地质学报2011，Vol.85Issue(12)：1994-2002,9.DOI:11-1951/P.20111206.1222.008
豫西二郎坪地区O型埃达克岩的厘定及其地质意义
Identification of O-type Adakitic Rocks in Erlangping Area, Western of Henan Province, and Its Geological Significance
摘要
Abstract
The Xizhuanghe granodiorite is distributed in the Erlangping area, northern Xixia County, western Henan Province. This paper studied petrography and geochemistry, and zircon U-Pb geochronology and Hf isotopic compositions, with an emphasis on its petrogenesis and geological significance. The Xizhuanghe granitoid consists mainly of plagioclase and quartz, with minor amphibole and biotite. Geochemical studies indicate that the Xizhuanghe granitoid is high in SiO2 (66. 84%- 71. 57), Al2O3 (14.11%～16. 78%), Na2O (Na2O contents vary from 3. 45% to 4. 78% and the ratios of Na2O/K2O are between 1.06 and 2.40) and Sr (327. 04×10-6～613. 97×10-6), but low in MgO (MgO contents range between 0. 88% and 1. 0%, and the index of Mg# is vary from 0. 43 to 0. 46). But, Y (12. 30 × 10-6 ～ 17.17×10-6) and Yb (1. 36 × 10-6 ～1. 88 × 10-6), with high Sr/Y ratios ranging from 24 to 38). The Xizhuanghe granitoid has relative high REE contents (86. 79 × 10～6 ～ 197. 04 × 10～6) with strong fractionations between LREE and HREE ((La/Yb)N = 12. 35～34. 89), and no Eu negative or Eu positive anomalies (0. 97～1. 34). The chondrite-normalized REE diagram demonstrates enrichment of LREEs and K, RB, Ba, Th and Sr, and negative anomalies of Nb, Ta, P and Ti. Primitive mantle normalized trace element spider patterns show obvious enrichment in LILE and LREE such as Rb, Ba, Th, U, etc. And relative depletion in HSFE and HREE such as Nb, Ta, Ti, etc. , showing geochemical features of Otype adakites are related to subduction of oceanic slab. Zircon LA-ICP-MS dating yielded a formation age of 461 Ma for the Xizhuanghe granodiorite, which is consistent to that (460 ～ 473 Ma) of Erlangping basic volcanic rocks paragenetic with the granodiorite. Combined with the geochemical features of the Otype adakite, all evidence suggests existence of the oceanic basin and subduction event of the oceanic crust in the Erlangping areas of western Hennan Provience during Paleozoic of 460～470 Ma.关键词
地球化学/锆石U-Pb年代学和Hf同位素/埃达克岩/豫西Key words
geochemistry/ zircon U-Pb dating and Hf isotope/ adakite/ Xizhuanghe, western Henan Province引用本文复制引用
郭彩莲,陈丹玲..豫西二郎坪地区O型埃达克岩的厘定及其地质意义[J].地质学报,2011,85(12):1994-2002,9.基金项目
本文为西北大学大陆动力学国家重点实验室科技部专项经费,国家基础研究规划"973"项目(编号2009CB825003),国家自然科学基金项目(编号41072051)资助成果. （编号2009CB825003）
