本文關(guān)鍵詞： 中莊鋪 中生代火山巖 地球化學(xué) 火山斷陷盆地　出處：《太原理工大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：渾源中莊鋪地區(qū)是山西東北部中生代火山巖出露最全的地區(qū),是研究中生代火山巖的理想場所。筆者通過火山巖的野外詳細(xì)觀察、剖面實測,并采集火山巖新鮮樣品,在火山巖巖相學(xué)特征研究基礎(chǔ)上,結(jié)合主量元素、微量元素、稀土元素等地球化學(xué)特征研究,對中莊鋪地區(qū)中生代火山巖巖漿物質(zhì)特征及來源、巖漿形成構(gòu)造環(huán)境及動力學(xué)背景主要得出以下認(rèn)識：1、中莊鋪地區(qū)火山巖始于中侏羅世晚期,終于早白堊世后期,形成四個火山噴發(fā)旋回。各旋回火山巖巖性特點表現(xiàn)在早期為堿性的中基性火山巖類,晚期為鈣堿性的酸性火山巖類,早期多以溢流一噴溢相熔巖為主,晚期多以強烈爆發(fā)相碎屑巖為主。2、主量元素地球化學(xué)研究表明,中莊鋪火山巖總體上為一套以準(zhǔn)鋁質(zhì)、鉀玄巖系列為主,個別為高鉀鈣堿性系列的火山巖,隨著火山巖巖漿酸性程度的逐漸增強,堿性程度逐漸減弱,呈現(xiàn)出堿性向鈣堿性過渡演化的特點。3、通過與晉東北地區(qū)靈丘太白維山、塔地、左云舊高山火山盆地對比,發(fā)現(xiàn)不同地區(qū)同時期火山巖巖性、主量元素、稀土及微量元素具有相似性,稀土微量元素配分曲線與微量元素蛛網(wǎng)圖均為右傾型且近于平行,反映在不同地區(qū)同時期火山巖巖漿物質(zhì)來源與巖漿作用具有一致性。早白堊世張家口早期各地區(qū)搶風(fēng)嶺段火山巖富集Rb、Ba等大離子親石元素,虧損Nb、Y等高場強元素,可能是殼幔物質(zhì)混染的結(jié)果。張家口晚期巖漿作用發(fā)生了斜長石結(jié)晶分異作用,各地區(qū)向陽村段火山巖稀土元素配分曲線均顯示負(fù)Eu異常。中莊鋪地區(qū)早白堊世張家口早期與義縣晚期、左云舊高山地區(qū)早白堊晚期玄武巖的Th/Ta、Ta/Hf、Nb/Zr等特征微量元素比值,反映山西北東部中生代火山巖形成于大陸板內(nèi)拉張裂谷環(huán)境。4、中莊鋪地區(qū)火山巖的形成受控于古太平洋板塊向歐亞板塊的俯沖碰撞作用,中侏羅晚期到早白堊晚期中莊鋪一帶上地幔和下地殼物質(zhì)部分熔融的混合,構(gòu)成中莊鋪地區(qū)火山活動的巖漿物質(zhì)來源。在區(qū)域拉張應(yīng)力作用下,渾源中莊鋪一帶發(fā)生裂谷作用。在中侏羅世早期,起初在斷陷盆地中首先形成了陸相砂礫堆積,隨著拉張作用的進(jìn)一步加強,已形成的巖漿沿盆地邊緣斷裂上侵,噴出地表,形成了四個早期以堿性的中基性巖漿溢流作用為主,晚期以鈣堿性酸性巖漿爆發(fā)作用為主的旋回的火山巖。
[Abstract]:The Zhongzhuangpu area of Hunyuan is the most exposed area of Mesozoic volcanic rocks in northeastern Shanxi, and is an ideal place to study Mesozoic volcanic rocks. Based on the study of the petrographic characteristics of volcanic rocks and the geochemical characteristics of major elements, trace elements and rare earth elements, the material characteristics and sources of Mesozoic volcanic magma in Zhongzhuangpu area are studied. The tectonic environment and dynamic background of magmatic formation are as follows: 1. The volcanic rocks in Zhongzhuangpu area began in the late Middle Jurassic and finally in the late early Cretaceous. Four volcanic eruptive cycles were formed. The lithologic characteristics of volcanic rocks in each cycle were characterized by alkaline volcanic rocks in the early stage, acidic volcanic rocks in the later period, and overflow and spillage facies lava in the early stage. In the late period, the main element geochemical study showed that Zhongzhuangpu volcanic rock was a set of volcanic rocks with quasialuminite, potash series and high potassium calc-alkaline series, and the main element geochemical study showed that the volcanic rocks in the late period were mainly explosive facies clastic rocks. With the increasing acidity of volcanic magma and the weakening of alkalinity, it shows the characteristics of transition from alkalinity to calc-alkalinity. It is compared with the old alpine volcanic basins of Lingqiu Taibai Wei Mountain, Tadi and Zuoyun in northeast Shanxi. It is found that the lithology, principal elements, rare earth elements and trace elements of volcanic rocks in different regions are similar at the same time. The distribution curves of rare earth elements and cobwebs of trace elements are all right-tilted and nearly parallel. The source of magmatic material and magmatism are consistent in different regions. In early Cretaceous Zhangjiakou early Zhangjiakou volcanic rocks enriched in large ion lithophile elements, such as Rbnb Ba and so on, and depleted high field strength elements, such as NbGY, and the volcanic rocks in the early Cretaceous Zhangjiakou area were rich in large ion lithophile elements. It may be the result of the mixing of crust and mantle materials. The plagioclase crystallization differentiation occurred in the late Zhangjiakou magmatism. The REE distribution curves of volcanic rocks in Xiangyangcun section showed negative EU anomalies. The ratios of Th/ Ta-Ta-Ta-Hfnb / Zr in the early Cretaceous Zhangjiakou early Cretaceous and the late Yixian and Zuo Yun Old Alpine basalts in Zhongzhuangpu area, etc. The results show that the Mesozoic volcanic rocks in the eastern part of Shanxi Province were formed in the extensional rift environment of continental plate, and the formation of volcanic rocks in Zhongzhuangpu area was controlled by the subduction and collision between the paleo-Pacific plate and the Eurasian plate. The partial melting of the mantle and the lower crust in the Zhongzhuang Pu belt from the late Middle Jurassic to the late Cretaceous constitutes the source of magmatic material for volcanic activity in the Zhongzhuang Pu area. In the early Middle Jurassic, the continental sandstones were first formed in the faulted basin. With the further strengthening of the extensional process, the magma formed along the margin of the basin and ejected out of the surface. Four cycles of volcanic rocks were formed in the early stage and in the late period were mainly calc-alkaline acid magmatic eruptions mainly by alkaline intermediate basic magma spillage and in the late stage by calc-alkaline acid magma eruption.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P588.14

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