摘要:基于控制降温速率的动力结晶实验，对五大连池老黑山钾质玄武质熔岩的冷却结晶过程中橄榄石晶体形态随降温速率变化动力学演变进行了研究。实验研究表明，老黑山钾质玄武岩的熔融温度发生在1 022 ℃～1 260 ℃之间，峰值为1 166.3 ℃～1 186.5 ℃；实验产物主要由橄榄石和玻璃质组成，新生的橄榄石晶体形态差异较大，有针状骸晶、铁轨状骸晶、羽毛状雏晶、细长条状和粒状微晶。橄榄石晶体的生长、尺寸和形态、分布和实验产物的结晶程度与降温速率之间存在着密切关联。随着降温速率的变慢，橄榄石从针状（0.075 ℃ /min～0.5 ℃ /min）、铁轨状（0.075 ℃ /min～0.5 ℃ /min）、放射状与羽毛状（0.046 8 ℃ /min～0.075 ℃ /min）、细长条状（0.062 5 ℃ /min）等晶体演变为粒状微晶（0.03 ℃ /min）；同时，岩石的结晶程度逐渐增强，橄榄石晶体尺寸逐渐变大、自形程度逐渐变高，玻璃相和气孔逐渐减少。这种新生橄榄石形态的变化与降温速率的内在关联性，对认识老黑山熔岩流固结的动力结晶机制、熔岩流的运动机制有一定科学意义。
关键词: 五大连池/
橄榄石/
动力结晶/
降温速率
Abstract:The dynamic crystallization directly controls the movement of the lava flow. Based on the experiment of dynamic crystallization under the condition of controlling the cooling rate, the kinetic evolution of the olivine crystal morphology with the cooling rate during the cooling crystallization process of the potassic basaltic lava of Laoheishan volcano in Wudalianchi was studied in this work. The experimental results showed that the melting temperature of potassic basalt of Laoheishan volcano ranges from 1 022 ℃～1 260 ℃, along with a peak temperature of 1 166.3 ℃～1 186.5 ℃. The experimental products are mainly composed of olivine and vitreous matrix. The newly crystallized olivine crystals are quite different, which include acicular skeleton crystals, rail-like skeleton crystals, feathery skeleton crystals, slender and granular crystallites. Furthermore, the growth, size, morphology and distribution of olivine as well as the crystallinity of experimental products have a close correlation with the cooling rate. As the cooling rates slow down, olivines evolve from acicular （0.075 ℃/min～0.5 ℃/min）, rail-like （0.075 ℃/min～0.5 ℃/min）, radial and feathery （0.046 8 ℃/min～0.075 ℃/min）, slender strip （0.062 5 ℃/min） crystals to granular crystallites （0.03 ℃/min）. Meanwhile, as the crystallinity of the products is gradually enhanced, the olivine crystal is enlarged, the euhedral degree of olivine increases and the vitreous and vesicular content decreases. The internal correlation between the morphological changes of the newly produced olivine and the cooling rate and time is of scientific significance for understanding the movement mechanism of lava flows in Laoheishan volcano and their dynamic crystallization mechanism.
Key words:Wudalianchi/
Olivine/
Dynamic crystallization/
Cooling rate
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