CAJ | 학술논문

西乌旗地区大石寨组火山岩以流纹岩为主，LA-ICP-MS锆石U-Pb同位素测定结果及全岩主量、微量和稀土元素分析结果表明，本区流纹岩的年龄为280.3Ma±1.4Ma，形成于早二叠世；大石寨组火山岩属高钾过铝质钙碱性火山岩，其中SiO2、K2O、Al2O3含量均较高。稀土元素配分曲线总体向右缓倾斜，轻稀土元素相对于重稀土元素富集，Eu呈明显的负异常，重稀土元素亏损不明显。Rb、Th、U、K等大离子亲石元素富集明显，Ba表现为弱亏损，高场强元素具有明显的Ta、Sr、P及Ti亏损， Zr、Hf相对富集。研究认为，该地区流纹岩可能是由玄武岩、安山岩等中基性火山岩分离结晶作用形成的，且形成的构造环境为大陆边缘弧。
서오기지구대석채조화산암이류문암위주，LA-ICP-MS고석U-Pb동위소측정결과급전암주량、미량화희토원소분석결과표명，본구류문암적년령위280.3Ma±1.4Ma，형성우조이첩세；대석채조화산암속고갑과려질개감성화산암，기중SiO2、K2O、Al2O3함량균교고。희토원소배분곡선총체향우완경사，경희토원소상대우중희토원소부집，Eu정명현적부이상，중희토원소우손불명현。Rb、Th、U、K등대리자친석원소부집명현，Ba표현위약우손，고장강원소구유명현적Ta、Sr、P급Ti우손， Zr、Hf상대부집。연구인위，해지구류문암가능시유현무암、안산암등중기성화산암분리결정작용형성적，차형성적구조배경위대륙변연호。
The Dashizai Formation volcanic rocks in Xi Ujimqin Banner area consist mainly of rhyolite. LA-ICP-MS zircon U-Pb dating and whole-rock major, trace and rare earth elements analyses show that the age of the rhyolite in this area is 280.3Ma±1.4Ma, implying early Permian. Dashizhai volcanic rocks belong to high potassium peraluminous calc-alkaline volcanic rocks, and the con-tent of SiO2, K2O and Al2O3 is high. Chondrite-normalized REE patterns are generally right-oblique with the enrichment of the LREE, Eu exhibits negative anomalies, there exists no significant loss of HREE, Rb, Th, U, K and other LILE elements show signifi-cant enrichment, Ba exhibits weak losses, HFSE exhibit obvious Ta, Sr, P and Ti losses, and Zr, Hf shows relative enrichment. It is held that the rhyolite of this area was probably formed by fractional crystallization of basalt, andesite and other basic volcanic rocks, and the tectonic environment for the formation of the rhyolite in this area was continental marginal arc.