Post-250 Ma thermal evolution of the central Cathaysia Block (SE China) in response to flat-slab subduction at the proto-Western Pacific margin
Post-250 Ma thermal evolution of the central Cathaysia Block (SE China) in response to flat-slab subduction at the proto-Western Pacific margin
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DOI：
10.1016/j.gr.2019.03.019
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发表时间：
2019-11
影响因子：
6.1
通讯作者：
Ni Tao;Zheng‐Xiang Li;M. Danišík;N. Evans;Rongxi Li;Chong‐Jin Pang;Wu-Xian Li;F. Jourdan;
中科院分区：
文献类型：
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作者：
Ni Tao;Zheng‐Xiang Li;M. Danišík;N. Evans;Rongxi Li;Chong‐Jin Pang;Wu-Xian Li;F. Jourdan;
提出了平板式俯冲模型来解释中国东南部作为西太平洋边缘的中、新生代复杂的大地构造记录。本文研究了韶关-陇南地区250 Ma以后的热历史，评价了在平面俯冲模式下局部沉积和岩浆岩的时温演化。我们的多年代学方法包括锆石U-Pb年代学、钾长石和黑云母的40Ar/39Ar年龄、锆石和磷灰石的(U-Th)/He年龄、基底和/或沉积岩中磷灰石的裂变径迹年龄，以及煤层的镜质组反射率分析。锆石U-Pb法测定了伏溪花岗岩早志留世结晶年龄(约438 Ma)，梨园花岗岩结晶年龄(约162 Ma)。下侏罗统砂岩的同沉积/前沉积单颗粒锆石(U-Th)/He年龄记录了中三叠世的折返冷却，反映了印支造山作用，可能是由平板俯冲事件引起的。晚侏罗世蒙东花岗岩的40Ar/39Ar年龄(约156 Ma)和下侏罗世煤样的最大镜质组反射率为1.7%-2.3%，表明晚侏罗世存在一个热峰值，可能与俯冲古太平洋板块拆沉引起的先前区域岩浆活动有关。伏溪花岗岩的钾长石40Ar/39Ar坪年龄(约125Ar Ma)和锆石(U-Th)/He平均年龄(152115 Ma)记录了白垩纪期间通过钾长石和部分锆石保留带的长期冷却。白垩纪的冷却作用符合区域抬升剥蚀对板块下沉和岩石圈反弹的预测。由磷灰石裂变径迹中心年龄(72-39 Ma)和磷灰石(U-Th)/He平均年龄(38-33 Ma)记录的古新世-始新世快速冷却反映了南中国海开放前新生代裂谷作用。
The flat-slab subduction model has been proposed to explain the complex Mesozoic–Cenozoic geotectonic record of SE China as part of the Western Pacific margin. Here we investigate the post-250 Ma thermal history of the Shaoguan-Longnan region to evaluate the time-temperature evolution of local sedimentary and magmatic rocks in the context of the flat-subduction model. Our multi-chronological approach includes zircon U-Pb geochronology,40Ar/39Ar dating of K-feldspar and biotite, (U-Th)/He dating of zircon and apatite, and fission-track dating of apatite from basement and/or sedimentary rocks, as well as vitrinite reflectance analysis of coal seams. Zircon U-Pb dating revealed Early Silurian and Late Jurassic crystallization ages for the Fuxi (ca. 438 Ma) and Liyuan (ca. 162 Ma) granites, respectively. Syn-/pre-depositional single-grain zircon (U-Th)/He ages from Lower Jurassic sandstones record a Middle Triassic exhumational cooling, interpreted to reflect the Indosinian Orogeny, possibly caused by a flat-slab subduction event. Late Jurassic biotite40Ar/39Ar age (ca. 156 Ma) obtained from the Late Triassic Mengdong granite, together with maximum vitrinite reflectance values of 1.7%–2.3% measured from a Lower Jurassic coal sample, document a thermal maximum in the Late Jurassic, likely related to the prior regional magmatism arising from delamination of the subducting Paleo-Pacific plate. K-feldspar40Ar/39Ar plateau age from the Fuxi granite (ca. 125 Ma), and zircon (U-Th)/He mean ages (152–115 Ma) record a protracted cooling through the K-feldspar Ar and the zircon He partial retention zones during the Cretaceous. The Cretaceous cooling is in accord with the prediction of regional uplift and erosion in response to foundering of the flat-slab and consequent lithospheric rebound. The rapid cooling during the Paleocene–Eocene, recorded by apatite fission-track central ages (72–39 Ma) and apatite (U-Th)/He mean ages (38–33 Ma), is interpreted to reflect Cenozoic rifting in the leadup to the opening of the South China Sea.