粤北大沟谷热水沉积钠长石岩岩石化学及稀土元素  

Chemical Composition and REE Pattern of Hydrothermally Deposited Albitite in Northern Guangdong Province

作　　者：梁华英[1] 王秀璋[1] 程景平[1] 

机构地区：[1]中国科学院广州地球化学研究所,广州510640

出　　处：《沉积学报》2001年第3期415-420,共6页Acta Sedimentologica Sinica

基　　金：国家自然科学基金 (批准号 :49772 1 1 4 );中国科学院重点项目KZ952 - 91 - 4 35资助项目

摘　　要：大沟谷含金钠长石岩带上为层状下为脉状产于震旦系乐昌峡群片岩中 ,主要由钠长石岩及碳酸盐岩组成。钠长石岩多为块状及条带状构造。钠长石岩和片岩化学成分不同 ,钠长石岩相对富集Al2 O3 、TiO2 、MnO、Na2 O、P2 O5,而贫Fe2 O3 、FeO、MgO、CaO、K2 O。在主要氧化物组成的直角坐标图上 ,钠长石岩和片岩位于不同的区域及具不同的变化趋势。钠长石岩稀土元素含量较低 ,在 12 .5 6× 10 -6～ 5 5 .6 6× 10 -6之间 ,具较低的La/Yb(1.82～ 6 .42 )、La/Sm(0 .96～ 2 .99)、Gd/Yb(0 .99～ 2 .71)比值 ,较大的δEu异常范围 (0 .41～ 0 .8) ,弱的δCe异常。Dagougu gold bearing albitite belt, composed of albitite and carbonate rock, occurred as stratiform in the upper part and filled veins in the lower part in the Lechangxia Group Schist, Sinian Period. The albitite usually with banded and massive structure is composed primary of albite (80%±), quartz (1%～15%±), carbonate rock (1%～5%±), rutile (1%±), apatite (1%±) and pyrite with minor tourmaline and magnetite; the carbonate rock, occurred in the same occurrence as those of albitite, consists predominantly of dolomite (ankerite) ( >75%), calcite (>15%), albite (5%±) with the same minor minerals as those of albitite. Main element compositions of the albitite differ from that of the Lechangxia Group Schist, the former is rich in Al 2O 3, TiO 2, MnO, Na 2O, P 2O 5 and poor in Fe 2O 3, FeO, MgO, CaO, K 2O. The albitite and adjacent Lechangxia Group Schist lie in different domains in the major oxides variation diagram including TiO 2 Al 2O 3, Al 2O 3 SiO 2, MgO SiO, TiO 2 SiO 2, FeO Fe 2O 3, MgO CaO and reveal different variation tendency. The albitite has lower REE content, varing from 12.56×10 -6 to 55.66×10 -6 , with lower La/Yb:1.82～6.42, La/Sm:0.96～2.99, Gd/Yb:0.99～2.71 ratios, negative Eu anomalies and weakly Ce anomalies. Chondrite normalized patterns of REE in albitite differ from those of the Lechangxia Group Schist. Combined field and geochemical data indicate that the Dagougu gold bearing stratiform albitite do not represent the normal clastic sediments altered by sodium rich fluid, but owe its origin to hydrothermal sedimentation at or below the sediment water interface in alkaline environment.

关 键 词：钠长石岩 稀土元素 热水沉积 岩石化学 稀土元素 

分 类 号：P588.2[天文地球—岩石学] P595[天文地球—地质学]