【摘要】：華南位于古特提斯和濱太平洋兩大構(gòu)造域的交接部位,中生代構(gòu)造活動(dòng)復(fù)雜,經(jīng)歷了華南板塊與華北板塊、華南板塊與印支板塊的陸陸碰撞,以及之后太平洋板塊向歐亞板塊的俯沖等事件。在華南地區(qū),中生代早期經(jīng)歷了重要的構(gòu)造轉(zhuǎn)換。印支期表現(xiàn)出的強(qiáng)烈擠壓作用,不僅導(dǎo)致了大規(guī)模的沖斷變形和不整合的發(fā)育,同時(shí)還伴隨巖漿活動(dòng)和韌性變形；燕山期則表現(xiàn)出強(qiáng)烈的伸展作用,導(dǎo)致了大規(guī)模的巖漿作用和北東-北東東走向的斷陷盆地發(fā)育。因此,本論文以印支期擠壓過程和燕山期的伸展過程為突破口,以華南東北部中生代盆地、中生代巖墻群和古老巖石單元為研究對(duì)象,以變形分析、熱年代學(xué)分析、地球化學(xué)分析和鋯石SHRIMP年代學(xué)分析為主要手段,揭示華南東北部構(gòu)造變形的轉(zhuǎn)換過程。本次研究主要取得了以下幾點(diǎn)認(rèn)識(shí)：(1)通過浙贛地區(qū)中生代擠壓變形特征的分析,以及浙西南地區(qū)發(fā)育的240Ma糜棱巖和一系列240-220Ma左右的變質(zhì)巖和同造山花崗巖,表明該地區(qū)的印支期變形開始于240Ma左右；這一變形從東南往北西方向傳播,在早侏羅世的中晚期傳播到江西上饒地區(qū),導(dǎo)致早侏羅世及以前的地層的強(qiáng)烈變形,而傳播到江西的萍鄉(xiāng)、宜春等地的時(shí)間可能在中侏羅世時(shí)期。(2)通過浙贛地區(qū)中生代盆地的分析,發(fā)現(xiàn)浙贛地區(qū)的中生代斷陷盆地在發(fā)育時(shí)間上,從內(nèi)陸逐漸向沿海變晚的特點(diǎn),弋陽盆地和金衢盆地的開始發(fā)育時(shí)間大致是在140-135Ma,而到了東部杭嘉湖盆地從100Ma以后才開始發(fā)育；但是杭嘉湖盆地的總伸展率達(dá)到了30%,而弋陽盆地和金衢盆地的總伸展率只有15%左右,晚白堊世時(shí)期的伸展作用要強(qiáng)于早白堊世的伸展作用。白堊紀(jì)末,浙贛地區(qū)的盆地都存在一個(gè)構(gòu)造反轉(zhuǎn)期,導(dǎo)致了地層的變形和抬升剝蝕。(3)通過陳蔡群雜巖和里浦閃長(zhǎng)巖的鋯石、磷灰石裂變徑跡和熱史模擬工作,結(jié)合晚三疊世地層的沉積學(xué)特征,認(rèn)為陳蔡群及里浦閃長(zhǎng)巖自古生代以來至少經(jīng)歷了三期構(gòu)造抬升事件才致被剝露至地表,分別為晚三疊世(烏灶組T3w沉積時(shí)期)的逆沖推覆、早白堊世(134-105Ma)伸展背景下的相對(duì)抬升以及晚白堊世末-古近紀(jì)(66-41Ma)的區(qū)域整體抬升,并建立了其構(gòu)造熱演化模式。(4)通過江西上饒、浙江諸暨王家宅和浙江麗水楓坪花崗斑巖的研究,并結(jié)合前人的研究成果,分析的了浙贛地區(qū)巖墻的發(fā)育規(guī)律。江西上饒中性巖墻為安山玢巖,形成于中侏羅世(160±3Ma),為富鋁的亞堿性巖石,具有富集輕稀土元素和大離子親石元素Th、U和低放射成因Pb,虧損高場(chǎng)強(qiáng)元素Nb、Ti的特點(diǎn)。其球粒隕石標(biāo)準(zhǔn)化曲線呈一致的右傾模式,具輕微Eu負(fù)異常,其源區(qū)曾受到來自俯沖太平洋板塊的脫水作用所致的流體交代作用。王家宅雙峰式侵入巖形成于早白堊世(127Ma左右),巖石組合為輝綠巖-花崗斑巖組合,其中輝綠巖為堿性鉀玄巖,呈輕稀土元素較富集,重稀土元素平坦的形式,基本無Eu異常(6Eu=0.99-1.09),富集Rb、Ba、Pb及La,虧損Nb、Ta和Ti；花崗斑巖的輕稀土元素含量較輝綠巖大,重稀土元素差別不大,但具弱Eu負(fù)異常(δEu=0.85-0.87),富集大離子親石元素Rb、Ba、Th、Pb、Zr,虧損Nb、Ta,Sr和Ti,具有A型花崗巖的特點(diǎn)。雙峰式侵入巖輝綠巖和花崗斑巖的出現(xiàn)標(biāo)志著區(qū)域地殼發(fā)生大規(guī)模的伸展減薄。麗水楓坪花崗斑巖形成于早白堊世(130+1Ma),具有富硅、鋁,堿含量中等,貧錳、鎂、鈦、磷的特點(diǎn),其球粒隕石標(biāo)準(zhǔn)化曲線呈向右傾的“海鷗”型且具強(qiáng)Eu負(fù)異常,屬于典型的地殼重熔型花崗巖。其巖漿源區(qū)為華南古老的地殼物質(zhì),為富砂質(zhì)和富泥質(zhì)的原巖發(fā)生部分熔融而成。(5)結(jié)合變形特征、盆地和巖墻發(fā)育特征、巖漿作用和變質(zhì)作用特征和古老巖石的剝露過程分析,提出了華南東北部中生代從擠壓到伸展的構(gòu)造轉(zhuǎn)換過程。本文認(rèn)為華南東北部印支期擠壓變形開始于240Ma左右,這一變形從西南往北西方向傳播,傳播到江西萍鄉(xiāng)、宜春等地可能在中侏羅世時(shí)期。在160Ma左右,華南東北部地區(qū)的構(gòu)造應(yīng)力發(fā)生了轉(zhuǎn)變,由擠壓作用轉(zhuǎn)變?yōu)樯煺棺饔谩r石圈的伸展作用首先從江西吉安-上饒地區(qū)開始,發(fā)育了吉安堿性橄欖玄武巖和上饒安山玢巖等與伸展作用有關(guān)的巖漿作用；140Ma左右,華南東北部全面進(jìn)入伸展構(gòu)造環(huán)境,開始發(fā)育斷陷盆地、A型花崗巖或堿性侵入巖、變質(zhì)核雜巖、雙峰式火山巖和基性巖墻(群)。140Ma的大規(guī)模伸展總體表現(xiàn)從江西吉安-上饒地區(qū)往沿海地區(qū)遷移,東部沿海地區(qū)的大規(guī)模伸展集中在110-90Ma。到了晚白堊世時(shí)期,華南東北部發(fā)生了大規(guī)模的構(gòu)造反轉(zhuǎn),結(jié)束了晚中生代的伸展作用。本論文提出了華南中生代從擠壓向伸展轉(zhuǎn)換的時(shí)間節(jié)點(diǎn)和大陸動(dòng)力學(xué)演化過程,成果對(duì)了解區(qū)域中生代構(gòu)造轉(zhuǎn)換有著重要的地質(zhì)意義。
[Abstract]:Southern China is located in the junction of the two tectonic domains of Gut Tis and the Pacific Ocean, and the Mesozoic tectonic movement is complex. It experienced the continental collision between the Southern China plate and the North China plate, the Southern China plate and the Indo Chinese plate, and the subduction of the Pacific plate to the Eurasian plate. In Southern China, the early Mesozoic experienced an important structural transformation. The strong extrusion effect of the Indosinian period not only resulted in large scale deformation and unconformity, but also accompanied by magmatic activity and ductile deformation, while the Yanshan period showed a strong extension, resulting in large-scale magmatism and the development of a faulted basin in the east to North East and East. Therefore, this paper is Indosinian The period of the extrusion process and the extension process of Yanshan period are the breakthrough. Taking the Mesozoic basin in northeastern Southern China, the Mesozoic rock wall group and the ancient rock unit as the research object, the transformation process of tectonic deformation in Northeast of Southern China is revealed by deformation analysis, thermal chronology analysis, geochemistry analysis and zircon SHRIMP chronology analysis. The main achievements are as follows: (1) through the analysis of the Mesozoic extrusion deformation characteristics of the Zhejiang and Jiangxi areas, and the 240Ma mylonite and a series of 240-220Ma metamorphic and orogenic granites developed in Southwestern Zhejiang, it shows that the Indosinian deformation of the region begins at about 240Ma, and this deformation is from Southeast to North West. Spread to the middle and late stage of the early Jurassic to the Shangrao area of Jiangxi, leading to the strong deformation of the early Jurassic and the previous strata, and the time in Pingxiang and Yichun, Jiangxi, may be in the Middle Jurassic period. (2) through the analysis of Mesozoic basin in Zhejiang Jiangxi region, the Mesozoic fault basin in Zhejiang Jiangxi region was developed in the development time, The development time of the Yiyang basin and Jinqu basin is approximately 140-135Ma, and the development of the eastern hang Jia Lake Basin has been developed only after 100Ma, but the total extension rate of the hang Jia Lake Basin reaches 30%, while the total extension rate of the Yiyang basin and the Jinqu basin is only about 15%, and the late Cretaceous. The extension of the period is stronger than the early Cretaceous extension. At the end of the Cretaceous, there was a tectonic reversal period in the basins in the Zhejiang Jiangxi region, which resulted in the deformation and uplift and denudation of the strata. (3) through the zircon from the Chen Caiqun complex and the Lipu diorite, the apatite fission track and the thermal history model work, combined with the sedimentary characteristics of the late three fold strata. It is considered that Chen Caiqun and Lipu diorite has been exposed to the surface at least three tectonic uplifting events since the Paleozoic, which are the thrust nappe of the late three fold (T3w period), the relative uplift under the early Cretaceous (134-105Ma) extension background and the regional overall uplift of the late Cretaceous and Paleogene (66-41Ma). The tectonic thermal evolution model has been established. (4) through the study of Jiangxi Shangrao, Zhejiang Zhuji Wang house and Lishui Maple granite porphyry in Lishui, Zhejiang, the development law of the rock walls in the Zhejiang and Jiangxi areas is analyzed. The neutral rock wall of Jiangxi Shangrao is an annite porphyrite, which is formed in the Middle Jurassic (160 + 3Ma) and is a subalkaline rock rich in aluminum. There are abundant light rare earth elements and large ion stone elements Th, U and low radiogenic Pb, which have the characteristics of loss of high field and strong element Nb, Ti. The chondrite standardization curve of the chondrites has a consistent right deviation model with a slight negative Eu anomaly, and its source area has been subjected to fluid metasomatism from the dehydration of subducted Pacific plate. Shuangfeng type invasion of Wang Jia residence The rocks are formed in the early Cretaceous (about 127Ma). The rocks are composed of diabase and granite porphyry assemblage. The diabase is alkaline potash basalt, which is enriched in light rare earth elements and is flat in heavy rare earth elements. It is basically without Eu anomaly (6Eu=0.99-1.09), enriches Rb, Ba, Pb and La, loses Nb, Ta and Ti, and the light REE content of granite porphyry is larger than diabase. There is little difference in heavy rare earth elements, but with a weak Eu negative anomaly (delta Eu=0.85-0.87), rich in large ion stone elements Rb, Ba, Th, Pb, Zr, loss Nb, Ta, Sr and Ti, with the characteristics of A type granite. The occurrence of Shuangfeng intrusive diabase and granite porphyry marked the extensive extension and thinning of the regional crust. The Lishui Maple Ping granite porphyry was formed in early white. The Cretaceous (130+1Ma) has the characteristics of rich silicon, aluminum, alkali content, manganese poor, magnesium, titanium and phosphorus. The chondrite standardization curve is a right leaning "Seagull" type and has a strong Eu negative anomaly. It belongs to the typical crustal remelting granite. Its magma source area is the ancient crustal substance in Southern China, which partially melted the sand rich and mud rich rocks. (5) according to the characteristics of deformation, development characteristics of basin and rock wall, characteristics of magmatism and metamorphism and the process of denudation of ancient rocks, the tectonic transformation process from extrusion to extension of Mesozoic in northeastern Southern China is put forward. This paper holds that the Indosinian compression deformation in northeastern Southern China began to be around 240Ma, and this deformation from southwest to North West. The spread to Jiangxi Pingxiang, Yichun and other places may be in the Middle Jurassic period. Around 160Ma, the tectonic stress in the northeastern part of Southern China changed to extension. The extension of the lithosphere started from the Ji'an Shangrao region of Jiangxi, and the Ji'an alkaline olivine basalt and Shangrao porphyrite were bred. The magmatism related to extension and so on; around 140Ma, the northeastern part of Southern China entered the extensional tectonic environment, and began to develop fault basin, A type granite or alkaline intrusive rock, metamorphic core complex, Shuangfeng type volcanic rock and basic rock wall (Group).140Ma extensive extension from Jiangxi Ji'an Shangrao region to coastal area, The large-scale extension of the eastern coastal areas was concentrated from 110-90Ma. to the late Cretaceous period, and a large-scale tectonic reversal occurred in northeastern Southern China, ending the late Mesozoic extension. In this paper, the time node of the Mesozoic transition from extrusion to extension in Southern China and the evolution process of the continental dynamic mechanics were put forward, and the achievements were made to understand the Mesozoic in the region. Structural transformation has important geological significance.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P542

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相關(guān)期刊論文 前2條

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本文編號(hào)：2162258