Ilimin kasa na Ghana
 Ilimin kasa na Ghana | |
|---|---|
| Bayanai | |
| Ƙaramin ɓangare na | ilmin duwatsu |
Kimiyyar ilimin ƙasa ta ƙasar Gana ita ce dutsen ginshiƙi na dindindin na dā, belts na dutsen wuta da kwandon shara, waɗanda lokutan ayyukan ƙazantawa da manyan abubuwan gina ginin dutse guda biyu suka shafa. Baya ga raƙuman ruwa na zamani da wasu duwatsun da aka kafa a cikin shekaru miliyan 541 da suka gabata na Phanerozoic Eon, a bakin tekun, yawancin duwatsun da ke Ghana sun kasance kusan shekaru biliyan daya da suka gabata ko kuma tsofaffi wanda ke haifar da nau'ikan nau'ikan adon gwal guda biyar, wanda ya ba da yankin tsohon sunansa Gold Coast.
Stratigraphy, Tectonics & Tarihin ilimin kasa[gyara sashe | gyara masomin]
Tsoffin duwatsu daga Paleoproterozoic, Neoproterozoic kuma wataƙila farkon Paleozoic ya rufe kusan Ghana duka, ban da kusa da bakin tekun inda duwatsun Paleozoic, Mesozoic da Cenozoic suka zama ruwan dare.
Babban rukunin dutsen Precambrian sun haɗa da metamorphosed da folded Dahomeyan, Birimian, Tarkwaian System, Togo Series, da Buem Formation. Duwatsun Paleozoic sun haɗa da Tsarin Voltaian, da Tsarin Sekondi-Accraian.[1]
Paleoproterozoic (shekaru 2.5-1.6 da suka wuce)[gyara sashe | gyara masomin]
Rukunan Paleoproterozoic na Birimian Supergroup, gama gari a Yammacin Afirka, sun mamaye arewa maso yamma da kudu maso yammacin Ghana. Birimian Supergroup yana da raka'a biyu, ɗaya jeri na duwatsu masu ɗimbin yawa waɗanda suka haɗa da phyllite, tuff da greywacke waɗanda suka haɗu da haɗin gwiwa, sandstone da shale da ɗayan jerin magma na tholeiitic. Da farko, masanan ilmin ƙasa sun raba raka'a zuwa Ƙananan Birimiya da Babban Birimiya, amma binciken da ya biyo baya ya gano cewa dutsen mai aman wuta yana samar da bel ɗin kilomita ɗari da yawa a cikin babban rukunin, tare da ƙarancin ƙimar metamorphism na dutsen tholeiitic lava.
Belt ɗin dutsen mai aman wuta daga arewa zuwa kudu shine Lawra Belt, Bole-Navrongo Belt, Sefwi Belt, Asankrangwa Belt, Ashanti Belt da Kibi-Winiba Belt. Ban da Lawra Belt, duk suna tafiya arewa maso gabas-kudu maso yamma. Tsakanin ɗamara daban -daban akwai kwanduna cike da dacite, argillite, volcaniclastic da granitoid duwatsu tare da isocline folding. A sauye-sauye tsakanin kwandunai da beltsan tsaunukan ƙananan ƙananan ɓoyayyun ɓoyayyun ɓarna, carbonates da manganese mai ɗimbin yawa, waɗanda aka ƙaddara su zama ragowar abubuwan fashewa waɗanda suka haifar da bel ɗin dutsen.[2]
An nade duwatsu masu aman wuta da duwatsu a lokacin Eburnean orogeny shekaru 2.2 zuwa biliyan 2.0 da suka gabata kuma granitoids suka kutsa kai. Har ila yau, orogeny ya ɗaga kuma ya lalata duwatsun, ya cika babban graben tare da jerin molasse mai lanƙwasa na sabbin duwatsu, wanda aka sani da Tarkwaian Group. Kusan lokaci guda, an sake kutsawa cikin rukunin Birimian Supergroup, a wannan karon ta Cape Coast type batholith granites da granodiorite, tare da nau'in Winneba wanda ke da asalin sikelin Archean daga saman mafi girman mayafin. Har ila yau, Ghana tana da wasu nau'ikan granite daga wannan lokacin, ciki har da nau'in Dixcove, wanda ya haifar da kutse a cikin bel ɗin dutsen mai fitad da wuta da kuma ƙarancin granitoids na Bongo, wanda ya samo asali bayan Eburnean orogeny.[3]
Neoproterozoic (shekaru biliyan 1 da miliyan 541 da suka gabata)[gyara sashe | gyara masomin]
A cikin Neoproterozoic, Pan-African orogeny ya shafi Ghana. A yau, Pan-African mobile bel terrane ya ratsa gabas da kudu maso gabashin Ghana, tare da raka'a daban-daban. Tsarin Dahomeyan ya ƙunshi mafic da felsic gneiss yayin da Togo Series ya haɗa da ma'adini, shale da ƙananan adadin serpentinite. Ƙungiyar Buem cakuda sinadarai ne da duwatsu masu ƙyalli, gami da shale, sandstone, basalt, trachyte da duwatsu masu aman wuta.
Gindin Volta da aka kafa a lokacin Neoproterozoic kuma ya haɗa da rairayin rairayin bakin rairayi da ƙaƙƙarfan kilo mita ɗaya na Bambouaka Supergroup, wanda ya taso tsakanin biliyan 1.1 zuwa miliyan 700 da suka gabata. A cikin Neoproterozoic, taron Snowball Earth ya haifar da glaciation a cikin abin da ke yanzu Afirka. Rushewar glacial ya haifar da rashin daidaituwa tsakanin Bambouaka Supergroup da Pendjari Supergroup (wanda kuma aka sani da Oti Supergroup), wanda a wasu lokuta kai tsaye yana kan saman dutsen ginshiki na dindindin. Kauri mai tsawon kilomita 2.5, Pendjari Supergroup mai shekaru miliyan 600 zuwa 700 yana da farar ƙasa da dolomitic limestone, mai wadataccen barite da silixite a gindinsa da siltstone da argillite a saman sa. Babban naúrar ta uku a cikin Basin Volta ita ce Tamale Supergroup, tare da kaurin mita 500, yumɓu da siltstone a gindinsa, yana ba da hanya ga ƙanƙara. Masana kimiyyar yanayin ƙasa suna muhawara kan shekarun Tamale Supergroup wanda wataƙila ya samo asali ne a ƙarshen Neoproterozoic ko wataƙila a cikin Cambrian na farkon zamanin Paleozoic.[4]
Phanerozoic (shekaru miliyan 541 da suka gabata-yanzu)[gyara sashe | gyara masomin]
Phanerozoic, halin da ake ciki a yanzu wanda rayuwar ɗimbin yawa ya zama sananne galibi ana yin rikodin shi a gabar tekun Ghana. An sanya jerin Accraian a cikin farkon Devonian da Devonian na Tsakiya yayin da jerin Sekondian suka kasance tsakanin Tsakiyar Devonian da Early Cretaceous, tare da Late Jurassic zuwa Rukunin Amisian na Farko. Late Cretaceous Apollonian Group yana daga cikin rukunin rukunin dutsen na baya -bayan nan. Shekaru miliyan 66 da suka gabata na Cenozoic galibi ana yin rikodin su da duwatsu na ruwa, lagoonal da kogin ruwa tare da abubuwan da ba a haɗa su ba waɗanda ke rufe yawancin ƙasar da samar da ƙasa.[4]
Hydrogeology[gyara sashe | gyara masomin]
Manyan sassan guda uku na Kogin Volta muhimmin ruwa ne a gabashin Ghana tare da raguwa sosai, idan akwai, rabe -rabe tsakanin juna. Tsakanin Pendjari Supergroup da Obosum Group sandstones, mudstones da siltstones galibi suna da ƙarancin ma'adinai, amma suna ɗauke da wasu fluoride, yayin da zurfin Bambouaka Supergroup duwatsu suna da babban sulfate, ƙarfe da manganese da yawa kuma a wasu wurare fluoride da babban gishiri. Kodayake gabaɗaya ba za a iya jurewa ba, raƙuman ruwa da suka fashe a cikin duwatsu na ƙasa suna rufe yawancin kudanci da yammacin Ghana tare da ɗan acidity, ƙarancin gishiri, ƙarancin ƙarfi da iodine, amma babban fluoride. A wasu wurare a kudu maso yammacin Ghana, ruwan karkashin kasa daga dutsen ginshiki yana dauke da manyan sinadarin arsenic da ke hade da zinare a cikin jijiyoyin ma'adinai.
Ba a yin nazarin karancin ruwan ƙarƙashin ƙasa a Ghana sai dai rijiyoyi 15 da ake kula da su a arewa maso gabas.[5]
Ilimin na albarkatun ƙasa[gyara sashe | gyara masomin]
Zinariya tana taka muhimmiyar rawa a cikin tattalin arzikin Ghana, tare da ton na zinari har zuwa 1500 da aka samar a duk tarihin ta. Ghana tana da manyan nau'ikan zinari guda biyar. Zinare na asali a cikin tsattsarkan jijiyoyin ma'adini a cikin yankuna masu rarrafe a gefen rafukan Birimiya, arsenopyrite a cikin sassan sulfur, yaɗa ma'adinan a cikin duwatsun granitoid da gwal na alluvial placer na zinari a cikin kogunan ruwa a cikin tsakuwa sune manyan hanyoyin zinare. A wasu lokuta, tsohuwar zinaren zinare ya haƙa ƙasa kuma ya sake haɗawa tare da wasu ma'adanai irin su magnetite da hematite a cikin ƙungiyoyin ma'adini na ƙungiya ta Tarkwaian.
Daga karshen karni na 15 har zuwa tsakiyar karni na 19, an kiyasta kashi biyu bisa uku na samar da zinare na Afirka ya samo asali ne daga Tekun Gwal. Yawan shekara-shekara a farkon shekarun 1980 shine 12,000-15,000 kg. Ana samun manyan lodin zinare a cikin yanki mai sheƙa tsakanin ƙananan Birimian phyllites da Upper Birimian greenstones, kuma ya ƙunshi jijiyoyin ma'adini da reefs na lenticular. Yawancin gwal yana tare da arsenopyrite. Ma'adinai da ke gefen yamma na haɗin gwiwar Tarkwa sun haɗa da Obuasi Gold Mine, da waɗanda ke Prestea da Konongo. Ana samun gwal mai ɗanɗano a cikin haɗin gwiwar Banket kusa da gindin Tarkwaian. Wannan ya hada da Iduapriem Gold Mine, Teberebie Mine, da waɗanda ke Tarkwa, da Abosso, waɗanda ke gefen gefen layin Tarkwa syncline. Abokan ma'adanai sun haɗa da rutile, zircon, da hematite detrital, duk a cikin tsaunukan tsakuwa. An haƙa gwal na placer a rafin Ofin a Dunkwa-on-Offin. Bugu da ƙari, eluvium, yashin rairayin bakin teku, filaye, da rafin rafi na Pleistocene suna ɗauke da gwal mai ɗorewa.[6][7]
Ana samun mahimman adon lu'u -lu'u a cikin tsaunukan kogi a tsakiya da gabashin Ghana, duk da cewa ƙasar ba ta da bututun kimberlite inda lu'u -lu'u suka samo asali a tarihin ƙasa. Awaso, a kudu maso yammacin kasar Ghana na karbar bakuncin ma'adanai da Kamfanin Bauxite na Ghana ke gudanarwa. Bauxite ya samo asali ne daga yanayin yanayin Paleoproterozoic phyllite. Nsuta a gundumar Sekyere ta Tsakiya na Yankin Ashanti yana da manganese oxide da carbonate mine. Har ila yau, ƙasar tana da ƙananan, asbestos, chromite, andalusite, mica, barite, cassiterite, columbite, monazite, beryl, spodumene da molybdenite. Har ila yau, yana da syenite na dangi da kuma rarar alluvial na rutile da ilmenite. Kasar Ghana tana da yalwar yashi, tsakuwa, kaolin da sauran abubuwan da aka tanada don gina tituna da gine -gine gami da samar da tubali.[8]
Manazarta[gyara sashe | gyara masomin]
- ↑ Kesse, G.O. (1984). Foster, R.P. (ed.). The occurrence of gold in Ghana, in Gold '82: The Geology, Geochemistry and Genesis of Gold Deposits. Rotterdam: Geological Society of Zimbabwe, A.A. Balkema. pp. 648–650. ISBN 906191504X.
- ↑ Schluter, Thomas (2006). Geological Atlas of Africa. Springer. pp. 116–117.
- ↑ Eisenlohr & Hirdes (1992). "The structural development of the early Proterozoic Birimian and tarkwaian rocks of southwest Ghana, West Africa". Journal of African Earth Sciences (and the Middle East). Journal of African Earth Sciences. 14 (3): 313–325. doi:10.1016/0899-5362(92)90035-B.
- ↑ 4.0 4.1 Schluter 2014, p. 116-117.
- ↑ "Hydrogeology of Ghana". British Geological Survey.
- ↑ Wright, J.B.; Hastings, D.A.; Jones, W.B.; Williams, H.R. (1985). Wright, J.B. (ed.). Geology and Mineral Resources of West Africa. London: George Allen & UNWIN. pp. 45–47. ISBN 9780045560011.
- ↑ Taylor, Ryan; Anderson, Eric (2018). Quartz-Pebble-Conglomerate Gold Deposits, Chapter P of Mineral Deposit Models for Resource Assessment, USGS Scientific Investigations Report 2010-5070-P (PDF). Reston: US Dept. of the Interior, USGS. p. 9.
- ↑ Schluter 2014, p. 118-119.