不同降温速率约束下橄榄石晶体形态演变及其地质意义  

Morphological evolution and geological significance of olivine crystals under different cooling rate constraints: Experiment of dynamic crystallization on the potassic basaltic lava of Laoheishan volcano in Wudalianchi

作　　者：彭年[1] 崔莹 刘永顺[1] 乔学斌 聂保锋[1] Peng Nian;Cui Ying;Liu Yongshun;Qiao Xuebin;Nie Baofeng(College of Resource,Environment and Tourism,Capital Normal University,Beijing100048;School of Physics and Electronic Engineering,Jiangsu Normal University,Xuzhou,Jiangsu221116)

机构地区：[1]首都师范大学资源环境与旅游学院,北京100048 [2]江苏师范大学物理与电子工程学院,江苏徐州221116

出　　处：《地质科学》2020年第1期254-269,共16页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：基金资助:国家自然科学基金项目(编号:41372343,40872062)和北京市自然科学基金项目(编号:1082006)资助。

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1022 t^1260t之间,峰值为1166.31186.5 t;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 T/min-0.5 X./min)、铁轨状(0.075 t/min^0.5 V./min)、放射状与羽毛状(0.0468 X./min^0.075°C/min)、细长条状(0.0625 t/min)等晶体演变为粒状微晶(0.03 X/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。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 1022℃~1260℃,along with a peak temperature of 1166.3℃~1186.5℃.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(0.0468℃/min^0.075℃/min),slender strip(0.0625℃/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.

关 键 词：五大连池 橄榄石 动力结晶 降温速率 

分 类 号：P579[天文地球—矿物学] P588.114[天文地球—地质学]