Segev, Amit; Goldshmidt, Vladimer; Itamar, Arych; Rybakov, Michael (1996) Effects of Mesozoic magmatism on composition, structure, and metallic mineralization in the Ramon area (southern Israel): Magnetometric and gravimetric evidence. Israel Journal of Earth Sciences, 45. 89-112
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Effects of Mesozoic magmatism on composition, structure, and metallic mineralization in the Ramon area (southern Israel): Magnetometric and gravimetric evidence | ||
| Journal | Israel Journal of Earth Sciences | ||
| Authors | Segev, Amit | Author | |
| Goldshmidt, Vladimer | Author | ||
| Itamar, Arych | Author | ||
| Rybakov, Michael | Author | ||
| Year | 1996 | Volume | < 45 > |
| Page(s) | 89-112 | ||
| Original Entry | Segev, Amit; Goldshmidt, Vladimir; Itamar, Aryeh; Rybakov, Michael (1996): Effects of Mesozoic magmatism on composition, structure, and metallic mineralization in the Ramon area (southern Israel): magnetometric and gravimetric evidence. Israel Journal of Earth Sciences 45, 89-112. | ||
| Classification | Not set | LoC | Not set |
| Mindat Ref. ID | 16308145 | Long-form Identifier | mindat:1:5:16308145:2 |
| GUID | 0 | ||
| Full Reference | Segev, Amit; Goldshmidt, Vladimer; Itamar, Arych; Rybakov, Michael (1996) Effects of Mesozoic magmatism on composition, structure, and metallic mineralization in the Ramon area (southern Israel): Magnetometric and gravimetric evidence. Israel Journal of Earth Sciences, 45. 89-112 | ||
| Plain Text | Segev, Amit; Goldshmidt, Vladimer; Itamar, Arych; Rybakov, Michael (1996) Effects of Mesozoic magmatism on composition, structure, and metallic mineralization in the Ramon area (southern Israel): Magnetometric and gravimetric evidence. Israel Journal of Earth Sciences, 45. 89-112 | ||
| In | Link this record to the correct parent record (if possible) | ||
| Abstract/Notes | A magnetometric and gravity survey accompanied by studies on petrophysical properties (density, porosity, and magnetic susceptibility of the local country rocks) was carried out in Makhtesh Ramon and neighboring areas to determine the subsurface mine the subsurface structure and composition of the Ramon area, which was affected intensively by the Mesozoic magmatism. High gravity anomalies (+9 to +10 mGal) are interpreted as basic (gabbro) intrusions with densities of 2.81-2.85 g/cm³. Negative gravity anomalies (-3 to -4 mGal) are considered to be acid (quartz-syenite) intrusions (2.50 g/cm³). The multiphase magmatic activity in the central Negev continued intermittently from Late Triassic/ Early Jurassic to Early Cretaceous over a period of 100 million years. The regional high-density Ramon block is bounded to the e north by a sharp gravity gradient associated with linear magnetic anomalies, while south of the Ramon Fault the subsurface structure changes gradually. The negative gravity zone at its northern end may reflect local Early Cretaceous (post magmatic) basins filled by a thick section of Hatira Formation sandstones. The highest negative anomaly there (Mizpe Ramon) indicates the existence of a subsurface acid igneous body. Six major intrusions were delineated, four of which are basic, the Saharonim, Arod, Laccolith, and Hare Govay, and two acidic, Shen Ramon-Gavnunim and Ma'ale HaAzma'ut. Of these, the largest (Arod) extends over an area of 14 ×4 km; the smallest (Laccolith and Ma'ale HaAzma'ut), over about 4 x 1 km. All intrusions are relatively shallow-seated and emplaced in the upper part of the sedimentary column. Their tops are found at depths of 0-0.5 km, and at Shen Ramon-Gavnunim they appear to be at the surface. Their bottoms vary from a depth of 1.5 km (Saharonim) to more than 3 km (Hare Govay). The Saharonim basic intrusion has significantly lower magnetic susceptibility than the nearby basic intrusions. The presence of a Late Triassic/Early Jurassic basalt with low magnetic susceptibility over this intrusion suggests that both are of the same magmatic phase (the first Mesozoic event). The geophysical models as well as the field observations suggest that locally the Laccolith, and the Shen Ramon-Gavnunim, as well as Hare Govay and Ma'ale. HaAzma'ut (subsurface and indirect data) intrusions are of a basic/acid mixed rock association. All these subalkaline to alkaline intrusions were emplaced during the Early Cretaceous, ~140 to 122 Ma (the second Mesozoic event) following relatively high fractional crystallization processes. The distribution of acid magmatic bodies has been identified from the Mizpe Ramon region at the north down to the southern end of this block and particularly between the Hare Govay and Arod basic intrusions. The models also suggest that the lowest-density zones within the quartz syenite are highly altered in places intimately associated with small bodies with high magnetic susceptibility. This alteration may be an indication of hydrothermal activity accompanied by metallic mineralization. The Arod intrusion is the youngest Early Cretaceous magmatic activity (third Mesozoic event). Its extrusive phase (~108 to 111±2 Ma) is characterized by extensive alkali-olivine basalt and basanite flows mainly in western Makhtesh Ramon. High frequency linear magnetic anomalies extending from the Arod intrusion probably express locally covered volcanic vents of the same event along the Ramon block boundaries and fractured zones. The horizontal displacement of the Shen Ramon and Gavnunim quartz-syenite bodies relative to their subsurface counterparts south of the Ramon Fault supports a dextral motion along this fault, of about 1.3 km. The folding of the Ramon asymmetric anticlinorium may have been influenced by the Mesozoic shallow intrusions and the fracture zone along the Ramon Fault. | ||
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