Usoro Petrografik na Nyocha Nkume
Petrography bụ ngalaba nke geology nke lekwasịrị anya na nkọwa na nkọwa nke nkume dabere na ihe mejupụtara mineral ha, udidi ha, na nhazi ime ha. Usoro petrographic bụ otu n'ime ụzọ kachasị mkpa na nyocha nkume n'ihi na ọ nwere ike "ịgụ" akụkọ ihe mere eme nke nhazi nkume site na nlele ozugbo, ọkachasị site n'enyemaka nke microscope polarizing. Site na igneous na sedimentary ruo na nkume metamorphic, petrography na-enyere ndị ọkà mmụta ala aka ịghọta usoro geological dịka magma crystallization, deposition, diagenesis, deformation, metamorphism, na hydrothermal change.
1. Echiche Ndị Bụ Isi nke Petrography
N'ozuzu, a na-ekewa petrography n'ime isi ihe abụọ: macroscopic petrography na microscopic petrography. A na-eme macroscopic petrography site na ileba anya kpọmkwem na nkume (ihe atụ aka), dịka ọmụmaatụ site na ilele agba, nha ọka, ihe na-egbuke egbuke nke mineral, porosity, ma ọ bụ ọnụnọ nke akwụkwọ. Ka ọ dị ugbu a, a na-eme petrography microscopic site na ilele obere akụkụ nke nkume n'okpuru microscope polarizing iji chọpụta mineral na udidi nke anya na-anaghị ahụ anya.
Ike nke petrography dị n'ikike ya ijikọta njirimara anụ ahụ nke nkume na usoro ndị mepụtara ha. Dịka ọmụmaatụ, nkume igneous nwere udidi porphyritic na-egosi ọkwa abụọ nke oyi magma, ebe nkume metamorphic nwere akwụkwọ siri ike na-egosi ọnụnọ nke nrụgide dị iche iche kachasị.
2. Usoro nke Usoro Petrografik
Usoro petrographic maka nyocha nkume na-agbaso ọtụtụ usoro dị mkpa: nnwale, nkwadebe akụkụ dị gịrịgịrị, nlele obere ihe, nkọwa, na akụkọ. Nkebi ọ bụla chọrọ nkenke, ebe ọ bụ na obere mmejọ nwere ike ibute nkọwa na-ezighi ezi.
a. Ịnwale ihe
Nkebi mbụ bụ nchịkọta ihe atụ nkume sitere na ubi ma ọ bụ isi ihe eji egwu mmiri. N'ụzọ kacha mma, ihe atụ kwesịrị ịbụ ihe nnọchianya nke nkume a ga-enyocha ma ghara ịcha oke ihu igwe. N'ọmụmụ ihe gbasara ala ubi, a na-esokarị ihe nlele ahụ na ndekọ zuru ezu: ebe, nhazi, mmekọrịta stratigraphic, ihe owuwu ala gbara ya gburugburu, na ọnọdụ mgbanwe. Maka nkume sedimentary, ọ dịkwa mkpa ịmara ntụziaka nke ihe ndina na ihe owuwu sedimentary. Maka nkume metamorphic, a ga-edekọ ntụzịaka foliation na lineation n'ihi na ha nwere ike ịdị mkpa na nkọwa microtextural.
b. Nkwadebe nke Nkebi Dị Mkpirikpi
Akụkụ dị gịrịgịrị bụ ihe e ji akwadebe nkume nke dị ihe dị ka maịkromita iri atọ ka ìhè wee banye n'ime mineral ndị ahụ. Usoro imepụta akụkụ dị gịrịgịrị gụnyere ịkpụ ihe nlele ahụ, itinye ya na ihe mmịpụta iko site na iji resin, igwepịa ya, ịchacha ya, na mgbe ụfọdụ itinye ihe mkpuchi.
Ọdịdị nke akụkụ dị gịrịgịrị dị oke mkpa. Oke ọkpụrụkpụ na-adịghị nhata nwere ike ịgbanwe ọdịdị nke agba ndị na-akpata nsogbu mineral, na-eme ka njirimara sie ike. Na mgbakwunye na akụkụ dị gịrịgịrị nkịtị, enwere nkwadebe pụrụ iche, dị ka akụkụ ndị a kpụchara akpụcha, maka inyocha mineral ndị na-adịghị ahụkebe (dịka ọmụmaatụ, pyrite, magnetite) site na iji microscope na-egosipụta.
c. Nlele site na iji igwe onyonyo Polarizing
A na-ejikarị igwe microscope polarizing eme ihe nlele petrographic nke nwere ụdị abụọ bụ isi: ọkụ parallel polarized (Plane Polarized Light/PPL) na ọkụ cross polarized (Cross Polarized Light/XPL).
1. A na-eji PPL eme ihe iji hụ:
– Agba nke mineral (agba)
- Pleochroism (mgbanwe agba mgbe a na-atụgharị ya)
– Enyemaka (ọdịiche nke mineral na matrix)
– Ụdị kristal (euhedral, subhedral, anhedral)
- Mkpụcha na mgbawa
2. A na-eji XPL eme ihe iji hụ:
– Agba ndị na-akpata nsogbu
– Ejima, dịka ọmụmaatụ na plagioclase
- Nkuku mkpochapu
– Birefringence (ogo nke ọdịiche dị na ndeksi refractive)
- Mmekọrịta kristal na nke dị n'etiti
N'ime nyocha ahụ, ndị ọkà mmụta ala ga-achọpụta mineral ndị bụ isi (dịka ọmụmaatụ quartz, feldspar, pyroxene, amphibole, mica) na mineral ndị ọzọ (zircon, apatite, titanite) yana mineral ndị ọzọ sitere na mgbanwe (sericite, chlorite, epidote, calcite).
d. Nyocha Ọdịdị na Nhazi
Na mgbakwunye na ihe mejupụtara mineral, petrography na-emesikwa ike inyocha udidi (nha, ọdịdị, na mmekọrịta dị n'etiti mkpụrụ/mineral) na nhazi (ihe ndị buru ibu, ndị a haziri nke ọma karị). Ihe atụ nke udidi dị mkpa:
– Ọdịdị Porphyritic: nnukwu phenocrysts n'ime ala mara mma, na-egosi akụkọ ihe mere eme nke oyi nwayọọ nwayọọ n'ime nkume igneous.
– Ọdịdị Granular: mkpụrụ dị iche iche, nke a na-ahụkarị na granite ma ọ bụ ụfọdụ nkume metamorphic.
– Udidi Vesicular: oghere ndị sitere na gas, nke a na-ahụkarị na basalt.
– Udidi Klasik: iberibe nkume/ihe ndị e ji matriks ma ọ bụ simenti kee, nke a na-ahụkarị n'ime nkume sedimentary.
– Udidi Lepidoblastic ma ọ bụ nematoblastic: ntụzi nke mica ma ọ bụ amphibole na nkume metamorphic.
– Mylonitic udidi: mgbanwe siri ike n'ihi ịkwa akwa, nke na-eme ka mkpụrụ dị nro ma sie ike.
N'ime nkume sedimentary, petrography nwere ike ikpughe oke nhazi, gburugburu ọka, ụdị simenti (silica, calcite, iron oxide), na porosity. Na nkume metamorphic, petrography nwere ike ịchọpụta mineral metamorphic index dị ka garnet, staurolite, kyanite, na sillimanite, nke bara uru n'ịchọpụta oke metamorphism.
e. Ngụkọta: Ịgụta Isi na Nhazi
Iji mee ka ihe doo anya, a na-ejikarị ụzọ ọnụọgụgụ dịka ịgụta isi ihe eme ihe. Site na usoro a, onye na-ekiri ihe na-agbakọ pasentị nke mineral dabere na ọtụtụ isi ihe nlele sistemụ dị na obere akụkụ. A na-eji nsonaazụ ya maka nhazi, dịka ọmụmaatụ:
– eserese QAPF maka nkume plutonic igneous (quartz–alkali feldspar–plagioclase–feldspathoid)
- eserese TAS (a na-ahụkarị maka nkume mgbawa sitere na kemịkalụ, mana petrography nwere ike inye aka na nkwenye mineralogic)
– Nhazi nke nkume ájá (dịka ọmụmaatụ quartz arenite, arkose, litharenite) dabere na nhazi nke iberibe quartz-feldspar-lithic
- Nkewa nke nkume metamorphic dabere na mineral na udidi kachasị (schist, gneiss, marble, quartzite)
Ịgụta ihe ndị dị n'ime ala bara uru maka inyocha ịdị mma nke ebe nchekwa mmiri na ọmụmụ ihe gbasara ala mmanụ na gas, dịka ọmụmaatụ ọdịnaya nke simenti carbonate nke na-ebelata porosity.
3. Nkọwa nke Usoro Geological
Isi uru nke petrography bụ nkọwa. Site na data mineralogical na textural, ndị ọkà mmụta ala nwere ike ịhazigharị usoro ndị mepụtara nkume. Ụfọdụ ihe atụ nke nkọwa:
– Ọnụnọ nke plagioclase mpaghara dị na nkume igneous nwere ike igosi mgbanwe na nhazi magma n'oge kristal.
– Mmeghachi omume dị iche iche dịka imepụta garnet site na chlorite na biotite na-egosi mmụba na okpomọkụ na nrụgide.
– Simenti silica na ájá na-egosi ọkwa diagenetic, ebe recrystallization nwere ike ịbawanye ma ọ bụ belata mma oghere.
– Mgbanwe hydrothermal dịka sericitation, chloritization, ma ọ bụ silicification nwere ike ịbụ ihe na-egosi sistemụ mineralization nke ọla.
Ya mere, petrography anaghị aza naanị "ihe e ji mee nkume a", kamakwa "kedu ka e si kpụọ ma gbanwee nkume a".
4. Uru na Mmachi nke Ụzọ Petrografik
Ptrography nwere ọtụtụ uru: ọ dị ọnụ ala ma e jiri ya tụnyere nyocha geochemical zuru oke, na-enye ozi bara ụba gbasara ederede, ọ dịkwa irè maka ịchọpụta mineral na mmekọrịta ha. Agbanyeghị, petrography nwekwara oke. Enwere ike ịchọpụta mineral ndị a na-akpọ "fine grained minerals", mineral ndị a na-anaghị ahụ anya chọrọ usoro pụrụ iche, nkọwa ndị a na-ahụ anya nwekwara ike imetụta ya. Ya mere, a na-ejikọkarị petrography na ụzọ ndị ọzọ dịka XRD (X-ray diffraction), SEM-EDS, geochemical analysis, ma ọ bụ isotope analysis iji kwado nsonaazụ.
5. Mmechi
Usoro petrographic bụ ntọala dị mkpa na nyocha nkume n'ihi na ha na-ejikọta nlele ozugbo, nchọpụta ihe ndị dị n'ime ala, nyocha udidi, na nkọwa nke usoro geological. Site na usoro nhazi - site na nlele na nhazi dị mkpụmkpụ ruo na nlele obere na nhazi - petrography nwere ike imepụta foto zuru oke nke agwa nkume na akụkọ ihe mere eme nke geological. N'oge a, petrography ka dị mkpa ma dịkwa ike karịa mgbe ejikọtara ya na usoro nyocha ndị ọzọ, na-enye nghọta ziri ezi nke ike ụwa na ike akụrụngwa geological.
