Abstract

In many instances the sulphide mineralization is associated with quartz vein-related hydrothermal alteration zone. The syntectonic quartz veins display preferred orientation as their intrusion is controlled by normal stress (σ_n) acting across the foliation/fracture planes and the fluid pressure (P_f) of the quartz veins. The P_f and paleostress (ϕ = tectonic stress ratio) are measurable by using stereoplot and 3D Mohr plot. We have determined the above parameters from the quartz veins in the Cu–Pb–Zn mineralization belt of South Delhi terrane, NW India. The mineralization occurs in the mica schist and metabasalt. The rock types show three phases of folding (F₁–F₃), greenschist facies metamorphism and multiple phases of granite intrusion. Attitude of 170 quartz veins have been measured, the NE–SW direction is the most prominent. Though some of the quartz veins show a cross-cutting relationship, we have treated them broadly synchronous. Stereoplot shows a girdle distribution pattern with an elliptical void area at the centre and σ₁σ₂ plane strikes N52° E. Further, σ₁ = 120°/75°, σ₂ = 052°/07°, and σ₃ = 323°/07° indicate that maximum extension was NW–SE. The θ₂ = 12°, θ₃ = 40°. R ' = 0.95, ϕ = 0.90 indicate high value for R ' leading to dilation of wide range of fractures and the high ϕ value suggesting uniaxial extension. 3D Mohr plot indicates that P_f fluctuated between σ₂ < P_f < σ₁. Since sulphide mineralization is related to quartz vein intrusion, we interpret similar stress field for mineralization.

中文翻译：

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印度西北部安巴吉地区南德里地形的石英静脉定向数据中使用3D莫尔圆进行的静脉开口古应力和流体压力分析

摘要

在许多情况下，硫化物矿化与石英脉相关的热液蚀变带有关。作为它们侵入由正常应力（σ控制的同构造石英脉显示优选取向_Ñ）横跨面理/断口面和流体压力（作用P _˚F石英脉）。的P _˚F和古应力（φ=构造应力比）是通过使用stereoplot和3D莫尔情节可测量。我们已经从印度西北印度南部德里的Cu–Pb–Zn矿化带的石英脉中确定了上述参数。矿化发生在云母片岩和玄武岩中。岩石类型显示出三个折叠阶段（F ₁ –F ₃），绿片岩相变质作用和花岗岩侵入的多个阶段。已经测量了170条石英脉的姿态，其中NE–SW方向最为突出。尽管某些石英脉显示出横切关系，但我们已将它们大致同步处理。Stereoplot示出了具有在中心和σ椭圆空隙区域腰带分布图案_1个σ ₂平面撞击N52°E.此外，σ ₁ = 120°/ 75°，σ ₂ = 052°/ 07°，σ ₃ = 323 °/ 07°表示最大延伸量为NW–SE。该θ ₂ = 12°，θ ₃ = 40°。R  '= 0.95，ϕ = 0.90表示R的高值 导致大范围的骨折扩张和高ϕ值，提示单轴延伸。3D莫尔图指示P _˚F波动σ之间₂ < P _˚F <σ ₁。由于硫化物矿化与石英脉侵入有关，因此我们解释了类似的应力场。