The Semail Ophiolite near Oman mountains is a big slab of oceanic crust that's made of volcanic rocks and the Earth's upper mantle that got overthrusted.[1] It is located on the northeastern corner of the Arabian Peninsula[2] (Fig. 1) and it covers an area of approximately 100,000 km2.[1] Based on U-Pb dating the Semail ophiolite formed in the late Cretaceous.[3] It is primarily made of SiO2 range from 45-77 wt%.[4] The Semail ophiolite is very important because it provides valuable information about the ocean floor and the upper mantel on land and allow geologist to study it.[1] However, geologist studied the area for a while and trying to come up with the best model that explain how the Semail Ophiolite formed.
Geologic Formations edit
The Arabian continental margin formed in early Paleozoic and possibly late Proterozoic. After that the thrust sheets are from low to high structurally: the Seamount rocks, the Ophiolite, and the Batinah complex.[5]
- The Seamount Rocks
Include the Sumeini group, the Hawasina complex, and the Haybi complex. They are making the continental slope with age rage from Middle Triassic to Late Cretaceous.[5]
- The Ophiolite
It is consists of a basal metamorphic sole (150–200 m), peridotite tectonic (8–12 km), igneous peridotite and gabbro (0.5-6.5 km), sheeted dikes (1-1.5 km), lavas (0.5-2.0 km).[5]
- The Batinah complex
It came from beneath the ophiolite during late-stage extensional faulting and then slid into the ophiolite late in the emplacement history.[5]
Tectonic Models edit
There are three different models that may explain how Semail ophiolite could form and overthrust a continental:
- The Gravity sliding model: A 7 to 20 km Thick ophioitic terrane could slide onto a continental margin. This will requires an elevated source region that's why geologies think about other models. This model is the least model spurted by geologist.[6]
- The Suprasupduction Model: The oceanic crust obducted continental lithosphere and then followed by volcanic arc (Fig. 2). Figure 2-A, older than 101 to 95 Ma the mid-ocean ridge is spreading and the ocean crust sub-ducted under the continental lithosphere on the right while the other side is over riding the oceanic crust on the left. Also, that's where the Semail start to form and volcanism start to form a volcanic arc. Figure 2-B, from 95 to 87 Ma the mid-ocean ridge is spreading and a volcanic arc have formed. Figure 2-C, from 87 to 76 Ma the mid-ocean ridge is spreading and the ocean crust being pushed and over thrusted the continental lithosphere by the help of the volcanic arc.[7]
- The Obducting model: The oceanic crust obducted continental lithosphere (Fig. 3). Figure 3-A, older than 101 to 95 Ma the mid-ocean ridge is spreading and the ocean crust sub-ducted under both continental lithosphere. Also, The Semail Ophiolite initial place marked on the right oceanic crust. Figure 3-B, from 95 to 87 Ma the mid-ocean ridge stopped spreading and there is an intra-oceanic thrusting. Where the left oceanic crust sub-ducted under the right oceanic crust with Semail Ophiolite. Figure 3-C, from 87 to 76 Ma the Semail Ophiolite overthrusting the continental lithosphere and emplaced onto craton. This model is more spurted by geologist.[1][5]
References edit
- ^ a b c d e Jan Schreurs. "Ophiolites a natural wonder" (PDF). Retrieved 10 October 2013.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ MOL Scientific Magazine. 2008.
{{cite journal}}: Missing or empty|title=(help) - ^ Wilson, H. Hugh (July 2000). "THE AGE OF THE HAWASINA AND OTHER PROBLEMS OF OMAN MOUNTAIN GEOLOGY". Journal of Petroleum Geology. 23 (3): 345–362. doi:10.1111/j.1747-5457.2000.tb01023.x. S2CID 128840838.
{{cite journal}}: CS1 maint: date and year (link) - ^ "Suprasubduction-zone ophiolites: Is there really an ophiolite conundrum?". The Geological Society of America. Special Paper 438: 191–222. 2008.
- ^ a b c d e f Hacker, Bradley R. (April 1991). "THE ROLE OF DEFORMATION IN THE FORMATION OF METAMORPHIC GRADIENTS: RIDGE SUBDUCTION BENEATH THE OMAN OPHIOLITE". Tectonics. 10 (2): 455–473. doi:10.1029/90TC02779.
{{cite journal}}: CS1 maint: date and year (link) - ^ "Reinhardt BM 1974 Geology of the Oman mountains". . Verhandelingen Koninklijk Nederlands Geologisch Mijnbouwkundidg Genootschap. 31: 423.
- ^ Oxburgh ER (1972). "Flake Tectonics and Continental Collision". Nature. 239 (5369): 202–204. doi:10.1038/239202a0. S2CID 4186536.