Archean crustal evolution of the northern Tarim craton, NW China: Zircon U-Pb and Hf isotopic constraints
Archean crustal evolution of the northern Tarim craton, NW China: Zircon U-Pb and Hf isotopic constraints
复制标题
DOI：
10.1016/j.precamres.2010.05.001
复制
发表时间：
2010-07
影响因子：
3.8
通讯作者：
X. Long;C. Yuan;M. Sun;Guochun Zhao;W. Xiao;Yujing Wang;Yue-heng Yang;A. Hu
中科院分区：
文献类型：
--
作者：
X. Long;C. Yuan;M. Sun;Guochun Zhao;W. Xiao;Yujing Wang;Yue-heng Yang;A. Hu
塔里木克拉通是中亚地区的主要克拉通之一。克拉通的基底岩石，如TTG片麻岩，主要出露在北方（库鲁克塔格地区）和东部（阿尔金山）。近年来，阿尔金山基底岩石的太古宙年龄只有少数几个可靠的结果。为了揭示塔里木克拉通复杂的历史，对库鲁克塔格地区出露的正片麻岩进行了年代学和地球化学研究。岩石的锆石U-Pb定年结果表明，其原岩形成于新太古代晚期-古元古代早期，其207 Pb/206 Pb加权平均年龄分别为2516±6、2575±13和2460± 3 Ma。晚新太古代正片麻岩具有低Sr/Y（4-19）和低Mg#（35-44），Sr亏损，Nb、Ta、Ti负异常，稀土元素分异强烈（（La/Yb）N=13-62），显示出典型的弧火成岩地球化学特征。早古元古代正片麻岩具有高SiO2、Sr/Y（37-67）和Mg#（46-67）、（La/Yb）N=9-89的稀土分异模式、轻微的Sr富集和Eu正异常等特征，类似于俯冲玄武质板熔体中的高SiO2埃达克岩。晚新太古代TTG具有较低的Hf（t）值（-5 ~+1）和初始Hf成分（0.280987-0.281160），中太古代两阶段模式年龄（TDM 2 =2.9-3.3Ga），表明该区基底岩石的地壳物质最初是从晚古-中太古代亏损地幔中提取的，并在晚新太古代受到改造。其地壳生长历史与华北和扬子板块不同，因而其地壳演化相对较晚。古元古代早期正片麻岩中的锆石具有高的Hf（t）值（+4 ~+10）和年轻的新太古代两阶段模式年龄（2.5-2.7Ga），反映了晚新太古代的一次年轻地壳生长事件。由于在其他两个克拉通中没有同时代的幼年地壳生长记录，我们建议在古元古代早期之前远离其他两个克拉通的北方塔里木克拉通是一个单独的地壳演化。
Tarim craton is one of the major cratons in Central Asia. Basement rocks of the craton, such as TTG gneisses, are dominantly exposed in the northern (Kuluketage area) and the Eastern (Altyn Tagh Mountain). Recent years, only a few reliable Archean ages have been obtained for the basement rocks in the Altyn Tagh Mountain. Geochronological and geochemical studies have been conducted on the orthogneisses exposed in the Kuluketage area in order to unravel complex history of the Tarim craton. Zircon U–Pb dating of the rocks yielded three weighted mean207Pb/206Pb ages of 2516±6, 2575±13 and 2460±3Ma, indicating that their protoliths were formed in the late Neoarchean to early Paleoproterozoic. The late Neoarchean orthogneisses exhibit low Sr/Y ratios (4–19) and Mg#values (35–44), with depleted Sr contents, negative Nb, Ta and Ti anomalies and strongly fractionated REE patterns ((La/Yb)N=13–62), displaying typical geochemical features of arc igneous rocks. In contrast, the early Paleoproterozoic orthogneisses are characterized by high-SiO2contents, Sr/Y ratios (37–67) and Mg#values (46–67), with variably fractionated REE patterns ((La/Yb)N=9–89), slight Sr enrichment and positive Eu anomalies, resembling high-SiO2adakites derived from subducted basaltic slab-melts. The late Neoarchean TTGs have low ɛHf(t) values (–5 to +1) and initial Hf compositions (0.280987–0.281160) with Mesoarchean two-stage model ages (TDM2=2.9–3.3Ga), suggesting that the crustal materials of the basement rocks in this area were initially extracted from a depleted mantle in the late Paleo- to Mesoarchean and were reworked in the late Neoarchean. The history of crustal growth is different from that of the North China and Yangtze cratons and thus implies relatively younger cratonization than the North China and Yangtze cratons. Zircons in the early Paleoproterozoic orthogneisses have high ɛHf(t) values (+4 to +10) and young Neoarchean two-stage model ages (2.5–2.7Ga), revealing a juvenile crustal growth event in the late Neoarchean. Because there is no record of coeval juvenile crustal growth in the other two cratons, we suggest a separate crustal evolution for the northern Tarim craton which was stayed far from the other two cratons before the early Paleoproterozoic.