南大西洋洋中脊玄武岩中斜长石特征及其岩石学意义
发布时间：2018-09-17 13:32
【摘要】：本文利用电子探针技术分析了南大西洋洋中脊玄武岩中斜长石的结构构造和物质组成特征,讨论了该区岩浆过程在斜长石中的记录。按粒径大小可将研究区玄武岩中的斜长石分为斑晶、微晶和基质三类,斑晶斜长石核部平均An值为74,属于培长石,而边部平均An值为69,属于拉长石,呈正环带构造,微晶斜长石平均An值为67,与斑晶斜长石边部成分近似,且其粒径与斑晶斜长石边部宽度接近,约在30μm,极可能是同一时期形成。基质斜长石平均An值为63,略小于微晶斜长石。利用马西兹修改后的斜长石结晶温度计算公式,估算出斑晶斜长石核部结晶温度约为1 214℃,斑晶斜长石边部结晶温度约为1 085℃,微晶斜长石的结晶温度约为1 081℃,而基质斜长石的结晶温度约为1 056℃。由此推测,高An值(78~80)的斑晶斜长石的核部可能是形成于岩浆源区的捕掳晶。斑晶斜长石的边部、微晶斜长石及基质斜长石的结晶温度相近,说明三者可能近乎同时结晶;但由于它们的颗粒大小变化范围较大,很可能分别形成于岩浆房、岩浆通道及喷出洋壳表面后等环境中。与冲绳海槽玄武岩中斜长石比较,本区斜长石平均An值跨度以及结晶温度跨度均比冲绳海槽小,本区An值为74~63,结晶温度为1 214~1 056℃,而冲绳海槽An值为86~47,结晶温度为1 250~950℃。这表明相对于岩浆物理化学环境曾经历快速变化的弧后盆地来说,慢速洋中脊的岩浆活动的物理化学环境则相对稳定。
[Abstract]:In this paper, the structure, structure and material composition of plagioclase in the basalt of the mid-ocean ridge of the South Atlantic Ocean are analyzed by electron probe technique, and the records of magmatic process in the plagioclase in this area are discussed. The plagioclase in basalt in the study area can be divided into three types according to its particle size. The average An value in the core of porphyry plagioclase is 74, which belongs to the feldspar, while the average An in the edge is 69, which belongs to elongated rock and positive ring structure. The average An value of microcrystalline plagioclase is 67, which is similar to the edge component of porphyry plagioclase, and its particle size is close to the width of the edge of porphyry plagioclase, about 30 渭 m, which is probably formed at the same time. The average An value of matrix plagioclase is 63, which is slightly smaller than that of microcrystalline plagioclase. Based on the modified formula of crystallization temperature of plagioclase, it is estimated that the crystallization temperature of porphyry plagioclase core is about 1 214 鈩，
本文编号：2246073
[Abstract]:In this paper, the structure, structure and material composition of plagioclase in the basalt of the mid-ocean ridge of the South Atlantic Ocean are analyzed by electron probe technique, and the records of magmatic process in the plagioclase in this area are discussed. The plagioclase in basalt in the study area can be divided into three types according to its particle size. The average An value in the core of porphyry plagioclase is 74, which belongs to the feldspar, while the average An in the edge is 69, which belongs to elongated rock and positive ring structure. The average An value of microcrystalline plagioclase is 67, which is similar to the edge component of porphyry plagioclase, and its particle size is close to the width of the edge of porphyry plagioclase, about 30 渭 m, which is probably formed at the same time. The average An value of matrix plagioclase is 63, which is slightly smaller than that of microcrystalline plagioclase. Based on the modified formula of crystallization temperature of plagioclase, it is estimated that the crystallization temperature of porphyry plagioclase core is about 1 214 鈩，
本文编号：2246073
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