發(fā)布時(shí)間：2018-04-12 17:34

  本文選題：梵凈山群 + 地層序列��； 參考：《中國(guó)地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：江南造山帶是上揚(yáng)子陸塊與華夏陸塊間的地殼縫合帶,主體為一北東東—南西西向延展的新元古代變質(zhì)巖帶。梵凈山群發(fā)育于江南造山帶的西北端,主體出露于黔東北的梵凈山地區(qū),主要為一套陸源碎屑巖、淺變質(zhì)火山巖巖系,角度不整合于下江群之下。本文綜合運(yùn)用沉積地質(zhì)學(xué)、巖石大地構(gòu)造學(xué)、構(gòu)造地層學(xué)等理論、方法,重點(diǎn)研究以銅廠組為代表的梵凈山群上碎屑巖系的沉積地質(zhì)特征,并結(jié)合火山巖系的大地構(gòu)造屬性探討了梵凈山群上碎屑巖系的原型盆地及構(gòu)造古地理格局,主要取得以下新的進(jìn)展:1.恢復(fù)了梵凈山群的地層序列,查明其主體為灰色中厚層變質(zhì)砂巖、粉砂巖及變凝灰砂巖及絹云千枚巖、板巖,以及多層中、基性火山巖等。2.野外實(shí)測(cè)了銅廠組、洼溪組中、粗粒濁積砂巖中發(fā)育的小型斜層理,經(jīng)水平校正,前積層的傾向玫瑰花圖解分析顯示,黔東北梵凈山群上亞群的濁積碎屑巖系古流向總體指向北、北東,證明其物源來(lái)自南方,它們?cè)丛床粩嗟南虮碧峁┧樾嘉镔|(zhì)。3.銅廠組及洼溪組粗砂巖骨架顆粒統(tǒng)計(jì)分析及骨架顆粒成分三角圖解顯示,梵凈山群上碎屑巖系沉積地層的物源為火山島弧。4.野外采集了回香坪組中的具典型枕狀構(gòu)造的玄武巖及安山質(zhì)集塊火山巖樣品。樣品的全巖地球化學(xué)特征分析結(jié)果表明,其形成的構(gòu)造環(huán)境為活動(dòng)大陸邊緣,形成于弧后伸展。5.綜合以上研究成果,結(jié)合與廬山地區(qū)筲箕洼組以及星子巖群玄武巖進(jìn)行相同構(gòu)造環(huán)境圖解判別的對(duì)比,推測(cè)梵凈山群上碎屑巖系板塊構(gòu)造環(huán)境應(yīng)為弧后伸展盆地,即邊緣海。再結(jié)合前人研究成果,分析判斷梵凈山群與出露于桂北及黔南地區(qū)的四堡群相對(duì)應(yīng),形成完整的弧盆系統(tǒng)。進(jìn)而推論梵凈山群上部碎屑巖系沉積期間,江南造山帶為一西太平洋型俯沖造山帶或西太平洋型活動(dòng)大陸邊緣。
[Abstract]:The Jiangnan orogenic belt is a crustal suture zone between the upper Yangtze and Cathaysian blocks, and the main body is a Neoproterozoic metamorphic belt extending from north to west to west to west.The Fanjingshan Group is developed at the northwest end of the Jiangnan orogenic belt, and its main body is the Fanjingshan area in the northeast of Guizhou, which is mainly composed of a set of continental clastic rocks and shallow metamorphic volcanic rock series, and the angle is unconformity under the Lower Yangtze Group.Based on the theories of sedimentary geology, lithotectonics and tectonostratigraphy, this paper focuses on the sedimentary geological characteristics of the upper clastic rock series of the Fanjingshan Group, represented by the Tongchang formation.The prototype basin and tectonic paleogeographic pattern of the upper clastic rock series of the Fanjingshan Group are discussed based on the geotectonic attributes of the volcanic rock series.The stratigraphic sequence of the Fanjingshan Group is restored, and the main bodies are found to be grey medium thick metamorphic sandstone, siltstone and metagglutinite sandstone and sericite phyllite, slate, and multilayer, basic volcanic rocks, etc.The small diagonal bedding developed in the coarse turbidite sandstone in Tongchang formation, Waxi formation and in the Tongchang formation was measured in the field.The turbidite clastic rocks of the upper subgroup of the Fanjingshan group in northeastern Guizhou generally point to the north and the north to the east, which proves that their provenance comes from the south, and they continue to supply the clastic material .3to the north.Statistical analysis of coarse sandstone skeleton particles and triangular diagram of skeleton grain composition in Tongchang and Waxi formations show that the source of sedimentary strata of upper clastic rock series in Fanjingshan group is volcanic island arc .4.Samples of basalt and Anshan mass volcanic rocks with typical pillow structure in Huixiangping formation were collected in the field.The analysis of the geochemical characteristics of the whole rock shows that the tectonic environment is active continental margin and formed in the back-arc extension of .5.Based on the above research results and the comparison of the same tectonic environmental diagrams with the Shaojiwa formation and the basalt of the Xingzi group in Lushan area, it is inferred that the tectonic environment of the upper clastic rock series of the Fanjingshan group should be a back-arc extensional basin, that is, the marginal sea.Combined with the previous research results, it is analyzed and judged that the Fanjingshan group corresponds to the Sibao group exposed in northern Guangxi and southern Guizhou to form a complete arc basin system.It is inferred that during the depositional period of the upper clastic rock series in the upper part of the Fanjingshan Group, the Jiangnan orogenic belt is a west Pacific subduction orogenic belt or a western Pacific active continental margin.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：P548;P512.2

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