Ndzavisiso wa Vredefort Dome

Valavisisi va laha kaya

Endzhaku e Afrika Dzonga, hambi leswi, nhluvuko wa xi sayense awulave kuhi hundza hikwala tlhelo. Hi 1916, S.J. Shand u sungule ku hlamusela hi melt-rock phenomenon leswi aswivula ‘pseudotachylite’ kambe anga kaneti leswaku kungava kuve na volcano leswaku kutava na ribye. Vulavisisi lebyi hlamuselaka kahle byo sungula bya sayense eka dome, lebyingava kona hi 1925, byi kume leswaku dome yivangiwe hi kubuluka ka gasi ya volcano lokukulu. Hi 1936, valavisisi vambirhi vavike leswaku ku gandliwa loku hikona kunga endla leswaku kuva na dome, kambe leswi aswitekeriwangi enhlokweni hi valavisisi.

Lexi axiva sivela ngopfu akuri xivumbeko xa Dome hi xoxe. Swinga endlekisa kuyini leswaku ku gandliwa kusuka e henhla swiendla leswaku kuva na kutlakuka ka misava? Kahle kahle kunghenelela kumbe ku buluka endzeni kungava ku endle leswaku kuhuma xivumbeko lexi kungari ku gandliwa hi le handle. Hambiswiritano, hi 1947, mutivi wa sayense loyi ativekaka hi R.A. Daly nayena u langutisise ku gandliwa loku laha anga hlamusela leswaku ku chucheka ka ntshikelelo endzhaku ko gandliwa kungava swona leswinga endla leswaku kuva na xivumbeko lexi. Mutivi nkulu wa geology e Afrika Dzonga, Alex du Toit, u sale anga tshembi laha anga vika leswaku dome yi vangiwe hi maendlelo ya tectonic.

Ku kanetana swiya emahlweni

Kuringana malembe, kukanetana swiye emahlweni. Mavonelo yo huma ematikweni yale handle hile tlhelo ra xikolo xaku gandliwa. Kambe valavisisi va Afrika Dzonga vaye emahlweni vahumesa maphepha lawa ya hlamuselaka ntumbuluko walendzeni ka misava (magmatic or tectonic). Hiva 1960s, xiviko kusuka eka Geological Survey of Ottawa xikote kuhambanyisa eka tinxaka timbirhi ta swirhengele leswi: leswi swinga anama kuringana tikilomitara tintsongo, leswitalaka kuva na xivumbeko xa xindhichani xikan’we na leswinga anama swinene leswi swinga kukumuka laha exikarhi switlhela swirhandzeriwa hi maribye na tileyara tintsongo.

Xivumbeko xa xirhengele lexi xa ‘complex’ axi fana swinene Vredefort. Hambiswiritano, vativi va sayense vayise emahlweni ntirho wa vona, laha ava amukela na ntirho wa vativi va matiko yale handle lava nga ntokota hi cryptoexplosion, Walter Bucher, loyi ayima hi rito raku swivumbeko swa dome aswivangiwe hiku buluka ka gasi yo hisa leyi ayi pfuta hileka tindzhawu to vevuka ta misava.

Shock Metamorphics

Handle ko kanetana ka valavisisi valaha kaya, kutwisisiwa ka shock metamorphics kuye emahlweni ku andza. Hi 1968, kuvile na khonferense ya matiko hinkwawo ehansi ka nhloko mhaka leyi, leswinga tisa vativi votala swinene kusuka eka matiko yo hambana hambana. Leswi switise matwisiselo yantshwa naswona endzhaku ka malembe nyana kuve na kuhumelela kokarhi loku endliweke. Kuve na swiviko kusuka eka swirhengele, swikombiso swa maribye ya lunar na mbuyelo wa swikambelwani swale laboratory leswinga ya emahlweni kuva swihumesela mbuyelo lowu fanaka, naswona swisungule ku voyamela eka hypothesis. Eku heleni ka malembe yava 1970s, swivumbeko swa 120 swikumekile eka tindzhawu to hambana hambana ta misava naswona swikomba swilo leswi endlaku maribye lawa yanga hlamuseriwe eka swirhengele leswi. Maribye lawa loko yahlanganile ya vuriwa ‘impactites’ – rito leri tisaka swirho swati klilasi yati aerobics emihleketweni, kumbe vanhu lavanga tlimbana endzhawini yin’we.

Hiva 1980s, vativi votala vale matikweni yale handle ava tshembile naswona ti yunivhesithi tale handle ati dyondzisa leswaku Vredefort Dome ayi endliwe hiku gandliwa. Kambe kungari e Afrika Dzonga. Laha, vapfumeri nkulu (varhangeriwe hi geologist Louis Nicolaysen) ava yima na ripfumelo ra vona ra leswaku dome yisukela eka cryptovolcanic. Eku heteleleni, ku vitaniwile khonferense leswaku kuta kumiwa xitshunxo eka ntlimbo lowu. Yive kona e Parys hi 1987 naswona vativi vohambana hambana vavulavurile eka nhlengeletano leyi. Nhlengeletano leyi ayi tswalanga mihandzu hikuva ava pfumelelanangi hi nchumu emakumu. Leswi swivange leswaku kuva na nhlawulo emakumu ka nhlengeletano leyi laha nhlayo leyikulu nyana ya va ngheneleri yinga seketela kusungula ka yona eka exogenic (external impact).

Eka xiyimo xa Atomic

Kukomisa xitori lexi xo leha, malembe ya khume lawa yanga landzela aya tele hi swiviko kusuka eka valavisisi e Afrika Dzonga nale misaveni hinkwayo. Dome yi lavisisiwile swinene hiti geologists, naswona kantsongo kantsongo, vumbhoni byive kona. Coesite na Shishovite swikumekile, kukumeke nati micro-deformations ta quartz crystals letinga vonaka xikan’we na ntumbuluko wa metamorphism eka maribye yanga dyondziwa swinene. Ekuheteleleni, hi 1997, Hughes Leroux u kote ku langutisisa swikombiso swinwana swa maribye eka xiyimo xa atomic. Leswi anga swikuma hileswaku Vredefort Dome yivavisekile endzhaku kaku gandliwa loku leswinga khumba na maribye lawa yanga eka ndzhawu liya. Ku hleketelela swivuye swihela eku heteleleni.

Translated by Ike Ngobeni