鲁西地区侏罗系坊子组的物源:对郯庐断裂带构造属性的制约
首发时间:2013-06-13
摘要:郯庐断裂带是中国东部一条重要的断裂带,在华北克拉通东部中生代构造演化中扮演着重要角色。本文报道了鲁西地区侏罗系坊子组中碎屑锆石LA-ICP-MS U-Pb定年和原位Hf同位素的分析结果,对碎屑沉积物的沉积时代和物源属性以及郯庐断裂带的构造属性进行了制约。周村和蒙阴盆地坊子组中碎屑锆石的U-Pb定年结果分别给出了8个年龄峰(2494 Ma、1844 Ma、927 Ma、465 Ma、323 Ma、273 Ma、223 Ma和159 Ma)和11个年龄峰(2498 Ma、1847 Ma、932 Ma、808 Ma、540 Ma、431 Ma、315 Ma、282 Ma、227 Ma和175 Ma)。上述定年结果结合碎屑锆石Hf同位素组成表明,周村和蒙阴盆地坊子组的沉积下限分别为159 Ma和175 Ma;沉积岩中2.5-1.85 Ga的锆石主要来源于华北克拉通前寒武纪基底岩石、新元古代 (939-804 Ma) 和部分三叠纪岩浆锆石主要来源于苏鲁地体、323-273 Ma锆石年龄记录了华北克拉通北缘古生代的岩浆事件、175-159 Ma锆石则与华北克拉通东部同时期的火成岩相对应。鲁西侏罗系坊子组沉积物中苏鲁造山带物源的存在,暗示郯庐断裂带在中侏罗世(~ 175 Ma)以后没有发生巨大的左行平移。
关键词: 岩石学 碎屑锆石 坊子组 新元古代 郯庐断裂带 鲁西
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Provenance of the Jurassic Fangzi Formation in the western Shandong Province: Constraints on the nature of the Tan-Lu Fault Zone
Abstract:The Tan-Lu Fault Zone (TLFZ), a major fault in eastern China, played a key role in the Mesozoic tectonic evolution of the eastern margin of North China Craton (NCC). In present study, with the aim of constraining the depositional ages and provenances of these strata as well as the tectonic nature of the TLFZ, it is reported that the results of LA-ICP-MS U-Pb dating and in situ Hf isotope analysis of detrital zircons from the Jurassic Fangzi Formation in western Shandong. U-Pb dating for detrital zircons from the Fangzi Formation in the Zhoucun and Mengyin basins yield 8 main groups (2494 Ma, 1844 Ma, 927 Ma, 465 Ma, 323 Ma, 273 Ma, 223 Ma, and 159 Ma) and 11 main groups (2498 Ma, 1847 Ma, 932 Ma, 808 Ma, 540 Ma, 431 Ma, 315 Ma, 282 Ma, 227 Ma, and 175 Ma) of age population, respectively. U-Pb dating results and Hf isotopic data of the detrital zircons indicate that: (1) Fangzi Formation deposited after the Middle-Late Jurassic; (2) the detrital zircon grains of 2.5-1.85 Ga were sourced from the ancient Precambrian basement rocks of the NCC; (3) the Neoproterozoic (932-808 Ma) and part of the Late Triassic magmatic zircon grains were sourced from the Su-Lu terrane; (4) the detrital zircon ages of 323-273 Ma could be linked to the Palaeozoic magmatisms in the northern margin of the NCC; (5) Middle-Late Jurassic (175-159 Ma) detrital zircons were sourced from the Mesozoic igneous rocks in the eastern NCC. The Neoproterozoic zircons and some of the Triassic zircons from the Mesozoic Fangzi Formation in western Shandong were sourced from the Su-Lu terrane, indicating that the large-scale sinistral strike-slip movement along the TLFZ did not happen after the Middle Jurassic (ca. 175 Ma).
Keywords: Petrology;detrital zircons;Fangzi Formation;Neoproterozoic;Tan-Lu Fault Zone;western Shandong
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鲁西地区侏罗系坊子组的物源:对郯庐断裂带构造属性的制约
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