Petrology and geochemistry of the Shuiquangou syenitic complex, northern margin of the North China Craton
Petrology and geochemistry of the Shuiquangou syenitic complex, northern margin of the North China Craton
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DOI：
10.1144/0016-764903-144
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发表时间：
2005-01
影响因子：
2.7
通讯作者：
Neng Jiang
中科院分区：
文献类型：
--
作者：
Neng Jiang
水泉沟杂岩体是华北陆块北方缘沿着分布的一个重要正长岩体，其中赋存有多个金矿床。尽管复杂的结构和模式矿物学，矿物成分，全岩化学以及放射性同位素组成方面的异质性表现出良好的约束岩浆演化趋势。全岩主量元素和稀土元素的变化趋势与以单斜辉石、角闪石和副矿物为主的分离结晶作用基本一致。初始Nd-Sr同位素组成表明，母岩浆的复杂最终来自富集地幔具有相对较高的初始87 Sr/86 Sr比值和负的Nd-Nd值。地幔源区的富集可能继承于华北陆下较古老的岩石圈地幔。Sr同位素数据表明，Rb-Sr系统受到后期蚀变过程的干扰，而Nd同位素基本上不受影响，并表现出广泛的趋势与同时分离结晶和国家岩石同化（AFC）。定量模拟表明，一个非常高的整体分配系数的Nd和低同化结晶的比率，需要产生所观察到的Nd同位素的演变趋势。
The Palaeozoic Shuiquangou complex is a major syenitic intrusion along the northern margin of the North China Craton that hosts a number of gold deposits. Despite the heterogeneity of the complex in terms of texture and modal mineralogy, mineral compositions, whole-rock chemistry as well as radiogenic isotope compositions show a well-constrained magmatic evolutionary trend. The whole-rock major element and REE trends are broadly consistent with fractional crystallization dominated by clinopyroxene, amphibole and accessory minerals. Initial Nd–Sr isotopic compositions suggest that the parent magmas to the complex were ultimately derived from an enriched mantle with relatively high initial 87Sr/86Sr ratios and negative ϵNd values. The enrichment of the mantle source was probably inherited from an older lithospheric mantle beneath the North China Craton. Sr isotopic data indicate that the Rb–Sr system was disturbed by later alteration processes, whereas Nd isotopes are essentially unaffected and exhibit a broad trend consistent with simultaneous fractional crystallization and country-rock assimilation (AFC). Quantitative modelling indicates that a very high bulk distribution coefficient for Nd and low ratios of assimilation to crystallization are needed to produce the observed Nd isotope evolutionary trend.