林周盆地晚白堊世—早始新世關(guān)鍵地質(zhì)事件對青藏高原南部構(gòu)造演化的制約
發(fā)布時間：2018-10-05 15:20
【摘要】：晚白堊世-早始新世拉薩地塊南部的構(gòu)造演化包括三個關(guān)鍵的地質(zhì)事件,分別是:晚白堊世海相沉積向陸相沉積的轉(zhuǎn)換過程;K-T界線附近陸相沉積層強烈的褶皺變形及不整合事件;早始新世強烈的巖漿噴發(fā)所夾持的火山活動休眠期事件。這些關(guān)鍵地質(zhì)事件記錄了印度大陸與亞洲大陸碰撞前后青藏高原南部構(gòu)造演化的豐富信息,通過對它們進行系統(tǒng)而精確的年代學(xué)研究,可為復(fù)原高原演化模型,限制碰撞時代奠定基礎(chǔ)。位于拉薩地塊東南緣的林周盆地,由于晚白堊世-第三紀(jì)地層保存完整,層間界面清晰,擁有上述的三個關(guān)鍵事件良好的地質(zhì)記錄,分別表現(xiàn)為塔克那組海相沉積向設(shè)興組陸相沉積的轉(zhuǎn)換,設(shè)興組強烈褶皺變形以及林子宗群火山巖不整合覆蓋,典中組火山巖與帕那組火山巖之間的年波組沉積。為系統(tǒng)構(gòu)建拉薩地塊南緣關(guān)鍵地質(zhì)事件的年代學(xué)格架,還原晚白堊世-第三紀(jì)拉薩地塊南緣的構(gòu)造演化過程提供了良好的條件。本文選取林周盆地林周縣南、北、洛巴堆、甲榮、典中村北、強噶鄉(xiāng)北共6條剖面對塔克那組、設(shè)興組以及林子宗群火山巖進行詳細的地層學(xué)及巖石學(xué)研究,并在剖面關(guān)鍵位置挑選35件樣品進行系統(tǒng)的鋯石U-Pb年代學(xué)研究。結(jié)果表明:研究區(qū)出露的塔克那組為淺海相沉積,其頂部砂巖的沉積時代,與設(shè)興組底部火山巖夾層年齡共同將海陸轉(zhuǎn)換的時代限定為95~83Ma。設(shè)興組為河流相沉積,可分為上下兩段,下段的曲流河沉積于~78Ma轉(zhuǎn)變?yōu)樯隙蔚霓p狀河沉積;未卷入變形的閃長玢巖切割了強烈褶皺的設(shè)興組,結(jié)晶年齡~72Ma,早于上覆火山巖的最老時代(~69Ma),進一步限定林周盆地上白堊統(tǒng)強烈變形的時代為78~72Ma。林子宗群火山巖是一套火山-沉積巖相的地層,自下而上可分為典中組、年波組和帕那組,其中帕那組又可以分為帕那組一段和帕那組二段兩個巖性段。林周盆地林子宗群火山巖的年齡范圍為66~47Ma,與拉薩地塊西部的林子宗群范圍相似,但滯后于中部。其中典中組:66~59Ma;年波組:56~54Ma;帕那組一段:54~50Ma;帕那組二段:49~47Ma。典中組與年波組之間存在一個~3Ma平行不整合,而年波組和上覆的帕那組之間為連續(xù)過渡。研究區(qū)上白堊統(tǒng)為一套弧后前陸盆地沉積,其間岡底斯弧持續(xù)隆升并提供主要物源。由于新特提斯洋俯沖角度的增加,~66Ma時岡底斯弧后地區(qū)的應(yīng)力背景由擠壓撓曲轉(zhuǎn)為拉張伸展,林周盆地的性質(zhì)也由早期的弧后前陸盆地(95~66Ma)轉(zhuǎn)為火山弧及山間盆地(66~47Ma)。
[Abstract]:The tectonic evolution of the southern Lhasa block from late Cretaceous to early Eocene includes three key geological events. They are: late Cretaceous marine sedimentary to continental sedimentary conversion process / strong fold deformation and unconformity event near K-T boundary; early Eocene strong magmatic eruption held by volcanic activity dormant event. These key geological events record abundant information on tectonic evolution of the southern Qinghai-Xizang Plateau before and after the collision between the Indian continent and the Asian continent. Through systematic and accurate chronological studies of them, they can be used as a model for the restoration of the plateau evolution. Limiting the collision era laid the foundation. The Linzhou Basin, located in the southeast margin of Lhasa block, has a good geological record of the three key events mentioned above, due to the integrity of the late Cretaceous to Tertiary strata and the clear interlayer interface. They are characterized by the transformation of marine facies deposits from Takana formation to the continental facies deposits of the Shenxing formation, the strong fold deformation of the Xingxing formation, the unconformity overburden of volcanic rocks in the Linzizong group, and the deposition of the annual wave formation between the volcanic rocks of the Dianzhong formation and the Pana formation. It provides a good condition for systematically constructing the chronological framework of the key geological events in the southern margin of the Lhasa block and reducing the tectonic evolution process of the southern margin of the Lhasa block from late Cretaceous to Tertiary. In this paper, six sections are selected from the south, north, Lobabadi, Jia Rong, Danzhong Village and Qianggaxiang North of Linzhou Basin to carry out detailed stratigraphic and petrological studies on volcanic rocks of Tana formation, Xingxing formation and Linzongzong Group. 35 samples were selected at the key position of the section for systematic zircon U-Pb chronological study. The results show that the Tucker formation exposed in the study area is shallow marine sedimentary, and the sedimentary age of the top sandstone, together with the age of volcanic rock intercalation at the bottom of the Shexing formation, limits the age of sea-land transition to 95 ~ 83 Ma. The formation is a fluvial deposit, which can be divided into upper and lower sections. The meandering stream deposit in the lower member was transformed into braided river deposit of the upper member at 78 Ma, and the diorite porphyrite, which was not involved in the deformation, was cut into the strong fold formation. The crystallization age of 72Mais earlier than the oldest age of overlying volcanic rocks (69Ma), and the age of strong deformation of Upper Cretaceous in Linzhou Basin was 7872Ma. The volcanic rock of the Linzizong group is a set of volcanic sedimentary facies, which can be divided into three groups from the bottom to the top: the Dianzhong formation, the Nimbo formation and the Pana formation, in which the Pana formation can be divided into two lithologic sections: the first member of the Pana formation and the second member of the Pana formation. The age range of the volcanic rocks of the Linzizong Group in Linzhou Basin is 660.47 Ma, which is similar to the range of Linzong Group in the west of Lhasa block, but lags behind the middle part. Among them, the second segment of the Pana group, is composed of: 66 / 59 Ma.; the second stage of the Pana group is 1: 4947 MaA; the second stage of the Pana group is: 56, 56, 54 Ma. There is a parallel unconformity of 3 Ma between the canonical group and the Nian wave group, and a continuous transition between the Nimbo formation and the overlying Pana formation. The Upper Cretaceous in the study area is a set of back-arc Foreland basins, during which the Gangdis arc continues to uplift and provide the main provenance. Due to the increase of the subduction angle of the Neo-Tethys Ocean, the stress background of the Gangdis back-arc area changed from compressional flexure to extensional extension at 66Ma, and the nature of the Linzhou basin changed from the early back-arc Foreland basin (95~66Ma) to the volcanic arc and intermountain basin (66~47Ma).
【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】：2017
【分類號】：P542
，
本文編號：2253884
[Abstract]:The tectonic evolution of the southern Lhasa block from late Cretaceous to early Eocene includes three key geological events. They are: late Cretaceous marine sedimentary to continental sedimentary conversion process / strong fold deformation and unconformity event near K-T boundary; early Eocene strong magmatic eruption held by volcanic activity dormant event. These key geological events record abundant information on tectonic evolution of the southern Qinghai-Xizang Plateau before and after the collision between the Indian continent and the Asian continent. Through systematic and accurate chronological studies of them, they can be used as a model for the restoration of the plateau evolution. Limiting the collision era laid the foundation. The Linzhou Basin, located in the southeast margin of Lhasa block, has a good geological record of the three key events mentioned above, due to the integrity of the late Cretaceous to Tertiary strata and the clear interlayer interface. They are characterized by the transformation of marine facies deposits from Takana formation to the continental facies deposits of the Shenxing formation, the strong fold deformation of the Xingxing formation, the unconformity overburden of volcanic rocks in the Linzizong group, and the deposition of the annual wave formation between the volcanic rocks of the Dianzhong formation and the Pana formation. It provides a good condition for systematically constructing the chronological framework of the key geological events in the southern margin of the Lhasa block and reducing the tectonic evolution process of the southern margin of the Lhasa block from late Cretaceous to Tertiary. In this paper, six sections are selected from the south, north, Lobabadi, Jia Rong, Danzhong Village and Qianggaxiang North of Linzhou Basin to carry out detailed stratigraphic and petrological studies on volcanic rocks of Tana formation, Xingxing formation and Linzongzong Group. 35 samples were selected at the key position of the section for systematic zircon U-Pb chronological study. The results show that the Tucker formation exposed in the study area is shallow marine sedimentary, and the sedimentary age of the top sandstone, together with the age of volcanic rock intercalation at the bottom of the Shexing formation, limits the age of sea-land transition to 95 ~ 83 Ma. The formation is a fluvial deposit, which can be divided into upper and lower sections. The meandering stream deposit in the lower member was transformed into braided river deposit of the upper member at 78 Ma, and the diorite porphyrite, which was not involved in the deformation, was cut into the strong fold formation. The crystallization age of 72Mais earlier than the oldest age of overlying volcanic rocks (69Ma), and the age of strong deformation of Upper Cretaceous in Linzhou Basin was 7872Ma. The volcanic rock of the Linzizong group is a set of volcanic sedimentary facies, which can be divided into three groups from the bottom to the top: the Dianzhong formation, the Nimbo formation and the Pana formation, in which the Pana formation can be divided into two lithologic sections: the first member of the Pana formation and the second member of the Pana formation. The age range of the volcanic rocks of the Linzizong Group in Linzhou Basin is 660.47 Ma, which is similar to the range of Linzong Group in the west of Lhasa block, but lags behind the middle part. Among them, the second segment of the Pana group, is composed of: 66 / 59 Ma.; the second stage of the Pana group is 1: 4947 MaA; the second stage of the Pana group is: 56, 56, 54 Ma. There is a parallel unconformity of 3 Ma between the canonical group and the Nian wave group, and a continuous transition between the Nimbo formation and the overlying Pana formation. The Upper Cretaceous in the study area is a set of back-arc Foreland basins, during which the Gangdis arc continues to uplift and provide the main provenance. Due to the increase of the subduction angle of the Neo-Tethys Ocean, the stress background of the Gangdis back-arc area changed from compressional flexure to extensional extension at 66Ma, and the nature of the Linzhou basin changed from the early back-arc Foreland basin (95~66Ma) to the volcanic arc and intermountain basin (66~47Ma).
【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】：2017
【分類號】：P542
，
本文編號：2253884
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