Basin geofluids

Lawrence, Stephen R.; Cornford, C.

doi:10.1111/j.1365-2117.1995.tb00090.x

Cited by 18 publications

(7 citation statements)

References 15 publications

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“…1987; Tucker & Wright 1990). Formation waters are here defined as waters initially trapped during sedimentation that changed their composition during basin evolution due to diagenetic reactions (after Lawrence & Cornford 1995). The molar ratios of Sr/Ca of the uppermost brackish host‐rock are characteristic of being precipitated from formation waters, whereas the molar ratios of Ca/Fe indicate the influence of meteoric waters; the molar ratios of Mg/Ca indicate either precipitation from meteoric or formation waters.…”

Section: Discussionmentioning

confidence: 99%

“…The molar ratios of Sr ⁄ Ca and Ca ⁄ Fe of the host marine limestone are consistent with precipitation from formation waters whereas the molar ratios of Mg ⁄ Ca are consistent with precipitation from either meteoric or formation waters (Table 2; Skougstad & Horr 1963;Kinsman 1969;McIntire 1963;Tucker & Howson et al 1987;Tucker & Wright 1990). Formation waters are here defined as waters initially trapped during sedimentation that changed their composition during basin evolution due to diagenetic reactions (after Lawrence & Cornford 1995). The molar ratios of Sr ⁄ Ca of the uppermost brackish hostrock are characteristic of being precipitated from formation waters, whereas the molar ratios of Ca ⁄ Fe indicate the influence of meteoric waters; the molar ratios of Mg ⁄ Ca indicate either precipitation from meteoric or formation waters.…”

Section: Diagenesis Of the Host-limestonesmentioning

confidence: 99%

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Diagenesis of the Amposta offshore oil reservoir (Amposta Marino C2 well, Lower Cretaceous, Valencia Trough, Spain)

et al. 2010

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Samples from the Amposta Marino C2 well (Amposta oil field) have been investigated in order to understand the origin of fractures and porosity and to reconstruct the fluid flow history of the basin prior, during and after oil migration. Three main types of fracture systems and four types of calcite cements have been identified. Fracture types A and B are totally filled by calcite cement 1 (CC1) and 2 (CC2), respectively; fracture type A corresponds to pre-Alpine structures, while type B is attributed to fractures developed during the Alpine compression (late Eocene-early Oligocene). The oxygen, carbon and strontium isotope compositions of CC2 are close to those of the host-rock, suggesting a high degree of fluid-rock interaction, and therefore a relatively closed palaeohydrogeological system. Fracture type C, developed during the Neogene extension and enlarged by subaerial exposure, tend to be filled with reddish (CS3r) and greenish (CS3g) microspar calcite sediment and blocky calcite cement type 4 (CC4), and postdated by kaolinite, pyrite, barite and oil. The CS3 generation records lower oxygen and carbon isotopic compositions and higher 87 Sr ⁄ 86 Sr ratios than the host-limestones. These CS3 karstic infillings recrystallized early within evolved-meteoric waters having very little interaction with the host-rock. Blocky calcite cement type 4 (CC4 generation) has the lowest oxygen isotope ratio and the most radiogenic 87 Sr ⁄ 86 Sr values, indicating low fluid-rock interaction. The increasingly open palaeohydrogeological system was dominated by migration of hot brines with elevated oxygen isotope ratios into the buried karstic system. The main oil emplacement in the Amposta reservoir occurred after the CC4 event, closely related to the Neogene extensional fractures. Corrosion of CC4 (blocky calcite cement type 4) occurred prior to (or during) petroleum charge, possibly related to kaolinite precipitation from relatively acidic fluids. Barite and pyrite precipitation occurred after this corrosion. The sulphur source associated with the late precipitation of pyrite was likely related to isotopically light sulphur expelled, e.g. as sulphide, from the petroleum source rock (Ascla Fm).

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Section: Discussionmentioning

confidence: 99%

Section: Diagenesis Of the Host-limestonesmentioning

confidence: 99%

Diagenesis of the Amposta offshore oil reservoir (Amposta Marino C2 well, Lower Cretaceous, Valencia Trough, Spain)

et al. 2010

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“…Drawing upon paleomagnetic, rock magnetic, structural geologic, and geochemical studies of the remagnetization which affected the Appalachian region of North America during the late Paleozoic time, we conclude with speculations on the process of remagnetization of the Paleozoic strata of Bolivia. ,-86.9øN, 273.5øE, A95 = 3.0 ø' 30 Ma,-80.5øN, 287.3øE, A95 = 2.7ø; 50 Ma,-78.9øN, 307.0øE, A95 = 4.3 ø' 60 Ma, -80.5øN, 340.7øE, A95 = 4.2ø; 80 Ma, -78.9øN, 3.0øE, A95 = 3.1 ø' 130 Ma,-83.8øN, 60.3øE, A95 = 4.3 been driven by either a "squeegee" effect of the developing thrust belt [Oliver, 1986] or in response to a gravitationally driven hydraulic gradient [Garven and Freeze, 1984;Lawrence and Cornford, 1995]. The synfolding remagnetization of Paleozoic strata over large areas of Bolivia during Andean deformation could have followed a similar sequence of processes.…”

Section: Discussionmentioning

confidence: 99%

“…The suggestion from the paleomagnetic data that remagnetization occurred when the beds were only 20% deformed is explained by a ChRM which remained stable during subsequent fold and thrust deformation. This stability is likely if orogenic fluid composition did not change dramatically during subsequent deformation [Lawrence and Cornford, 1995].…”

Section: Discussionmentioning

confidence: 99%

Tertiary remagnetization of Paleozoic rocks from the Eastern Cordillera and sub‐Andean Belt of Bolivia

Libarkin¹,

Butler²,

Richards³

et al. 1998

J. Geophys. Res.

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“…Metamorphism will lead to the release of fluids by devolatization, with processes such as dehydration, decarbonation and desulphidation producing H,O + CO, + H,S fluids of low salinity (Phillips et al 1994;Lawrence & Cornford 1995). High fluid pressures at depth may have driven a sufficiently large fluid flux to provide a source of ore-fluid from which the Rio Tinto massive sulphides could have been deposited.…”

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confidence: 99%

Discussion on extensional tectonics and magmatism as drivers of convection leading to Iberian Pyrite Belt massive sulphide deposits?

1996

JGS

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G. Digges La Touche writes: Boulter’s (1996) paper on the mechanisms leading to the formation of massive sulphide deposits in the Iberian Pyrite Belt, at Rio Tinto, interprets them as a sill sediment complex, with magmatism and extensional tectonics acting as the driving forces behind fluid convection. From the evidence presented by Boulter (1996) this interpretation appears plausible, although there do appear to be several inconsistencies in the ore-fluid convection model proposed. Boulter (1996) invokes two mechanisms for convective fluid flow. The first of the mechanisms put forward is an adaptation of the sea water convection model of Russell (1978) . It is proposed that during extensional tectonics sea water flowed down syn-sedimentary faults to be heated at depth and then flowed upwards again due to buoyancy through fracture networks or some other high permeability zone. The problem with this model is that it is essentially a low-volume system with flow down and up descrete fault and fracture zones. In order to achieve the ore-fluid volumes necessary to create the Rio Tinto massive sulphides unrealistically large long lived fluxes would be necessary. It is not suggested that this mechanism was not occurring, just that it would not have contributed significantly to the metal budget. Additional problems with the extension driven convective cell mechanism exist in that it is hard to understand why in the model of Russell (1978) sea water should flow down extensional faults, considering that the sediments in which the syn-extensional faults are forming would already be fully saturated

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Basin geofluids

Cited by 18 publications

References 15 publications

Diagenesis of the Amposta offshore oil reservoir (Amposta Marino C2 well, Lower Cretaceous, Valencia Trough, Spain)

Diagenesis of the Amposta offshore oil reservoir (Amposta Marino C2 well, Lower Cretaceous, Valencia Trough, Spain)

Tertiary remagnetization of Paleozoic rocks from the Eastern Cordillera and sub‐Andean Belt of Bolivia

Discussion on extensional tectonics and magmatism as drivers of convection leading to Iberian Pyrite Belt massive sulphide deposits?

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