Petrogenesis of magmatic rocks and tungsten mineralization of the Tumentsogt deposit, Eastern Mongolia: Insights from zircon and wolframite geochronology, Hf isotopes, and mineral geochemistry

IF 2.5 2区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Lithos Pub Date : 2025-10-13 DOI:10.1016/j.lithos.2025.108284

Lkhagvasuren Dagva-Ochir , Huan Li , Sarantuya Oyungerel , Dashdorjgochoo Odgerel , Dorjsuren Otgonbaatar

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Abstract

The Central Asian Rift System, which developed during the Late Paleozoic to Early Mesozoic, represents a major post-collisional extensional event within the Central Asian Orogenic Belt (CAOB) following the closure of the Mongol-Okhotsk Ocean. However, the origin and geodynamic significance of the associated magmatism and rare-metal mineralization remain debated. Here, we present the first integrated dataset of zircon and wolframite UPb geochronology, LuHf isotopes, and mineral chemistry and whole-rock geochemistry for the Tumentsogt (TT) tungsten deposit in the North Gobi Rift zone, a key intracontinental rift structure in the southern CAOB. We investigate three groups of magmatic rocks, enabling us to reconstruct a regional evolution from syn- to post-collisional and intraplate extensional magmatism associated with W mineralization. Group 1 (∼152 Ma) consists of highly evolved, peraluminous A-type leucogranites (SiO₂ = 73.9–76.0 wt%; A/CNK > 1) with strong negative Eu (Eu/Eu* = 0.08–0.13) and Ti anomalies, pronounced enrichment in Th (15.7–55.2 ppm) and U (6.1–35.7 ppm), Nb/Ta = 3.1–11.7, Rb/Sr = 4.2–12.8, and flat to weakly fractionated REE patterns. Although no Hf isotopic data are available, their trace-element signatures indicate extreme magmatic differentiation and crustal anatexis under intraplate extensional conditions. Group 2 (∼213 Ma) comprises peraluminous felsic granites (SiO₂ = 73.5–77.1 wt%; A/CNK < 1.1) with moderate LREE enrichment, weak negative Eu anomalies (Eu/Eu* = 0.2–0.3), lower Th (6.7–9.4 ppm) and U (1.0–2.4 ppm) than Group 1, La/Yb = 11.0–18.2, Nb/Ta = 9.9–16.0, and zircon ε_Hf(t) = +8.5 to +13.7 (TDM = 319–540 Ma), consistent with juvenile crustal melting. Group 3 (∼273 Ma) includes metaluminous mafic-intermediate intrusions (SiO₂ = 49.4–58.6 wt%; A/CNK < 1.1) with LREE-enriched, HREE-depleted REE patterns, no Eu anomaly, moderate Nb/Ta (4.0–18.6) and Rb/Sr (0.5–3.3), and ε_Hf(t) = +7.9 to +10.0 (TDM = 520–601 Ma), indicating predominantly mantle-derived melts with minor crustal assimilation. Together, these data record a three-stage tectonomagmatic evolution in the eastern CAOB: (1) Permian syn-collisional mafic magmatism related to Mongol-Okhotsk Ocean subduction; (2) Late Triassic syn- to post-collisional felsic magmatism and juvenile crustal growth; and (3) Late Jurassic intraplate extension driven by continued lithospheric extension and asthenospheric upwelling. Notably, the Group 1 leucogranites are geochemically fertile, enriched in volatiles and ore-related elements (Rb, Cs, Sn, W, Nb, Ta, Th, U), and genetically linked to tungsten mineralization. Muscovite from the greisenised granite captures the transition from magmatic to hydrothermal stages, with rims enriched in W, Sn, and alkalis, while wolframite compositions reveal fluid evolution from greisen to quartz-vein mineralization. In situ wolframite UPb ages of 150.1 ± 3.4 Ma (greisen) and 144.4 ± 5.9 Ma (quartz vein) indicate a protracted (∼6 Myr) hydrothermal history after granite emplacement. Overall, these results demonstrate that the TT deposit is a typical post-collisional W system, where late-stage A-type granites act as the primary source of heat and ore-bearing fluids, underscoring the metallogenic significance of the North Gobi Rift zone.

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东蒙古Tumentsogt矿床岩浆岩成因与钨成矿作用：来自锆石和黑钨矿年代学、Hf同位素和矿物地球化学的启示

中亚裂谷系发育于晚古生代至早中生代，是继蒙古-鄂霍次克洋闭合后中亚造山带内的一次重大碰撞后伸展活动。然而，伴生岩浆作用和稀有金属成矿作用的成因及其地球动力学意义仍存在争议。本文首次建立了北戈壁裂谷带图门索特（TT）钨矿的锆石和黑钨矿UPb年代学、LuHf同位素、矿物化学和全岩地球化学的综合数据集。我们研究了三组岩浆岩，使我们能够重建与W矿化有关的从同碰撞到后碰撞和板内伸展岩浆活动的区域演化。第1组（~ 152 Ma）由高度演化的过铝质A型浅花岗岩（SiO₂= 73.9-76.0 wt%; A/CNK > 1）组成，具有强烈的负Eu （Eu/Eu* = 0.08-0.13）和Ti异常，Th （15.7-55.2 ppm）和U （6.1-35.7 ppm）富集，Nb/Ta = 3.1-11.7, Rb/Sr = 4.2-12.8， REE呈平至弱分馏模式。虽然没有Hf同位素资料，但它们的微量元素特征表明，在板内伸展条件下，岩浆分异剧烈，地壳深熔。第2组（~ 213 Ma）由过铝长英质花岗岩（SiO₂= 73.5 ~ 77.1 wt%; A/CNK < 1.1）组成，LREE富集适中，Eu负异常较弱（Eu/Eu* = 0.2 ~ 0.3）， Th （6.7 ~ 9.4 ppm）和U （1.0 ~ 2.4 ppm）低于第1组，La/Yb = 11.0 ~ 18.2, Nb/Ta = 9.9 ~ 16.0，锆石εHf(t) = +8.5 ~ +13.7 (TDM = 319 ~ 540 Ma)，与早期地壳熔融一致。第3组（~ 273 Ma）包括成矿基性-中间侵入体（SiO₂= 49.4-58.6 wt%; A/CNK < 1.1），具有lree富集，hree贫的模式，无Eu异常，中等Nb/Ta（4.0-18.6）和Rb/Sr (0.5-3.3), εHf(t) = +7.9 ~ +10.0 (TDM = 5.2 - 601 Ma)，表明主要是地幔源熔体，地壳同化作用较小。综上所述，这些资料记录了中国东部构造岩浆演化的三个阶段：(1)与蒙古-鄂霍次克洋俯冲有关的二叠纪同碰撞基性岩浆活动；(2)晚三叠世同-碰撞后长英质岩浆作用与幼年地壳生长；(3)由岩石圈持续伸展和软流圈上升流驱动的晚侏罗世板内伸展。值得注意的是，第1组亮花岗岩地球化学上肥沃，富含挥发物和与矿有关的元素（Rb、Cs、Sn、W、Nb、Ta、Th、U），与钨矿化有关。灰色花岗岩中的白云母反映了岩浆到热液阶段的过渡，其边缘富集W、Sn和碱，而黑钨矿的组成则反映了从灰色到石英脉成矿的流体演化过程。原位黑钨矿UPb年龄分别为150.1±3.4 Ma（格雷森）和144.4±5.9 Ma（石英脉），表明花岗岩侵位后存在漫长的（~ 6 Myr）热液历史。综上所述，TT矿床为典型的后碰撞W体系，晚期a型花岗岩为主要热源和含矿流体来源，凸显了北戈壁裂谷带的成矿意义。

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来源期刊

Lithos 地学-地球化学与地球物理

CiteScore

6.80

自引率

11.40%

发文量

286

审稿时长

3.5 months

期刊介绍： Lithos publishes original research papers on the petrology, geochemistry and petrogenesis of igneous and metamorphic rocks. Papers on mineralogy/mineral physics related to petrology and petrogenetic problems are also welcomed.