Kodi Metamorphism ndi Zitsanzo za Contact ndi Chiyani?
Kusinthika kwa zinthu ndi njira yosinthira mwala woyambirira (protolith) kukhala mwala watsopano chifukwa cha kusintha kwa zinthu zakuthupi ndi zamakemikolo mkati mwa nthaka ya Dziko Lapansi. Kusinthaku kumakhudzidwa kwambiri ndi kutentha, kupanikizika, ndi kupezeka kwa madzi (monga madzi otentha, okhala ndi mchere wambiri). Mtundu umodzi wosavuta kumvetsetsa wa kusintha kwa zinthu chifukwa chakuti njira yake ndi "yapafupi" ndipo gwero lake la kutentha ndi lomveka bwino ndi kusintha kwa zinthu. Kusintha kwa zinthu ndi maginito kumachitika pamene mwala wozungulira "umaphikidwa" ndi kutentha kuchokera ku magma komwe kumalowa mu nthaka ya Dziko Lapansi. Nkhaniyi ikufotokoza tanthauzo la kusintha kwa zinthu ndi maginito, njira yomwe kumachitika, makhalidwe a miyala, ndi zitsanzo zodziwika bwino.
Kumvetsetsa kusintha kwa ma contact
Kusinthasintha kwa magma m'malo mwa magma (monga anthulith, laccolith, sill, kapena dike) komwe kumalowa m'mwala womwe ulipo. Pamene magma yotentha kwambiri ilowa kenako n’kuzizira pang'onopang'ono, kutentha kumafalikira ku mwala wapafupi (country rock). Miyala yomwe ili pafupi ndi kukhudzana kwa magma imakumana ndi "kutentha" kwakukulu, zomwe zimapangitsa kuti mchere wawo usinthe, ukhalenso watsopano, kapena uchitepo kanthu kuti upange mchere watsopano womwe umakhala wokhazikika pa kutentha kwakukulu.
Chizindikiro chachikulu cha kusintha kwa kutentha kwa thupi ndi kutentha kwambiri kuposa kupanikizika. Kupanikizika nthawi zambiri sikukhala kwakukulu chifukwa nthawi zambiri kumachitika pansi pa nthaka yozama kwambiri. Zotsatira zake, miyala yosinthika yomwe imachokera ku kusintha kwa thupi nthawi zambiri imakhala ndi mawonekedwe osasinthika (osasinthika), mosiyana ndi miyala yambiri ya m'deralo, yomwe imakonda kukhala masamba chifukwa cha kupanikizika kolunjika.
Kodi njira ya kusintha kwa kukhudzana imachitika bwanji?
Njira yolumikizirana ndi metamorphism ikhoza kufotokozedwa m'magawo angapo:
1. Kulowa kwa Magma
Magma imatuluka mkati mwa Dziko lapansi ndipo imalowa m'ming'alu kapena m'malo otsetsereka. Kulowa kumeneku kumatha kukhala ngati matupi akuluakulu a magma (ma theoliths) kapena mapepala opyapyala (ma dikes/sills).
2. Kusamutsa kutentha kupita ku miyala yam'mbali
Chifukwa cha kusiyana kwakukulu kwa kutentha, kutentha kumasuntha kuchokera ku magma kupita ku thanthwe lozungulira kudzera mu conduction ndipo nthawi zina mothandizidwa ndi madzi otentha a hydrothermal.
3. Kubwezeretsanso ndi kupanga mchere watsopano
Miyala yakale imakhala yosakhazikika kutentha kwatsopano. Makristalo amatha kukula (kubwezeretsanso) kapena kupanga mchere wosiyanasiyana kudzera mu zochita za mankhwala. Mwachitsanzo, dongo ndi mchere wina wosalala m'miyala ya sedimentary amatha kusintha kukhala mchere wokhazikika.
4. Kupanga kwa aureole yosinthika
Malo omwe kutentha kumakhudza kuzungulira kulowererako amatchedwa metamorphic aureole. Aureole iyi nthawi zambiri imasonyeza madera osinthika: pafupi ndi kulowererako mulingo wa kusintha kwa zinthu ndi wapamwamba kwambiri, kenako umachepa pamene mukuyenda.
5. Kuziziritsa ndi "kuzizira" kwa zinthu zosinthika
Kulowa kwa nthaka kukazizira, kutentha kumachepa ndipo kusintha kwa mchere kumasiya. Mwala wosinthika womwe umabwera chifukwa cha kulowa kwa nthaka "umatsekedwa" ngati mbiri ya geological ya kulowa kwa nthaka.
Makhalidwe a kusintha kwa kukhudzana
Makhalidwe ena ofala omwe amapezeka mu contact metamorphism:
- Malo ozungulira kulowererako: kachitidwe ka kufalikira kamatsatira thupi la kulowererako, ndikupanga aureole.
– Yolamulidwa ndi kutentha kwambiri: kupanikizika sikwabwino monga kusintha kwa chilengedwe.
– Kapangidwe kake nthawi zambiri sikamakhala ndi masamba: kamapanga miyala ikuluikulu yambiri monga hornfels kapena marble.
– Kusintha kwa mchere kwa kutentha kwambiri: kuwoneka kwa mchere wina wosonyeza kuwonjezeka kwa kutentha.
– Nthawi zambiri zimagwirizanitsidwa ndi ntchito ya hydrothermal: madzi otentha amatha kufulumizitsa zochitika ndikusuntha zinthu za mankhwala.
Miyala yochokera ku kusintha kwa ma contact (zitsanzo)
Nazi zitsanzo za miyala yomwe nthawi zambiri imapangidwa chifukwa cha kusintha kwa ma contact, pamodzi ndi ma protolith ndi makhalidwe awo.
1. Hornfels (mwala wa nyanga)
Hornfels ndi mwala wodziwika bwino wolumikizana ndi zinthu zina, womwe nthawi zambiri umapangidwa kuchokera ku miyala yopyapyala monga shale kapena siltstone. Chifukwa chakuti umatenthedwa mofulumira ndipo sugwiritsa ntchito mphamvu zambiri, hornfels imakhala ndi kapangidwe kakang'ono, kolimba komanso tinthu tating'onoting'ono ta mchere. Mwala uwu nthawi zambiri umawoneka ngati "wophikidwa," ndipo mabala ake amatha kukhala akuthwa.
- Ma protoliths ambiri: shale, matope, miyala ya silt
- Makhalidwe: osapanga masamba, osalala, olimba, mtundu ukhoza kukhala wakuda
- Zachilengedwe: pafupi ndi kulowerera kwa magma
Kawirikawiri mbalame za Hornfels ndi umboni wamphamvu wakuti derali lakhala likutentha kwambiri chifukwa cha kulowetsedwa.
2. Marble
Marble amapangidwa kuchokera ku kusintha kwa limestone kapena dolostone. Pa kutentha kwakukulu, mchere wa calcite kapena dolomite womwe uli mu limestone umapangidwanso kukhala makhiristo akuluakulu olumikizana. Chifukwa chake, marble nthawi zambiri amakhala ndi mawonekedwe a kristalo ndipo amatha kupukutidwa bwino.
- Ma protolith wamba: miyala yamwala, miyala ya dolostone
– Makhalidwe ake: osathiridwa ndi masamba, ofiira, amakumana ndi asidi (pa calcite marble)
- Kugwiritsa ntchito: zipangizo zomangira, ziboliboli, zokongoletsera
Mu ma aureole olumikizana ndi zinthu zozungulira kulowerera, miyala yamchere imatha kusintha kukhala miyala ya marble mwachangu kwambiri.
3. Quartzite
Quartzite imapangidwa kuchokera ku miyala ya mchenga ya quartz. Kutentha kumapangitsa kuti tinthu ta quartz tizilumikizana bwino kwambiri ndikubwezeretsanso, zomwe zimapangitsa kuti thanthwe likhale lolimba kwambiri. Mu quartzite, malire pakati pa tinthu tating'onoting'ono nthawi zambiri "amatha" ngati fuse yatsopano ya makristalo.
- Protolith yodziwika bwino: miyala ya mchenga ya quartz
- Makhalidwe: olimba kwambiri, osathira masamba, okhala ndi quartz
- Ntchito: miyala yomangira, miyala yokongoletsera, miyala ina yokongoletsera
Quartzite yolumikizana nthawi zambiri imawonekera pamene kulowererako kukutentha gawo la mchenga wa quartz lomwe lili pafupi.
4. Skarn (chitsanzo cha kusintha kwa majini m'thupi)
Ma Skarn ndi zitsanzo zofunika chifukwa amasonyeza kusintha kwamphamvu kwa kukhudzana ndi madzi, makamaka pamene magma intrusions imagwirizana ndi miyala ya carbonate (limestone/dolomite). Madzi otentha okhala ndi silica ndi zitsulo zambiri angayambitse kusintha kwa metasomatic, kupanga mchere monga garnet, pyroxene, ndi wollastonite, zomwe nthawi zambiri zimagwirizanitsidwa ndi mchere wa ore.
- Protolith yathunthu: miyala ya carbonate + mphamvu ya kulowerera kwa magma
– Makhalidwe: mchere wa calc-silicate (garnet/pyroxene), womwe nthawi zambiri umagwirizanitsidwa ndi miyala yamtengo wapatali
– Mtengo wachuma: ukhoza kukhala ndi Cu, Fe, W, Zn, Pb, ndi zina zotero.
Skarn nthawi zambiri imakhala chandamale chofufuzidwa chifukwa cha kuthekera kwake kobweretsa chuma chambiri.
5. Miyala ya silicate yokhala ndi Calc
Ngati miyala ya sedimentary ili ndi chisakanizo cha carbonate ndi dongo/quartz, kusintha kwa contact metamorphism kumatha kupanga miyala ya calc-silicate yokhala ndi mchere monga diopside, epidote, tremolite, kapena vesuvianite. Mitundu iyi nthawi zambiri imapezeka mu aureole mozungulira kulowerera komwe kumalowa m'magawo a sedimentary amitundu yosiyanasiyana.
- Protolith: matope osakanikirana a carbonate ndi silicate
– Makhalidwe: wolemera mu mchere wa calcium silicate, wobiriwira mpaka bulauni mu mtundu
- Nkhani: malo pafupi ndi malo olowera, nthawi zambiri pafupi ndi miyala ya marble kapena skarn
Zitsanzo za malo okhala ndi kusintha kwa majini
Kusintha kwa ma contact metamorphism kumatha kuchitika m'malo osiyanasiyana a tectonic, koma nthawi zambiri kumapezeka mu:
– Ma arcs a volcanic ndi subduction zones: magma ambiri amalowa m'madzi ndi kuuma mu kutumphuka.
– Malo a Plutonic: malo olamulidwa ndi miyala ya igneous yolowerera monga granite.
– Malo osaya kwambiri olowera: makoma ndi zipilala zomwe zimatenthetsa miyala yapafupi pamlingo wocheperako.
M'munda, akatswiri a za nthaka nthawi zambiri amazindikira kusintha kwa ma contact morphism mwa kusintha kwa mtundu wa miyala yozungulira kulowerera. Mwachitsanzo, kuyambira shale kutali ndi kulowerera mpaka hornfels pafupi ndi kulowerera; kapena miyala yamwala mpaka marble m'dera lolumikizana.
Kuyerekeza mwachangu: kusintha kwa contact metamorphism vs kusintha kwa dera
Kuti musasokonezeke, nayi kusiyana kwachidule:
– Kusintha kwa kutentha: kutentha kwambiri, komwe kumachitika mozungulira kulowerera, kusatulutsa masamba ambiri, kupanga ma aureole.
– Kusintha kwa madera: kukhudzidwa ndi kutentha + kuthamanga kwambiri pamalo ambiri (monga mapiri okhudzidwa), masamba ambiri (schist, gneiss), digiri ya kusintha kwa madera imasiyana pamlingo wa madera.
Kutseka
Kusintha kwa maginito ndi njira yosinthira miyala yomwe imachitika chifukwa cha kutentha kwambiri kuzungulira kulowerera kwa magma. Chifukwa chakuti imayendetsedwa ndi kutentha kwambiri komanso malo enaake, kusinthaku kumapanga miyala yomwe nthawi zambiri siili ndi masamba ndipo imapanga metamorphic aureole kuzungulira kulowererako. Zitsanzo za miyala yomwe nthawi zambiri imapanga ndi monga hornfels, marble, quartzite, ndi mitundu yosiyanasiyana yovuta monga miyala ya skarn ndi calc-silicate. Kupatula kukhala yofunika kumvetsetsa mbiri ya geological ya dera, kusintha kwa maginito kumakhalanso ndi phindu, makamaka pankhani yopanga miyala yamtengo wapatali, monga yomwe ili mu machitidwe a skarn.
Ngati mukufuna, nditha kuwonjezeranso chithunzi cha metamorphic aureole (madera ochokera pafupi ndi kulowerera mpaka kutali), kapena kupanga mtundu wa nkhaniyi womwe umayang'ana kwambiri zitsanzo za ku Indonesia.
