Supplementary materials for "Geochemical and geochronological study on the middle-late Permian granitic magmatism in Siziwangqi area, Inner Mongolia and its tectonic implications" in American Journal of Science

Abstract

This dataset is Supplementary materials for "Geochemical and geochronological study on the middle-late Permian granitic magmatism in Siziwangqi area, Inner Mongolia and its tectonic implications" in American Journal of Science. It includes on one supplementary document and six supplementary tables (i.e., Tables S1–S6). This research proposes that the middle‑late Permian granitic magmatism in the Siziwangqi and adjacent areas of the middle segment of the Inner Mongolia marks a shift from earlier continental‑arc magmatism to widespread crustal reworking, driven by intensive tectonic contraction caused by collision related to the final closure of the Paleo‑Asian Ocean (PAO). This contrasts with the limited crustal shortening typical of the Central Asian Orogenic Belt (CAOB) accretionary zone. To test this, we collected 26 granitic samples, divided into Group I (batholith, ~266–262 Ma) and Group II (stocks, ~257–255 Ma). Zircon U‑Pb dating (LA‑ICP‑MS) yielded weighted mean ages of 262 ± 3 Ma, 266 ± 3 Ma, and 263 ± 2 Ma for the batholith, and 255 ± 1 Ma, 257 ± 2 Ma, and 256 ± 3 Ma for the stocks. Zircon Lu‑Hf isotopes show negative εHf(t) values (‑11.4 to ‑18.5) with two‑stage model ages of 2.4–1.8 Ga; whole‑rock Nd isotopes are similarly enriched (εNd(t) ‑11 to ‑14). Whole‑rock geochemistry (XRF, ICP‑MS) reveals high SiO₂ (>70 wt%), Na₂O+K₂O (7.4–8.7 wt%), and low Zr/Hf (20–38), indicating highly evolved, crust‑derived magmas. Sr‑Nd isotopic ratios were measured by MC‑ICP‑MS. Analytical procedures are detailed in the Supporting Information. Our findings include: (1) both granite groups originated mainly from partial melting of Paleoproterozoic North China Craton (NCC) crust and/or some metasomatized lithospheric mantle, followed by fractional crystallization; (2) the magmatic suite is non‑arc, characterized by crustal reworking rather than mantle input; (3) the timing coincides with regional thrust‑nappe structures, foreland basins, and sedimentary hiatus, evidencing synchronous crustal shortening and uplift. Interpretation: The isotopic and geochemical data demonstrate that middle‑late Permian magmatism was dominated by anatexis of ancient crust, with limited juvenile addition. Combined with structural and sedimentary records, this supports a model where southward subduction of the PAO culminated in continental collision, causing significant crustal thickening and reworking along the NCC margin. In contrast, the widespread accretionary zone within the CAOB experienced only weak contraction. Thus, our data, provide evidence for direction‑dependent tectonic responses to PAO closure, with implications for Phanerozoic crustal growth and orogenic processes.