IAMR - InterAmerican Resources, Inc. (fka IAMR)

[chucka]

Whew, half a year on file systems. I get that same feelig here. Or on the Boards in general. LOL
Chuckamynewnamefor MAZAMA: from below: Mt~iotis
MY OLD files scanned into WORD par example :
und salt in
caLL
CeLL

[97
for, by NoI tnt red dila
doll

dollay!

[ml frem ess





C AR BC

~t in tea ta






will, respect to be precipitathg that dolomite
its in sea saner





- In sea-easer revel,e reacItalt equahbna tnt, i.e. ted by contact

and theoretic a] ~rux of alias hat the most up-to)~ The inability must be catLqed lank factor- In skit to misc from be (Pig. 29-13). na, CD> iotts. and Mt~iotis
[.06 A~ Mg
eaiLe is Lacar41+ 151 tsycr-hyit from the onion
5e~rIm1tnxto&o&/ (Jo ccxl a’

,4~’y~o,’ A% 9
~t/4~9Lt&voL42

tired for the face-by-face groosiD —
· - 29-! 31’). These are Thought to jticlude slow
4>6C~’n’

growLs ann -
dfiute lank acIuLIons (see helow).
A tIem pta to precipit ate 101am ites under laboratory conditions at Earth Cu face temperal nrc, [sad to The formation of m apsesian ealeites which lack the ordering of the true dolomite lattice- Under certain conditions. howecer. a n,etastahle form of dokimite may be produced by primary precipitation or by the alteration at’ pmexisl kg aragonite or calcite. The vrc.edolondlcs thus funned me best defined forntafly as nietactable sinslephase rhombeshedral carbonatcs which deviate from [lie composition of the dolomite that is stable in a given en vtrn ament. or are tiaperfeetly ordcred or both, hut which possess a high degree of cation order as witnessed by the unambiguous rresence of order reflections in Xray dilYr action patter” a’ (Gaines I 977). Protodoloiiiite appears as a precurace to dolomite in replacement reacLIOnS. Protndolomites are in elfect calcia n dolosnites tel fit an excess of Ca’~ hi their lattices (Cat4 Mgt~ (CO,).. High temper at ares &.- C) are nee&d to precipitate pure dolomite iti the labiiratory.
Having discussed the various them ical difficulties ‘ivolved in d isec I dolomite precipitat io,i from sea water. let us turn to discuss the Thrce major secondary sic Iorttttsatton mechanisni 5 wIll eli have been proposed in rcctmt YearS. These are conveniently referred to as the evalicrite brine-residue model the frcsh phres tic/tn silas groundwater mising model, and the formation water model.
The exaporite hajoc-snidue nodal is based ILpoII die observ~l C bent ical and mineralog [cal changcs taking plain just ti osler die surfaee of the broad supratidal pla his around the Artst~ an U ulf k nowit as ssbkhas (see also Cbs 23 & 30). Very widespread dolontit isa, kin It as taken place In ‘tess sediment. ins. otv ing the replacement of
mtlgoni tic sediment by a very ‘tie grained petit odol ottiTte modroets (111th9 scat 1965. Kinsman [966). Analysis eaf the pore waters (Fig 29.14) at cartons points over ole
Cu rfaee of the sable It a (froln the lagoon niand) raveals stem atie ehem leal changes indicative of large- sc~e
remosal of Ca2~ and SO> ions as gypsum. followed by massive dolomitisation of ara~on itie sediment grains of fite former tagoon sediments. The gypsum ia precipi toted as nods les cii II in tite dolomitised carNin ates (C h. 30). The chemical changes reaultiitg in dolorolt earon are caused by progressive eoneenftation of sea water by Cs aporation ~51O 3 to 7) from pores at tite sahkha rfaee (Kin ate an [966)- Pore-water replant 55 ment
—o ot~
P
lagoon
alas1 flat
MODELS FOR DOLOMI
sahkha
P C
2 to
Concentrstioo I Is sea water)
rtgne~ 2~. 4 Rels’ lons t~cese” molar eonvcetraLioa of iono. tiw mole, ratis M& - : C end h.i.,e eon~ntrstttm [a be Aba litiahi catilehe (sites K ins man 19661

occurs by poritylic storm flood evenls. aress fiathesi from the lagoon being replen shed less frequently and hence showing greatest coneentraiiott 5 of Mg³+.
Prom the shove evidence it seems that the kinetic cnn stsainta upon dolomite pteeipitation are overcome La systensa Than contain a high order ratio of Mg Ca, th as faciti toting replainment dolom itisation of a C aCO, pry-en sor. The Mg: Ca ratio reaches a value of over I 0 on so me portions of The sabk ha. Increased Mg Ca ratios of this magnitude are only possible by massive removal of Ca2 — as gy psu ni and anhydrite evaporites- It is likely that SO> re Inoval is esseli Li al it any ease since dokajite is
rafrdtv dissolved in the lace of S05-6ch ground waters
(see below).
mom pIes of sahkha brine dolotnitisatia U are widespread tn the geological record but kes4tahtv after the ins roductioti of the model in The early E 960a it was applied wilt v-ti i [ly to aneient dolomite oceurrences Ii at hardly fitted the ntin,ate constraints demanded by lie nt ode I (see Zenger 1972)- A particular ruse was to appesi to The subsurface sin king or tel) ux of Mg), Mg ;Cn ratio brines wli ich could Iheti dolomitise vast ‘areas of the vadose and parLo of the phreatie zoaes~ Such models were applied eveLt in the face of the relatively feeble presence of a few e vaporitie hands very tltick, regionaflj extensive dolomites.
The gaonadntes mIxIng model for dolontitisatioti has revoltitionised the field, providing a reedy and rational explanat ion hr th~ numerous examples of sticieat