| Petrological Significance of Zoned Plagioclase in Eldjurti Granite and Mafic Microgranular Enclaves,North Caucasus,Russia |
| |
| 作者姓名： | 朱永峰 |
| |
| 作者单位： | GeologicalDepartment,PekingUniversity,Beijing100871 |
| |
| 摘 要： | Plagioclase phenocrysts from mafic enclaves and plagioclase from its host granite possess a pat-tern of complex zonation .A plagioclase phenocryst can generally be divided into three parts:an oscillatory, locally patchy zoned core (An47-19),a ring with dusty, more calcic plagioclase (An64-20) and a normally zoned rim composed of sodic plagioclase (An22-3.3). Major discontinuities in zoning coincide with resorption surfaces that are overgrown by the more calcic plagioclase.The cores of large plagioclase phenocrysts from mafic enclaves and host granite show similar zoning patterns and similar compositions, indicating their crystallization under the same conditions .Steep normal zoning of the rims of plagioclases both from host granite and mafic enclaves illustrates a drastic decrease in An content which is considered to have resulted from the continuous differentiation of hybrid magma and efficient heat loss because of the upward emplacement of the residual magma.Wide rims of plagioclases from the host granite against the discrete rims of plagioclases from mafic enclaves indicate that differentiation and cooling lasted much longer in the host granite than in the mafic enclaves.
|
| 关 键 词： | 花岗岩 斜长岩 混合岩浆 铁镁质岩浆 高加索山脉 俄罗斯 |
Petrological significance of zoned plagioclase in Eldjurti granite and mafic microgranular enclaves,North Caucasus,Russia |
| |
| Zhu Yongfeng.Petrological Significance of Zoned Plagioclase in Eldjurti Granite and Mafic Microgranular Enclaves,North Caucasus,Russia[J].Chinese Journal of Geochemistry,1994,13(2):142-155. |
| |
| Authors: | Zhu Yongfeng |
| |
| Institution: | (1) Geological Department, Peking University, 100871 Beging |
| |
| Abstract: | Plagioclase phenocrysts from mafic enclaves and plagioclase from its host granite possess a pattern of complex zonation. A
plagioclase phenocryst can generally be divided into three parts: an oscillatory, locally patchy zoned core (An47-19), a ring
with dusty, more calcic plagioclase (An64-20) and a normally zoned rim composed of sodic plagioclase (An22-3.3). Major discontinuities
in zoning coincide with resorption surfaces that are overgrown by the more calcic plagioclase. The cores of large plagioclase
phenocrysts from mafic enclaves and host granite show similar zoning patterns and similar compositions, indicating their crystallization
under the same conditions. Steep normal zoning of the rims of plagioclases both from host granite and mafic enclaves illustrates
a drastic decrease in An content which is considered to have resulted from the continuous differentiation of hybrid magma
and efficient heat loss because of the upward emplacement of the residual magma. Wide rims of plagioclases from the host granite
against the discrete rims of plagioclases from mafic enclaves indicate that differentiation and cooling lasted much longer
in the host granite than in the mafic enclaves. |
| |
| Keywords: | host granite (HG) mafic microgranular enclave (MME) plagioclase hybrid magma mafic magma sialic magma |
| 本文献已被 维普 SpringerLink 等数据库收录！ |
