LECTURES ON GEOCHEMICAL !N1 ERPRETATION OF ...

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PageDOUBLE- DIFFUSIVE CORVECTIOR AS A KECHAHISH FOR TRARSFBRRIRG HEATWHILE MAIIITAIHIIIG CHEKICAL GRADIEllTS IH THE SALTOH SRA BRIBEInt~oduction- ---- --- --------------- ------------ --------------- ---- 55Double- diffusive convection------------ --------------------------- 55Application to the Salton Sea system- ----------------------------- 56Tempe~atu~e - depth p~ofile fo~ doublediffusive convection- --- 56Calculation of the density of a fluid sample f~om theSalton Sea ~cservoir--------------------------------------- 58Conclusions--------------------------------- ---------- ------------ 62Refe~ences -- --------------------- - --------------------- - ----- -----Figures631 . Ideali zed temperature-dept h profile within the Salton Seageothermal system showing details of effects of doublediffusive2. convection---------------------------- ------------ 57Chloride molality versus the density difference between theindicated salt and NaCl at 300°C- ___ ________________ ________ 60Tables1. Pre- flashed concentrations of selected elements and total2.dissolved solids in brine in the State 2- 14 well- - ----------Calculation of specific density of pre- flashed brine at58305°C in the State 2- 14 well-------------------------------- 61WATER- MAGMA IUTERACTIOH RELATED TO EPISODIC IHFLATIOH AHD DEFLATIOHOF THE YELLOWSTORE CALDBRA, WYOMIIIGIntroduction- ----------------------- ------------------------------Geothermal flux and depth of meteoric water circulation- ----------6566Crystallization of magma as a source of heat and aqueous fluids--- 67Volumetric changes associated with crystallization of magma------ -Episodic intrusion of basalt and continuous crystallization69of rhyolite------- ------------ ---------------- -------------Accumulation of magmatic gas at lithostatic p~essure ---------7071Conclusions---------- ------ --------------------------- --------- - - - 72References-------------------------------------------------------- 73Figure 1. Schematic diagram showing circulation of meteoric waterextracting heat from a crystallizing and cooling bodyof magma-------------------------------------- ---------- 66lii
- 1 -CARBONATE TRANSPORT AND DEPOSITION IN HYDROTHERMAL SYSTEMSRobert O. FournierU.8. Geological Su~ey. Menlo Park, California 94025 U.S.A.INTRODUCTIONThe alkali carbonates, Na, K, and Li, are relatively soluble at alltemperatures and generally precipitate only where there is extreme evaporati on. In contrast, the alkaline earth carbonates. Ca. Ht, Sr, and Ba, aremoderately to sparingly soluble and commonly precipitate in bydrothecmalsystems. Calcite is by far the most abundant and important carbonate foundin hydrothermal systems, and more solubility data are available for it thanfor any of the other carbonates. In natural hydrothe~l solutions manydissolved constituents and 8 variety of chemical reactions involvingsolids. liquids. and gases influence the dissolution and deposition ofcalcite. In particular, its solubility is strongly influenced by pH. thepartial pressure of carbon dioxide, PC02' temperature, and the presence ofother dissolved salts. The situation is particularly complex when boilingoccurs. Sophisticated computer programs, such as the WATCH programs(Svararsson, 1981), are the best way t o handle these complex reactions.However, all too frequently such programs are employed with little regardor appreciation for the factors that influence the results of the computations.It is the intent of this presentation to highlight the factors thatcontrol the solution and deposition of carbonate in geothcrma1 systems, andto show that it is possible to make good estimates of the likely magnitudeof calcite transport and deposition in natural waters usi ng hand-held,programmable calculators. These procedures are very useful even though afew simplifying assumptions are required, and only the most importantdissolved species are included. The ensuing discussion follows the generalprocedures presented in Henley et al. (1984).
Page 1 and 2: ,. ,O~KUSTOFNUNNATIONAL ENER GY AUT
Page 3 and 4: PREFACESince the foundation of the
Page 5: P~eTHE SOLUBILITY OF SILICA IV HYDR
Page 10 and 11: - 4ca~bonic acid (Table 3). Equatio
Page 12 and 13: - 6 -Values of y a~ewater and the r
Page 14 and 15: - 8 -The s implest equation ~ep~ese
Page 16 and 17: - 10 -c0"0"'0>,'"0>>-.- .D"0"'Q)Q'"
Page 18 and 19: - 12 -The effect of partitioning of
Page 20 and 21: - 14 -FIGURE 5. The computed activi
Page 22 and 23: - 16 -REFEREYCESA~o~sson.S .• 191
Page 24 and 25: TABLE 2.Coefficients for use with e
Page 26 and 27: - 20 -TABLE 4. Values of ionie cnar
Page 28 and 29: - 22 -vapor pressure of pure water
Page 30 and 31: - 24 -Figure 2 shows the solubility
Page 32 and 33: - 26 -TABLE 2. Temperatures, enthal
Page 34 and 35: - 28 -800600~ci>E 400NoVi200o 500 1
Page 36 and 37: - 30 -800~ 600"- 0>E 400NoVi200o 50
Page 38 and 39: - 32 -has an enthalpy L , and the r
Page 40 and 41: - 34 -tempe~atu~e in kelvins. Molal
Page 42 and 43: - 36 -SILICA SCALING POT ENTIAL AS
Page 44 and 45: - 38 -and no silica scaling will oc
Page 46 and 47: - 41 -CATION GEOTHERKOKETRYRobert O
Page 48 and 49: - 43 -fo~ dilute solutions). Thus,
Page 50 and 51: - 45 -3.002.50~ 2.00Q-;"1.50z~g-' 1
Page 52 and 53: - 47 -whe~e ~ is 1/3 fo~ wate~s equ
Page 54 and 55: - 49 -Kg concent~ations in geotherm
Page 56 and 57:
- 51 -Na/l00070IMMATURE WATERSK/l00
Page 58 and 59:
- 53 -CONCLUSIONSIn evaluating cati
Page 60 and 61:
55CONVECTION AS A MECHANISM FOR TRA
Page 62 and 63:
57and mainly wi thin interconnectin
Page 64 and 65:
59During drilling, the mud weight r
Page 66 and 67:
61TABLE 2. Calculation of specific
Page 68 and 69:
63REFERENCESG~iffiths.R.W., 1981. L
Page 70 and 71:
66Temperature __, t 1/
Page 72 and 73:
68crystallizing about 0.1 km 3 of r
Page 74 and 75:
70usually to the side along a ~ift
Page 76 and 77:
72Although the above calculations a
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