| 魏振宏,李康宁,汤庆艳,王玉玺,何彤彤,袁 臻,蔡 龙,脱世博.西秦岭夏河—合作地区果木沟组碎屑岩地球化学与锆石 U-Pb 年龄特征及其地质意义[J].甘肃地质,2026,35(2):1-14 |
| 西秦岭夏河—合作地区果木沟组碎屑岩地球化学与锆石 U-Pb 年龄特征及其地质意义 |
| GEOCHEMISTRY AND ZIRCON U-Pb AGE OF DETRITAL ROCKS WITHIN THE GUOMUGOU FORMATION IN XIAHE-HEZUO AREA OF THE WESTERN QINLING MOUNTAINS AND THEIR GEOLOGICAL IMPLICATIONS |
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| DOI： |
| 中文关键词: Hf同位素；U-Pb年龄 早三叠世；碎屑岩；果木沟组；西秦岭 |
| 英文关键词:Hf Isotope U-Pb Age Early Triassic detrital rocks Gumugou Formation West Qinling Mountains |
| 基金项目:国家自然科学基金(3217022);甘肃省科技计划(24YFGA015、22YF7GA050);甘肃省地质勘查基金项目(202202-D01);新一轮找矿突破战略行动科技支撑项目(ZKK]202410、ZKKJ1202427);甘肃省自然资源大数据和国上空间治理能力基础建设项目地质资料数据中心建设”(HT-GJGK2022169-02)。 |
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| 中文摘要: |
| 果木沟组是西秦岭地区三叠纪最早沉积的一套地层，主体为一套半深海斜坡相细碎屑岩复理石建造，主要岩性为长石砂岩、泥质板岩。 碎屑岩中SiO2含量52. 83% ～ 65. 54%，平均值58. 88%；Al2O3含量15. 17% ～ 19. 51%，平
均 值 16. 78% ；FeO 含 量 3. 07% ～ 5. 45% ， 平 均 值 4. 54% ；CaO 含 量 0. 34% ～ 5. 97% ， 平 均 值 3. 20% ；K2O 含 量2. 14% ～ 3. 66%， 平均值2. 80%。 稀土元素总量较高，ΣREE为162. 19 × 10-6 ～ 284. 89 × 10-6， 平均值210. 79 × 10-6，LREE ／ HREE为8. 42 ～ 10. 17，平均值9. 35；δEu为0. 51 ～ 0. 65，平均值0. 58，具有明显的负异常；富集Th、U、Rb等高场强元素和大离子亲石元素 ，亏损Ba、Nb、Ta、Sr、P、Ti等元素。 176Lu ／ 177Hf为0. 000 679 ～ 0. 002 236；176Hf ／ 177Hf为0. 282 504 ～ 0. 283 059；二阶段模式年龄TDM2为258 ～ 1 369 Ma，主要集中在900 Ma、1 300 Ma附近；εHf（t）为-3. 4～ 17. 0，主要集中在3. 8、5. 2附近 ，范 围 较 大 且 正 值 负 值 均 有 。 锆 石 的 年 龄 主 要 集 中 在 古 生 代 （峰值266 Ma、386Ma、483 Ma）、中元古代（峰值1 650 Ma）和古元古代（峰值1 858 Ma）三个阶段。 通过碎屑岩主微量元素地球化学、锆石U-Pb年龄、Hf同位素测试分析，结合区域地质背景综合判断，果木沟组源区的构造环境主要呈现出大陆岛弧 、活动大陆边缘的特征 ，物 源 主 要 是 来 自 上 地 壳 的 长 英 质 火 山 岩 ：绝 大 多 数 来 自 祁 连 造 山 带 、华 北 板 块 南 缘 的 变 质基底及西秦岭同期岩浆岩，少量来自北秦岭构造带。 |
| 英文摘要: |
| The Guomugou Formation is the earliest set of Triassic sedimentary strata in the West Qinling area, which is mainly composed of a set of fine clastic flysch formation of the bathyal slope facies, and the main lithology is feldspathic sandstone and argillaceous slate. In the clastic rocks , SiO2 contents range from 52.83% to 65.54%（average 58.88%）; Al2O3 contents range from 15.17% to 19.51%（average 16.78%）; FeO contents range from 3.07% to 5.45%（average 4.54%）; CaO contents range from 0.34% to 5.97%（average 3.20%）; K2O contents range from2.14% to 3.66%（average 2.80%）; The total amount of rare earth elements is higher, ΣREE from 162.19 × 10-6 to 284.89 × 10-6（average 210.79 × 10-6）, The LREE / HREE ratios are high (8.42 ~to 10.17, average 9.35); Eu has obvious negative anomaly (δ Eu range from 0.51 to 0.65, average 0.58); The clastic rocks are enriched in high field strength elements such as Th, U, Rb, but depleted in Ba, Nb, Ta, Sr, P, Ti and other elements. The ratio of 176Lu / 177Hf ranged from 0.000679 to 0.002236, and 176Hf / 177Hf range from 0.282504 to 0.283059. The two-stage model age(TDM2): tdm2 range from 258Ma to 1369Ma, mainly around 900Ma and 1300Ma; ɛHf(t) range from -3.4 to 17.0, mainly around 3.8 and 5.2, with large range and positive and negative values. The zircon ages are mainly concentrated in three stages: Hercynian Indosinian (258-399Ma), Caledonian (444-721Ma), Mesoproterozoic Archean (1526-2897 Ma). According to the geochemical and Hf isotopic characteristics of the main and trace elements of the clastic rocks, combined with the regional geological background, the tectonic environment of the source area of the Guomugou Formation mainly presents the characteristics of the continental island arc and the active continental margin, and the provenance mainly comes from the felsic volcanic rocks of the upper crust: most of them come from the metamorphic basement of the Qilian orogenic belt and the southern margin of the North China plate and the contemporaneous magma of the West Qinling A few of them come from the North Qinling structural belt. |
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