摘要
麻坪花岗岩体产于华北克拉通南缘,岩石类型主要为花岗斑岩,具斑状结构,斑晶主要为钾长石和石英。LA-ICPMS锆石U-Pb定年结果表明,岩体的形成时代为1600Ma。所有样品高SiO 2（70.51%-75.69%）、富碱（K2O＋Na2O=7.42%-10.27%,K2O/Na2O〉23）,贫MgO（0.24%-0.58%）、CaO（0.06%-0.12%）、P2O5（0.04%-0.08%）和MnO（0.01%）,以及Eu、Sr和Ti负异常,表明它们在演化过程中经历了钾长石、斜长石、铁钛氧化物等的分离结晶作用。它们高的铝饱和指数（A/CNK〉1.11）,显示强过铝质特征。然而,麻坪花岗斑岩高的Ga/Al比值以及高的锆石饱和温度（870-953℃）,显示典型的A型花岗岩特征。因此,麻坪花岗斑岩为强过铝质A型花岗岩。麻坪花岗斑岩的地球化学特征、锆石Hf同位素组成以及二阶段模式年龄表明其来自太华群高温条件下部分熔融,同时基性岩浆的底侵作用为之提供了相应的热源。麻坪花岗斑岩的产生是裂谷岩浆活动的产物,其形成可能与Columbia超大陆的裂解有关。
The Maping pluton in the southern margin of the North China Craton（ NCC） mainly consists of porphyritic granite.Phenocryst minerals include K-feldspar and quartz. LA-ICP-MS zircon U-Pb dating shows that the pluton was emplaced at 1600 Ma. All rocks are rich in SiO 2（ 70. 51% - 75. 69%） and alkaline（ K2 O ＋ Na2 O = 7. 42% - 10. 27%,K2 O / Na2 O 23）,but poor in MgO（ 0. 24% - 0. 58%）,CaO（ 0. 06% - 0. 12%）,P2O5（ 0. 04% - 0. 08%） and MnO（ 0. 01%） with negative Eu,Sr and Ti anomalies,indicating that they experienced fractional crystallization during magmatic evolution. Their high aluminum saturation index（ A/CNK 1. 11） show an affinity to that of strongly peraluminous granite. However,their high Ga/Al ratios along with high zircon saturation temperatures（ 870 - 953℃）,indicate that the Maping granite porphyry is similar to A-type granite. Combined with their strong peraluminous nature, the Maping granite can be classified as strongly peraluminous A-type granite. Their geochemical signatures,along with zircon Hf isotopic compositions and two-stage model ages of the Maping granite porphyry,suggest that they were dominantly derived from high-temperature partial melting of Taihua Group with the underplating of mafic magmas,which provided heat that triggered partial melting of crust. Integrated with regional data,the generation of the Maping granite porphyry was most likely the products of rifting magmatism that was related to the break-up of the Columbia supercontinent.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第6期1621-1635,共15页
Acta Petrologica Sinica
基金
国家重点基础研究发展计划973项目(2012CB416606)资助
关键词
A型花岗岩
成因
中元古代
华北克拉通南缘
Columbia超大陆
A-type granite
Petrogenesis
Mesoproterozoic
Southern margin of the North China Craton
Columbia supercontinent
