APPLICATION OF REGIONAL GEOCHEMICAL DATA IN GEOLOGICAL MAPPING IN STRONGLY WEATHERED AREA IN SOUTHERN CHINA
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摘要: 自区域化探全国扫面计划开始以来，区域化探数据在矿产勘查、环境、生态及农业等方面均发挥了很大作用，但对其在地质填图中的应用研究比较少。在中国南方花岗岩广泛分布的地区，化学风化强烈，风化层覆盖厚，植被发育，基岩裸露少，岩性识别和界线划分困难，严重影响了填图的速度和精度。通过对区域化探数据的处理分析，筛选特征指示元素编制地球化学图，发现对侵入岩体具明显指示的元素地球化学分区。通过野外实地验证，元素地球化学分区可以揭示不同期次侵入体的分布范围，利用元素地球化学分区可以有效提高强风化区地质填图的效率和精度。Abstract: Since Regional Geochemistry-National Reconnaissance Program (RGNR) carried out in 1978, the immense amount of geochemical data obtained played a big role in mineral exploration, environmental, ecological and agricultural studies, but its application in geological mapping was quite less. In southern China, granites are widespread and covered by thick intense chemical weathered layers and vegetations, which severely affected the speed and accuracy of geological mapping. Some geochemical maps prepared by using regional geochemical data showed a significant geochemical partition. According to field validation, the chemical zones coincide well with the outcrops of granitic intrusions of different ages. So this can increases the efficiency and accuracy of geological mapping in strongly weathered areas.
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Key words:
- regional geochemical /
- strongly weathering /
- geological mapping method /
- South China /
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图 9 生江镇婆髻山白垩系花岗斑岩(照片镜向100°)
Figure 9. Photos of the Cretaceous Granite porphyry at Shengjiang Town
表 1 研究区侵入岩填图单位一览
Table 1. Mapping units for intrusive rocks in the study area
地质时代 代号 岩性 构造旋回 纪 世 燕山期 白垩纪 晚白垩世 ηγK2 花岗斑岩 早白垩世 γπK2 中粒黑云母二长花岗岩 侏罗纪 晚侏罗世 ηγJ3 中粒斑状黑云母二长花岗岩 早侏罗世 ηγJ1 中粒斑状角闪黑云母二长花岗岩 γδJ1 细粒角闪花岗闪长岩 海西—印支期 三叠纪 中三叠世 ηγT2 红柱石堇青石黑云母二长花岗岩 早三叠世 ηγT1 弱片麻状中细粒(斑状)二长花岗岩 二叠纪 晚二叠世 γδP3 片麻状细粒花岗闪长岩 δοβP3 中粒黑云母英云闪长岩 加里东期 志留纪 早志留世 ηγS1 条带状细粒黑云母二长花岗岩 
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表 2 元素地球化学特征
Table 2. Geochemical characteristics of the selected elements
元素 最小值 最大值 X S X-3S X-2S X-S X+S X+2S X+3S F(X±S) F(X±2S) F(X±3S) K2O 0.12 4.27 2.01 0.70 -0.09 0.61 1.31 2.71 3.41 4.11 74.42 94.84 98.04 Li 8.70 78.53 28.10 14.33 -14.89 -0.56 13.77 42.43 56.76 71.09 82.21 93.59 96.79 U 0.25 12.80 4.25 2.48 -3.19 -0.71 1.77 6.73 9.21 11.69 78.47 95.02 98.22 La 3.00 131.17 52.16 22.99 -16.81 6.18 29.17 75.15 98.14 121.13 77.04 94.48 97.33 Y 5.00 82.85 30.05 14.78 -14.29 0.49 15.27 44.83 59.61 74.39 77.41 94.85 97.70 Zr 81.00 877.00 417.81 140.58 -3.93 136.65 277.23 558.39 698.97 839.55 76.16 93.60 97.87 注:样本数N=562;X—均值; S—标准方差; F(X±S)—落入X±S的频率, %; K2O单位为%, 其他为10-6
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表 3 不同时代侵入岩地球化学判别表
Table 3. Geochemical characteristics of intrusive rocks in different ages
侵入岩 K2O/% Li/10-6 U/10-6 La/10-6 Y/10-6 Zr/10-6 加里东期(ηγS1, 泗纶岩体) 1.55~2.0 ＜32 3.75~5.0 ＞60 ＜24 ＞420 海西—印支期(γT, 那蓬岩体) ＞2.0 ＞40 ＞5.0 ＞60 ＞32 ＞420 燕山早期(γJ, 筋竹岩体) ＞2.9 ＜32 ＞5.0 ＞60 ＞32 ＞420 燕山晚期(γK2, 八帘山岩体) 1.55~2.0 ＞40 ＜3.75 ＜24 ＞32 ＜240
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