II.2. Basic/Mafic igneous rocks

GABBRO

Appearance: Dark green or greenish black coloured, medium or coarse grained intrusive igneous rock. Compositionally similar to diorite but the anorthite content of plagioclases is more than 50mol%.

Mineral content:

Essential minerals: Ca-rich plagioclase, clino- and/or orthopyroxene, olivine, amphibole

Accessory minerals: apatite, magnetite, ilmenite; and may contain less amount of quartz, alkali feldspar or olivine and feldspathoids

Secondary minerals: chlorite, titanite, serpentine group minerals, epidote

Rock types (variations):

Considering the presence of quartz or feldspathoid, and the relative proportion of alkali feldspar and plagioclase we can differentiate varieties of gabbros such as monzogabbro, quartz-gabbro and quartz-monzogabbro as well as foid-gabbro, foid-bearing gabbro, foid-bearing monzogabbro and foid-monzogabbro.

Figure II.21. – Gabbro (Tardos quarry, Szarvaskő, SW Bükk)

Figure II.22. – Typical gabbro

Figure II.23. – Typical anorthosite

Figure II.24. – Cross section of an oceanic ridge, a typical tectonic setting of the formation of gabbros. After Perfit et al. (1994 Geology, 22, 375-379)

Locations in the Carpathian-Pannonian region: Tardos and Tóbérc quarries (SW-Bükk, close to Szarvaskő; Early Jurassic), boreholes around Darnó-hill (Triassic), ophiolites at the Maros valley (Apuseni Mts., Jurassic).

Figure II.25. – Typical microscopic photos of a gabbró from the Tardos quarry (SW Bükk). Left with one nicol, right with crossed nicols.

Figure II.26. – Typical microscopic photos of a subophitic microgabbro from the Tardos quarry (SW Bükk). Left with one nicol, right with crossed nicols.

Figure II.27. – Typical microscopic photos of a subophitic microgabbro from the Darnó hill (SW Bükk). Left with one nicol, right with crossed nicols.

BASALT s.l.

Appearance: Dark, mostly aphyric rock with minor amount of phenocrysts (mostly olivine, rarely clinopyroxene and/or plagioclase). The effusive equivalent of gabbro. It occurs almost every plate-tectonic setting.

Mineral content:

Essential minerals: olivine, Ca-rich plagioclase, clinopyroxene

Accessory minerals: spinel (usually as inclusions in olivine and clinopyroxene), apatite, magnetite, ilmenite, nepheline and leucite (in alkaline basalts), K-feldspars (in Si-saturated basalts), rarely amphibole

Secondary minerals: serpentine group minerals, chlorite, carbonate materials

Rock types:

Figure II.28. – Basalt from Somoskő (Nógrád-Gömör)

Figure II.29. – Olivine phenocryst in basalt

Formation of basaltic rocks:

Figure II.30. – Active pahoehoe basaltic lava flow (left; Kilauea, Hawaii) and already solidified pahoehoe basaltic lava rock (right, Reykjanes, Iceland; photos: Szabolcs Harangi)

Figure II.31. – Pahoehoe and aa basaltic lava flows (Kilauea, Hawaii) és aktív aa-lávafolyás (Etna, 1992; photos: Lukács Réka és Szabolcs Harangi)

Figure II.32. – Thin compound pahoehoe basaltic lava flow rocks (Tenerife) and cross section of a basaltic aa lava (Etna; photos: Szabolcs Harangi)

Figure II.33. – Basaltic lava lake in the Erta Ale (Ethiopia) (photo: Ildikó Ipach)

Figure II.34. – Characteristic submarine pillow lava rock: Reykjanes, Iceland (photo: Szabolcs Harangi)

Figure II.35. – Slowly cooled basalt lava with three-tired columnar structure (left, Racos, Persány Mts.) and fan-shaped columnar structured vent-filled basalt (right, Ság hill)

Figure II.36. – Typical microscopic photos of a basalt with olivine phenocrysts (Vasas, Mecsek). Left with one nicol, right with crossed nicols.

Figure II.37. – Typical microscopic photos of a basalt with olivine phenocrysts (Sőreg/Surice, Cseres Mts., Nógrád-Gömör). Left with one nicol, right with crossed nicols.

Figure II.38. – Typical microscopic photos of a basalt with clinopyroxene glomerocrysts (Steinberg, Styrian basin). Left with one nicol, right with crossed nicols.

Locations in the Carpathian-Pannonian region: Boreholes at Darnó hill and Bódva valley (Triassic to Jurassic); Szarvaskő (Early Jurassic); Maros valley (Apuseni; Jurassic); Eastern Mecsek and basement of the Great Hungarian Plain (Early Cretaceous); Miocene-Quaternary alkali basalt volcanic fields: Styrian basin (4.9-1.9 Ma), Burgenland (11.5-11.0 Ma), Kemenesalja (5.5-4.5 Ma), Bakony-Balaton Upland (7.9-2.6 Ma), Nógrád-Gömör (7-0.4 Ma), Selmec (7 és 100 ezer év), Persány (1.2-0.6 Ma). Calc-alkaline basalts: Vlchi vrch, Ziar nad Hronom (Central Slovakian volcanic field; 9-10 Ma), Sárospatak borehole (9 Ma)

Figure II.38. – Locations of the Mesozoic (symbol of volcano without eruption) and Miocene to Quaternary (symbol of volcano with eruption) basalts in the Carpathian-Pannonian region.

Mesozoic basalts:

Figure II.38. – Locations of the Mesozoic basalts in the Carpathian-Pannonian region based on the work of Harangi et al. (1996, Int. Geol. Rev.). In the Fig. C occurrences of basaltic rocks in the area of Darnó (boreholes) and Bódva-valley can be seen.

Figure II.39. – Early Jurassic basaltic (tholeiite) pillow lava at Szarvaskő.

Figure II.40. – A closer view of Early Jurassic basaltic (tholeiite) pillow lava at Szarvaskő.

Figure II.41. – Typical microscopic photos of the pillow lava basalt at Szarvaskő. In the aphyric rock plagioclase and clinopyroxene needles (variolitic texture) can be seen. Left with one nicol, right with crossed nicols.

Figure II.42. – Typical microscopic photos of the pillow lava basalt at Szarvaskő. In the aphyric rock plagioclase and clinopyroxene needles (variolitic texture) can be seen. Left with one nicol, right with crossed nicols.

Figure II.43. – Typical microscopic photos of variolitic pillow lava basalt from a borehole near Darnó hill. Left with one nicol, right with crossed nicols.

Figure II.44. – Early Cretaceous volcanic rocks in the Eastern Mecsek based on the work of Harangi, 1994 in Lithos

Figure II.45. – Classification of the Early Cretaceous volcanic rocks in the TAS diagram based on the work of Harangi, 1994 in Lithos

Figure II.46. – Basaltic pillow lava in the Síngödör and lava breccia in the Márévári valley

Figure II.47. – Reconstruction of the paleoenvironment during the submarine volcanic activity in the Mecsek area

Figure II.48. – Characteristic microscopic feature of the Early Cretaceous ankaramites from the Eastern Mecsek. They contain large, complex zoned clinopyroxene phenocrysts in addition to smaller olivines. Crossed nicols, the length of the lower side of the picture is 2.99 mm.

Figure II.49. – Characteristic microscopic feature of the Early Cretaceous alkali basalts from the Eastern Mecsek. They contain clinopyroxene, plagioclase and ilmenite phenocrysts. Crossed nicols, the length of the lower side of the picture is 2.99 mm.

Figure II.50. – Characteristic carbonate filled vesicles with ilmenite-rich reaction corona around it in the Early Cretaceous alkali basalts from the Eastern Mecsek. Photo with one nicol, the length of the lower side of the picture is 2.99 mm.

Miocene-Quaternary basalts – Styrian basin

Figure II.51. – Miocene-Quaternary basalts and Miocene K-rich trachyandesites in the western part of the Pannonian region. The buried trachyte volcano at Pásztori is also indicated based on borehole data. (after Harangi, 2001, Acta Vulcanologica)

Figure II.52. – Klöch: basalt quarries

Figure II.53. – Erosional remnants of maar volcanoes: Kapfenstein at left and Riegersburg at right (Photos: Szabolcs Harangi)

Figure II.54. – Lithoclast-rich maar deposit at Kapfenstein (Photos: Szabolcs Harangi)

Figure II.55. – Lithoclast-rich maar deposit at Riegersburg (Photos: Szabolcs Harangi)

Figure II.56. – Typical microscopic photos of the basalts from Klöch. Left with one nicol, right with crossed nicols.

Figure II.57. – Typical microscopic photos of the nephelinite from Stradner Kogel. Left with one nicol, right with crossed nicols.

Figure II.58. – Typical microscopic photos of the nephelinite from Stradner Kogel. Left with one nicol, right with crossed nicols.

Figure II.59. – Typical microscopic photos of the basanite from Steinberg. Note the abundance of clinopyroxenes occurring often in glomerophyric groups. Left with one nicol, right with crossed nicols.

Figure II.60. – Typical microscopic photos of the basanite from Steinberg. Note the abundance of clinopyroxenes occurring often in glomerophyric groups. Left with one nicol, right with crossed nicols.

Figure II.61. – Typical microscopic photos of the olivine-basanite from Pauliberg. Note the abundance of clinopyroxenes occurring often in glomerophyric groups. Left with one nicol, right with crossed nicols.

Figure II.62. – Typical microscopic photos of the olivine-basanite from Pauliberg. Note the abundance of clinopyroxenes occurring often in glomerophyric groups. Left with one nicol, right with crossed nicols.

Miocene-Quaternary basalts – Kemenesalja and the Bakony-Balaton Upland:

Figure II.63. – Locations of the basaltic rocks (volcanoes) in Kemenesalja and the Bakony-Balaton Upland region.

Figure II.64. – Basaltic volcanoes of Kemenesalja: the Ság hill (left) and Kissomlyó (right; photos: Szabolcs Harangi)

Figure II.65. – Basaltic volcanoes of Kemenesalja: vent-filling basalts (left) and phreatomagmatic pyroclastic sequence (right) in Ság hill (photos: Szabolcs Harangi)

Figure II.66. – Basaltic volcanoes of Kemenesalja: scoria cone cut by a vent-filling basalts (left) and spatter deposit formed by lava fountaining (right) in Ság hill (photos: Szabolcs Harangi)

Figure II.67. – Basaltic volcanoes of Kemenesalja: phreatomagmatic sequence overlain by basaltic pillow lava (left) and a closer view of the pillow lava rock (right) in Kissomlyó (photos: Szabolcs Harangi)

Figure II.68. – Typical microscopic photos of the olivine-phyric basalt from Ság hill. Left with one nicol, right with crossed nicols.

Figure II.69. – Typical microscopic photos of the olivine-phyric basalt from Ság hill. Left with one nicol, right with crossed nicols.

Figure II.70. – Typical microscopic photos of the phreatomagmatic lapilli tuff from Ság hill (left) and the phreatomagmtic tuff from Kissomlyó. Note the angular sideromelan glass shards on left and the abundance of xenocrysts such as quartz and muscovite on right – all of these are typical of phreatomagmatic products. Left with one nicol, right with crossed nicols.

Figure II.71. – Typical microscopic photos of the vesicular basaltic scoria from Sitke. Left with one nicol, right with crossed nicols.

Figure II.72. – Typical microscopic photos of the vesicular basaltic scoria from Sitke. Left with one nicol, right with crossed nicols.

Figure II.73. – Typical microscopic photos of olivine-phyric basalt with porphyritic intergranular texture from Somló. Left with one nicol, right with crossed nicols.

Figure II.74. – The basaltic volcanoes of the Bakony-Balaton Upland volcanic field: from left to right: Halyagos, Csobánc, Tóti hill, Gulács, Badacsony, Szent György hill (photo: Szabolcs Harangi)

Figure II.75. – The basaltic volcanoes of the Bakony-Balaton Upland volcanic field: columnar jointed basalts in Hegyestű (left) and Szent György-hill (right; photo: Szabolcs Harangi)

Figure II.76. – The basaltic volcanoes of the Bakony-Balaton Upland volcanic field: The Kab hill basaltic shield volcano (photo: Szabolcs Harangi)

Figure II.77. – The basaltic volcanoes of the Bakony-Balaton Upland volcanic field: the lithoclast-rich (with Permian red sandstone blocks) maar volcanic product at left and a ballistic block with a deep impact sag (right; photo: Szabolcs Harangi)

Figure II.78. – The basaltic volcanoes of the Bakony-Balaton Upland volcanic field: the lithoclast-rich basaltic pyroclastic flow deposit at left and gas segregation pipes in this deposit (right; photo: Szabolcs Harangi)

Figure II.79. – Typical microscopic photos of olivine-phyric basalt from Uzsa. Left with one nicol, right with crossed nicols.

Figure II.80. – Typical microscopic photos of olivine-phyric basalt with porphyritic intergranular texture from Csobánc. Left with one nicol, right with crossed nicols.

Figure II.81. – Typical microscopic photos of olivine-phyric basalt with porphyritic intergranular texture from Gulács. Left with one nicol, right with crossed nicols.

Figure II.82. – Typical microscopic photos of clinopyroxene-phyric basalt from the Halom hill. Left with one nicol, right with crossed nicols.

Figure II.83. – Typical microscopic photos of the olivine-phyric basalt from Halyagos. Left with one nicol, right with crossed nicols.

Figure II.84. – Typical microscopic photos of clinpyroxene-phyric basalt from the Hegyesd. Left with one nicol, right with crossed nicols.

Figure II.85. – Typical microscopic photos of the olivine-phyric basalt from Hegyestű. Left with one nicol, right with crossed nicols.

Figure II.86. – Typical microscopic photos of the olivine-phyric basalt from Hegyestű. Left with one nicol, right with crossed nicols.

Figure II.87. – Typical microscopic photos of the olivine-phyric basalt from Hegyestű. Left with one nicol, right with crossed nicols.

Figure II.87. – Typical microscopic photos of the olivine-phyric basalt from Király-kő, Kapolcs. Left with one nicol, right with crossed nicols.

Figure II.87. – Typical microscopic photos of the olivine-phyric basalt from the Kovácsi hill. Left with one nicol, right with crossed nicols.

Figure II.88. – Typical microscopic photos of the olivine-phyric basalt from the Kovácsi hill. Left with one nicol, right with crossed nicols.

Figure II.89. – Typical microscopic photos of the olivine-phyric basalt from the Szent György hill. Left with one nicol, right with crossed nicols.

Figure II.90. – Typical microscopic photos of the olivine-phyric basalt from the Szent György hill. Left with one nicol, right with crossed nicols.

Figure II.91. – Typical microscopic photos of the olivine-phyric basalt from the Badacsony. Left with one nicol, right with crossed nicols.

Figure II.92. – Typical microscopic photos of the olivine-phyric basalt from the Badacsony. Left with one nicol, right with crossed nicols.

Figure II.92. – Typical microscopic photos of the olivine-and clinopyroxene-phyric basalt from the Szigliget. Left with one nicol, right with crossed nicols.

Figure II.93. – Typical microscopic photos of the olivine-and clinopyroxene-phyric basalt from the Szigliget. Left with one nicol, right with crossed nicols.

Figure II.94. – Typical microscopic photos of the olivine-phyric basalt from the Tóti hill. Left with one nicol, right with crossed nicols.

Figure II.95. – Typical microscopic photos of the olivine-phyric basalt from the Tóti hill. Left with one nicol, right with crossed nicols.