哀牢山构造带及其两侧地区早古生代和早中生代地层碎屑锆石U-Pb年代学和Hf同位素组成：物源示踪及其构造意义

发布时间：2018-03-03 09:52

  本文选题：碎屑锆石　切入点：U-Pb和Hf同位素　出处：《中国科学院大学(中国科学院广州地球化学研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：哀牢山古特提斯洋的打开和闭合时限及其缝合带的具体位置对理解哀牢山古特提斯洋构造演化具有非常重要的意义。本文利用碎屑锆石年代学及其Hf同位素示踪方法,分析了哀牢山构造带两侧不同时期地层沉积物源的特征及其变化,解译了其物源差别所指示的哀牢山古特提斯洋盆打开和闭合时限、缝合带的构造位置以及其在冈瓦纳大陆的位置。碎屑锆石年代学结果显示,两侧上志留统碎屑锆石都记录一个~450 Ma的年轻的峰值和一个1100~800 Ma年龄群信息;不同于上志留统,构造带东侧下泥盆统的碎屑锆石缺失~450 Ma的峰值年龄,西侧下泥盆统继承上志留统U-Pb年龄分布模式记录~450 Ma峰值年龄信息。综合区域上年代学和其它地质资料,我们认为哀牢山古特提斯洋盆的打开时限应该在晚志留-早泥盆世,而哀牢山构造带代表了哀牢山缝合带的位置。构造带两侧中-上三叠统碎屑锆石显示略有差异的年龄频谱特征:构造带内中三叠统碎屑锆石峰值年龄为~350 Ma和480~560 Ma,其εHf(t)变化范围分别属于-11.56~+17.14和-13.81~+12.63;而东侧中三叠统的碎屑锆石明显记录了230~270 Ma、327~340 Ma和490~520 Ma的年龄峰值信息,其εHf(t)变化范围分别属于-5.58~+13.88,-6.20~12.00,-15.66~+13.36。东侧和构造带内上三叠统都记录了~230 Ma和~300Ma的主峰值年龄信息以及450~560 Ma的次峰值年龄信息,具有一致的年龄频谱和锆石的Hf同位素分布特征(~230 Ma的碎屑锆石的εHf(t)属于-3.4~1.29,~300 Ma的碎屑锆石的εHf(t)属于-8.4~8.8),并分别与哀牢山构造带内的岩浆活动时限及其Hf同位素分布极为吻合,说明二者晚三叠世物源都来自于哀牢山构造带,再综合该区域前人P3-T3地层碎屑锆石年代学、Hf同位素以及岩浆岩和地层学等其它资料,认为哀牢山洋至少在T1时已经开始闭合隆升了。本文重新整理比对了样子和思茅-印支、保山-Sibumasu等东南亚各地块早古生代地层大量碎屑锆石U-Pb年龄数据,发现这些地块寒武-奥陶纪都记录了500~600 Ma和950~1000 Ma的峰值年龄信息具有典型的亲Gondwana超大陆的性质,认为华南、思茅-印支地、保山、南羌塘地块寒武纪古地理位置接近,可能位于Gondwana超大陆边缘的印度板块和澳大利亚板块之间位置,但更多的接受来自印度和喜马拉雅地块的沉积。
[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.
【学位授予单位】：中国科学院大学(中国科学院广州地球化学研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P597.3;P548
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本文编号：1560530