太原西山煤田微量元素地球化学特征及其地质意义

Geochemical Characteristics and Geological Significance of Trace Elements in Xishan Coalfield,Taiyuan

为了弄清太原西山煤田煤岩的形成环境,选取西山煤田8号煤层中煤样、煤层顶板、夹矸和黄铁矿结核,应用电感耦合等离子质谱技术(ICP-MS)测定了它们的微量元素,并在此基础上讨论了这些微量元素的分布、赋存特征及其成煤环境意义。这些分析样品的稀土元素含量变化大,其值为(11.1~455)×10^(-6)(平均200×10^(-6))。稀土元素(REE)及V、Co、Ni、Sr、Ba、Th、U等元素在煤层的顶板及夹矸中明显富集,显示了其陆相来源和以无机相赋存为主。轻/重稀土元素比值(LREE/HREE)在10.3~37.6之间(平均18.6)。整体表现出明显的轻稀土(LREE)富集,且LREE元素间分馏程度较大,重稀土(HREE)间分馏程度较小,具有较强的Eu负异常和弱的Ce负异常的特征。Ce、Eu异常系数比值(δCe/δEu)在1.24~1.81之间(平均1.56),Sr/Ba值在0.45~11.5之间(平均3.74),Th/U值在0.20~4.28之间(平均1.83),V/Ni值在1.41~14.12间(平均5.4),V/(Ni+V)值在0.58~0.93之间(平均0.8),表明太原组形成于受海水影响的高盐度、缺氧还原条件下的海陆交互相环境。

In order to clarify the formation environment of coal and rock in Xishan Coal field,the contents of trace elements of coal,coal seam,coal gangue and pyrite nodules in No. 8 coal of Xishan Coalfield are determined by ICP-MS and had a discussion on distribution,storage feature and environmental significance of these trace element. The study show that the contents of these rare earth elements change greatly which distribute range from 11 ×10- 6to 455 × 10- 6,with an average of 200 × 10- 6. Rare earth element（ REE） and V、Co、Ni、Sr、Ba、Th、U was enriched in coal seam roof and gangue,shows its continental source and inorganic phase storage. LREE / HREE was between10. 3 and 37. 6,with an average of 18. 6. The whole show obvious characteristic such as enrichment of LREE、large degree of LREE,small degree of HREE,strong Eu negative and weak Ce negative anomaly. Ratio of abnormal coefficient of Ce and Eu（ δCe / δEu） distribute range from 1. 24 to 1. 81,with an average of 1. 56,Sr / Ba distribute range from 0. 45 to 11. 5,with an average of 3. 74,Th / U distribute range from 0. 20 to 4. 28,with an average of 1. 83,V / Ni distribute range from 1. 41 to 14. 1,with an average of 5. 4,and V /（ Ni ＋ V） distribute range from 0. 58 to 0. 93,with an average of 0. 8 which showed that No. 8 coal formed in Paralic environment which influenced by seawater salinity and anoxic conditions.