Heavy-mineral and garnet compositions of stream sediments and HP-UHP basement rocks from the Western Gneiss Region, SW Norway
Heavy-mineral and garnet compositions of stream sediments and HP-UHP basement rocks from the Western Gneiss Region, SW Norway
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DOI：
10.17850/njg96-1-02
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发表时间：
2016-01-01
影响因子：
0.8
通讯作者：
von Eynatten, Hilmar
中科院分区：
文献类型：
--
作者：
Krippner, Anne;Meinhold, Guido;von Eynatten, Hilmar
我们目前的重矿物和石榴石的地球化学数据，最近流沉积物和HP-UHP基岩从Flatraket和Ulvesund的深成岩体，从岛的Runde，西部片麻岩区，挪威西南部，测试在何种程度上的重矿物和石榴石的地球化学流沉积物中反映的地质情况在源区。水系沉积物的重矿物组合包括石榴石、绿色钙质角闪石和绿帘石族矿物，反映了源区绿片岩相和高级变质作用。石榴石的地球化学数据表明其变质程度较高。重矿物和石榴子石地球化学数据反映了物源区的地质情况，证实了重矿物在沉积物源分析中的应用和重要性。重矿物的地球化学数据通常显示在沉积物中的分布比在基岩中测量的重矿物数据更宽。然而，我们的研究结果表明，情况并非总是如此。在基岩中测得的一些石榴石，特别是低级和超高级变质石榴石，只是次要的，或者在沉积物中缺乏。这可能是由于某些源岩中石榴子石的粒度大于所研究的沉积物粒度窗口，或者是因为这些石榴子石被来自含有较高含量石榴子石的源岩的大量石榴子石稀释了。
We present heavy-mineral and garnet geochemical data of recent stream sediments and HP-UHP bedrock from the Flatraket and Ulvesund-plutonic bodies and from the island of Runde, Western Gneiss Region, SW Norway, to test to what extent the heavy minerals and the garnet geo-chemistry in stream sediments reflect the geological situation in the source area. The heavy-mineral assemblages of the stream sediments contain garnet, green calcic amphibole and epidote-group minerals, which reflect greenschist-facies and higher grade metamorphism in the source area. The geochemical data of garnets point to high-grade metamorphic conditions. Overall, the heavy-mineral and garnet geochemical data reflect the geological situation in the source area, which confirms the application and the importance of heavy minerals in sedimentary provenance analysis. Geochemical data of heavy minerals usually show a wider distribution in the sediments than the data of heavy minerals measured in the bedrock. However, our results demonstrate that this is not always the case. Some garnets measured in the bedrock, especially lower grade and ultra-high-grade metamorphic garnets, are only of secondary importance or they are lacking in the sediments. This probably results either from larger grain sizes of garnets in some source rocks than in the studied grain-size window of the sediments, or because those garnets are diluted by a high input of garnets from source rocks containing higher amounts of garnets.