| 华北克拉通东部显生宙地幔演化 |
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| 引用本文： | LU Feng-xiang,郑建平,张瑞生,陈美华.华北克拉通东部显生宙地幔演化[J].地学前缘,2005,12(1):61-67. |
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| 作者姓名： | LU Feng-xiang 郑建平 张瑞生 陈美华 |
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| 作者单位： | 中国地质大学,地球科学学院,湖北,武汉,430074;中国地质大学,地球科学学院,湖北,武汉,430074;中国地质大学,地球科学学院,湖北,武汉,430074;中国地质大学,地球科学学院,湖北,武汉,430074 |
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| 基金项目： | 高等学校博士学科点专项科研项目;国土资源部国际合作与科技司研究项目 |
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| 摘 要： | 华北克拉通东部显生宙以来的地幔可以划分为3种类型:克拉通型地幔,大陆活动带型地幔和大陆裂谷型地幔。1 700 Ma—古生代末,地幔属于克拉通型:ε(Nd,t)值高于-5,为弱富集型;层圈相互作用以幔源的熔体和/或流体与古老的岩石圈地幔的作用为主,但规模较小,范围局部。100 Ma以前的中生代地幔属于“大陆活动带型”:ε(Nd,t)值低,在-5以下,为富集型;地幔中含有地壳的组分,层圈相互作用以下地壳与弱化的岩石圈地幔之间的作用为主;发生的时间为190~100 Ma,高峰期在130 Ma左右;发生的部位邻近莫霍面,导源的岩浆多为钙碱性系列,部位浅,活动范围广泛。100 Ma至新生代,地幔属于“大陆裂谷型”:为亏损型的软流圈地幔,ε(Nd,t)值高,几乎均为正值。层圈相互作用转变为软流圈岩石圈地幔之间的作用,转变的时间具有约40 Ma的过渡时期,前锋开始于100~109 Ma,导源的岩浆大致沿NWW和NEE向的大型断裂带分布。进一步证实了软流圈地幔上隆的不均匀性和主动性。
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| 关 键 词： | 克拉通型地幔 大陆活动带型地幔 大陆裂谷型地幔 弱化的岩石圈地幔 |
| 文章编号： | 1005-2321(2005)01-0067-07 |
| 修稿时间： | 2005年2月20日 |
Phanerozoic mantle secular evolution beneath the eastern North China craton |
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| LU Feng-xiang,ZHENG Jian-ping,ZHANG Rui-sheng,CHEN Mei-hua.Phanerozoic mantle secular evolution beneath the eastern North China craton[J].Earth Science Frontiers,2005,12(1):61-67. |
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| Authors: | LU Feng-xiang ZHENG Jian-ping ZHANG Rui-sheng CHEN Mei-hua |
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| Abstract: | Three mantle types of lithospheric mantle can be recognized in eastern North China craton. They are:1 craton type; 2 continental mobile belt type; and 3 continental rifting type. From 1 700 Ma to the end of the Palaeozoic, the lithospheric mantle in the study area is of the craton type with less enrichment and (ε(Nd,t)>-5.) During this time, the asthenospheric mantle-derived silicic / carbonatitic melt and fluids interacted with old refractory lithospheric mantle. In the Mesozoic (190～100 Ma), the lithospheric mantle experienced a vast secular evolution and changed into a continental mobile belt type with lower ε(Nd,t)from -5 to -18. The available data of basic and intermediate-basic volcanic rocks show that the mantle sources contained lower crust components obviously. The main interaction was that of a delaminated continental lower crust with a weakening lithospheric mantle.As a result, the depth of magma sources was confined to near the Moho. Almost all magma types during this time were of calc-alkaline affinity,with depleted HFSE. These rocks are common in study area with an emplacement peak time at about 130 Ma . Considerable thinning of the lithosphere resulted in the doming and uplift from 100 Ma to the Cenozoic. This led to another secular evolution. The mantle was of the continental rifting type with OIB～MORB-like Sr-Nd isotopic signatures and different from Palaeozoic and Mesozoic mantle. The (ε(Nd,t)>0) and changed progressively from OIB to near MORB with the decreasing age. The transition of deep-seated interaction of crust-mantle to L-A interaction lasted approximate 40 Ma beginning at 107～100 Ma. Volcanic rocks are tholeiitics and alkaline basalts. These volcanic rocks are distributed along NWW- and NEE-trending fault, which shows that the uplifting asthenosphere was extended during that time. It might demonstrate the heterogeneity and activeness of the asthenosphere uplifting. |
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| Keywords: | craton type mantle continental mobile belt mantle continental rifting mantle weakening lithospheric mantle |
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