| 四合屯—大康保地区义县组火山—沉积岩地质特征 |
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| 引用本文：陈树旺,张立东,郭胜哲,张长捷,彭艳东,贾斌,邢得和,丁秋红,郑月娟.2002.四合屯—大康保地区义县组火山—沉积岩地质特征[J].地球学报,23(3):217-222. |
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| 基金项目:中国地质调查局项目“北票、上园、义县、地藏寺等4幅1∶5万区域地质调查(编号J4.1.12) |
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| 中文摘要:四合屯－大康堡地区所出露的义县组火山－沉积岩可分为上、中、下3个层位。下部层位是以玄武质、玄武安山岩质以及安山质火山岩类为主的基性、中基性火山－沉积岩；中部是以流纹质及英安质火山岩为主的中酸性火山－沉积岩；而义县组的上部层位是以玄武岩、玄武玢岩为代表的基性火山岩。薄层状的沉凝灰岩、凝灰质粉砂岩及钙质页岩等作为火山活动间歇期的产物，常不同程度地发育于义县组火山溶岩或集块岩的底部。野外工作发现：在义县组下部层位的沉凝灰岩层中发育有以鹦嘴龙为主的古脊椎动物类化石；四合屯－大康堡一带富含有热河生物群化石的沉积层属义县组火山－沉积岩系的中部层位。稀土元素分析表明，在相同层位的火山－沉积岩岩，沉凝灰岩，凝灰质粉砂岩和钙质页岩及其与火山熔岩存在密切的相关性；而不同层位间则存在一定的差异性。稀土元素配分特征不反映出，不同的义县组火山－沉积岩内、凝灰质粉砂岩和钙质页岩及其与火山溶岩存在密切的相关性；而不同层位间则存在一定的差异性。稀土元素分特征还反映出，不同的义县组火山－沉积岩层位之间具有相似的物源关系。 |
| 中文关键词:地质特征 火山-沉积岩 义县组 |
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| Geological Characteristics of the Volcano-Sedimentary Rocks of Yixian Formation in Sihetun-Dakangpu Area |
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| Abstract:There are three beds in the volcano sedimentary rocks of Yixian formation in Sihetun Dakangpu area. The lower bed consists mainly of basic and intermediate basic volcanic sedimentary basaltic or basaltic andesite rocks; the middle bed is made up chiefly of intermediate acidic volcanic sedimentary rhyolitic or dacitic rocks; and the upper bed is composed predominantly of the basaltic volcanic basalt and basaltic porphyrite. Being products of the volcano inactive period, the thin beds of tuffite, tuffaceous siltstone and calcareous shale usually occur at the bottom of lava or agglomarate. Field mapping and comprehensive study also show that there are Palaeo vertebrate fossils (mainly of Psittacosaurus) in the tuffite of the lower beds of Yixian Formation, and that "Jehe Biota" (including precious birds) fossils rich sedimentary beds in the area of Sihetun Dakangpu belongs to the middle bed of Yixian formation. REE analysis implies that there are intimate relationships between the thin beds of tuffite, tuffaceous siltstone and calcareous shale and the lava of the same beds in Yixian Formation, and that there exist some differences between different beds of Yixian Formation. The REE pattern also indicates that different beds of Yixian Formation have similar material sources. |
| keywords:geological characteristics volcano-sedimentary rocks Yixian formation |
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