【摘要】：以往華北克拉通早前寒武紀地質(zhì)的研究主要集中于東、西部陸塊的2.5Ga事件及中部帶的2.2~2.0Ga、1.95~1.8Ga事件的研究,最近通過工作發(fā)現(xiàn)東部陸塊內(nèi)部亦有~2.1Ga、~1.8Ga事件的記錄。我們通過對冀東石門變質(zhì)基性巖墻群進行離子探針鋯石U-Pb測年和地球化學(xué)研究,表明基性巖墻的形成年齡為2162±27Ma,經(jīng)歷了1820±7.8Ma的變質(zhì)作用;其圍巖英云閃長質(zhì)片麻巖形成于2531±14Ma,緊接著經(jīng)歷了2513±15Ma的麻粒巖相變質(zhì),雖與石門基性巖墻共同經(jīng)歷了~1.8Ga變質(zhì)作用,但并沒有新生的該期變質(zhì)鋯石記錄。石門基性巖墻SiO_2含量介于50.38%~51.08%,MgO含量為4.29%~5.81%,具有較低的Mg#值(32~41),屬于拉斑玄武巖類;其輕稀土略為富集,具有弱的負銪異常,富集大離子親石元素(Rb、Ba),虧損高場強元素(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模式年齡與基性巖墻的形成年齡接近,介于2206~2338Ma,推測石門基性巖墻的玄武質(zhì)巖漿來自于虧損地幔的部分熔融并經(jīng)歷了結(jié)晶分異和地殼混染過程,形成于陸內(nèi)裂谷的構(gòu)造背景。本文認為~2.1Ga的巖漿活動為華北陸塊在新太古代末克拉通化后,經(jīng)歷的一次強烈的伸展事件,可能導(dǎo)致了原有基底發(fā)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 鹵27 Ma and experienced 1820 鹵7.8Ma metamorphism, and its surrounding rock Yingyun diorite gneiss was formed at 2531 鹵14 Ma, followed by gneiss metamorphism of 2513 鹵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 鹵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，

本文編號：2501465