Zircon geochronological and geochemical study of the Baogaigou Tin deposits, southern Great Xing'an Range, Northeast China: Implications for the timing of mineralization and ore genesis

Abstract

Tin deposits in China mainly occur in South China, while extensive Sn mineralization also occurred in the southern Great Xing'an Range (SGXR) of Northeast China. The Baogaigou deposit is a small typical greisen‐type Sn deposit in the SGXR, yielding 1,136 t of Sn reserves with an average grade of 0.48% Sn. New whole‐rock geochemical, zircon geochronological, whole‐rock Sr–Nd isotope and zircon in situ Hf–O isotopic data are presented for granites from Baogaigou deposit. Two granite samples from the Baogaigou deposit yield identical secondary ion mass spectrometry zircon U–Pb ages of 145.6 ± 0.8 Ma and laser ablation inductively coupled plasma mass spectrometry ages of 145.6 ± 0.4 Ma, consistent with regional magma activity relating to Sn mineralization ages and prior to regional Sn mineralization ages (142–135 Ma) in the SGXR. The granites are strongly peraluminous, calc‐alkaline granites enriched in light rare earth elements (LREEs), with fractionation of light over heavy REEs (LREE/HREE = 10.1–7.6) and strong negative Eu anomaly with Eu/Eu* values of 0.03–0.04. Primitive‐mantle‐normalized granitoid compositions display negative Ba, Nb, Ta, Pb, Sr, P, Eu and Ti anomalies, and positive Th, U and Nd anomalies. The granites have initial 87Sr/86Sr ratios, εNd(t) values, and TDM(Nd) ages of 0.70532–0.70325, +2.5 to +2.1, and 783–743 Ma, respectively, with zircon εHf(t) values of 5.1–1.6, TDM2 model ages of 1,086–880 Ma, and δ18O values of 5.70–4.91‰. Geochemical and Sr–Nd–Hf–O isotopic data for the Baogaigou granites indicate they are A2‐type peraluminous granites and were probably formed through partial melting of juvenile lower crust originating from a depleted mantle. The Baogaigou granite with Sn content (5.7–13.7 ppm; average = 9.6 ppm) contributed most of the ore‐forming materials, while the highly fractionated and low magma fO2 (Ce4+/Ce3+ and Eu/Eu* range from 1.0 to 49.3 and 0.03 to 0.04) nature of the Baogaigou granites would have facilitated development of Sn mineralization. Under extensional environment, the asthenosphere upwelling would result in large‐scale transport of magma and heat from the mantle, and then extensive re‐melting of the crust, generating magma and fluid to form a tectonic–magmatic–fluid metallogenic system.

Geochronology and Geochemistry of Early Cretaceous A‐type Granites in Central–Eastern Inner Mongolia, China: Implications for Late Mesozoic Tectonic Evolution of the Southern Great Xing'an Range

“…Granitic rocks related to Sn mineralization are mostly shallow porphyries (with a porphyritic or porphyritic-like texture), belonging to calc-alkaline to high-K calc-alkaline series (highly differentiated) I-or A-type granites (Chen et al, 2021). Their Hf isotopic compositions are mainly characterized by positive ε Hf (t) values (+1.4 to +10.2) and young Hf twostage model ages (T DM2 ; 922-556 Ma) (Mi et al, 2020;Chen et al, 2021;Ji et al, 2021).…”

Geochronology, Geochemistry, and Lu-Hf Isotopic Compositions of Monzogranite Intrusion from the Chang’anpu Mo Deposit, NE China: Implications for Tectonic Setting and Mineralization

“…The molybdenum deposits in China are mainly the products of the late Indosinian to Yanshanian magmatism, which is different from the late Cretaceo-Oligocene molybdenum deposits in foreign countries [7][8][9]. The study of geochronology and petrogeochemistry of intrusions which the porphyry deposits occurred in is not only helpful to understand the process of diagenesis and mineralization [10][11][12][13][14][15], but can also reflect the tectonic evolution process controlling the formation of intrusions and ore deposits [16][17][18][19][20].…”