本文選題：徐尼烏蘇組 + 早志留世��； 參考：《巖石學(xué)報(bào)》2017年10期

【摘要】：本文對白乃廟地區(qū)徐尼烏蘇組沉積特征、原巖建造、變質(zhì)火山巖及變質(zhì)碎屑巖的年代學(xué)和地球化學(xué)進(jìn)行了研究,探討了白乃廟地區(qū)早古生代構(gòu)造演化。本次研究采集了徐尼烏蘇組中具有代表性的變質(zhì)含礫粗粒雜砂巖、變質(zhì)英安質(zhì)晶屑凝灰?guī)r和變質(zhì)長石石英細(xì)砂巖樣品,進(jìn)行了鋯石LA-ICP-MS U-Pb年代學(xué)和巖石地球化學(xué)分析。結(jié)果顯示,2個(gè)變質(zhì)英安質(zhì)晶屑凝灰?guī)r鋯石的加權(quán)平均年齡分別為440.9±1.8Ma(MSWD=0.10)和440.9±1.7Ma(MSWD=0.15),鋯石Th/U比值為0.46~1.59,自形程度較好,發(fā)育有典型的巖漿鋯石振蕩環(huán)帶結(jié)構(gòu),顯示為巖漿成因鋯石的特點(diǎn),表明徐尼烏蘇組的形成時(shí)代為早志留世。變質(zhì)含礫粗粒雜砂巖的碎屑鋯石年齡在452.0±1.3Ma~535.0±1.0Ma之間,最高峰值年齡為490Ma左右;變質(zhì)長石石英細(xì)砂巖碎屑鋯石年齡則在440.1±5.7Ma~3268.9±57.7Ma之間,最小諧和年齡為440.1±5.7Ma,峰值年齡為490Ma左右,另有1.0Ga、1.6Ga、1.8Ga和2.5Ga四個(gè)明顯的峰值年齡。根據(jù)研究區(qū)徐尼烏蘇組巖性組合與結(jié)構(gòu)構(gòu)造,可將該組劃分為3個(gè)不同的沉積旋回。結(jié)合白乃廟地區(qū)徐尼烏蘇組測年結(jié)果、巖石地球化學(xué)特征、原巖建造及區(qū)域巖漿巖資料,白乃廟弧后盆地沉積可劃分為三個(gè)演化階段:早期快速堆積階段(452.3~440.9Ma),形成了一套成熟度較低的粗碎屑巖建造,物源主要來源于白乃廟巖漿弧中的巖漿巖;中期火山噴發(fā)階段(440.9~440.1Ma),以火山沉積作用為主,為火山碎屑巖建造夾有碳酸鹽建造和少量碎屑巖建造,碎屑物質(zhì)主要來源于該時(shí)期的火山活動;晚期穩(wěn)定沉積階段(440.1Ma),形成一套細(xì)碎屑巖建造和碳酸鹽建造,為淺海相穩(wěn)定沉積,此時(shí)物源廣泛,分別來源于華北克拉通基底、興蒙造山帶和白乃廟早古生代火山弧。根據(jù)徐尼烏蘇組的沉積建造和火山建造特征,結(jié)合白乃廟火山弧巖漿活動特征,認(rèn)為徐尼烏蘇組形成于早古生代弧后盆地中,此時(shí)華北板塊北緣屬于安第斯型活動大陸邊緣。
[Abstract]:In this paper, the geochronology and geochemistry of Xunisu formation, protolith formation, metamorphic volcanic rock and metamorphic clastic rock are studied, and the early Paleozoic tectonic evolution in Bainaimiao area is discussed. The typical samples of metamorphic gravel-grained complex sandstone, metamorphic amphitic tuff and metamorphic feldspar quartz fine sandstone in Xunisu formation were collected in this study. The zircon LA-ICP-MS U-Pb geochronology and petrogeochemical analysis were carried out. The results show that the weighted mean zircon ages of the two metamorphic amphitic tuff rocks are 440.9 鹵1.8 Ma (MSWD0. 10) and 440.9 鹵1.7 Ma (MSWD0. 15), respectively. The ratio of zircon to zircon Th/ U is 0. 46- 1. 59. The zircon has a good automorphic degree. There is a typical magmatic zircon oscillatory ring structure, which shows the characteristics of magmatic zircon. It shows that the formation age of Xuniwusu formation is early Silurian. The zircon age of metamorphic coarse grained sandstone is between 452.0 鹵1.3 Ma and 535.0 鹵1.0 Ma, and the highest peak age is about 490 Ma, while that of metamorphic feldspar quartz fine sandstone is between 440.1 鹵5.7 Ma and 3268.9 鹵57.7 Ma, the minimum harmonic age is 440.1 鹵5.7 Ma, and the peak age is about 490 Ma. There are also four distinct peak ages of 1.0Ga1.Ga1.8Ga and 2.5Ga. According to the lithologic assemblage and structural structure of Xunisu formation in the study area, the formation can be divided into three different sedimentary cycles. Combined with the dating results of Xuniwusu formation, petrogeochemical characteristics, original rock formation and regional magmatic rock data in the Bainaimiao area, The sediments of the back arc basin of Bainaimiao can be divided into three stages: the early rapid accumulation stage (452.3N 440.9 Ma), which formed a set of low-maturity coarse clastic rocks, mainly derived from the magmatic rocks in the bainaimiao magmatic arc; The middle stage of volcanic eruption (440.9 ~ 440.1 Ma) is dominated by volcanic sedimentation, which is composed of carbonate formation and a small amount of clastic rock formation in the volcanic clastic rock formation. The clastic material is mainly derived from volcanic activity in this period. In the late stable sedimentary stage (440.1 Ma), a set of fine clastic rock formation and carbonate formation were formed, which are shallow marine facies stable deposits. At this time, their provenances are extensive and are derived from the North China craton basement, the Xingmeng orogenic belt and the early Paleozoic volcanic arc of the Bainaimiao, respectively. According to the sedimentary formation and volcanic formation characteristics of Xunisu formation, combined with the characteristics of bainaimiao volcanic arc magmatic activity, it is considered that the Xuniwusu formation was formed in the early Paleozoic back-arc basin, and the northern margin of the North China plate belongs to the active continental margin of the Andes type.
【作者單位】： 吉林大學(xué)地球科學(xué)學(xué)院;東北師范大學(xué)地理科學(xué)學(xué)院;吉林省地震局;
【基金】：國家自然科學(xué)基金項(xiàng)目(41272223) 中國地質(zhì)調(diào)查局項(xiàng)目(1212011120709、1212011220459、1212011085252)聯(lián)合資助
【分類號】：P534.4;P542

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