Chemical composition and crystallization conditions of trachybasalts from the Dzhida field, Southern Baikal volcanic area: Evidence from melt and fluid inclusions
Chemical composition and crystallization conditions of trachybasalts from the Dzhida field, Southern Baikal volcanic area: Evidence from melt and fluid inclusions
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南贝加尔火山区 Dzhida 油田粗面玄武岩的化学成分和结晶条件：来自熔体和流体包裹体的证据
DOI：
10.1134/s0016702906030062
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发表时间：
2006
影响因子：
0.8
通讯作者：
V. Yarmolyuk
中科院分区：
文献类型：
--
作者：
V. Naumov;M. Portnyagin;M. Tolstykh;V. Yarmolyuk
对南贝加尔火山区吉达火山区粗面玄武岩中的橄榄石斑晶（Fo 81-79）进行了熔体和流体包裹体研究。熔体夹杂物均质化，淬火，并在电子和离子微探针上分析。对9种包裹体玻璃的研究表明，玄武岩熔体（SiO2 = 47.1- 50.3wt%，MgO = 5.0- 7.7wt%，CaO = 7.1- 11.1wt%）具有高含量的Al 2 O3（17.1-19.6重量%）、Na 2 O（4.1-6.2重量%）、K 2 O（2.2-3.3重量%）和P 2 O 5（0.6-1.1重量%）。挥发物含量低（重量%）：0.24-0.31 H2O、0.08 F、0.03 Cl和0.02 S。4个粗面玄武岩样品中橄榄石的原生流体包裹体含有高密度CO2（0.73-0.87 g/cm 3），表明在1200-1300°C时CO2流体压力为4.3-6.6 kbar，橄榄石结晶深度为16-24 km。对20个玻璃熔体包裹体的微量元素离子探针分析表明，贝加尔裂谷岩浆中富集不相容元素，不同于大洋裂谷玄武岩，类似洋岛玄武岩。我们的数据比较粗面玄武岩的吉达字段与现有的数据在东图瓦火山高地在南贝加尔火山区的橄榄石熔体和流体包裹体的挥发分，主要和微量元素的含量相似。
Melt and fluid inclusions have been studied in olivine phenocrysts (Fo 81–79) from trachybasalts of the Southern Baikal volcanic area, Dzhida field. The melt inclusions were homogenized, quenched, and analyzed on an electron and ion microprobe. The study of homogenized glasses of nine inclusions showed that basaltic melts (SiO2 = 47.1–50.3 wt %, MgO = 5.0–7.7 wt %, CaO = 7.1–11.1 wt %) have high contents of Al2O3 (17.1–19.6 wt %), Na2O (4.1–6.2 wt %), K2O (2.2–3.3 wt %), and P2O5 (0.6–1.1 wt %). The volatile contents are low (in wt %): 0.24–0.31 H2O, 0.08 F, 0.03 Cl, and 0.02 S. Primary fluid inclusions in olivines from four trachybasalt samples contain high-density CO2 (0.73–0.87 g/cm3), indicating a CO2 fluid pressure of 4.3–6.6 kbar at 1200–1300°C and olivine crystallization depths of 16–24 km. Ion microprobe analyses of 20 glasses from melt inclusions for trace elements showed that the magmas of the Baikal rift were enriched in incompatible elements, thus differing from oceanic rift basalts and resembling oceanic island basalts. A comparison of our data on melt and fluid inclusions in olivine from trachybasalts of the Dzhida field with preexisting data on the Eastern Tuva volcanic highland in the Southern Baikal volcanic area showed that they had similar contents of volatiles, major, and trace elements.