胶东郭家岭岩体固结冷却轨迹与隆升剥蚀

Consolidation and cooling paths of the Guojialing granodiorites in Jiaodong Peninsula:Implication for crustal uplift and exhumation

胶东郭家岭岩体位于华北克拉通东南缘,其详细的冷却固结条件缺乏系统研究,而对岩体形成与金矿之间的关系也存在争议。本文利用岩浆锆饱和温度计、角闪石全铝压力计、角闪石-斜长石温度计、角闪石-黑云母温压计、二长石温度计,结合已有的锆石U-Pb年龄和角闪石、黑云母40Ar-39Ar同位素年龄,探讨郭家岭岩体的冷却固结史及其隆升机制。花岗岩QAb-Or标准矿物共结压力图解、角闪石全铝压力计及角闪石-黑云母压力计均得到岩体就位压力约4~5kbar。锆饱和温度计、角闪石-斜长石温度计、角闪石-黑云母温度计、二长石温度计所获得温度分别为726~800℃、657~717℃、650~700℃、570~580℃,结合角闪石、黑云母的40Ar-39Ar封闭温度确定了郭家岭岩体最有可能的冷却轨迹。郭家岭岩体（130~126Ma）侵位深度约13±1.6km,侵入郭家岭岩体的艾山岩体（116±2Ma）侵位压力在1kbar左右,对应深度约2.7km,表明郭家岭岩体在约10Myr内,隆升剥蚀量达10km左右。这种快速剥蚀的机制可能与华北东部中生代岩石圈减薄导致的地壳浅部隆升有关。

The Guojialing granodiorites are located in the Jiaodong Peninsula,southeastern margin of the North China Craton. In order to shed light on crustal uplift and exhumation,this paper provides detailed study on its consolidation and cooling conditions using the method of mineral thermal-barometers,intergrating with mineral isotopic data. As a result,the Guojialing granodiorites were approximately solidified at pressure of 4 - 5kbar in normalized Q-Ab-Or diagram,highly consistent with those calculated by the barometers of aluminum in amphibole and amphibole-biotite. Whereas,temperatures calculated by the methods of zircon saturation in magmas（ T Zr）,amphibole-plagioclase,amphibole-biotite and two-feldspar thermometers vary in range of 726 ~ 800℃,657 ~ 717℃,650 ~ 700℃ and 570 ~ 580℃,respectively. Taking into account isotopic argon closed temperature of amphibole and biotite,we give possible cooling paths for the Guojialing granodiorites. The emplacing depth of the Guojialing granodiorites（ U-Pb age of 130 ± 2Ma） is estimated to be of 13 ± 1. 6km and the Aishan granite（ U-Pb age of 116 ± 2Ma） intruding the Guojialing granodiorites was estimated to be of ~ 2. 7km,suggesting that the Guojialing granodiorites were exhumed approximately up to shallow crust for 10 km in a short time of10 Myr. The exhumation mechanism is linked to lithosphheric thinning which led large-scale crustal uplift,stretch and detachment in eastern China.