冀东古元古代基性岩墙群的年龄及地球化学:～2.1Ga伸展及～1.8Ga变质
发布时间：2019-06-18 11:47
【摘要】：以往华北克拉通早前寒武纪地质的研究主要集中于东、西部陆块的2.5Ga事件及中部带的2.2~2.0Ga、1.95~1.8Ga事件的研究,最近通过工作发现东部陆块内部亦有~2.1Ga、~1.8Ga事件的记录。我们通过对冀东石门变质基性岩墙群进行离子探针锆石U-Pb测年和地球化学研究,表明基性岩墙的形成年龄为2162±27Ma,经历了1820±7.8Ma的变质作用;其围岩英云闪长质片麻岩形成于2531±14Ma,紧接着经历了2513±15Ma的麻粒岩相变质,虽与石门基性岩墙共同经历了~1.8Ga变质作用,但并没有新生的该期变质锆石记录。石门基性岩墙SiO_2含量介于50.38%~51.08%,MgO含量为4.29%~5.81%,具有较低的Mg#值(32~41),属于拉斑玄武岩类;其轻稀土略为富集,具有弱的负铕异常,富集大离子亲石元素(Rb、Ba),亏损高场强元素(Nb、Ta、Ti),具有低正的εNd(t)值(1.47)和正的εHf(t)值(1.88~8.80),其Hf模式年龄与基性岩墙的形成年龄接近,介于2206~2338Ma,推测石门基性岩墙的玄武质岩浆来自于亏损地幔的部分熔融并经历了结晶分异和地壳混染过程,形成于陆内裂谷的构造背景。本文认为~2.1Ga的岩浆活动为华北陆块在新太古代末克拉通化后,经历的一次强烈的伸展事件,可能导致了原有基底发生了裂解。
[Abstract]:In the past, the study of early Precambrian geology in the North China craton mainly focused on the 2.5Ga event in the eastern and western continental blocks and the 2.22.0Ga1.95 1.8GA events in the central belt. Recently, it was found that there were also ~ 2.1Gaand 1.8GA events in the eastern continental block. Based on the ion probe zircon U-Pb dating and geochemistry of Shimen metaphorical basic rock wall group in eastern Hebei Province, it is shown that the basic rock wall was formed at 2162 卤27 Ma and experienced 1820 卤7.8Ma metamorphism, and its surrounding rock Yingyun diorite gneiss was formed at 2531 卤14 Ma, followed by gneiss metamorphism of 2513 卤15Ma. Although it has experienced ~ 1.8Ga metamorphism with Shimen basic rock wall, there is no new metamorphism zircon record in this period. The SiO_2 content of Shimen basic rock wall is between 50.38% and 51.08%, and the Mg# content is 4.29% 5.81%. It has a lower Mg# value (32 卤41) and belongs to the type of lamellar basalt. The light rare earth elements are slightly enriched, with weak negative europium anomalies, enriched in large ion lithophile elements (Rb,Ba), deficient in high field strength elements (Nb,Ta,Ti), with low positive 蔚 Nd (t) values (1.47) and positive 蔚 Hf (t) values (1.88 鈮，
本文编号：2501465
[Abstract]:In the past, the study of early Precambrian geology in the North China craton mainly focused on the 2.5Ga event in the eastern and western continental blocks and the 2.22.0Ga1.95 1.8GA events in the central belt. Recently, it was found that there were also ~ 2.1Gaand 1.8GA events in the eastern continental block. Based on the ion probe zircon U-Pb dating and geochemistry of Shimen metaphorical basic rock wall group in eastern Hebei Province, it is shown that the basic rock wall was formed at 2162 卤27 Ma and experienced 1820 卤7.8Ma metamorphism, and its surrounding rock Yingyun diorite gneiss was formed at 2531 卤14 Ma, followed by gneiss metamorphism of 2513 卤15Ma. Although it has experienced ~ 1.8Ga metamorphism with Shimen basic rock wall, there is no new metamorphism zircon record in this period. The SiO_2 content of Shimen basic rock wall is between 50.38% and 51.08%, and the Mg# content is 4.29% 5.81%. It has a lower Mg# value (32 卤41) and belongs to the type of lamellar basalt. The light rare earth elements are slightly enriched, with weak negative europium anomalies, enriched in large ion lithophile elements (Rb,Ba), deficient in high field strength elements (Nb,Ta,Ti), with low positive 蔚 Nd (t) values (1.47) and positive 蔚 Hf (t) values (1.88 鈮，
本文编号：2501465
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