【摘要】：本文以滇西蘭坪盆地古近紀(jì)沉積充填為研究對(duì)象,利用巖石學(xué)、沉積學(xué)、沉積地球化學(xué)等理論知識(shí),綜合前人研究的地質(zhì)成果,通過對(duì)盆地不同剖面古近紀(jì)砂巖樣品的碎屑成分特征、地球化學(xué)特征以及粒度分布特征進(jìn)行分析對(duì)比,研究古近紀(jì)蘭坪盆地的充填特征及沉積環(huán)境。主要取得以下認(rèn)識(shí)與結(jié)論:(1)研究區(qū)古近紀(jì)砂巖碎屑成分分析中石英類型主要為單晶石英,長(zhǎng)石類型主要以穩(wěn)定的鉀長(zhǎng)石為主,巖屑類型有沉積巖+變質(zhì)巖+(偶見)火成巖巖屑,以沉積巖巖屑為主;盆地云龍組→果郎組→寶相寺組砂巖中的Q/(F+R)指數(shù)呈遞減的特點(diǎn);根據(jù)Qt-F-L、Qm-F-Lt和Qm-P-K三角圖解可知,研究區(qū)物源主要來(lái)源于大陸塊的沉積巖區(qū);Qp-Lv-Ls三角圖解顯示出研究區(qū)碎屑物源成分主要落在了克拉通前緣的碰撞縫合線及褶皺-逆掩帶物源區(qū)內(nèi)。(2)研究區(qū)常量元素特征指出,研究區(qū)古近紀(jì)碎屑沉積物成熟度較高,巖石樣品以長(zhǎng)石砂巖為主;砂巖物源區(qū)呈現(xiàn)由中性火成巖物源區(qū)向大陸石英質(zhì)物源區(qū)演化的趨勢(shì);云龍期物源以來(lái)自盆地東緣(大陸島弧)為主,至果郎期和寶相寺期有盆地西緣(被動(dòng)大陸邊緣)物源的加入,而寶相寺期物源主要來(lái)自盆地西緣(被動(dòng)大陸邊緣)。(3)研究區(qū)微量元素特征顯示物源區(qū)物質(zhì)主要以長(zhǎng)英質(zhì)巖石為主,沉積環(huán)境為陸相氧化環(huán)境,源巖以沉積巖為主,母巖碎屑主要來(lái)自于大陸上地殼;物源具有多期多階段的特點(diǎn),早期(云龍期)以大陸島弧構(gòu)造背景為主,晚期(果郎組)逐漸過渡為大陸島弧+被動(dòng)大陸邊緣構(gòu)造背景,尤其是到了寶相寺期則主要由被動(dòng)大陸邊緣構(gòu)造區(qū)域提供物源。(4)研究區(qū)古近紀(jì)砂巖粒度概率累積曲線主要包括:“一跳一懸夾過渡”式、“一跳一懸式”;古近紀(jì)砂巖粒度分布特征表明,研究區(qū)砂巖偏度值在正偏—很正偏范圍之間,峰度屬中等尖銳—尖銳范疇,分選好至很好;運(yùn)用結(jié)構(gòu)參數(shù)散點(diǎn)圖投點(diǎn)以及判別函數(shù)計(jì)算確定云龍組和果郎組砂巖代表河流、三角洲、湖泊相沉積,為一套陸相沉積環(huán)境,寶相寺組砂巖為沖積扇相沉積環(huán)境。
[Abstract]:In this paper, Paleogene sedimentary filling in Lanping basin, western Yunnan, is taken as the research object, and the geological results of previous studies are synthesized by using the theoretical knowledge of petrology, sedimentary geochemistry and so on. By analyzing and comparing the characteristics of clastic composition, geochemistry and granularity distribution of Paleogene sandstone samples in different sections of the basin, the filling characteristics and sedimentary environment of Paleogene Jiilanping basin are studied. The main conclusions are as follows: (1) in the clastic composition analysis of Paleogene sandstone, the quartz type is mainly single crystal quartz, and the feldspar type is mainly composed of stable potassium feldspar. There are sedimentary rocks metamorphic rocks (occasionally) igneous rocks and cuttings mainly sedimentary lithoclasts. The Q / (F R) index in the sandstones of the Yunlong formation and the Yunguolang formation is decreasing. According to the Qt-F-L,Qm-F-Lt and Qm-P-K triangular diagrams, the source of the studied area is mainly derived from the sedimentary rock area of the continental block. The Qp-Lv-Ls triangulation shows that the clastic source materials in the study area are mainly located in the collision suture of the front edge of the craton and the source area of the fold-overthrust belt. (2) the characteristics of the major elements in the study area are pointed out. The Paleogene clastic sediments in the study area have a high maturity and the rock samples are mainly feldspathic sandstone. The sandstone provenance shows a trend of evolution from neutral igneous source to continental quartz provenance. The source of Yunlong period is mainly from the eastern margin of the basin (continental island arc), and to the Guolang period and Baoxangsi period there is the addition of the western margin of the basin (passive continental margin). The trace element characteristics of Baoxangsi period mainly came from the western margin of the basin (passive continental margin). (_ 3). The source area was mainly composed of felsic rocks, the sedimentary environment was continental oxidation environment, and the source rocks were mainly sedimentary rocks. The parent rock clastic mainly comes from the continental upper crust; The provenance is characterized by multi-period and multi-stage. In the early stage (Yunlong period), the continental island arc was the main tectonic background, and the late stage (Guolang formation) was gradually transitioned to the passive continental margin tectonic setting of the continental island arc. Especially in Baoxangsi period, the source is mainly supplied by the passive continental margin tectonic area. (4) the grain size probability accumulation curve of Paleogene sandstone in the study area mainly includes: "one jump and one suspension transition", "one jump and one suspension"; The grain size distribution characteristics of Paleogene sandstone show that the sandstone deviation value in the study area is between positive deviation and very positive deviation, and the kurtosis belongs to the category of medium sharp and sharp, and the sorting is very good. It is determined that the sandstone of Yunlong formation and Guolang formation represent fluvial, delta and lacustrine facies by using structural parameter scatter plot and discriminant function calculation, which is a set of continental sedimentary environment, and that of Baxiangsi formation sandstone is alluvial fan sedimentary environment.
【學(xué)位授予單位】：東華理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P512.2

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相關(guān)期刊論文 前1條

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本文編號(hào)：2298497