内蒙古中部乌兰陶勒盖地区晚二叠世二长花岗岩的成因及其构造意义OA
Petrogenesis and tectonic implications of the Late Permian monzogranite in the Wulantaolegai Area,central Inner Mongolia
中亚造山带是全球规模最大的显生宙增生型造山带,内蒙古中部是目前被广泛认为的中亚造山带古亚洲洋闭合部位.作为约束古亚洲洋闭合后构造体制转换的关键区段,内蒙古中部复杂的构造-岩浆演化长期以来受到关注.本文对乌兰陶勒盖地区出露的二长花岗岩开展了岩石学、全岩主微量元素地球化学、LA-ICP-MS锆石U-Pb定年和锆石Hf同位素组成研究,以限定其成岩时代、岩浆来源与形成的构造背景.结果表明,该二长花岗岩的锆石U-Pb年龄为259.2±3.8 Ma(MSWD=1.2),表明其形成于晚二叠世.全岩地球化学显示,该岩体具有高硅(SiO2=73.43％～75.15％)、富铝(Al2O3=13.32％～14.24％)、高碱(Na2O+K2O=8.18％～8.61％)和低铁镁的特征,铝饱和指数(A/CNK)为1.05～1.11,富集轻稀土元素及Rb、Th、K等大离子亲石元素,亏损重稀土元素及Nb、Sr、P和Ti等元素,整体以Eu负异常为主,属于弱过铝质Ⅰ型花岗岩.锆石Hf同位素组成显示,其εHf(t)值介于-16.44～-2.04之间,二阶段Hf模式年龄(tDM2)介于2 322～1 413 Ma之间,指示岩浆主要来源于古老地壳物质的部分熔融,并可能混入极少量更亏损组分.结合区域构造-岩浆演化序列,认为乌兰陶勒盖晚二叠世二长花岗岩形成于古亚洲洋闭合后岩石圈减薄或伸展背景下的地壳重熔作用,反映内蒙古中部地区在晚二叠世已进入后碰撞-造山后伸展构造体制.
The Central Asian Orogenic Belt(CAOB)is the largest Phanerozoic accretionary orogenic belt on Earth,and central Inner Mongolia is widely regarded as the key segment marking the final closure of the Paleo-Asian Ocean within the CAOB.As a critical region for constraining the tectonic transition that followed the closure of the Paleo-Asian Ocean,central Inner Mongolia has long attracted considerable attention owing to its complex tectono-magmatic evolution.In this study,the monzogranite exposed in the Wulantaolegai area was investigated through petrography,whole-rock major-and trace-element geochemistry,LA-ICP-MS zircon U-Pb geochronology,and zir-con Hf isotopic analyses to constrain its emplacement age,magma source,and tectonic setting.The results show that the monzogranite yields a zircon U-Pb age of 259.2±3.8 Ma(MSWD=1.2),indicating emplacement in the Late Permian.Whole-rock geochemical data indicate that the pluton is characterized by high silica(SiO2=73.43％～75.15％),elevated Al2O3(13.32％～14.24％),high total alkalis(Na2O+K2O=8.18％～8.61％),and low Fe-Mg contents,with aluminum saturation indices(A/CNK)of 1.05～1.11.It is enriched in light rare earth ele-ments and large-ion lithophile elements such as Rb,Th,and K,but depleted in heavy rare earth elements and in Nb,Sr,P,and Ti,and is dominated by negative Eu anomalies,thus belonging to weakly peraluminous Ⅰ-type granite.Zircon Hf isotopic compositions yield εH f(t)values of-16.44 to-2.04 and two-stage Hf model ages(tDM2)of 2 322～1 413 Ma,suggesting that the magma was derived predominantly from partial melting of ancient crustal materials,with the possible involvement of a very minor depleted component.In combination with the re-gional tectono-magmatic evolutionary framework,we propose that the Late Permian monzogranite in the Wulantaole-gai area was generated by crustal remelting under a post-closure lithospheric thinning or extensional regime following the closure of the Paleo-Asian Ocean,indicating that central Inner Mongolia had entered a post-collisional to post-orogenic extensional tectonic regime by the Late Permian.
高栋;焦建刚;陈圣;陈泳帆;伍明媚;刘龙龙;王佳新;吴才来
岭南师范学院地理科学学院,广东湛江 524048||长安大学西安市关键金属成矿与高效利用重点实验室,陕西西安 710054||长安大学地球科学与资源学院,陕西西安 710054||中国地质科学院地质研究所,北京 100037长安大学西安市关键金属成矿与高效利用重点实验室,陕西西安 710054||长安大学地球科学与资源学院,陕西西安 710054岭南师范学院地理科学学院,广东湛江 524048岭南师范学院地理科学学院,广东湛江 524048岭南师范学院地理科学学院,广东湛江 524048岭南师范学院地理科学学院,广东湛江 524048长安大学地球科学与资源学院,陕西西安 710054中国地质科学院地质研究所,北京 100037
天文与地球科学
二长花岗岩锆石U-Pb年龄岩石成因构造意义乌兰陶勒盖古亚洲洋
monzogranitezircon U-Pb agepetrogenesistectonic significanceWulantaolegaiPaleo-Asian Ocean
《岩石矿物学杂志》 2026 (3)
427-446,20
长安大学中央高校基本科研业务费专项资金(300102273502)岭南师范学院高层次人才引进项目(000302302635)国家自然科学基金项目(41872071,42102161) Fundamental Research Funds for the Central Universities,Chang'an University(300102273502)The High-level Talent Introduction Project of Lingnan Normal University(000302302635)National Natural Science Foundation of China(41872071,42102161)
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