冲绳海槽Jade热液场烟囱物稀土元素和锶、钕同位素地球化学特征
Rare earth element and strontium-neodymium isotope characteristics of hydrothermal chimney in Jade area in the Okinawa Trough
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摘要: 热液烟囱物是弧后扩张盆地现代海底热液活动成矿系统的重要产物.冲绳海槽中的伊是名(Izena)海洼Jade热液活动区烟囱物稀土元素特征表现为轻稀土元素相对富集,并具有铕的较强的正异常.87Sr/86Sr和143Nd/144Nd的平均值分别为0.708928和0.512292,介于冲绳海槽海水和海槽酸性浮岩中的值之间.这些特征表明,Jade热液活动区的热液硫化物矿床的成矿物质来源于下伏的酸性火山岩.矿床的成矿机制可描述为:下渗的海水被加热,它与酸性火山岩发生水-岩热化学交换反应时淋滤出大量的成矿物质形成以富含轻稀土元素为特征的热水溶液;当热液喷出并发生快速结晶沉淀时,形成了以具有轻稀土元素相对富集和铕的正异常为特征的铜-锌硫化物和重晶石-非晶质SiO2型矿石.Abstract: Hydrothermal chimney is an important product of modern hydrothermal mineralizing system at the seabed of the back arc spreading basin.The rare earth element components of hydrothermal chimney in Jade area in the Izena depression are charact erized by enriched light rare earth element and high positive europium abnormity.The average value of 87Sr/86Sr and 143N d/144N d is 0.708928 and 0.512292 respectively.These values are between the values of seawater and acidicfloat rock in the Okinawa Trough.All these characteristics indicate that the acidiclava is maybe the main source of hydrothermal sulfide deposits in the Jadearea.The mineralizing mechanism of hydrothermal sulfide deposits in the Jade area can be described as follows.Large amounts of materials are produced in the course of seawater rock thermo chemistry reactions when the embedding seawater is heated up and contacted with the acidic volcanic rocks.The materials mix with seawater and becomea type of thermal liquor which is characterized by enriched lightrare earth element.When this type of thermal liquid spurts out from the seafloor and cryst allizes or deposits rapidly.The cuprumrincum sulfide and barite-noncrystal SiO2 mineral will be created with enriched light rare earth element and high positive europium abnormity.
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Key words:
- hydrothermal chimney /
- rare earth element /
- strontium-neodymium isotope
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