【摘要】：侵入巖可以侵位于不同的地殼層次,其侵位機制復(fù)雜,常被視作為是大陸板塊剛性化及古應(yīng)力狀態(tài)最直接的地質(zhì)標志,同時也是巖石圈(或地殼)地幔伸展的重要標志,以及古板塊恢復(fù)再造的重要標志。巖墻群作為原生巖漿的代表,充填在火山或侵入體的補給通道中,用于反演源區(qū)的物質(zhì)組成和巖漿噴出的歷史;巖墻群充填在某種構(gòu)造裂隙中,其特殊的空間配置方式可反映當時的構(gòu)造應(yīng)力場;同時,巖墻群所充填的裂隙也是成礦流體賴以上升的良好通道,使其成為有效的找礦標志。巖墻群在一個造山旋回可以貫穿始終,對于再造區(qū)域地質(zhì)演化具有十分重要的意義。本文通過野外踏勘及樣品采集,查明脈巖群在工作區(qū)的空間展布,對于出露較好的地區(qū),進行大比例尺填圖,并對構(gòu)造接觸部位進行素描。通過認識脈巖群巖石組合特征、與圍巖接觸關(guān)系、巖石地球化學(xué)特征及同位素年代學(xué)特征,分析脈巖群形成時代,結(jié)合前人對脈巖群的研究資料,綜合探討該區(qū)脈巖群形成大地構(gòu)造環(huán)境以及與礦產(chǎn)的關(guān)系。得出以下幾點認識:①研究區(qū)巖墻群廣泛發(fā)育,大多呈北西向展布,與圍巖呈順層侵入接觸關(guān)系。區(qū)內(nèi)巖墻群均產(chǎn)出于奧陶系以及奧陶系以前的地質(zhì)體,并且種類繁多,中-基性、酸性以及超鎂鐵質(zhì)巖墻群均有分布。②中基性巖墻群巖石地球化學(xué)特征為高鉀質(zhì)的鈣堿性拉斑玄武巖系列,酸性墻群具有過鋁質(zhì)、富硅、低鎂、低鈣、高鉀和鈉的巖石化學(xué)特點,屬于鈣堿性巖墻群。③研究區(qū)巖墻群捕獲的鋯石大多集中在460Ma和480Ma兩個年齡段,其成巖結(jié)晶年齡為都集中在430Ma-440Ma之間。捕獲鋯石的時間段正是區(qū)域上巖漿活動的高峰期,能與區(qū)域上的兩期巖漿活動對應(yīng)起來。巖墻群的結(jié)晶成巖年齡近一致,形成于早志留世,這與寬譜系巖墻群形成時代一致相對應(yīng),為該地區(qū)巖墻群符合寬譜系巖墻群的特征提供了年代學(xué)證據(jù)。④巖墻群形成于碰撞后拉伸環(huán)境中。結(jié)合年代學(xué)特征,早志留世時期中祁連板塊和北祁連板塊俯沖造山作用結(jié)束之后,該區(qū)域進入相對穩(wěn)定階段,然后逐漸進入后碰撞(后造山)階段,這一時期整個祁連地區(qū)正處于由俯沖造山向碰撞造山的轉(zhuǎn)換時期。研究區(qū)寬譜系巖墻群的出現(xiàn)標志著俯沖造山作用的結(jié)束。
[Abstract]:Intrusive rocks can be located at different crustal levels, and their emplacement mechanism is complex, which is often regarded as the most direct geological symbol of the rigidity and paleo-stress state of continental plate, and also an important symbol of lithosphere (or crust) mantle extension. And the important symbol of the restoration and reconstruction of the palaeo-plate. As the representative of the primary magma, the dikes are filled in the supply channels of volcanoes or intrusions, and are used to reverse the material composition and the history of magma exhalation in the source area. The rock dike group is filled in some kind of structural fracture, and its special spatial configuration can reflect the tectonic stress field at that time, meanwhile, the fissure filled by the rock wall group is also a good way for the ore-forming fluid to rise, which makes it an effective prospecting mark. The dike group can run through a orogenic cycle all the time, which is of great significance to the reconstruction of regional geological evolution. In this paper, through field survey and sample collection, the spatial distribution of dike groups in the working area is found out, and the large-scale mapping of the well exposed areas is carried out, and the structural contact parts are sketched. Based on the understanding of rock assemblage characteristics, contact relationship with surrounding rock, rock geochemical characteristics and isotopic chronological characteristics of vein rock group, the forming age of vein rock group is analyzed, and combined with previous research data of vein rock group, The formation of geotectonic environment and its relationship with mineral resources in the dike-rock groups in this area are discussed in this paper. The conclusions are as follows: (1) the rock dikes in the study area are widely developed, most of which are distributed in the northwest direction, and the relation between the dike groups and the surrounding rock is bedding intrusive contact. All the rock dikes in the area occur in Ordovician and previous Ordovician geological bodies, and there are a variety of medium-to-basic types. The acidic and ultramafic dyke groups are distributed. 2 the basic dyke group is characterized by high potash calc-alkaline tholeiite series, and the acidic wall group is characterized by superaluminous, silicon-rich, low-magnesium and low-calcium, and the other is characterized by high potash calc-alkaline tholeiite series. The petrochemical characteristics of high potassium and sodium belong to calc-alkaline dyke group. 3 most of the zircon captured by the rock wall group in the study area are concentrated in 460Ma and 480Ma ages, and their diagenetic crystallization ages are between 430Ma-440Ma. The time period during which zircon is captured is the peak of magmatic activity in the region, which corresponds to two periods of magmatic activity in the region. The crystalline diagenetic age of the dike group is nearly the same, which was formed in the early Silurian, which corresponds to the forming age of the broad-spectrum dyke group. It provides chronological evidence for the characteristics of the rock dikes in this area in accordance with the broad spectrum rock dikes. 4 the dikes are formed in the post-collision extensional environment. Combined with the chronological characteristics, after the end of the subduction orogeny of the Qilian plate and the North Qilian plate during the early Silurian period, the area entered a relatively stable stage and then gradually entered the post-collision (post-orogenic) stage. During this period, the whole Qilian area is in the transition period from subducted orogenic to collisional orogenic. The appearance of broad spectrum dykes in the study area marks the end of subduction orogeny.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.12

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