摘要
海南晨星地区发育一套变安山质火山岩,呈透镜状或层状夹于晚古生代变沉积地层中。该安山质火山岩SiO2含量为52.87%～65.27%;富Al2O3(15.59%～21.55%),具有较高的稀土元素丰度(ΣREE=166.80×10-6～246.21×10-6),平均204.39×10-6,(La/Yb)N=5.78～7.47,(Gd/Yb)N=1.24～1.58;大离子亲石元素富集、高场强元素Nb-Ta和Ti-P亏损明显,Eu弱负异常(δEu=0.72～0.90);在Nb/Y-(Zr/TiO2)×10-4和La/Yb-Sc/Ni图解上落入安山质大陆岛弧型火山岩区。火山岩样品10HN13B的LA-ICP-MS锆石U-Pb年代学测试表明,该安山质火山岩形成年龄为345±4Ma,表明在早石炭世晚期(～345Ma)在海南中部存在有安山质弧岩浆作用。该年龄的获得表明晨星地区夹持该安山质火山岩的原下二叠统峨查组很可能为一套石炭-二叠纪海相火山-碎屑沉积建造,或需要进一步解体。
The volcanic rocks in the Chenxing area （Hainan Island） , interlayered with Paleozoic siliticlastics, ex- perienced greenschist- and amphibolite-facies metamorphism. These volcanic rocks are andesitic with SiO2 and AlO3 contents varying in ranges of 51.70% - 64. 14% and 15.59% - 21.55% , respectively. They show high REE abundance （EREE=（166.80 -246.21） ×10-6, with （La/Yb）N of 5.78-7.47, （Gd/Yb）N of 1.24 - 1.58 and 8Eu of 0.72 -0.90）. These rocks are characterized by enrichment in LILE and depletion in HFSE with significant Nb-Ta and P-Ti negative anomalies, showing an affinity to island-arc rocks. 10HN13B samples, repre- sentative of the andesite in the Chenxing area, yielded LA-ICP-MS zircon U-Pb ages of 241 - 2312 Ma with three age-clusters of 546±10 Ma, 431 ±5 Ma and 345±4 Ma. The age of 345 ±4 Ma was interpreted to be the crystalli- zation age. Our data show that late Paleozoic sequence in the Chenxing area might be deposited at early Carbonifer- ous period. In combination with other geological observations, it is inferred that early Carboniferous andesitic island possibly occurred along the Banxi-Chenxing area, central Haiuan.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2013年第1期99-108,共10页
Geotectonica et Metallogenia
基金
国家自然科学基金(批准号:40902062
408256009)
中国科学院重大项目(编号:KZCX1-YW-15-1)联合资助
