文章摘要
吴挺煌,童英,孙蓓蕾,文雪琴,赵庆,孙会一,杨伟.北山西南部二叠纪青墩峡杂岩体的成因及其构造意义[J].矿产勘查,2026,17(1):12-29
北山西南部二叠纪青墩峡杂岩体的成因及其构造意义
Petrogenesis of the Qingdunxia complex in the southwest Beishan Orogen and its tectonic implications
投稿时间：2025-03-12  
DOI：10.20008/j.kckc.202601002
中文关键词: 柳园洋  二叠纪  花岗岩  北山  中亚造山带
英文关键词: Liuyuan Ocean  Permian  granite  Beishan  Central Asian Orogenic Belt
基金项目:本文受国家自然科学基金项目“中国西部造山系多尺度岩浆-成矿时空发育规律”(U2244217)和中国地质调查局项目“中国大陆三维构造格架建模和数据库建设”(DD20220100201)联合资助。
作者单位
吴挺煌 中国地质科学院地质研究所,深地探测与矿产勘查全国重点实验室,北京 100037
中国地质科学院地质研究所,北京离子探针中心,北京 100037
太原理工大学地球科学与测绘工程学院,山西太原 030024 
童英 中国地质科学院地质研究所,深地探测与矿产勘查全国重点实验室,北京 100037
中国地质科学院地质研究所,北京离子探针中心,北京 100037 
孙蓓蕾 太原理工大学地球科学与测绘工程学院,山西太原 030024 
文雪琴 太原理工大学地球科学与测绘工程学院,山西太原 030024 
赵庆 中国地质科学院地质研究所,深地探测与矿产勘查全国重点实验室,北京 100037
中国地质科学院地质研究所,北京离子探针中心,北京 100037 
孙会一 中国地质科学院地质研究所,北京离子探针中心,北京 100037 
杨伟 中国地质科学院地质研究所,深地探测与矿产勘查全国重点实验室,北京 100037
中国地质科学院地质研究所,北京离子探针中心,北京 100037 
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中文摘要:
      中亚造山带南缘的二叠纪构造环境一直存在争议，位于其最南端的北山造山带发育大量的二叠纪岩浆岩，为解决这个问题提供了理想的对象。青墩峡中酸性杂岩体出露于北山造山带最南缘的石板山单元西段，主要由黑云母花岗闪长岩和碱长花岗岩组成。SHRIMP锆石 U-Pb测年结果显示，炮台花岗闪长岩和峡口碱长花岗岩分别形成于(284.5±2.6)Ma和(287.5±3.2)Ma，为早二叠世岩浆活动产物。炮台黑云母花岗闪长岩富 SiO2(62.13%~66.94%)，低 K2O(0.62%~2.51%)和 Na2O(2.32%~3.11%)，相对富 Fe2O3T(5.53%~7.82%)、(12.78%~13.82%)准铝质-过铝质 I型花岗岩，轻稀土MgO(2.51%~3.66%)和 Al2O3属低钾钙碱性、元素富集，重稀土元素亏损，弱负 Eu异常，富大离子亲石，元素(Rb、Th、U)和亏损 Ba、Sr、P、Ti，具有高 ISr (0.7099~0.7126)和低 εNd(t)值(.6.85~.6.43)。相对而言，峡口碱长花岗岩具有高 SiO2，(75.37%~75.77%)富 K2O(4.52%~4.69%)和 Na2O(3.36%~3.55%)，低 Al2O3(12.10%~12.36%)、CaO(0.67%~1.12%)、Fe2O3T(1.55%~2.07%)、MgO(0.19%~0.22%)和 P2O5属于高钾钙碱性 I型花岗岩特征，(< 0.02%)稀土配分曲线及微量元素蛛网图与炮台黑云母花岗闪长岩相类似，但，Eu负异常和 Sr、P、T亏损较为明显，具有低 ISr(0.7042~0.7082)和相对较高的 εNd(t)值(.0.82~.0.65)。结果显示这两类花岗岩具有不同的成因，前者可能是古老地壳的重熔，而后者则主要是幔源岩浆底侵导致新生地壳发生部分熔融和古老地壳的重熔，经历不同比例混合和不同程度的结晶分异作用而成。结合北山南部二叠纪岩浆岩研究成果以及沉积记录，表明二叠纪之前柳园地区的古亚洲或其分支洋盆已闭合，而北山南部地壳在早二叠世经历了强烈伸展，引发了新的洋盆(柳园洋)开启，从而形成了区内洋盆与大量的超基性—基性岩、I型和 A型花岗岩共存的局面。
英文摘要:
      The Permian tectonic environment in the southern margin of the Central Asian Orogenic Belt re-mains debated. The Beishan orogen, hosting numerous Permian magmatic rocks, provides a key area for resolvingthis issue. The Qingdunxia medium-acidic complex, exposed in the western part of the Shibanshan unit, mainly con-sists of biotite granodiorite and alkali-feldspar granite. SHRIMP zircon U-Pb dating indicates that the Paotai biotitegranodiorite and Xiakou alkali-feldspar granite formed at (284.5±2.6) Ma and (287.5±3.2) Ma, respectively. ThePaotai biotite granodiorites are rich in SiO2 (62.13%-69.4%), with low K2O (0.62%-2.51%), and Na2O (2.32% -3.11%). It is relatively enriched in TFe2O3, MgO, Al2O3 and are classified as low-potassium calc-alkaline, peralu-minous to slightly peraluminous I-type granite. They show enrichment of LREEs, depletion of HREEs, weak nega-tive Eu anomaly, enrichment of LILE (Rb, Th, U), and depletion of Ba, Sr, P, and Ti. They have high ISr (0.7099-0.7126) and low εNd(t) values (.6.85 -.6.43). In contrast, the Xiakou alkali-feldspar granites are highly enriched in SiO2 (75.37%-75.77%), K2O (4.52%-4.69%), and Na2O (3.36%-3.55%), with low Al2O3, CaO, TFe2O3, MgO, and P2O5. They exhibit characteristics of High-K calc-alkaline fractionated I-type granite. Their REE distribution andtrace element patterns are similar to those of the Paotai biotite granodiorite but show more pronounced negative Euanomalies and depletions of Sr, P, and Ti. It has low ISr (0.7042-0.7082) and higher εNd(t) values (.0.82 -.0.65).These results suggest that these biotite granitoids likely formed through mantle underplating, causing partial meltingof juvenile crust and remelting of ancient crust, followed by mixing in different crust-mantle proportions and vary-ing degrees of fractional crystallization. Combining the research on Permian magmatic rocks sedimentary records inthe southern Beishan, it is indicated that the Paleo-Asian Ocean or its branch in this region already closed beforethe Permian. Meanwhile, the southern Beishan crust experienced extension in the early Permian, triggering theopening of a new ocean (Liuyuan Ocean). This led to the coexistence of oceanic basins with a large number of vol-ume ultramafic-mafic rocks, I-type and A-type granites in the region.
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