| 福建上杭盆地发现3.4 Ga碎屑锆石 |
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| 引用本文：江思宏,梁清玲,王少怀,张莉莉,刘春花,刘翼飞.2016.福建上杭盆地发现3.4 Ga碎屑锆石[J].地球学报,37(5):645-656. |
| DOI：10.3975/cagsb.2016.05.12 |
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| 基金项目:国土资源部公益性行业科研专项(编号: 200911007-1-17) |
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| 中文摘要:碎屑锆石已经成为研究区域地质演化的一种重要手段。本文对华夏地块东部上杭盆地底部产出的含砾石英砂岩中的碎屑锆石开展了LA-MC-ICP-MS U-Pb测年和Hf同位素测量。结果表明, 这些碎屑锆石主要是岩浆锆石, 锆石年龄变化于328~3 403 Ma, 至少记录了10期的岩浆活动事件, 表明该地区曾经历了长期复杂的地质演化历史。与华夏地块其他地区的碎屑锆石或捕获锆石一样, 上杭盆地这些碎屑锆石年龄数据记录下了诸如晚太古代—早元古代地壳生长事件、哥伦比亚超大陆和Rodinia超大陆的汇聚与裂解、冈瓦纳大陆的聚合等全球主要地质事件, 以及具有华夏地块特征的早古生代强烈的板内造山运动(武夷—云开运动)。最高峰值年龄出现在450 Ma, 表明研究区附近最为强烈的事件是加里东运动(当地称作武夷—云开运动, 或者广西运动)。Hf同位素数据表明, ?Hf(t)= ?27.2 ~ 19.8, 绝大多数εHf(t)值小于0, 两阶段亏损地幔Hf模式年龄(tDM2)介于1 124~3 979 Ma, 峰值1 800~1 900 Ma, 表明其早期岩浆活动主要与大规模的新生地壳有关, 而晚期主要表现为对早期形成地壳的大规模改造, 古老物质的再循环, 很少有新生地壳增生。 |
| 中文关键词:碎屑锆石 前寒武纪地质 华夏地块 上杭盆地 福建 |
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| The Discovery of 3.4 Ga Detrital Zircon in Shanghang Basin of Fujian Province |
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| Abstract:The detrital zircons have become one of the major tools for the study of regional geological evolution. In this paper, the authors conducted the LA-MC-ICP-MS U-Pb dating and Hf isotopic analysis for the detrital zircons from the conglomerate-bearing quartz sandstone occurring in the basal part of the Shanghang basin in Cathaysia Block. It is shown that these detrital zircons are magmatic in origin. The age data obtained from these detrital zircons range from 3 403 Ma to 328 Ma, which document at least 10 magmatic events in the region, indicating a long and complex geological evolution. Similar to ages of the detrital and captured zircons in other regions of the Cathaysia Block, the ages of the detrital zircons from the Shanghang basin reveal the global events, such as the Neoarchean–Paleoproterozoic crustal growth event, the assembly and breakup of supercontinents Columbia and Rodinia, and the assembly of Gondwana as well as regional events, such as the Early Paleozoic intense intraplate orogeny (Wuyi–Yunkai orogeny) with the characteristics of the Cathaysia Block. The most prominent 450 Ma peak indicates that the Caledonian orogeny (locally called Wuyi–Yunkai orogeny or Kwangsian orogeny) is the most important event in the region. The in situ Hf isotope compositions give a large range of εHf(t) values (?27.2 to 19.8) with two-stage model ages (tDM2) of 1 124~3 979 Ma (peak of 1 800~ 1 900 Ma). The Hf data suggest that the early magmatism was mainly associated with the large scale crustal growth, while the late one was related to the reworking of the early crust, involving the recycling of older crustal components with less juvenile crustal growth. |
| keywords:detrital zircon Precambrian geology Cathaysia Block Shanghang basin Fujian Province |
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