摘要
中国东南部广泛发育中生代A型花岗岩,按其空间展布,可区分为东南沿海和南岭内陆两个岩带.东南沿海A型花岗岩主要形成于晚白垩世(92～103 Ma),时间跨度不大,而南岭内陆A型花岗岩起始时间早,延续时间长(186～124 Ma),自早侏罗世至早白垩世均有发育.东南沿海A型花岗岩可区分为过碱性和铝质两种类型,但南岭内陆A型花岗岩基本均属铝质类型.与南岭内陆A型花岗岩相比,东南沿海A型花岗岩相对富SiO2,富Na2O,而K2O,Rb,Sr,Ba含量及FeO*/(FeO*+MgO)比值则相对偏低.Nd同位素示踪指示两带A型花岗岩均为壳幔混熔岩浆经高度分异演化结晶的产物,但不同地区A型花岗岩因区域引张程度不同,导致幔壳物质混熔比例存在差异.通过对两带A型花岗岩共生岩石组合及产出构造背景的综合分析,认为东南沿海A型花岗岩形成于与古太平洋板块西向俯冲有关的弧后伸展引张环境,而南岭内陆A型花岗岩的产出则主要受板内裂谷环境控制,可能与古特提斯及古太平洋构造域的联合制约有关.
The Mesozoic A-type granites are widely developed in southeastern China. Spatially, they can be further distinguished into the coastal area zone and the Nanling inland area zone. A-type granites in the coastal area zone were formed mainly in Late Cretaceous （92 - 103 Ma）, while those in the Nanling inland area zone were generated initially in Early Jurassic and lasted till Early Cretaceous （ 186 - 124 Ma）, thus has a long time duration for their formation. Lithologically, A-type granites in the coastal area zone can be further divided into peralkaline and aluminous s ps, while those in the Nanling inland area zone are predominantly of aluminous subgroup. Compared with the A-type granites in the Nanling inland area zone, those in the coastal area zone have more enriched SiO2, Na20 contents, and lower K20, Rb, Sr, Ba concentrations and FeO＊/（FeO＊ ＋MgO） ratios. Nd, Sr isotope tracing indicates that A-type granites in both zones were crystallized from highly evolved magmas, which were originally generated by mixing of crustal materials with variable amounts of mantle components due to different extension degrees in different regions. Integrated investigations on their rock associations and tectonic settings suggest that Atype granites in the coastal area zone were formed in a back-arc extension environment that related to the westward subduction of the Palaeo-Pacific plate beneath the Eurasia plate, while those in the Nanling inland area zone were generated mainly under a within-plate rift setting, which might be jointly constrained by the Tethyan and the Paleopacific tectonic dynamic systems.
出处
《高校地质学报》
CAS
CSCD
北大核心
2005年第3期404-414,共11页
Geological Journal of China Universities
基金
教育部新世纪优秀人才支持计划
国家自然科学基金项目(40132010
40221301
40272036)资助
关键词
A型花岗岩
地球化学
中生代
中国东南沿海及南岭内陆
A-type granites
geochemistry
Mesozoic
the coastal and the Nanling inland areas of SE China
