Laccolith

Laccolith
Bayanai
Ƙaramin ɓangare na	Dome (geology) da igneous intrusion (en)

Sashe na giciye na laccolith da ke shiga cikin da kuma lalacewa

laccolith wani jiki ne na dutse mai tsinkaye tare da siffar dome na sama da kuma matakin tushe, wanda aka ciyar da shi ta hanyar bututun daga ƙasa. A laccolith siffofi lokacin da Magma (ruwan dutse) tashi a cikin Duniya ta fara yadawa a kwance, da spying da host rock strata. Matsi na magma yana da girma sosai cewa an tilasta wa ɓangarorin da ke sama sama, suna ba da laccolith siffar dome-like.

A tsawon lokaci, rushewa na iya fallasa laccolith mai ƙarfi, wanda yawanci ya fi tsayayya da yanayi fiye da dutse mai masauki. Laccolith ɗin da aka fallasa ya zama tudu ko dutse. Duwatsun Henry na Utah, Amurka, misali ne na tsaunuka da suka hada da laccoliths da aka fallasa. A nan ne masanin ilimin ƙasa Grove Karl Gilbert ya gudanar da aikin farko a kan irin wannan shiga. Tun daga wannan lokacin an gano tsaunukan Laccolith a wasu sassan duniya.

Nau'ikan intrusions na asali:Samfuri:Ordered list Note: A matsayin doka ta gaba ɗaya, sabanin hayaki mai hayaki a cikin adadi, waɗannan sunayen suna nufin cikakkiyar sanyaya kuma yawanci miliyoyin shekaru masu tsufa, waɗanda sakamakon aikin magmatic ne da aka nuna.

Bayyanawa

Laccolith wani nau'i ne na intrusion na igneous, wanda aka kafa lokacin da Magma ya tilasta hanyarsa sama ta cikin ɓawon burodi na Duniya amma ya sanyaya kuma ya yi ƙarfi kafin ya kai saman. Laccoliths sun bambanta da sauran intrusions na igneous ta hanyar siffar dome-shaped saman surface da kuma matakin tushe. Ana zaton ana ciyar da su ta hanyar bututun daga ƙasa, kodayake wannan ba a fallasa shi da yawa. Lokacin da dutsen mai masaukin ya kasance dutsen wuta, ana kiran laccolith a matsayin cryptodome. Laccoliths suna samuwa ne kawai a zurfin zurfi a cikin ɓawon burodi, yawanci daga Matsakaicin abun da ke ciki magma, kodayake laccoliths na duk abubuwan da ke ciki daga silica-poor basalt zuwa silica-rich rhyolite sanannu ne.

An yi amfani da siffofin laccolith bayan shigar da takarda na farko tsakanin yadudduka na dutse. Idan shigarwar ta kasance iyakance a girman, tana samar da sill, inda sassan da ke sama da ƙasa da shigarwar suka kasance daidai da juna kuma shigarwar ta ci gaba da zama kamar takarda. Shigawar ta fara ɗagawa da kuma rufewa da ke kan iyaka ne kawai idan radius na Shigawar ya wuce radius mai mahimmanci, wanda shine kusan:

$r\geq {\frac {2T\tau }{P_{m}-P_{l}}}$

ina $P_{m}$ shine matsi na magma, $P_{l}$ shine matsi na lithostatic (nauyin overlying rock), $T$ shine kaurin duwatsun da ke sama, kuma $\tau$ Ƙarfin da ya fi ƙarfin dutsen. Misali, a cikin Dutsen Henry na Utah, Amurka, masanin ilimin kasa Grove Karl Gilbert ya gano a cikin 1877 cewa kullun ba su wuce 1 square kilometre (0.39 sq mi) a cikin yanki yayin da laccoliths koyaushe suna da girma fiye da murabba'in kilomita 1 a cikin yanki. Daga wannan, Gilbert ya kammala cewa sills sun kasance farkon laccoliths. Laccoliths sun samo asali ne daga sills kawai lokacin da suka zama babba don matsa lamba na magma don tilasta maɗaukakiyar maɗaukaki zuwa dome zuwa sama. Gilbert kuma ya ƙaddara cewa manyan laccoliths sun kafa a zurfin zurfi. Dukansu laccoliths da sills an rarraba su azaman kutsawa masu haɗaka, tun da yawancin kutse ba ya yanke shingen dutsen mai masaukin baki, amma yana shiga tsakani.

Binciken da aka yi kwanan nan game da laccoliths ya tabbatar da ƙaddamarwar Gilbert, yayin da yake inganta cikakkun bayanai. Dukkanin sills da laccoliths suna da ƙuƙwalwa maimakon gefuna masu kama da wedge, kuma sills na Dutsen Henry yawanci suna da kauri har zuwa mita 10 (33 yayin da laccolites suna da kauni har zuwa mita 200 (660 . Yankin laccolith na iya zama mai santsi, amma kuma yana iya samun tsinkaye masu kama da yatsa wanda ya dace da rashin daidaituwa na Rayleigh-Taylor na magma da ke turawa tare da strata. Misali na laccolith mai yatsa shine Shonkin Sag laccolith a Montana, Amurka. Matsakaicin radius don sauyawa zuwa laccolith yanzu ana zaton yana shafar viscosity na magma (yana da girma ga ƙananan viscous magma) da kuma ƙarfin dutsen mai masaukin. Tsarin zamani don siffar laccolith shine:

Siffar laccolith mai kyau

$z={\frac {3(P_{m}-\rho _{c}gT)}{16BT^{3}}}(r_{0}^{2}-r^{2})^{2}$

ina $z$ shine tsayin rufin laccolith, $g$ shine acceleration na nauyi, $B$ shi ne na roba modulus na rundunar dutsen, $r$ shine nisa a kwance daga tsakiyar laccolith, kuma $r_{0}$ shine radius na waje na laccolith. Saboda girman girman su, wanda ke rage saurin sanyaya, dutsen laccoliths yawanci ya fi girma fiye da dutsen sills.

Girman laccoliths na iya ɗaukar 'yan watanni idan aka haɗa shi da wani abu guda na allurar magma, ko har zuwa daruruwan ko dubban shekaru ta hanyar bugun magmatic da yawa da ke tara sills a saman juna kuma yana lalata dutsen mai masaukin baki a hankali.

A tsawon lokaci, rushewar ƙasa na iya samar da ƙananan tuddai har ma da duwatsu a kusa da tsakiya na tsakiya tunda dutsen da ke shiga yawanci ya fi tsayayya da yanayi fiye da dutsen mai karɓar bakuncin. Saboda wurin da laccolith ke sama da gadaje masu rufi, an kara sauƙin yanki kuma an hanzarta rushewa, don haka gadaje masu rufewa suna lalacewa don fallasa ƙwayoyin intrusive.

Magana

An fara amfani da kalmar a matsayin laccolite ta hanyar Gilbert bayan bincikensa na intrusions na diorite a cikin Henry Mountains na Utah a cikin kimanin 1875 . Kalmar laccolith an samo ta ne a cikin 1875-1880, daga Girkanci Lakko (s) (s) 'pond' tare da -lit 'dutse'.

Inda laccoliths ke samuwa

Laccoliths suna samuwa a zurfin zurfi kuma a wasu lokuta ana kafa su ne ta hanyar magmas mai tsinkaye, kamar waɗanda ke ƙyalli zuwa diorite, granodiorite, da granite. A waɗannan lokuta sanyaya a ƙarƙashin ƙasa na iya faruwa a hankali, yana ba da lokaci ga manyan lu'ulu'u su kasance a cikin magma mai sanyaya. A wasu lokuta ƙananan magma kamar shonkinite na iya samar da phenocrysts na augite a zurfi, sannan ya yi allura ta hanyar mai ciyarwa na tsaye wanda ya ƙare a cikin laccolith.

Shirin shinge yana da alaƙa da jagorancin mafi ƙarancin damuwa a cikin dutsen ƙasar da suka shiga. Don haka laccoliths suna da halaye na yankuna inda ake matse ɓawon burodi kuma jagorancin mafi ƙarancin damuwa yana tsaye, yayin da yankunan da ɓawon burodin ke cikin tashin hankali suna iya samar da dicks, tunda jagorancin mafi karancin damuwa shine a kwance. Misali, laccoliths na Belin Ortiz porphyry a New Mexico mai yiwuwa an kafa su ne a lokacin matsin Laramide na yankin shekaru miliyan 33 zuwa 36 da suka gabata. Lokacin da aka maye gurbin matsin Laramide daga baya ta hanyar tsawo, an maye gurbin wurin sills da laccoliths ta wurin wurin dicks. Ranar intrusions ta taimaka wajen tantance batun a lokacin geologic lokacin da aka maye gurbin matsawa da tsawo.

Misalan

Baya ga tsaunukan Henry, ana samun tsaunukan laccolith a kusa da Colorado Plateau a cikin tsaunukan La Sal da Abajo Mountains.

Gidan da aka cika kuma ya yi ƙarfi na Torres del Paine (Patagonia) yana ɗaya daga cikin mafi kyawun laccoliths da aka fallasa, wanda aka gina shi a hankali ta hanyar shiga cikin dutse da mafic magma a kan shekaru 162 ± 11. An ciyar da intrusions na kwance ta hanyar intrusions na tsaye.

Ƙananan Barber Hill syenite-stock laccolith a Charlotte, Vermont, yana da hanyoyi masu yawa na dutsen wuta da ke da alaƙa da shi. Molybdenite kuma yana bayyane a cikin outcrops a kan wannan laccolith da aka fallasa. A cikin Big Bend Ranch State Park, a kudu maso yammacin Ouachita orogeny, akwai Solitario. Ya ƙunshi ragowar lalacewa na laccolith, mai yiwuwa ana kiranta ne saboda ma'anar kaɗaici wanda masu kallo a cikin tsarin zasu iya samun, saboda ra'ayi na ɗan gajeren faɗin ba tare da iyaka ba a kowane bangare.

Ɗaya daga cikin manyan laccoliths a Amurka shine Pine Valley Mountain a yankin Pine Valley Mountain Wilderness kusa da St. George, Utah .

An fallasa tsarin laccoliths a tsibirin Elba na Italiya, wanda ya samar da tsarin laccolite na "Kirsimeti" wanda tsarin famfo guda ɗaya ya samar da laccolith da yawa a matakai daban-daban a cikin ɓawon burodi.

Matsalolin sake gina siffofin intrusions

Tsarin asali na intrusions na iya zama da wahala a sake ginawa. Misali, Hasumiyar Iblis a Wyoming da Needle Rock a Colorado dukansu ana zaton su ne wuyan dutsen wuta, amma ƙarin bincike ya ba da shawarar cewa laccoliths ne da aka lalata. A Hasumiyar Iblis, intrusion zai kasance dole ne ya sanyaya sosai a hankali don samar da ginshiƙai masu kama da fensir na phonolite porphyry da aka gani a yau. Koyaya, rushewar ƙasa ta cire dutsen da ke kewaye da shi, don haka ba zai yiwu a sake gina ainihin siffar shigarwar wuta ba, wanda zai iya ko bazai zama ragowar laccolith ba. A wasu wurare, kamar a cikin Dutsen Henry da sauran tsaunuka masu nisa na Colorado Plateau, wasu intrusions suna da siffofin laccoliths.

Laccoliths na waje

Akwai misalai da yawa na yiwuwar laccoliths a saman Wata. Wasu suna tsakiya a cikin craters tasiri kuma suna iya zama a matsayin wani ɓangare na juyin halitta na bayan tasiri na crater. Sauran suna tare da yiwuwar kuskuren ko fissures. Laccoliths a kan wata sun fi faɗi amma ba su da kauri fiye da waɗanda ke kan duniya, saboda ƙananan ƙarfin maganaɗiso na wata da ƙarin magmatism.

Hakanan an gano laccoliths masu yuwuwa a Mars, a yammacin Arcadia Planitia .