PETROGEOCHEMISTRY AND ORIGIN OF THE CENOZOIC VOLCANIC ROCKS IN FUXIN-ZHANGWU AREA, WESTERN LIAONING PROVINCE
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摘要: 辽西阜新-彰武地区新生代有两个火山旋回，即古近纪古新世那立闪旋回和新近纪中新世船底山旋回.通过1∶25万区域地质调查修测项目，根据野外岩石学、岩石地球化学、火山旋回、区域对比并结合前人资料进行了深入细致的研究和厘定.各旋回火山熔岩总体从基性→中基性演化，具有钠、硅、铝增高，铁、镁降低的特点.该时期火山岩各岩石过渡元素分配型式曲线基本协调一致，呈明显的“V”型，表明为同源岩浆分异产物.偏碱性岩石为富稀土岩石，正常岩石为贫稀土岩石，LREE/HREE值为8.2~18.84.各岩石均具轻稀土富集、分馏较好，重稀土亏损、分馏较弱的特点.Sm/Nd值在0.12~0.21之间，Eu/Sm值为0.28~0.86，反映该时期火山岩浆主要来源于地幔.Abstract: The Fuxin-Zhangwu area in Western Liaoning Province saw two Cenozoic volcanic cycles, i.e. the Paleogene Paleocene Nalishan cycle and Neogene Miocene Chuandishan cycle. During the 1:250 000 regional geological survey, detailed study and redefinition are carried out on the basis of petrology, petrogeochemistry, volcanic cycle, regional comparison and previous literatures. The volcanic lava of each cycle evolves from basic to intermediate-basic, with characteristics of increasing sodium, silicon and aluminum, but reducing iron and magnesium. The distribution pattern curves of transitional elements of the volcanic rocks are coordinated and consistent as obvious V-shape, which indicates the differentiated product from comagma. The meta-alkaline rocks are enriched in REE; while the normal rocks are poor in REE. The rocks are characterized by enrichment of LREE with well fractionation and depleted in HREE with poor fractionation. The LREE/HREE value is between 8.2 and 18.84, with Sm/Nd between 0.12 and 0.24, Eu/Sm between 0.2 and 0.86, showing that the magma is mainly originated from mantle source.
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Key words:
- Cenozoic volcanic rock /
- petrogeochemistry /
- origin /
- Fuxin-Zhangwu area /
- Liaoning Province
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