赞皇地区～2.5Ga A型花岗岩的成因及构造背景:以黄岔岩体为例

发布时间：2018-05-17 21:46

  本文选题：黄岔岩体 + 赞皇杂岩　； 参考：《岩石学报》2017年09期

【摘要】：位于华北克拉通中部的赞皇杂岩中保留有丰富的新太古代-古元古代岩石记录,是探究华北克拉通早期演化的重要地区之一。其中新太古代晚期TTG片麻岩和花岗岩的成因研究是探讨赞皇杂岩构造演化过程的关键。本文选择出露于河北省邢台市西部山区的黄岔花岗岩体进行研究。该岩体呈不规则的岩株产出,与周围地层主要呈构造接触关系,局部侵入于官都群石英岩中。岩体主要由片麻状、似斑状二长花岗岩组成,边缘相偶见细粒片麻岩包体,斑晶为长石和少量石英。LA-ICP-MS岩浆锆石的~(207)Pb/~(206)Pb加权平均年龄为2488±6Ma,代表岩体的形成时代。由于黄岔岩体侵入于官都群,根据该花岗岩的时代可以限定官都群地层时代为太古代,而非古元古代。但官都群与赞皇群的关系还需要进一步研究。黄岔岩体具有高硅(Si O2=72.64%~74.16%)、富钾(K_2O=3.53%~6.15%)、富碱(ALK=7.59%~9.07%)及铁(Fe_2O_3T=1.84%~3.03%),贫钙(CaO=0.67%~1.67%)、低钛(TiO_2=0.18%~0.28%)、低镁(MgO=0.31%~0.46%)的特征。岩石的稀土总量较高(ΣREE=364.2×10~(-6)~661.1×10~(-6)),轻重稀土元素分异较强烈((La/Yb)_N=18.7~29.8),并具有明显的负Eu异常(Eu/Eu*=0.23~0.33)。微量元素中,富Zr、Zn、Nb、Ga、Y,而贫Sr、V、Cr、Co、Ni等元素,Rb/Sr比值较高,介于0.73~2.72之间,平均1.96。岩石Ga/Al值(2.75×10-4~3.11×10-4)高,全岩Zr饱和温度为826~877℃,具有A型花岗岩特征。黄岔岩体锆石εHf(t)为0.96~6.2,单阶段和两阶段Hf模式年龄分别为2552~2746Ma和2576~2826Ma。黄岔岩体具有造山后A型花岗岩的特征,为2.7~2.5Ga的新太古代TTG片麻岩在造山后地壳拉张减薄初期的构造背景下部分熔融所形成。~2.5Ga的碱性花岗岩在华北不同地区分布,并形成于伸展的构造背景。该期碱性花岗岩的出现,标志华北克拉通在太古宙末期已经初步形成稳定的克拉通。
[Abstract]:The Zanhuang complex located in the central part of North China Craton contains abundant records of Neo-Archaeo-Paleoproterozoic rocks and is one of the important areas to explore the early evolution of North China Craton. The genetic study of TTG gneiss and granite in late NeoArchean is the key to study the tectonic evolution of Zanhuang complex. In this paper, Huangcha granite body exposed in western mountainous area of Xingtai City, Hebei Province is selected for study. The rock body is formed irregularly, mainly in tectonic contact with the surrounding strata, and partly intruded into the quartz rock of the Guandu group. The rock mass is mainly composed of granitic, porphyry monzonitic granites, the marginal facies of which are occasionally fine-grained gneiss inclusions, and the porphyry rocks are feldspar and a small amount of quartz .LA-ICP-MS magmatic zircon. The weighted average age of 2488 卤6Ma. Because the Huangcha rock intruded into the Guandu Group, the age of the granite can be defined as Archean, not Gu Yuan. However, the relationship between the official capital group and the Zanhuang group needs further study. The Huangcha rock mass has the characteristics of high Si-Si O _ 2 + 72.64 / 74.16, K _ 2O _ 3 ~ 3.53, K _ 2O _ 3, K _ 2O _ 3, alkali-rich ALK _ (7.59) and 9.07) and Fe2O3T ~ (1.84) ~ 3.03, Ca _ 2O _ (0.67) ~ (1.67), Ca _ 2O _ (0.67) ~ (1.67), Ti _ 2O _ 2O _ (2 / 0.18) 0.28T and mg _ 2O _ (0.31) ~ 0.46). The total amount of rare earth elements in rocks is relatively high (危 REE=364.2 脳 10 ~ (10) ~ (-6) ~ 661.1 脳 10 ~ (-1) ~ (10) ~ (-6) ~ (6), and the difference of heavy and heavy rare earth elements is stronger than that of La- / Yb ~ (2 +), and there is obvious negative EU / EU / EU / EU ~ (0.23) ~ (0.33). In the trace elements, Zirconium zinctorium (ZZN) and NbGA-GaOY are rich, but the ratio of Rb- / Sr is higher, ranging from 0.73 to 2.72, with an average of 1.96, which is poor in SrVV, Cr-CoC, Ni and other elements. The Ga/Al value of rock is 2.75 脳 10-4 (3.11 脳 10-4) and the saturation temperature of Zr in the whole rock is 826 ~ 877 鈩，

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