本文選題：碎屑鋯石　切入點：U-Pb和Hf同位素　出處：《中國科學院大學(中國科學院廣州地球化學研究所)》2017年碩士論文　論文類型：學位論文

【摘要】：哀牢山古特提斯洋的打開和閉合時限及其縫合帶的具體位置對理解哀牢山古特提斯洋構造演化具有非常重要的意義。本文利用碎屑鋯石年代學及其Hf同位素示蹤方法,分析了哀牢山構造帶兩側不同時期地層沉積物源的特征及其變化,解譯了其物源差別所指示的哀牢山古特提斯洋盆打開和閉合時限、縫合帶的構造位置以及其在岡瓦納大陸的位置。碎屑鋯石年代學結果顯示,兩側上志留統(tǒng)碎屑鋯石都記錄一個~450 Ma的年輕的峰值和一個1100~800 Ma年齡群信息;不同于上志留統(tǒng),構造帶東側下泥盆統(tǒng)的碎屑鋯石缺失~450 Ma的峰值年齡,西側下泥盆統(tǒng)繼承上志留統(tǒng)U-Pb年齡分布模式記錄~450 Ma峰值年齡信息。綜合區(qū)域上年代學和其它地質資料,我們認為哀牢山古特提斯洋盆的打開時限應該在晚志留-早泥盆世,而哀牢山構造帶代表了哀牢山縫合帶的位置。構造帶兩側中-上三疊統(tǒng)碎屑鋯石顯示略有差異的年齡頻譜特征:構造帶內中三疊統(tǒng)碎屑鋯石峰值年齡為~350 Ma和480~560 Ma,其εHf(t)變化范圍分別屬于-11.56~+17.14和-13.81~+12.63;而東側中三疊統(tǒng)的碎屑鋯石明顯記錄了230~270 Ma、327~340 Ma和490~520 Ma的年齡峰值信息,其εHf(t)變化范圍分別屬于-5.58~+13.88,-6.20~12.00,-15.66~+13.36。東側和構造帶內上三疊統(tǒng)都記錄了~230 Ma和~300Ma的主峰值年齡信息以及450~560 Ma的次峰值年齡信息,具有一致的年齡頻譜和鋯石的Hf同位素分布特征(~230 Ma的碎屑鋯石的εHf(t)屬于-3.4~1.29,~300 Ma的碎屑鋯石的εHf(t)屬于-8.4~8.8),并分別與哀牢山構造帶內的巖漿活動時限及其Hf同位素分布極為吻合,說明二者晚三疊世物源都來自于哀牢山構造帶,再綜合該區(qū)域前人P3-T3地層碎屑鋯石年代學、Hf同位素以及巖漿巖和地層學等其它資料,認為哀牢山洋至少在T1時已經(jīng)開始閉合隆升了。本文重新整理比對了樣子和思茅-印支、保山-Sibumasu等東南亞各地塊早古生代地層大量碎屑鋯石U-Pb年齡數(shù)據(jù),發(fā)現(xiàn)這些地塊寒武-奧陶紀都記錄了500~600 Ma和950~1000 Ma的峰值年齡信息具有典型的親Gondwana超大陸的性質,認為華南、思茅-印支地、保山、南羌塘地塊寒武紀古地理位置接近,可能位于Gondwana超大陸邊緣的印度板塊和澳大利亞板塊之間位置,但更多的接受來自印度和喜馬拉雅地塊的沉積。
[Abstract]:The time limit for opening and closing of the Ailao paleoTethys ocean and the specific location of the suture zone are of great significance for understanding the tectonic evolution of the Ailao paleoTethys ocean. In this paper, detrital zircon chronology and its HF isotope tracing method are used. This paper analyses the characteristics and changes of sedimentary sources in different periods on both sides of the Ailaoshan tectonic belt, and interprets the time limit of opening and closing of the ancient Tethys ocean basin in Ailao Mountain, which is indicated by the difference of its provenance. The tectonic location of the suture zone and its location in Gondwana continent show that both sides of upper Silurian detrital zircon record a young peak value of 450 Ma and an age group of 1 100 ~ 800 Ma, which is different from that of upper Silurian. The detrital zircon missing peak age of 450 Ma in the lower Devonian on the east side of the tectonic belt and the U-Pb age distribution model of upper Silurian inherited from the west side of the basin have recorded the peak age information of 450 Ma. We believe that the time limit for the opening of the ancient Tethys basin in the Ailao Mountains should be in the late Silurian and early Devonian. The Ailaoshan tectonic belt represents the location of the Ailaoshan suture zone. The middle and upper Triassic detrital zircons on both sides of the tectonic belt show slightly different age spectrum characteristics: the peak ages of the middle Triassic clastic zircons in the tectonic belt are 350Ma and 4800.560. The range of variation of 蔚 HfT is -11.56 ~ 17.14 and -13.81 ~ 12.63, respectively, while the age peak information of 230 ~ 270 Ma ~ 32727 ~ 340 Ma and 490 ~ 520 Ma is obviously recorded in the eastern Middle Triassic clastic zircon, and its variation range is -11.56 ~ 17.14 and -13.81 ~ 12.63, respectively. The range of 蔚 Hftvariation belongs to -5.58 ~ 13.88 ~ 6.20 ~ 12.00 ~ 15.66 ~ 13.366.The main peak age information and the sub-peak age information of Yi-230 Ma and Kui 300Ma are recorded in the east side and the upper Triassic in the tectonic belt, and the sub-peak age information of 450 Ma ~ 560 Ma is recorded in the east side and in the upper Triassic of the tectonic belt. It has a consistent age spectrum and a zircon HF isotopic distribution characteristic. The 蔚 Hftt of the detrital zircon at 230 Ma belongs to -3.4U 1.29 ~ 300 Ma) and belongs to -8.4- 8.80.It is in good agreement with the magmatic activity time and HF isotope distribution in the Ailaoshan tectonic belt, respectively, and the distribution of HF isotopic isotopes in the zircon is similar to that in the Ailaoshan tectonic belt, and the distribution of HF isotopes in the zircon is similar to that in the Ailaoshan tectonic belt. It is suggested that both the late Triassic provenances came from the Ailaoshan tectonic belt, and other data such as zircon dating of zircon dating, magmatic rocks and stratigraphy of the P3-T3 strata in the region were synthesised. It is considered that the Ailao ocean began to close its uplift at least at T1. The U-Pb age data of zircon from the early Paleozoic strata of the Simao Indosinian, Baoshan Sibumasu and other Southeast Asian blocks have been rearranged and compared in this paper. It is found that the Cambrian-Ordovician peak age information of the Cambrian-Ordovician in these blocks is typical of the Gondwana supercontinent. It is considered that the Cambrian paleogeography of the southern China, Simao Indosinian, Baoshan and Southern Qiangtang massif is close to the Cambrian paleogeography. It may be located between the Indian and Australian plates on the Gondwana supercontinental margin, but it is more likely to accept deposits from the Indian and Himalayan blocks.
【學位授予單位】：中國科學院大學(中國科學院廣州地球化學研究所)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P597.3;P548
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本文編號：1560530