Momwe mungatsatire chiyambi cha zinthu zakale pogwiritsa ntchito isotopes
Kutsata komwe chinthu chinachokera—kumene zinthu zake zopangira zinachokera, komwe chinapangidwira, komanso njira zake zamalonda—ndi chimodzi mwa zovuta zazikulu pa kafukufuku wa zinthu zakale ndi cholowa cha chikhalidwe. Kwa zaka zambiri, ofufuza akhala akugwiritsa ntchito kalembedwe ka zaluso, njira zopangira, ndi zomwe zapezeka kuti apeze “nkhani” kumbuyo kwa zinthu zakale. Komabe, njira imeneyi nthawi zina ingapangitse kuti zikhale zovuta kusiyanitsa pakati pa zisonkhezero za chikhalidwe ndi gwero lenileni la chinthucho. Apa ndi pomwe kusanthula kwa isotope kumakhala chida champhamvu: ma isotope amatha kugwira ntchito ngati “zala” za geochemical zomwe zili mu chinthucho, kuthandiza kujambula zizindikiro za chiyambi cha chinthucho molondola kwambiri nthawi zambiri kosatheka ndi njira zowonera zokha.
Kodi ma isotopes ndi chiyani ndipo n'chifukwa chiyani ndi othandiza?
Ma Isotope ndi mitundu yosiyanasiyana ya chinthu chimodzi (chiwerengero chomwecho cha ma proton) koma ndi ma neutroni osiyanasiyana, zomwe zimapangitsa kuti pakhale misa yosiyanasiyana. Mwachitsanzo, kaboni ili ndi ma isotope ^12C ndi ^13C, mpweya uli ndi ^16O ndi ^18O, ndipo strontium ili ndi ^87Sr ndi ^86Sr. Kusiyana kumeneku kungawoneke kochepa, koma chilengedwe chimapanga kusiyana koyezeka kwa ma isotope m'miyala, dothi, madzi, komanso zamoyo zosiyanasiyana. Chifukwa chakuti zinthu zopangidwa zimapangidwa kuchokera ku zinthu zomwe zinachokera m'malo enaake, ma isotope omwe ali m'zinthu zopangidwa nthawi zambiri amakhala ndi chidziwitso chokhudza malo omwe anachokera.
Ubwino waukulu wa ma isotope ndi kukhazikika kwawo. Ma isotope ambiri sasintha kwambiri zinthuzo zitapangidwa kapena zinthuzo zitapangidwa, makamaka ngati chitsanzocho chagwiritsidwa ntchito bwino ndipo kuipitsidwa kumawongoleredwa. Poyerekeza chiŵerengero cha isotope cha zinthuzo ndi "isoscape" kapena database yowunikira za geological, ofufuza amatha kudziwa ngati zinthuzo zinachokera ku dera A, B, kapena C—nthawi zambiri mpaka ku malo enieni a geological kapena komwe mgodi unachokera.
Mfundo zazikulu: "zolemba zala" za isotope ndi kufananiza kwawo
Kusanthula kwa Isotope kumagwira ntchito bwino kwambiri ngati pali zinthu ziwiri: (1) chinthu chopangidwa chomwe chimasunga chizindikiro cha isotopic, ndi (2) deta yoyerekeza kuchokera kuzinthu zomwe zingatheke. Ngati chinthu chopangidwa ndi bronze chikukayikiridwa kuti chimagwiritsa ntchito mkuwa wochokera ku migodi yosiyanasiyana, ofufuza ayenera kuyeza ma isotope mu chinthucho komanso mu zitsanzo za ore/slag/chitsulo kuchokera ku migodi imeneyo. Kufanana kwa ma isotope ratios kungathandize kulimbikitsa lingaliro la komwe chinthucho chinachokera.
Komabe, ndikofunikira kudziwa kuti "kufananiza" sikutanthauza nthawi zonse "zotsimikizika." Nthawi zina malo awiri amakhala ndi ma isotope ofanana, kapena zinthu zitha kukhala zitasakanizidwa kuchokera kuzinthu zosiyanasiyana. Chifukwa chake, ma isotope nthawi zambiri amaphatikizidwa ndi kusanthula kwa zinthu zotsalira, maphunziro a zitsulo, petrography, kapena deta ya zakale monga momwe malo alili.
Mtundu wofala wa isotope womwe umagwiritsidwa ntchito pofufuza komwe zinthu zakale zinachokera
1) Ma isotope a Strontium (^87Sr/^86Sr): ma genetiki otchuka
Strontium ndi yothandiza chifukwa chiŵerengero cha ^87Sr/^86Sr chimasiyana malinga ndi zaka ndi mtundu wa mwala. Miyala yakale yokhala ndi rubidium yambiri imakhala ndi ^87Sr yokwera chifukwa cha kuwonongeka kwa ^87Rb. Strontium imalowa m'nthaka ndi madzi, kenako zomera ndi nyama, ndipo pamapeto pake imalembedwa m'mano, mafupa, kapena zinthu zina zachilengedwe.
Pankhani ya zinthu zakale, strontium nthawi zambiri imagwiritsidwa ntchito pa:
- Kudziwa komwe munthu amachokera (monga pa enamel ya dzino la munthu kuti akafufuze za kuyenda kwa dzino), zomwe ndizofunikira kwambiri ngati chinthucho ndi chamoyo kapena chokhudzana ndi kuikidwa m'manda.
- Kutsata zinthu zinazake zopangira zomwe zimagwirizana ndi chilengedwe cha m'deralo, mwachitsanzo laimu, zipangizo zomangira, kapena zinthu zina zomwe zimayamwa Sr kuchokera m'madzi.
Mphamvu ya Sr ndi kuyandikira kwake ndi "siginecha" ya geology, koma imafuna mamapu abwino ofananiza ndipo iyenera kuwerengera kusintha komwe kungachitike pambuyo poika zinthu zina.
2) Ma isotope a lead (Pb): chinsinsi cha zitsulo ndi miyala
Ma isotope a lead monga ^206Pb, ^207Pb, ^208Pb (zopangidwa ndi uranium ndi thorium) ndizothandiza kwambiri pophunzira za zitsulo. Migodi yosiyanasiyana imatha kukhala ndi ma Pb ratios osiyana, zomwe zimathandiza kuti zinthu zachitsulo zomwe zili ndi lead zidziwike bwino (kapena kuipitsidwa kwa Pb kuchokera ku zitsulo). Njirayi imagwiritsidwa ntchito kwambiri pa:
- Kugwirizanitsa zinthu zopangidwa ndi bronze, tin, siliva, kapena lead ndi madera enaake a migodi.
- Kumvetsetsa netiweki yogulitsa zitsulo m'nthawi zakale komanso zakale.
Vuto lalikulu: njira yosungunula ndi kusakaniza zitsulo kuchokera kuzinthu zosiyanasiyana ingapangitse "kusakaniza" kwa ma isotope komwe kumabisa chiyambi chimodzi. Chifukwa chake, kusanthula nthawi zambiri kumaphatikizidwa ndi zinthu zochepa komanso nkhani ya zitsulo.
3) Ma isotope a okosijeni (δ^18O) ndi haidrojeni (δD): mapazi a madzi ndi nyengo
Mpweya ndi haidrojeni zimagwiritsidwa ntchito kwambiri pofufuza ubale pakati pa magwero a madzi ndi nyengo. Mu zinthu zina—monga carbonates, mafupa, mano, kapena ngakhale magalasi ndi zinthu zadothi—ma isotope ratios amatha kulemba kutentha kwa kapangidwe ka madzi m'deralo kapena kapangidwe kake.
Pa zinthu zakale, δ^18O ingathandize:
- Unikani ngati chinthu (monga chipolopolo, carbonate) chinapangidwa m'malo a m'nyanja poyerekeza ndi a padziko lapansi kapena m'dera linalake la nyengo.
- Imathandizira lingaliro la chiyambi cha malo pamene ikuphatikizidwa ndi Sr kapena deta ina.
Komabe, kutanthauzira kwa δ^18O nthawi zambiri kumakhala kovuta chifukwa kumakhudzidwa ndi nyengo, kutalika, mtunda kuchokera kugombe, ndi njira yotenthetsera panthawi yopanga.
4) Ma Isotope a kaboni (δ^13C) ndi nayitrogeni (δ^15N): momwe zinthu zilili komanso magwero a zamoyo
Ma isotope a C ndi N nthawi zambiri amagwiritsidwa ntchito pofufuza magwero achilengedwe: zakudya, mtundu wa zomera (C3 vs. C4), kapena komwe zinthu monga nsalu, mapepala, utomoni, ndi zotsalira za chakudya pa mbiya. Mu kafukufuku wa zinthu zakale:
- Zotsalira za chakudya pa mbiya zitha kufufuzidwa kuti zidziwike ngati zimachokera kumadzi kapena kumtunda.
– Ulusi wa nsalu ukhoza kupereka chidziwitso chokhudza malo omwe zomera zimamera (monga fulakesi, thonje) ngati pali deta yofananira.
Ma isotope amenewa ndi amphamvu kwambiri potanthauzira zachilengedwe ndi machitidwe a moyo, kenako amalumikizidwa ndi chiyambi kudzera mu chithandizo cha deta ya malo.
Kodi njira yotsatirira imachitidwa bwanji?
1) Dziwani mafunso ofufuza
Kusanthula kwa Isotope kuyenera kuyamba ndi funso lomveka bwino: kodi mukufuna kufufuza mgodi wachitsulo, komwe dothi la ceramic linachokera, komwe mwala unachokera, kapena komwe anthu ogwirizana ndi chinthu china chapadera amayendera? Funso lililonse limafuna ma isotope osiyanasiyana ndi njira zoyesera. Mwachitsanzo, Pb ndi yofunikira kwambiri pa zitsulo, pomwe Sr ndi O mu enamel ya mano ndi zomwe zimapezeka kwambiri pakuyenda kwa anthu.
2) Kusankha zitsanzo zowononga pang'ono
Popeza zinthu zakalezi ndi zamtengo wapatali komanso zotetezedwa, kutengera zitsanzo kumachitika mosamala kwambiri: pogwiritsa ntchito tchipisi tating'onoting'ono, kuboola zinthu zazing'ono, kapena kukanda zotsalira. Njira zosungira zinthu ndizofunikira kuti tipewe kuwonongeka kwa maso ndi kapangidwe kake. Kuphatikiza apo, ofufuza ayenera kuwonetsetsa kuti zitsanzozo sizikuipitsidwa ndi zinthu zamakono zosungira zinthu (guluu, zokutira) zomwe zingasinthe kapangidwe ka mankhwala.
3) Kukonzekera ndi kuyeza kwa labu
Zitsanzo nthawi zambiri zimatsukidwa, kusungunuka (pa zitsulo/minerals zina), kenako ma isotope awo amayesedwa pogwiritsa ntchito chida monga mass spectrometer (monga, TIMS kapena MC-ICP-MS). Zipangizozi zimatha kuyeza kusiyana kwa ma isotope ratios molondola kwambiri. Laboratory imagwiritsanso ntchito miyezo yapadziko lonse lapansi ndi malo opanda kanthu kuti zitsimikizire zotsatira zodalirika.
4) Yerekezerani ndi database ndi chitsanzo
Kenako, ma values a isotopic a zinthu zakale adayerekezeredwa ndi:
- Deta ya migodi/miyala ya m'deralo,
- Mamapu a isoscape a m'madera osiyanasiyana,
- Zosonkhanitsa zopezera zinthu zakale kapena zotsatira za kafukufuku wakale.
Kawirikawiri, zotsatira zake sizikusonyeza malo amodzi okha, koma m'malo mwake zimasonyeza "malo othekera" omwe amachepetsedwa ndi chidziwitso china—monga kalembedwe ka zokongoletsera, ukadaulo wopanga, kapena kugawa malonda kodziwika bwino.
5) Kutanthauzira mu nkhani ya zinthu zakale
Gawo lofunika kwambiri ndikuyika manambala a isotope mu nkhani ya zinthu zakale. Mwachitsanzo, ngati isotope ya Pb ikusonyeza chitsulo chochokera kudera lakutali la migodi, pomwe kalembedwe ka chinthucho ndi kakwanuko, ndiye kuti pali chizindikiro cha zinthu zopangira zomwe zachokera kunja koma zopangidwa m'deralo. Mosiyana ndi zimenezi, ngati zinthuzo ndi kalembedwe zonse zikusonyeza kuti chinthucho ndi chofunika kwambiri, mwina chinthucho ndi chofunika kwambiri.
Zoletsa ndi machenjezo
Kusanthula kwa Isotope si "GPS yakale." Pali zoletsa zingapo zofunika:
- Kusakaniza magwero: zitsulo nthawi zambiri zimabwezeretsedwanso kapena kusakanikirana, zomwe zimapangitsa kuti chizindikiro chikhale chosakanikirana.
– Kuipitsidwa ndi kusintha: kuikidwa m'manda kwa nthawi yayitali kungasinthe pamwamba pa chinthucho; chifukwa chake kusankha gawo la chitsanzo ndikofunikira kwambiri.
- Kupezeka kwa deta yoyerekeza: popanda database yowunikira ya chigawo, kutanthauzira kumakhala kongopeka.
- Kufanana kwa malo pakati pa madera: madera awiri osiyana akhoza kukhala ndi ma isotope ofanana, kotero deta ya multi-isotope kapena yowonjezera ikufunika.
Choncho, njira yabwino kwambiri ndikugwiritsa ntchito zizindikiro zingapo: mwachitsanzo kuphatikiza ma isotope a Pb ndi zinthu zochepa za zitsulo, kapena Sr + O pa maphunziro oyenda, ndipo nthawi zonse kulumikiza zotsatira ndi umboni wa zinthu zakale.
Kutsiliza: ma isotopes ngati makiyi a maukonde akale
Ndi kusanthula kwa isotope, zinthu zakale sizilinso zinthu zopanda moyo zokha, koma ndi malo osungiramo mankhwala omwe ali ndi chidziwitso chokhudza malo, migodi, ulimi, ndi kuyenda kwa anthu. Njirayi yathandiza kupeza njira zakale zamalonda achitsulo, mayendedwe a anthu, komanso magwero a zipangizo zomangira zazikulu. Ngakhale kuti si yopanda malire ake, njira ya isotope—makamaka ikaphatikizidwa ndi njira zina zasayansi ndi maphunziro ofukula zinthu zakale—imapereka njira yolondola kwambiri yotsatirira chiyambi cha zinthu zakale ndikumanganso maukonde a ubale pakati pa anthu akale.
