摘要
笋洞花岗岩体是粤北贵东复式花岗岩体的一个重要组成部分。锆石U-Pb年龄为189.1±0.7Ma,是燕山早期岩浆活动产物。该岩体的主要元素显示富硅、富碱、强过铝质和低 CaO/Na_2O比值等特征;微量元素方面,富集Rb,Th,U,Ce,Sm,Y,亏损 Ba,Sr,P,Ti;LREE轻微富集(LREE/HREE=6.6～8.8,(La/Yb)_N=6.44～10.74),Eu亏损明显(δEu=0.14～0.31);它具有低的ε_(Nd)(t)(-11.4～-9.3),高的δ^(18)O(10.2～12.7‰)、(^(87)Sr/^(86)Sr);(0.72949～0.74923)、^(206)Pb/^(204)Pb(18.180～18.488)、^(207)Pb/^(204)Pb(15.655～15.661)和古老的Nd模式年龄(1762～1933Ma)。上述这些特征表明,笋洞岩体属于典型的壳源型花岗岩,是在地壳伸展-减薄的构造背景下,通过以泥质成分为主的古-中元古代变质沉积岩部分熔融的方式形成。
The Sundong granites occur in the southeastern part of the Guidong granite composite which hosts several uranium deposits in northern Guangdong province. Zircon U-Pb dating of the granite yields an age of 189.1 0.7Ma, which suggests that this granite intruded during the early Yanshanian period. This granite is characterized by high silica and alkali, strongly peraluminous and low CaO/Na2O ratio. It is enriched in Rb, Th, U, Ce and Y, and depleted in Ba, Sr, P and Ti. This granite also shows strong LREE enrichment with LREE/HREE ratios of 6.6 similar to 8.8 and (La/Yb)(N) ratios of 6.44 similar to 10.74, and strong negative Eu anomaly with deltaEu values of 0.14 similar to 0.31. Isotope geochemical study reveals low initial epsilon(Nd) (t) values (-11.4 similar to -9.3), high delta(18)O values (10.2parts per thousand similar to 12.7parts per thousand), high initial Sr-87/Sr-86 ratios (0.72949 similar to 0.74923) homogeneous Pb isotope ratios (Pb-206/Pb-204 = 18.180 similar to 18.488, Pb-207/Pb-204 = 15.655 similar to 15.661), and old Nd model ages (1762 similar to 1933Ma) for the granite. All these features suggest that the Sundong granite is a typical crust-derived granite. The granitic magma may have been derived from partial melting of Paleoproterozoic-Mesoproterozoic meta-sedimentary rocks in a crustal extension-thinning tectonic environment.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2004年第3期413-424,共12页
Acta Petrologica Sinica
基金
国家自然科学基金(40132010)
创新群体项目(40221301)
973项目(G1999043211)研究成果之一
关键词
强过铝花岗岩
锆石U-PB定年
元素和同位素地球化学
粤北笋洞岩体
strongly peraluminous
zircon U-pb dating
elemental and isotopic geoehemistry
Sundong granite
northern Guangdong province
