Indlela yokulandelela imvelaphi yezinto zobuciko usebenzisa ama-isotope
Ukulandelela imvelaphi yento yobuciko—lapho izinto zayo zokusetshenziswa zivela khona, lapho yenziwa khona, ngisho nemizila yayo yokuhweba—kungenye yezinselele eziyinhloko ezifundweni zemivubukulo kanye nefa lamasiko. Sekuyiminyaka abacwaningi bethembele esitayeleni sobuciko, amasu okukhiqiza, kanye nomongo wezinto ezitholakele ukuze bathole “indaba” ngemuva kwezinto zasendulo. Kodwa-ke, le ndlela ngezinye izikhathi ingenza kube nzima ukuhlukanisa phakathi kwamathonya amasiko nomthombo wangempela wento. Yilapho ukuhlaziywa kwe-isotope kuba khona ithuluzi elinamandla: ama-isotope angasebenza “njengeminwe” ye-geochemical efakwe kule nto, esiza ekudwebeni imephu yemvelaphi yento yobuciko ngokunemba okuvame ukungenzeki ngezindlela ezibonakalayo zodwa.
Ayini ama-isotope futhi kungani ewusizo?
Ama-Isotope ayizinhlobo ezahlukene ze-chemical element efanayo (inani elifanayo lama-proton) kodwa anezinombolo ezahlukene zama-neutron, okuholela ezinhlotsheni ezahlukene. Isibonelo, ikhabhoni inama-isotope ^12C kanye ne ^13C, i-oxygen ine ^16O kanye ne ^18O, kanti i-strontium ine ^87Sr kanye ne ^86Sr. Lo mehluko ungase ubonakale umncane, kodwa imvelo idala izinhlobo ezahlukene zama-isotope ratios emadwaleni ahlukene, enhlabathini, emanzini, ngisho nasezintweni eziphilayo. Ngenxa yokuthi izinto ezenziwe ngezinto ezenziwe ngezinto ezenziwe ngezinto ezenziwe ezindaweni ezithile, izilinganiso zama-isotope ezintweni ezenziwe ngezinto ...
Inzuzo enkulu yama-isotope ukuzinza kwawo okulinganiselwe. Izilinganiso eziningi zama-isotope azishintshi kakhulu ngemva kokwakheka kwezinto noma ngemva kokwenziwa kwezinto zokwenziwa, ikakhulukazi uma isampula iphathwa kahle futhi ukungcola kulawulwa. Ngokuqhathanisa isilinganiso se-isotope sezinto zokwenziwa ne-"isoscape" noma isizindalwazi se-geological, abacwaningi bangaphetha ngokuthi izinto zivela esifundeni A, B, noma C—ngokuvamile kuze kufike endaweni ethile ye-geological basin noma imvelaphi yemayini.
Izimiso eziyisisekelo: "izimpawu zeminwe" ze-isotope kanye nokuqhathaniswa kwazo
Ukuhlaziywa kwe-Isotope kusebenza kahle kakhulu uma kunezinto ezimbili ezitholakalayo: (1) into yobuciko egcina isignali ye-isotopic, kanye (2) idatha yokuqhathanisa evela emithonjeni engaba khona. Uma into yobuciko yethusi isolwa ngokusebenzisa ithusi elivela ezimayini eziningana ezahlukene, abacwaningi kudingeka balinganise ama-isotope kuleyo nto yobuciko kanye namasampula e-ore/slag/metal avela kulezo zimayini. Ukufana kwezilinganiso ze-isotope kungaqinisa umbono mayelana nomthombo wento.
Nokho, kubalulekile ukuqaphela ukuthi "ukufanisa" akusho njalo ukuthi "kuqinisekile." Ngezinye izikhathi izindawo ezimbili zinezilinganiso ezifanayo ze-isotope, noma izinto kungenzeka ukuthi zixutshwe emithonjeni eminingi. Ngakho-ke, ama-isotope avame ukuhlanganiswa nokuhlaziywa kwe-trace element, izifundo ze-metallurgical, i-petrography, noma idatha yemivubukulo efana nomongo wendawo.
Uhlobo oluvamile lwe-isotope olusetshenziselwa ukulandelela imvelaphi yezinto zobuciko
1) Ama-isotope e-Strontium (^87Sr/^86Sr): ama-tracer adumile e-geological
I-Strontium iwusizo ngoba isilinganiso se-^87Sr/^86Sr siyahlukahluka kuye ngobudala kanye nohlobo lwedwala. I-BatuaAmatshe amadala, acebile nge-rubidium avame ukuba ne-^87Sr ephezulu ngenxa yokubola kwe-^87Rb. I-Strontium ingena enhlabathini nasemanzini, bese ingena ezitshalweni nasezilwaneni, futhi ekugcineni iqoshwa emazinyweni, emathanjeni, noma ezintweni ezithile eziphilayo.
Uma kukhulunywa ngezinto zobuciko, i-strontium ivame ukusetshenziselwa:
– Ukunquma imvelaphi yomuntu ngamunye (isb. ku-enamel yamazinyo omuntu ukuze kuhlolwe ukuhamba), okuyinto ebalulekile uma into yobuciko iyinsalela yemvelo noma ehlobene nokungcwaba.
– Ukulandelela izinto zokusetshenziswa ezithile ezisebenzisana nendawo ezungezile, isibonelo ilayisi, izinto zokwakha, noma izingxenye ezimunca i-Sr emanzini.
Amandla e-Sr aseduze kwayo "nesiginesha" se-geological, kodwa idinga amamephu amahle okuqhathanisa futhi idinga ukubheka ushintsho olungenzeka ngemuva kokubekwa kwezinye izinto.
2) Ama-isotope e-lead (Pb): isihluthulelo sezinsimbi kanye nama-ore
Ama-isotope e-lead njenge-^206Pb, ^207Pb, ^208Pb (imikhiqizo yokubola kwe-uranium ne-thorium) anolwazi kakhulu ekufundweni kwama-ore ensimbi. Izimayini ezahlukene zingaba nezilinganiso ze-Pb ezihlukile, okuvumela ukulandeleka kwezinto zensimbi eziqukethe i-lead (noma ukungcoliswa kwe-Pb okuvela kuma-ore). Le ndlela isetshenziswa kabanzi ku:
– Ukuhlanganisa izinto ezenziwe ngethusi, ithini, isiliva, noma i-lead nezindawo ezithile zokumba.
- Ukuqonda amanethiwekhi okuhweba ngensimbi ezikhathini zasendulo kanye ne-classic.
Inselele enkulu: inqubo yokuncibilikisa nokuxuba izinsimbi ezivela emithonjeni ehlukene ingakhiqiza "ingxube" yama-isotope afihla umsuka owodwa. Ngakho-ke, ukuhlaziywa kuvame ukuhlanganiswa ne-trace element kanye nomongo we-metallurgical.
3) Ama-isotope e-oxygen (δ^18O) kanye ne-hydrogen (δD): izinyathelo zamanzi nesimo sezulu
I-oksijini ne-hydrogen kusetshenziswa kabanzi ukulandelela ubudlelwano phakathi kwemithombo yamanzi nezimo zezulu. Kwezinye izinto—njenge-carbonates, amathambo, amazinyo, noma ngisho nengilazi kanye ne-ceramics kwezinye izimo—izilinganiso ze-isotope zingaqopha ukwakheka kwamanzi endawo noma amazinga okushisa okwakheka.
Ngezinto zobuciko, i-δ^18O ingasiza:
– Hlola ukuthi ngabe into ethile (isib. igobolondo, i-carbonate) yakheke endaweni yasolwandle uma kuqhathaniswa nomhlaba noma endaweni ethile yesimo sezulu.
– Isekela inkolelo-mbono yemvelaphi yendawo lapho ihlanganiswa ne-Sr noma olunye ulwazi.
Kodwa-ke, incazelo ye-δ^18O ivame ukuba yinkimbinkimbi ngoba ithonywa yisizini, ukuphakama, ibanga ukusuka ogwini, kanye nenqubo yokushisa ngesikhathi sokukhiqiza.
4) Ama-Isotopes e-carbon (δ^13C) kanye ne-nitrogen (δ^15N): umongo wezinto eziphilayo kanye nemithombo yezinto eziphilayo
Ama-isotope e-C kanye ne-N avame ukusetshenziselwa ukulandelela imithombo yezinto eziphilayo: ukudla, uhlobo lwesitshalo (C3 vs. C4), noma imvelaphi yezinto ezifana nezindwangu, iphepha, i-resin, kanye nezinsalela zokudla ezitsheni zobumba. Ocwaningweni lwezinto zobuciko:
– Izinsalela zokudla ezitsheni zobumba zingahlaziywa ukuze kutholakale ukuthi zisekelwe kakhulu olwandle noma emhlabeni.
– Imicu yendwangu inganikeza izinkomba mayelana nendawo ekhula kuyo izitshalo (isb., ifilakisi, ukotini) uma kukhona idatha yokuqhathanisa etholakalayo.
Lawa ma-isotope anamandla kakhulu ekuchazeni i-ecology kanye nemikhuba yokuphila, bese exhunyaniswa nemvelaphi ngokusekela idatha yendawo.
Inqubo yokulandelela yenziwa kanjani?
1) Nquma imibuzo yocwaningo
Ukuhlaziywa kwe-Isotope kufanele kuqale ngombuzo ocacile: ingabe ufuna ukulandelela imayini yensimbi, umthombo wobumba lwe-ceramic, umsuka wetshe, noma ukuhamba kwabantu abahlotshaniswa nento yobuciko? Umbuzo ngamunye udinga ama-isotope ahlukene namasu okuthatha isampula. Isibonelo, i-Pb ifaneleka kakhulu ngezinsimbi, kuyilapho i-Sr ne-O ku-enamel yamazinyo zivame kakhulu ukuhamba kwabantu.
2) Ukusampula okungacekeli phansi kakhulu
Ngenxa yokuthi lezi zinto zobuciko ziyigugu futhi zivikelwe, ukusampula kwenziwa ngokucophelela okukhulu: kusetshenziswa ama-chips amancane, ukubhoboza okuncane, noma ukuklwebha izinsalela. Izinqubo zokulondoloza zibalulekile ukuze kugwenywe umonakalo obonakalayo nowesakhiwo. Ngaphezu kwalokho, abacwaningi kumele baqinisekise ukuthi amasampula awangcoliswa yizinto zokulondoloza zesimanje (ama-glue, izimbozo) ezingashintsha ukwakheka kwamakhemikhali.
3) Ukulungiselela kanye nokulinganisa elebhu
Amasampula avame ukuhlanzwa, ancibilikiswe (kwezinye izinsimbi/amaminerali), bese ama-isotope awo elinganiswa kusetshenziswa ithuluzi elifana ne-mass spectrometer (isb., i-TIMS noma i-MC-ICP-MS). Lawa mathuluzi ayakwazi ukulinganisa umehluko kuma-isotope ratios ngokunemba okuphezulu. Ilabhorethri isebenzisa nezindinganiso zomhlaba wonke kanye nezimbobo ukuqinisekisa imiphumela ethembekile.
4) Qhathanisa nedatha kanye nemodeli
Amanani e-isotopic alezi zinto zobuciko abe eseqhathaniswa nalawa:
– Idatha yezimayini/yamadwala endawo,
- Amamephu e-isoscape yesifunda,
– Amaqoqo okubhekisela emyuziyamu noma imiphumela yocwaningo lwangaphambilini.
Ngokuvamile, imiphumela ayikhombisi indawo eyodwa, kodwa kunalokho ikhombe “indawo yamathuba” encishiswa ngolwazi olungeziwe—njengesitayela sokuhlobisa, ubuchwepheshe bokukhiqiza, noma ukusatshalaliswa kokuhweba okwaziwayo.
5) Ukuchazwa komongo wezinto zakudala
Isinyathelo esibaluleke kakhulu ukufaka izinombolo ze-isotope endabeni yemivubukulo. Isibonelo, uma i-isotope ye-Pb ikhomba insimbi evela esifundeni sokumba esikude, kuyilapho isitayela sento yobuciko singesendawo, khona-ke kukhona inkomba yezinto zokusetshenziswa ezingenisiwe kodwa ukukhiqizwa kwendawo. Ngokuphambene nalokho, uma izinto zokwakha kanye nesitayela kokubili kukhomba ngaphandle, into yobuciko cishe iyinzuzo ephelele.
Imikhawulo kanye nezixwayiso
Ukuhlaziywa kwe-Isotope akuyona "i-GPS yakudala." Kunemikhawulo embalwa ebalulekile:
– Ukuxubana kwemithombo: izinsimbi zivame ukuphinda zisetshenziswe noma zixutshwe, okuholela esignalini exubile.
– Ukungcola nokuguqulwa: ukungcwatshwa isikhathi eside kungashintsha ubuso bento esetshenzisiwe; ngakho-ke ukukhethwa kwesigaba sesampula kubaluleke kakhulu.
– Ukutholakala kwedatha yokuqhathanisa: ngaphandle kwesizindalwazi sokubhekisela sesifunda, ukuhumusha kuba ukuqagela.
– Ukufana kwe-geological phakathi kwezifunda: izifunda ezimbili ezahlukene zingaba nezilinganiso ze-isotope ezifanayo, ngakho-ke kudingeka idatha ye-multi-isotope noma eyengeziwe.
Ngakho-ke, umkhuba omuhle kakhulu ukusebenzisa izinkomba eziningi: isibonelo ukuhlanganisa ama-isotope e-Pb nezinto ezilandelanayo zezinsimbi, noma i-Sr + O ezifundweni zokuhamba, futhi njalo uxhumanisa imiphumela nobufakazi bemivubukulo.
Isiphetho: ama-isotope njengezihluthulelo zamanethiwekhi adlule
Ngokuhlaziywa kwe-isotope, izinto zobuciko azisezona nje izinto ezingaphili, kodwa ziseyizingobo zomlando zamakhemikhali ezigcina ulwazi mayelana nezindawo, izimayini, ezolimo, kanye nokuhamba kwabantu. Le ndlela isize ekutholeni imizila yokuhweba yensimbi yasendulo, ukunyakaza kwabantu, kanye nemithombo yezinto zokwakha ezinkulu. Nakuba kungengaphandle kwemingcele yayo, indlela ye-isotope—ikakhulukazi uma ihlanganiswa namanye amasu esayensi kanye nezifundo zemivubukulo—inikeza indlela enembile kakhulu yokulandelela imvelaphi yezinto zobuciko nokwakha kabusha amanethiwekhi obudlelwano phakathi kwemiphakathi yangaphambilini.
