实验室合成石盐包裹体的均一温度以及古气候意义  

Homogenization temperature of fluid inclusions in laboratory grown halite and its implication for paleotemperature reconstruction

作　　者：孟凡巍[1,2,3,4] 倪培[1,2,3] 葛晨东[5] 王天刚[1,2,3] 王国光 刘吉强[1,2,3] 赵超[1,2,3] 

机构地区：[1]南京大学内生金属矿床成矿机制研究国家重点实验室 [2]南京大学地质流体研究所 [3]南京大学地球科学与工程学院,南京210093 [4]中国科学院南京地质古生物研究所现代古生物学与地层学国家重点实验室,南京210008 [5]南京大学海岸与海岛开发教育部重点实验室,南京210093

出　　处：《岩石学报》2011年第5期1543-1547,共5页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40703018);中国博士后基金(20070411040);江苏省博士后基金(0701012C);南京大学内生金属矿床成矿机制研究国家重点实验室开放基金(14-08-15);中国科学院南京地质古生物研究所现代古生物学与地层学国家重点实验室开放基金(073108)联合资助

摘　　要：石盐是表生环境下形成蒸发岩系的主要矿物,在形成过程中捕获大量的原生包裹体。通过低温冷冻测温技术,可以得到石盐中原生包裹体的一系列均一温度,如何正确理解这些数据是应用石盐原生包裹体恢复古气候的关键。石盐沉积可以发生在气水界面以及水体底部,其均一温度记录了卤水结晶的温度。Lowenstein et al.(1998)曾经用水浴法在恒定水温下合成了人工合成石盐,进行原生包裹体的均一温度研究,然而如何用水温来恢复古气温是古环境解释的关键。本次实验通过40℃下(气温,烘箱中蒸发)人工合成石盐,在岩相学观察基础上,对形成于气水界面漏斗晶中的包裹体和在底水沉积人字晶中的包裹体的均一温度进行低温冷冻测温法测定。测温过程中石盐包裹体可以得到一系列均一温度(10.6～39.9℃),而只有最大均一温度才能反映卤水结晶时的温度,两种类型的包裹体也显示了相似的最大均一温度。因此在浅水环境下,两种包裹体都可以用来反映古气温。Halite is a major evaporate mineral in the surface environment,and it contains abundant fluid inclusions formed during crystal formation,which can record the brine temperatures of crystal growth in ancient oceanic salt ponds and salt lakes in geological history.Using the ＂cooling nucleation method＂,homogenization temperature of fluid inclusions in halite can be measured.However,the interpretation and application of the homogenization temperature in palaeotemperature reconstruction is not straightforward.Fluid inclusions in halite can be captured in cumulate halite crystals formed at the air-water interface or in chevron halite crystals formed at the water-sediment interface.Lowenstein et al.（1998）carried out a microthermometric analysis on halite crystals grown in the laboratory through evaporation of halite-saturated brines in flasks submerged in water baths;however how to translate brine temperature into air temperature is the key question of paleoclimate.In this study,we measured a series of homogenization temperature of fluid inclusions in both cumulate and chevron halite crystals grown in the laboratory at a temperature of 40℃（air temperature）in a thermostatic air drying oven in 20cm deep brine in order to reconstruct the paleotemperature using homogenization temperatures directly.The homogenization temperatures range from 10.6℃ to 39.9℃.The results show that only the maximum homogenization temperature of fluid inclusions（Th max）matches brine temperatures.Both cumulate halite and chevron halite have a similar Th max,both types of halite can be used in paleotemperature reconstruction in shallow water.

关 键 词：石盐 流体包裹体 低温冷冻测温法 最大均一温度 

分 类 号：P578.32[天文地球—矿物学]