本文選題：大巴山構(gòu)造帶　切入點：地質(zhì)流體　出處：《長安大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：大巴山構(gòu)造帶位于四川盆地北緣,秦嶺造山帶中段南側(cè),地處秦嶺構(gòu)造帶與下?lián)P子地塊的交接部位。通常以城口—房縣斷裂和鐵溪—巫溪隱伏斷裂為界,將大巴山構(gòu)造帶自北向南依次分為北大巴山逆沖—推覆構(gòu)造帶、南巴山前陸弧形沖斷褶皺帶(大巴山前陸構(gòu)造帶)以及大巴山前陸坳陷帶(四川盆地東北部)三個次級構(gòu)造單元。野外地質(zhì)調(diào)研發(fā)現(xiàn),大巴山構(gòu)造帶內(nèi)的構(gòu)造脈體發(fā)育十分普遍,且不同次級構(gòu)造單元內(nèi)發(fā)育的脈體特征不同,通過對脈體的野外宏觀觀察及室內(nèi)顯微鏡下分析,對其進行了期次劃分,分別為:第一期構(gòu)造脈體為揉皺脈體,脈體普遍發(fā)生了變質(zhì)、變形現(xiàn)象,主要分布于北大巴山逆沖—推覆構(gòu)造帶內(nèi),發(fā)育于古生界地層中,為前印支期地質(zhì)流體的產(chǎn)物;第二期構(gòu)造脈體為X型剪裂隙充填脈,脈體未發(fā)生變質(zhì)作用,主要分布于北大巴山逆沖—推覆構(gòu)造帶和大巴山前陸構(gòu)造帶內(nèi),發(fā)育于古生界和三疊系地層中,為印支期同構(gòu)造流體的產(chǎn)物;第三期構(gòu)造脈體為張裂隙充填的脈體,脈體平直且比較干凈,在整個大巴山構(gòu)造帶內(nèi)的前白堊系地層中均有分布,為燕山期同構(gòu)造流體的產(chǎn)物。分別采集不同期次的構(gòu)造脈體及其圍巖樣品,進行了碳氧同位素、氫氧同位素和微量稀土元素地球化學(xué)分析,指示了三期構(gòu)造脈體均形成于開放的氧化環(huán)境中,其物質(zhì)來源主要為圍巖碳酸鹽巖活化、重結(jié)晶以及大氣降水的溶解作用。脈體形成時的流體主要為建造水,該建造水是由大氣降水沿地層裂隙流動時與圍巖碳酸鹽巖發(fā)生水巖反應(yīng)形成的。運用構(gòu)造解析的方法分別對第二期和第三期構(gòu)造脈體進行了應(yīng)力場分析,證實了第二期脈體為印支末期近南北向構(gòu)造擠壓應(yīng)力場下形成,第三期構(gòu)造脈體形成于燕山期的近東西向構(gòu)造運動中。對第三期脈體的幾何特征(寬長比)和空間分布特征(產(chǎn)狀)進行了統(tǒng)計,推算出第三期構(gòu)造脈體形成過程中的應(yīng)力比(?=(σ2-σ3)/(σ1-σ3))、驅(qū)動應(yīng)力比(R’=(Pf-σ3)/(σ1-σ3))和流體超壓(Δsi=Pf-σ3),計算得到?=0.452,R’=0.313,反映了流體壓力小于中間主應(yīng)力,而計算出的流體超壓Δsi可達到167Mpa,說明了第三期構(gòu)造脈體形成時存在有異常高壓流體,且這種高壓流體可能是由燕山構(gòu)造運動造成。
[Abstract]:The Dabashan tectonic belt is located in the northern margin of Sichuan Basin and the south of the central Qinling orogenic belt. It is located at the junction of the Qinling tectonic belt and the lower Yangtze block. The boundary is usually the Chengkou Fangxian fault and the Tiexi-Wuxi hidden fault. The Dabashan tectonic belt is divided from north to south into the North Dabashan thrust-nappe tectonic belt. Three secondary tectonic units of the South Bashan Foreland Arc thrust fold Belt (Dabashan Foreland tectonic Belt) and the Dabashan Foreland Depression Zone (northeast Sichuan Basin). The development of tectonic veins in the Dabashan tectonic belt is very common, and the characteristics of veins developed in different secondary tectonic units are different. Through the field macroscopical observation of the veins and the analysis under the laboratory microscope, the stages and stages of the veins are classified. They are as follows: the first stage of tectonic vein body is crinkle vein body, the vein body has metamorphosed and deformed generally, mainly distributed in North Dabashan thrust-nappe tectonic belt, developed in Paleozoic strata, is the product of pre-Indosinian geological fluid; The second stage of tectonic vein is X-type shear fissure filling vein. The vein body has no metamorphism and is mainly distributed in North Dabashan thrust-nappe tectonic belt and Dabashan Foreland tectonic belt, and developed in Paleozoic and Triassic strata. It is the product of the same tectonic fluid of Indosinian epoch, the third tectonic vein is filled with extensional fissure, the vein body is straight and clean, and it is distributed in the pre-Cretaceous strata in the whole Dabashan tectonic belt. The samples of tectonic veins and their surrounding rocks were collected in different periods of Yanshanian period, and the carbon oxygen isotopes, hydrogen and oxygen isotopes and trace rare earth elements were analyzed. It is indicated that the three tectonic veins are formed in an open oxidation environment, and their material sources are mainly from the activation of the surrounding rock carbonate rocks, recrystallization and the dissolution of atmospheric precipitation. The formation water is formed by the reaction of water and rock to the carbonate rock of surrounding rock when the precipitation flows along the formation fissure. The stress field of the second and third tectonic veins is analyzed by the method of structural analysis, respectively. It is confirmed that the second vein body was formed under the compressive stress field of the late Indosinian near south-north direction. The third tectonic vein was formed in the near east-west tectonic movement of Yanshanian epoch. The geometric characteristics (width to length ratio) and spatial distribution (occurrence) of the third stage vein body were statistically analyzed, and the stress ratio during the formation of the third stage tectonic vein body was calculated. (蟽 2- 蟽 3 / (蟽 1- 蟽 3), driving stress ratio = Pf- 蟽 _ 3 / (蟽 _ 1- 蟽 _ 3) and fluid overpressure (螖 sig Pf- 蟽 _ 3), calculated? The results show that the fluid pressure is smaller than the intermediate principal stress, and the calculated fluid overpressure 螖 si can reach 167Mpa.This indicates that there is an abnormal high pressure fluid during the formation of the third tectonic vein, which may be caused by the Yanshanian tectonic movement.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P542

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