Nā Hana Uila Malemake i ka ʻImi ʻIli Minerala
ʻO ka ʻimi ʻana i nā minelala he hoʻāʻo ia e hoʻomaopopo i "nā mea ma lalo o ka ʻili" me ka ʻole o ka ʻeli mua ʻana. No ka mea he pipiʻi a he pilikia ka ʻeli ʻana, ʻo nā pae mua o ka ʻimi ʻana e hilinaʻi pinepine ʻia i nā ʻano geophysical e hoʻohaiki i nā pahuhopu. ʻO kahi hui koʻikoʻi o nā ʻano geophysical ʻo ia nā ʻano electromagnetic (EM). Hoʻohana kēia mau ʻano i ka pane uila o nā pōhaku i nā kahua uila a me nā magnetic e ʻike i nā wahi mineralized, ʻoiai nā mea conductive, e like me nā sulfides nui, graphite, a i ʻole kekahi mau wahi hoʻololi.
Nā Kumumanaʻo Kumu o nā Hana Uila
Hana nā ʻano hana electromagnetic ma muli o ke kumumanaʻo o ka hoʻokomo electromagnetic. Ke loli kahi kahua electromagnetic i ka hala ʻana o ka manawa, hoʻoulu ia i kahi au uila i loko o nā mea conductive ma lalo o ka ʻili. A laila hoʻoulu kēia au i hoʻokomo ʻia i kahi kahua magnetic lua e hiki ke ana ʻia ma ka ʻili a i ʻole mai ka lewa. ʻO ka ʻokoʻa ma waena o ka hōʻailona "mua" (i hoʻouna ʻia e ke kumu) a me ka hōʻailona "lua" (e puka mai ana mai lalo o ka ʻili) he mea nui ia i ka wehewehe ʻana i ke alo a me ke ʻano o nā kino conductive.
ʻO nā waiwai kino koʻikoʻi loa i nā anamanaʻo EM:
– ʻO ke alakaʻi uila (σ) a i ʻole kona inverse, resistivity (ρ). ʻO ka mineralization sulfide ma ke ʻano laulā he alakaʻi.
– Ka permeability magnetic (μ), ka mea e hoʻopilikia ai i ka pane ʻana i nā kahua magnetic, ʻoi aku hoʻi i nā pōhaku i waiwai i nā minelala magnetic.
– ʻO ka permittivity dielectric (ε), ʻoi aku ka mana ma nā alapine kiʻekiʻe loa, no ka laʻana ma ka radar penetrating ground (GPR).
Ma ka hoʻololi ʻana i nā palena anamanaʻo e like me ke alapine (frequency), ke ʻano nalu, a me ka mamao ma waena o nā mea ʻike, hiki i ke ʻano EM ke "ʻike" i nā hohonu a me nā unahi like ʻole o nā pahuhopu.
Ka Hoʻokaʻawale ʻana o nā Hana EM: Passive a me Active
Ma keʻano laulā, ua māhele ʻia ke ʻano EM i ʻelua:
1. Nā ʻano hana hana ʻole, e hoʻohana ana i nā kumu kahua kūlohelohe mai ka hana ionospheric a i ʻole ka uila. ʻO nā hiʻohiʻona koʻikoʻi ʻo magnetotellurics (MT) a me audio-magnetotellurics (AMT). He kūpono kēia mau ʻano hana no nā noiʻi ʻana o nā hohonu nui a hiki i ka ʻili pāpaʻu, me nā ʻōnaehana hydrothermal pae ʻāina.
2. Nā ʻano hana, e hoʻohana ana i nā kumu hana e like me nā wili hoʻoili a i ʻole nā au uila i kāohi ʻia. ʻO kēia kahi e hoʻohana pinepine ai ka ʻimi ʻana i nā minerala iā EM, no ka laʻana ʻo FDEM (Frequency-Domain EM), TDEM (Time-Domain EM), a me nā derivatives e like me Airborne EM.
Ka ʻĀpana Alapine (Frequency-Domain EM) (FDEM)
Ma FDEM, hoʻopuka ka mea hoʻoili i kahi kahua electromagnetic sinusoidal ma hoʻokahi a ʻoi aku paha mau alapine (frequencies). A laila ana ka mea hoʻokipa i ka pane ma ke ʻano o nā ʻāpana in-phase a me quadrature. Hoʻopili pinepine ka ʻāpana quadrature me ka conductivity, ʻoiai hiki ke hoʻopilikia ʻia ka in-phase e nā alakaʻi ikaika a me nā hopena magnetic.
Nā Pōmaikaʻi o FDEM:
– Nā ana wikiwiki a me ka pono no ka palapala ʻāina pāpaʻu-waena.
– Maikaʻi no ke kaha kiʻi ʻana i nā ʻokoʻa o ka conductivity lateral, e laʻa me nā ʻāpana hoʻololi, nā lepo conductive, a i ʻole nā mea haumia graphitic.
Nā Palena o FDEM:
– Ua kaupalena ʻia ka hohonu o ke komo ʻana, ma muli o ke alapine (frequency) a me nā kūlana ʻāina.
– Hiki ke paʻakikī ka wehewehe ʻana ma nā wahi me nā kumu hoʻopilikia he nui (nā laina uila, nā pā, nā ʻoihana).
Manawa-Domain EM (TDEM)
Hana ʻo TDEM ma ka hoʻopili ʻana i kahi au uila i ka wili transmitter a laila e pio koke. Ke ʻoki ʻia ke au, hiolo ke kahua magnetic mua, e hoʻoulu ana i nā au eddy (nā au eddy) ma lalo o ka ʻili. A laila palaho kēia mau au eddy i ka hala ʻana o ka manawa, a hoʻopaʻa ʻia kēia palaho e ka mea loaʻa ma ke ʻano he hana o ka manawa. ʻO nā "manawa mua" e hōʻike pinepine i nā kumu pāpaʻu, ʻoiai ʻo nā "manawa hope" e pili ana i nā hohonu nui aʻe.
Nā pono o TDEM:
– He mea kūpono loa no ka ʻike ʻana i nā alakaʻi ikaika e like me nā sulfides nui.
- Loaʻa iā ia nā hiki hohonu ʻoi aku ka maikaʻi ma mua o nā hoʻonohonoho FDEM he nui.
– Hiki ke hoʻololi ʻia ka ʻikepili palaho manawa i loko o kahi kumu hoʻohālike conductivity versus depth.
Nā Palena o TDEM:
– Pono ka hoʻolālā ana maikaʻi (loop, orientation, gating) i hiki ke heluhelu maopopo ʻia ka pahuhopu.
– Hiki ke hoʻopilikia ʻia ka wehewehe ʻana e nā alakaʻi waiwai ʻole e like me ka pālolo, ka wai lepo paʻakai, a i ʻole ka graphite.
Airborne EM (AEM): Anamanaʻo wikiwiki o ka pae ʻāina
I ka ʻimi ʻana o kēia au, ʻo Airborne EM (AEM)—me ka hoʻohana ʻana i nā helikopter a i ʻole nā mokulele—he mea nui ia no ka uhi wikiwiki ʻana i nā wahi nui. Hoʻopaʻa ʻia nā mea ʻike EM i loko o kahi "manu" a i ʻole ke kiʻi ma lalo o ka helikopter, e ʻae ana i nā ana hoʻohele lepo mau ma ke ala holoʻokoʻa. He mea pono loa ka AEM i nā pae mua o ka ʻimi ʻana, ʻoiai ma nā ʻāina paʻakikī, nā ululāʻau mānoanoa, a i ʻole nā wahi pulu.
Nā pono o AEM:
– Ka uhi wikiwiki ʻana i ka ʻāina a me ke kumukūʻai kūpono no kēlā me kēia kilomita kuea no nā wahi nui.
– Hiki ke ʻike i nā anomalies conductive a laila e hoʻonohonoho mua ʻia no nā ana ʻāina a me ka ʻeli ʻana.
Nā Palena AEM:
– ʻOi aku ka haʻahaʻa o ka hoʻonā o lalo o ka ʻili ma mua o nā ana kikoʻī o ka honua.
– Pilikia i ka walaʻau o nā moʻomeheu a me nā loli i ke kiʻekiʻe o ka lele ʻana.
Nā Hoʻohana Nui i ka ʻImi Minerala
ʻO ke ʻano EM kaulana loa no ka ʻike ʻana i nā kino conductive, e lilo ia i mea pono loa i nā waiwai a me nā wahi geological:
1. Sulfide nui (VMS, Ni-Cu sulfide, Pb-Zn)
ʻO nā minelala sulfide e like me pyrite, pyrrhotite, chalcopyrite, galena, a me sphalerite he kiʻekiʻe ka conductivity, ʻoiai ke hoʻohuihui ʻia. He kūpono loa ʻo TDEM lāua ʻo AEM i ka ʻike ʻana i nā "conductors like plate" hiʻohiʻona o nā sulfides nui.
2. Nā waihona nickel sulfide a me komatiite
Hoʻopili pinepine ʻia ka nickel sulfide me ka conductive pyrrhotite, e hoʻolilo ana iā EM i mea hana ʻimi mua, i hui pū ʻia me nā magnetics a me ka geochemistry.
3. Nā pōhaku graphite a me nā pōhaku kalapona
He alakaʻi nō hoʻi ka Graphite a hiki ke hana i nā anomalies EM ikaika. ʻO ka pilikia, hiki i ka graphite ke lilo i "maikaʻi wahaheʻe" inā ʻo ka pahuhopu mua he sulfide waiwai. No laila, hui pū ʻia ʻo EM me ka geology a me ka geochemistry e hoʻokaʻawale i ke kumu o ka anomaly.
4. Hoʻololi a me ka hoʻolālā ʻana o ke ʻano
Hiki i nā ʻāpana hoʻololi hydrothermal ke hoʻonui i ka conductivity ma muli o ke kūkulu ʻia ʻana o nā minelala lepo a i ʻole nā wai. Kōkua ʻo EM i ka palapala ʻāina i nā ʻano hewa a me nā pilina lithologic e kaohi ana i nā ala o nā wai mineralizing.
Hoʻolālā Anamanaʻo a me ka Wehewehe ʻIkepili
ʻAʻole hilinaʻi wale ka holomua o kahi anamanaʻo EM i ka mea hana, akā, i ka hoʻolālā anamanaʻo hoʻi. ʻO nā mea nui e komo pū ana:
– Ke kuhikuhi ʻana o ke ala hele i ke kuhikuhi o ka ʻano honua; pono ke ala hele e hui kū pololei i ke kuhikuhi hahau i manaʻo ʻia.
– Ka mamao o ke ala hele: hiki ke 200–400 m nā ana ʻāina, ʻoiai he 25–100 m paha nā ana kikoʻī.
– Nā palena loaʻa: ke koho alapine (FDEM), ka manawa gating (TDEM), ka hoʻonohonoho loop (in-loop, out-of-loop), a me ke kiʻekiʻe sensor (AEM).
No ka wehewehe ʻana, hana pinepine ʻia ka ʻikepili EM: ka hoʻoponopono ʻana i ka drift, ka kānana walaʻau, ka hoʻohālikelike ʻana, a me ka inversion e loaʻa ai nā hiʻohiʻona conductivity 1D/2D/3D. Ke lilo nei ka inversion 3D i mea maʻamau ma muli o kona hiki ke hōʻike maoli i ke ʻano o nā kino conductive, akā koi ia i ka ʻikepili kiʻekiʻe aʻe a me ka hoʻoikaika helu ʻana.
Nā Pōmaikaʻi a me nā Palena o ke ʻAno EM
Nā pono nui:
– Pilikia i ka mineralization conductive, ʻoiai nā sulfides.
– Hiki ke komo i loko o kekahi ukana ma luna a "ʻike" mau i ka pahuhopu ma lalo.
– Kūpono no nā pae ʻimi mai ka ʻāpana (AEM) a i nā kikoʻī (land TDEM).
Nā palena nui:
ʻAʻole nā minelala waiwai āpau he alakaʻi (e.g. ʻaʻole hāʻawi mau ke gula manuahi i loko o ka quartz i kahi anomaly EM pololei).
– Hiki i nā alakaʻi waiwai ʻole (lepo lepo, brine, graphite) ke hoʻohālike i ka pane mineralization.
– Hiki i ka walaʻau moʻomeheu a me nā kūlana topographic ke hoʻohaʻahaʻa i ka maikaʻi o ka ʻikepili.
Ka hopena
ʻO nā ʻano hana electromagnetic kahi kia koʻikoʻi o ka ʻimi mineral hou ma muli o ko lākou hiki ke ʻike i nā ʻano conductivity subsurface e pili pinepine ana i ka mineralization sulfide a i ʻole nā wahi hoʻololi. Me nā ʻano hana e like me FDEM, TDEM, MT, a me AEM, hiki ke hoʻopili ʻia ʻo EM mai nā unahi ʻāpana a hiki i nā pahuhopu ʻeli. ʻOiai he mau palena a he maʻalahi hoʻi i ka maopopo ʻole, ʻo ka hoʻohui ʻana iā EM me ka palapala ʻāina geological, magnetic, gravity, a me nā ana geochemical, a me ka ʻeli hōʻoia, e hopena i nā wehewehe ikaika loa. ʻO ka mea hope loa, ʻo ka waiwai nui o nā ʻano hana EM aia i ko lākou hiki ke hoʻolalelale i ka hoʻoholo ʻana—ke koho ʻana i nā pahuhopu kūpono loa, ka hōʻemi ʻana i ka pilikia, a me ka hoʻonui ʻana i nā kumukūʻai ʻimi.
