrain the magma source; (2) shed light on the petrogenesis of the dioritic–granitic rocks; and (3) provide insights into the tectonic setting that controlled the formation of the Early Cretaceous intermediate-felsic intrusive suite at Zalute
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