Petrogenesis of the Alubaogeshan intrusion in the Maodeng–Xiaogushan area, southern great xing'an range, NE China: Implications for magma evolution and tin–polymetallic mineralization

Abstract

• The Alubaogeshan intrusion formed at ca. 134 Ma and belongs to transitional I–A 2 -type granite . • The Alubaogeshan intrusion was formed by partial melting of a Neoproterozoic juvenile crust. • The syenogranite porphyry evolved from the porphyritic monzogranite. • Fluid–melt interaction is crucial for W mineralization. • The magma evolutionary degree influences the size of the Sn–polymetallic deposits in the SGXR. The Alubaogeshan intrusion, consisting of porphyritic monzogranite in the central part and syenogranite porphyry in the edge, is genetically related to the Maodeng–Xiaogushan Sn–polymetallic deposit. This paper aims to investigate the genetic link between these two granite phases and the relationship between magma evolution and Sn mineralization. LA-ICP-MS zircon U–Pb dating of the porphyritic monzogranite and syenogranite porphyry yielded ages of 134 ± 1.0 Ma and 133 ± 0.5 Ma, respectively. The Alubaogeshan intrusion has high SiO 2 and total alkali (Na 2 O + K 2 O) contents, with low Al 2 O 3 , Fe 2 O 3 , FeO, and MgO contents, belonging to high-K calc-alkaline metaluminous–weakly peraluminous granites. Chondrite-normalized rare earth element (REE) patterns are characterized by light REE enrichment and heavy REE depletion, with extremely negative Eu anomalies. In addition, the intrusion was also enriched in Rb, Th, U, K, Zr, Hf, and light REE and strongly depleted in Ba, Sr, P, and Ti. Mineralogical and geochemical characteristics, together with high zircon saturation temperature, indicate that the Alubaogeshan intrusion belongs to transitional I–A 2 -type granites. Compared with the porphyritic monzogranite, the syenogranite porphyry reveals higher SiO 2 content and lower TiO 2 , Al 2 O 3 , Fe 2 O 3 , FeO, CaO, MgO, and P 2 O 5 contents, with more obvious negative anomalies of Eu, Ba, Sr, P, and Ti. The temporal and spatial relationship and geochemical characteristics of the two rocks indicate that the syenogranite porphyry evolved from the porphyritic monzogranite. The modeling results show that the fractional crystallization of amphibole, plagioclase, K-feldspar, biotite, apatite, monazite, and allanite occurred during the magma evolution. The granitic magma differentiation plays a key role in the formation of the Maodeng–Xiaogushan Sn–polymetallic deposit. The ε Hf ( t ) values of zircon range from 2.58 to 7.08, and the two-stage Hf model ages range from 619 Ma to 850 Ma, implying that the Alubaogeshan intrusion was predominantly derived from partial melting of a Neoproterozoic juvenile crust. The TE 1,3 values of the ore-related granites from W–(Sn) deposits are generally higher than 1.1, suggesting that fluid–melt interaction is crucial for W mineralization. The degree of magmatic evolution is one of the controlling factors for the size of Sn–polymetallic deposits in the southern Great Xing′an Range.