埃达克岩(adakite)的地球化学特征及其构造意义

收稿日期: 1999-10-14

修回日期: 1999-12-27

刊出日期: 2000-04-28

ADAKITE: GEOCHEMICAL CHARACTERISTICS AND TECTONIC SIGNIFICANCES

- 1.
  Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029
- 2. Department of Geology, Northwest University, Xi’an 710069

Received Date: 14 October 1999

Revised Date: 27 December 1999

Publish Date: 28 April 2000

摘要: 埃达克岩(adakite)是一种特殊的岛弧安山岩、英安岩、流纹岩(以英安岩最常见)或英云闪长岩和奥长花岗岩。其地球化学特征表现为SiO256%,高铝(Al2O315%),MgO常小于3%(很少超过6%),富钠,一般Na2O>K2O,Na2O含量一般在4%±,K2O含量大多在1-2%±,Y和Yb含量较低(分别为18μg/g和1.9μg/g),Sr含量较高(>400μg/g),具正Eu、正Sr异常。87Sr/86Sr比值常常小于0.704。埃达克岩是由年轻的(<25Ma,因此是热的)俯冲板片以小角度俯冲、并在75-85km深处(相当于角闪岩-榴辉岩过渡带)发生板片部分深融作用形成的。它是板片俯冲作用开始的一种标志。
- 埃达克岩 /
- 地球化学 /
- 构造意义
Abstract: Adakite is a special kind of islan d-arc andesite, dacite and rhyolite (mainly dacite) or tonalite and trondhjemite. The main geochemical characteristics of adakite are SiO2 56%, high Al content (Al2O3 15%), MgO2O>K2O (Na2O-4%±; K2O-1-2%±), very low Y and Yb content (18μg/g and 1.9μg/g, respectively),relatively high Sr content (>400μg/g),and positive Eu and Sr analomy, and 87Sr/86Sr<0.704. Adakite is generated by young (<25Ma, thus hot) subducted slab dipping continuously at a shallow angle and partial melting at the depth of 75-85 km (amphibolite-eclogite transition zone). Adakite may represent the start of subduction of the oceanic crust.
- Adakite /
- Geochemistry /
- Tectonic significances

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