摘要
湘南荷花坪地区发育一系列燕山期花岗斑岩,少量花岗斑岩叠加锡铋矿化。这些花岗斑岩SiO2含量为75.00%～80.78%,P2O5含量为0.02%～0.09%,总体表现为富Si、高K、低P,ACNK集中在0.93～1.09,NK/A为0.31～0.72,属准铝质-弱过铝质钙碱性花岗岩;REE总量为206.17×10-6～447.99×10-6,δEu为0.06～0.26,具稀土含量高、重稀土富集、轻稀土分馏明显、强烈铕亏损的特点;强烈亏损Ba、Sr、Nb、P、Zr、Ti,富集Rb、Th、U、K、Pb等大离子亲石元素和Ta、La、Pr、Nd、Sm等高场强元素。在Nb、Y对10000Ga/Al判别图上,花岗斑岩样品点均落于A型花岗岩区。其(87Sr/86Sr)i比值为0.71208～0.71289;εNd(t)介于-7.2～-7.9之间,对应t2DM为1531～1586Ma;(176Hf/177Hf)i比值为0.282326～0.282736,少量岩浆锆石(176Hf/177Hf)i比值(0.282693～0.282736)与球粒陨石现代值(0.282772)接近,εHf(t)为-12.38～+2.11,峰值为-5.5,对应t2DM为1.08～1.99Ga,峰值为1.55Ga,Sr、Nd、Hf同位素数据揭示花岗斑岩源岩具壳幔混合的特点,源岩主要来自中元古代基底的重熔,地幔端元约占24%,形成于岩石圈伸展减薄、软流圈上涌的构造背景,与变质杂砂岩的深熔作用有关。
A series of Yanshanian granite porphyries developed in the Hehuaping area, few of which are superposed tin-bismuth mineralization. The rocks are rich in SiO2 （75.00% to 80. 78% ） and K20（3.48% to 5.45% ） , and poor in A1203 （ 11.06% to 12.44% ） and P205 （0.02% to 0.09% ） . Their ACNK ranges from 0.93 to 1.09, and NK/A is between 0.31 and 0.72, belonging to metaluminous-weak aluminum calcium alkaline granite. The rocks have the REE values of 206. 17μg/g to 447.99μg/g, the δEn values of 0.06 to 0.26, （La/Sm） N ratio of 2.93 to 6.66 and （Gd/Yb） N ratio of 0. 55 to 1.36, showing the characteristics of the high content of REE（ especially the HREE） , the high fractional degree of LREE and a severe depletion in Eu. The granite porphyris are rich in LILE（ such as Th, U, K）, HFSE（ such as Ga, Y, Zr, Nb） and strongly depleted in Ba, St, Nb, P, Zr and Ti. On the Nb, Y vs 10000Ga/Al diagrams, and all samples fall in the area of the A-type granite. The granite porphyries have a steady range of Sr isotopic compositon, with initial （ ^87 Sr/^86 Sr） i 0.71208 - 0.71289, and low end （t） values （ - 7.2 to - 7.9 ） , corresponding to the t2DM model age ranging from 1531 to 1586Ma. They have a wide range of Hf composition, with initial （^176Hf/^177Hf） i 0. 282693 -0. 282736, and εHf（t） - 12.38 ～＋2. 11 and an average of εHr（t） -5.5, corresponding to tDM2 = 1.08 ～ 1.99Ga and an average of tDM2 = 1.55Ga. The Sr, Nd, Hf isotopic data indicate that they are mainly derived from the Mesoproterozoic Crustal materials and few newly nmntle-derived components or juvenile components are involved. The mantle com- ponent of the granite porphyries source is about 24% in proportion. They were formed in an extensional tectonic setting and thinned continental crust and related to the anatexis of felsic rocks caused by upwelling of the asthenosphere and underplating of basic magma.
出处
《地质与勘探》
CAS
CSCD
北大核心
2013年第2期300-312,共13页
Geology and Exploration
基金
国家自然科学基金项目(编号:40972073)"湘南荷花坪锡多金属矿床成矿过程中的壳幔相互作用研究"资助
