Sayense yaku vumbeka ka Afrika Dzonga

© David Fleminger

Dominion Group

Ku tshembiwa leswaku masalela ya Dominion group ya cheriwile kumbe ku hangalaka kwalomu ka 3.07 wa mabiliyoni wa malembe lawa ya hundzeke, eka nkova lowungava kona loko crust leyinga e hansi ka craton yisungule ku tsanyuka. Ntshikelelo lowu wuvuye wu tatiwa hi igneous leyi ngheneke kusuka eka mantle. Tileyara tin’wani ta Dominion Group tina swipetlupetlu swa nsuku, leswi swinga ceriwa kambe kungavi na kuhumelela lokukulu. Aku tiveki swotala ngopfu hi Dominion Group, tani hileswi swinga humelela eka nkarhi lowunga hundza naswona akuri na tindzhawu tintsongo laha maribye lawa aya hlayisiwe kahle.

Eka ndzhawu ya Vredefort, xikombiso, Dominion Group yi hlamuseriwa tani hi leyara yo lala swinene ya lava leyinga erivaleni eka ndzhawu yin’we kumbe timbirhi. Loko kutava kuve na Dominion Group, swiphemu swa Kaapvaal craton swisungule kunyamalala hikokwalaho ka leswi se aku tala mati. Leswi swi endle leswaku kuva na lwandle lerikulu kutsemakanya tiko nkulu laha kunga sungula kukumeka swiphemu leswikulu swa muxaka lowu. Eka nkarhi lowu, swipfuna swinene kulangutisisa kahle eka xiave lexi mati ya xitlangaka eka kuva na ntshamiseko e tshakwini ra lwandle.

Supergroup ya Witwatersrand

Kahle kahle, mati hiwona ya fambisaka hinkwaswo leswi khukhuriweke kusuka eka maribye. Xipidi xa mati xitala ku hlamusela mpfhuka lowu mikhukhula leyi yingata famba wona. Loko nambu wuri na mati yotala (ku fana na lake kumbe lwandle), nkhuluko wuhunguta xipidi naswona swiphemu leswi switikaka swidzika swiya e hansi. Swiphemu leswintsongo kufana na sandi na ndhope switshama swiri endzeni ka mati kuringana nkarhi woleha naswona switala ku khukhuriwa kuya emakumu ka mati. Xikongomelo xakuva ndzi mibyela mhaka leyi yo nyanyula ikuva swita humela erivaleni endzhaku ka nkarhi.

Kuringana, kwalomu ka 2.97 wa mabiliyoni wa malembe lawa ya hundzeke, ti leyara ta maribye ya sedimentary yakumeka eka lwandle roka ringa entangi leswinga endla leswaku kuva na Afrika Dzonga leyi hi yivonaka eka siku ra namuntlha. Leswi swivuriwa West Rand Group naswona swivange swivumbeko leswi tsakisaka hiswivonaka, kufana na eponymous Witwatersrand ridge leyi kumekaka exikarhi ka Germiston na Krugersdorp. Nkarhi wunwana e ndzhaku, craton yitlakukile nyana kutani misava yiva na magova na swinkobyani. Milambu leyi khulukaka kusuka eka ti highlands e n’walungwini kuya e vupela dyambu kuya eka ti lakes na ntshikelelo, laha makhukhula ya salaka kona. Maribye lawa ya endlekaka hinkarhi lowu ya vuriwa Central Rand Group. Hiku hlangana, West Rand Group na Central Rand Group swivitaniwa Witwatersrand Supergroup.

Xihlamariso xa sayense

Central Rand Group ayi hlawulekile swinene, hambi swiritano, hikokwalaho ka swiphemu leswikulu swa nsuku leswi aswi hlantswiwa hi mati kuya emakumu na milambu, xikan’we na gravel. Leswi swiendle ndzhawu yo fuma swinene ya nsuku e misaveni, leyi yingana kuringana hafu ya ndzhawu ya nsuku laha misaveni. Endzhaku ka nkarhi, maribye lawa yangana nsuku lawa ya vuriwaka (ti reefs) ya mayiniwa hiku humelela lokukulu swinene. Laha swisukelaka kona swiphemu leswi swa nsuku, kufikela na sweswi, kahari xihlamariso lexikulu xa sayense.

Kwalomu ka 2.7 wa mabiliyoni wa malembe lawa hundzeke, Kaapvaal Craton yi chayisanile na Zimbabwe craton e n’walungwini. Leswi swiendle ntshava leyikulu swinene leyi namuntlha yivitaniwa Limpopo Mobile Belt. Leswi swi endle leswaku kuva na mikhukhula ya lava leyinga huma hilaha kunga pandzekela eka cratons, leyi nga khumbarheta maribye ya Witwatersrand Supergroup. Lava kusuka e hansi ka leyara ya Ventersdorp Supergroup.

Supergroup ya Transvaal

Kuhundzela nyana e mahlweni, kwalomu ka 2.5 wa mabiliyoni wa malembe lawa ya hundzeke, Kaapvaal Craton yihetelele yitshamiseka naswona yihetelela yiva lwandle leri hiritivaka namuntlha. Leswi switlhontlhe ntshamiseko lowukulu etshakwini leswi sweswi swinga vanga Transvaal Supergroup. Leswi swikotlana na ku hela ka Archaea naku sungula ka nkarhi wa Proterozoic, lowungava kona kufikela 570 wa malembe lawa ya hundzeke. Transvaal Supergroup i maribye yo tsakisa swinene lawa yanga hlengeletana.

Leyara ya wona yale hansi, yivuriwa Black Reef Formation, yina masalela ya nsuku. E henhla ka sweswo kuna Chuniespoort Group. Leyara leyi yina vumbhoni bya vutomi bya khale swinene bya laha misaveni – photosynthesising cyanobacteria. OK, kambe leswi asw tsakisi ngopfu, kambe ti microbial leti hanyaka ati humesa moya tani hileswinga lavekeki leswi vikiwaka leswaku kungava kuve swona leswinga endla leswaku kuva na moya wotala lowu hiwu hefemulaka sweswi laha misaveni. Moya lowu humesiwaka hi cyanobacteria wukote ku hlangana na mati ya lwandle kutani wu endla leswaku kuva na iron oxide yotala, leswinga vanga leswaku kuva na iron na manganese leyi ceriwaka namuntlha.

Malmani Dolomites

Tindzhawu ta ti bacteria tikurile eka mati lawa yoka yanga entanga, kufana na ti coral reefs, na carbon dioxide kusuka eka mati. Leswi swi endle leswaku calcium carbonate yi haha, leyi yinga sirhelela leyara yati bacteria. Ti bacteria tiye emahlweni ku tlhela ti mila ehenhla ka leyara ya calcium naswona maendlelo lawa ya tlhela ya endleka nakambe. Leswi swi endle xivumbeko xa dome xati bacteria, leswi hetelelaka swiva ti fossilis leswi cincaka swiva stromatolites. Xikombiso xa ti stromatolites leti chavisiweke tikumekile eka ndzhawu ya Vredefort naswona switiyisisiwe tani hi xiphemu xale handle eka World Heritage Site. Calcium carbonate nayona yi endla leyara ya maribye leyi vuriwaka Malmani dolomites.

Lawa yana nkoka hikuva dolomite yihetelela yi dyiwa hi mati lawa ya nghenaka emisaveni lawa yanga nghena hilaha maribye yanga pandzekela, kuva ya endla mabaku yohlaya. Endzhaku naswona, mabaku lawa ya hundzuka tindzhawu ta vutumbelo ta valehansi kufana na Mrs. Ples na Little Foot. Fossil yandhuma leyikumekaka e Cradle of Humankind, Sterkfontein, Makapansgat nale Taung yihuma eka leyara yaleyi ya limestone. Kuve na miehleketoya leswaku ku chayisa ka Vredefort kungava kuve na xiave eka ku endla leswaku kuva na kupandzekela ka maribye leswinga vanga mabaku, lawa yangava na nhlolhetelo eka kuva kutwisisiwa swinene eka ntumbuluko wa munhu.

Bushveld Igneous Complex

Endzhaku ka kutumbuluka ka Transvaal Supergroup, kuve naku fayana ka maribye kusuka e hansi. Kwalomu ka 2.06 wa mabiliyoni wa malembe lawa ya hundzeke, kuve na kubuluka kotala loku kunga kavanyetiwa kurhula eka cyanobacteria kutani ku khumbrhetiwa Kaapvaal Craton hi leyara ya maribye na nkuma. Laha eku heteleleni, kungava na kulongoloko ka mantle kunga susumeta nhlayo ya maribye ya igneous leyinga tshikelela swinene hile xikarhi ka maribye ya Transvaal, kambe ayi fikangi e henhla.

Kasi loko kuri subterranean magma chamber yihorile hikantsongo ntsongo kutani ri endla tileyara to hlaya ta Bushveld Igneous. Ri nava swinene eka tindzhawu totala tale Dzongeni wa Afrika naswona i xikombiso xirixoxe xa muxaka lowu e misaveni hinkwayo. Complex leyi yina yin’wana ya swipetlu swikulu swa platinum, chromium, copper, vanadium, titanium na nickel leswinga laha misaveni.

Ribye leri bulukaka e Vredefort

Kutani kuta xihlamariso lexikulu swinene. Malembe ya 2 billion lawa hundzeke, Vredefort bolide riwile kuya evuhuma dyambu. Akuri tikilomitara to hlaya nyana hiku anama naswona rifambile hi matimba swinene kuya e xikarhi ka Kaapvaal Craton. Ku chayisa ka kona aku chavisa swinene. Maribye lawa yale tshakwini yavuye yava na mati naswona tshaku rakona rivuye ri hundzuluxiwa, leswinga endla leswaku vasayense ya ximanguva lawa vakota ku vona matimu ya xikhale.

Vredefort bolide yi endle nyanyulo wukulu. Endzhaku ka chayisa loku, kuve na maribye yantshwa lawa nga tumbuluka e Dzongeni wa Afrika, naswona maendlelo ya xisayense lawa hlamuseriweke laha henhla yaha humelela na namuntlha. Hambi swiritano, vutihlamuleri bya sayense ya tiko rerhu byi tlula buku leyi. Ematshan’weni ya sweswo, sweswi hifanele ku tshika ku languta e hansi hi languta e henhla leswaku hita kota ku vona kahle ‘single energy release event’ leyi misava yinga se tshamaka yi yivona.

Translated by Ike Ngobeni