| 张 琳,王雪梅,梁金龙,谢世强,王显卿,赵 静.西秦岭造山带大桥金矿床含矿硅化角砾岩的地球化学、硅同位素组成及其地质意义[J].甘肃地质,2026,35(1):35-42 |
| 西秦岭造山带大桥金矿床含矿硅化角砾岩的地球化学、硅同位素组成及其地质意义 |
| GEOCHEMISTRY, SILICON ISOTOPIC COMPOSITION AND GEOLOGICAL SIGNIFICANCE OF MINERALIZED SILICIFIED BRECCIA IN THE DAQIAO GOLD DEPOSIT OF WESTERN QINLING OROGEN |
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| DOI：10.27027/j.cnki.ISSN2097-6704.2026.01.004 |
| 中文关键词: 硅化角砾岩 硅同位素 岩石成因 大桥金矿 |
| 英文关键词:silicified breccia silicon isotopes petrogenesis Daqiao gold deposit |
| 基金项目:成都理工大学地学核技术四川省重点实验室开放基金资助项目（gnzds202308）。 |
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| 中文摘要: |
| 大桥金矿是西秦岭地区代表性的超大型造山型金矿之一，矿体主要赋存于晚三叠世硅化角砾岩中。 然而对于含矿硅化角砾岩的岩石成因学术界还存在着较大的争议。 在详细野外勘查的基础上，本文通过对大桥金矿床中硅化角砾岩开展了全岩地球化学及硅同位素分析。 结果表明，含矿硅化角砾岩中与陆源碎屑有关的Al2O3含量较高（ > 3 %），全岩的硅同位素的变化范围（-0. 54‰ ~ + 0. 20‰，平均值 = -0. 13‰）与酸性岩一致，且在A1 ／ （Al + Fe +
Mn）- Al2O3 ／ TiO2图解中，样品多数落于含酸性火山碎屑沉积成因区域内及其附近。 以上证据均表明了硅化角砾岩的形成主要与陆源酸性火山碎屑物质沉积作用有关。 然而，岩石中热液石英脉的大量发育、与热液作用有关的Fe2O3 ／TiO2比值偏高（ > 1）以及Al2O3-δ30Si图，均暗示了大桥角砾岩并非单一成因，其形成受到了不同程度热液硅化作用的影响。 结合研究区已报道的晚三叠世酸性岩浆活动年龄和晚侏罗—早白垩世与成矿有关的热液活动时代，我们推测大桥金矿床中含矿硅化角砾岩是在晚三叠世酸性岩浆活动产生的火山碎屑物质经沉积作用形成， 随后受到了晚侏罗—早白垩世成矿热液硅化作用的叠加改造。 |
| 英文摘要: |
| The Daqiao gold deposit is one of the representative super -large orogenic gold deposits in the western Qinling Orogen, which is hosted by Late -Triassic silicified breccia. However, there is still great controversy about the petrogenesis of the ore-bearing siliceous breccia. Based on the detailed field exploration,this paper presents a whole-rock geochemical and silicon isotope analysis of the ore-bearing silicified breccia in the Daqiao gold deposit. The ore-bearing silicified breccia contains Al2O3 content （ > 3%）, which is a signal of terrigenous clasts. The silicon isotopic variation of the silicified breccia is from -0.54‰ ~ 0.20‰ （mean value - 0.13‰）, consistent with the δ30 Si value of felsic magmatic rocks. In the A1 ／ （Al + Fe + Mn）-Al2O3 ／ TiO2 diagram, most of the samples plot into the field of felsic terrigenous volcaniclastic with a sedimentary origin. All evidence illustrates that the silicified breccia might be generated by sedimentation of the felsic terrigenous volcaniclastic. However, the occurrence of hydrothermal quartz veins in the rocks, high Fe2O3 ／ TiO2 ratio （ > 1）, and Al2O3- δ30Si diagram suggest that the breccia is not of a single origin and it was affected by hydrothermal silicification to
different extents. Combined with the ages of the Late Triassic felsic magmatic activity and the Late Jurassic to Early Cretaceous hydrothermal fluids in relation to Au mineralization, we propose that the ore-bearing silicified breccia in the Daqiao deposit was initially deposited by the felsic terrigenous volcaniclastics in the Late Triassic and subsequently modified by hydrothermal silicification from Late Jurassic to Early Cretaceous. |
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