本文選題：揚子板塊 + 大洪山　； 參考：《地質學報》2017年11期

【摘要】：出露于揚子板塊北緣大洪山地區(qū)的花山群自下而上由一套以礫巖為主的粗碎屑沉積和一套以砂質板巖為主的細碎屑沉積組成,伴隨有拉斑玄武質巖漿活動�；ㄉ饺赫w變質程度不高,形成構造環(huán)境復雜,對其構造屬性及其與區(qū)內所謂的花山"蛇綠混雜巖"的時空關系一直存有爭議,它們對新元古代Rodinia超大陸在揚子板塊北緣的匯聚-裂解響應具有重要的制約意義。筆者在花山群六房咀組下部細砂巖中采集玄武質熔結凝灰?guī)r夾層樣品1件,碎屑巖樣品2件,在上覆地層南華系蓮沱組采集碎屑巖樣品1件;對玄武質熔結凝灰?guī)r進行了SHRIMP鋯石U-Pb同位素測年,對碎屑巖樣品進行了LA-MC-ICPMS鋯石U-Pb同位素測年。獲得玄武質熔結凝灰?guī)r鋯石U-Pb年齡814.7±7.3 Ma;花山群的碎屑鋯石U-Pb年齡譜存在三個明顯的峰值:~900 Ma、~2050Ma和~2650 Ma,最顯著峰值為~2650 Ma,上覆蓮沱組碎屑巖年齡譜的三個峰值為:~900 Ma、~2050 Ma和~2500 Ma,最顯著峰值為~2050Ma,三件碎屑巖樣品均與揚子板塊的碎屑鋯石U-Pb年齡統(tǒng)計峰值一致�；ㄉ饺旱乃樾荚磪^(qū)可能包括下伏中元古代打鼓石群、太古宙魚洞子雜巖以及崆嶺雜巖。結合前人年代學研究資料和區(qū)域構造成果分析,花山群沉積時代應為820~815Ma,形成于伸展構造背景,與花山"蛇綠混雜巖"不是同期同構造背景的產(chǎn)物;花山"蛇綠混雜巖"與花山群沉積建造依次反映了揚子板塊北緣由擠壓構造背景向伸展構造背景的轉換過程�；ㄉ饺褐械乃樾汲练e物與基性火山巖、火山碎屑巖屬于裂解背景下形成的同時代沉積-火山建造;結合前人在揚子板塊周緣發(fā)現(xiàn)的大量約820 Ma酸性—基性巖漿活動記錄以及同時代(820~800 Ma)的沉積地層,推測花山群形成于Rodinia超大陸裂解背景之下,與超級地幔柱活動有關。
[Abstract]:The Huashan Group, which is exposed to the northern margin of the Yangtze plate, consists of a set of coarse clastic deposits dominated by conglomerates and a set of fine clastic deposits dominated by sandy slate from the bottom to the top, accompanied by Black Tortoise magmatic activity. The whole metamorphic degree of Huashan Group is not high, and the tectonic environment is complex. The tectonic attributes and their spatiotemporal relationship with the so-called "ophiolite melange" in Huashan region have always been disputed. They are of great significance to the converging-pyrolysis response of the Neoproterozoic Rodinia supercontinent in the northern margin of the Yangtze plate. In this paper, 1 sample of Black Tortoise melt tuff intercalation, 2 samples of clastic rock and 1 sample of clastic rock are collected in the fine sandstone of the lower part of Liufangzui formation in Huashan Group, and in the Liantuo formation of the South China Series in the overlying strata. SHRIMP zircon U-Pb isotope dating and LA-MC-ICPMS zircon U-Pb isotope dating of clastic rock samples were carried out for Black Tortoise melt-formed tuff. The zircon U-Pb age of Black Tortoise melt-formed tuff is 814.7 鹵7.3Ma.The U-Pb age spectrum of clastic zircon in Huashan group has three distinct peak values of 2050Ma and 2650Ma, with the most significant peak value of 2650 Ma, and the three peaks of the clastic age spectrum of the Shangwuliantuo formation is: 0900 Ma2050 2050Ma. the most significant peak value is 2650Ma. the three peaks of the clastic age spectrum of the Shangwuliantuo formation are: 900Ma2050. Ma and Xian2500 Ma.The most significant peak value is 2050Ma.The three samples of clastic rock are in agreement with the U-Pb age peak of the Yangtze plate's detrital zircon. The detrital sources of the Huashan Group may include the Lower Proterozoic Dagu Group Archean Yudong Zi complex and the Kongling complex. Based on previous chronological data and analysis of regional tectonic achievements, the sedimentary age of Huashan Group should be 820 ~ 815 Ma.It was formed in the extensional tectonic setting and was not the product of the same tectonic setting as the Huashan "ophiolite". The "ophiolite melange" in Huashan and the sedimentary formation of the Huashan Group in turn reflect the transformation process from the compressional tectonic setting to the extensional tectonic setting of the northern Yangtze plate. The clastic sediments and basic volcanic rocks in the Huashan Group belong to the contemporaneous sedimentation-volcanic formation formed in the pyrolysis background. Combined with a large number of acid-basic magma activity records of 820 Ma and sedimentary strata of 820 Ma and 800 Ma found by predecessors around the Yangtze plate, it is inferred that the Huashan Group was formed in the Rodinia supercontinental pyrolysis background, which is related to the super-mantle plume activity.
【作者單位】： 中國地質調查局天津地質調查中心;湖北省區(qū)域地質礦產(chǎn)調查所;
【基金】：中國地質調查局項目(編號DD20160343-06) 湖北省國土資源廳項目“神農架群巖石地層序列和年代格架研究”聯(lián)合資助成果
【分類號】：P542

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