Editor''s note     

C. John Mann 《Mathematical Geology》1989,21(8):959-960

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DISCUSSION OF "Statistical Prediction Intervals for the Evaluation of Ground-Water Quality," by Robert D. Gibbons, July-August 1987 issue, v. 25, no. 4, pp. 455–465     

Charles B. Davis  Roger J. McNichols 《Ground water》1988,26(1):90-91

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Statistical Issues and Problems in Ground Water Detection Monitoring at Hazardous Waste Facilities     

Roger J. McNichols  Charles B. Davis 《Ground Water Monitoring & Remediation》1988,8(4):135-150

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Earth''s earliest continental lithosphere, hydrothermal flux and crustal recycling     

Maarten J. de Wit  Roger A. Hart 《Lithos》1993,30(3-4):309-335

The Kaapvaal craton in southern Africa and the Pilbara craton of northwestern Australia are the largest regions on Earth to have retained relatively pristine mid-Archaean rocks (3.0–4.0 Ga).The Kaapvaal craton covers about 1.2×10⁶ km², and varies in lithospheric thickness between 170 and 350 km. At surface, the craton can be subdivided into a number of Archaean sub-domains; some of the subdomains are also well defined at depth, and local variations in tomography of the lithosphere correspond closely with subdomain boundaries at surface.The Archaean history of the Kaapvaal craton spans about 1 Gyr and can be conveniently subdivided into two periods, each of about the same length as the Phanerozoic. The first period, from circa 3.7-3.1 Ga, records the initial separation of the cratonic lithosphere from the asthenosphere, terminating with a major pulse of accretion tectonics between 3.2 and 3.1 Ga, which includes the formation of “paired metamorphic belts”. This period of continental growth can be compared to plate tectonic processes occurring in modern-day oceanic basins. However, the difference is that in the mid-Archaean, these oceanic processes appear to have occurred in shallower water depths than the modern ocean basins. The second period, from circa 3.1-2.6 Ga, records intra-continental and continental-edge processes: continental growth during this period occurred predominantly through a combination of tectonic accretion of crustal fragments and subduction-related igneous processes, in much the same way as has been documented along the margins of the Pacific and Tethys oceans since the Mesozoic.The intra-oceanic processes resulted in small, but deep-rooted continental nucleii; the first separation of this early continental lithosphere could only have occurred when the mean elevation of mid-oceanicridges sank below sea-level. Substantial recycling of continental lithosphere into the mantle must have occurred during this period of Earth history. During the second period, at least two large continental nucleii amalgamated during collisional processes which, together with internal chemical differentiation processes, created the first stable continental landmass. This landmass, which is known to have been substantially bigger than its present outline, may have been part of the Earth's first supercontinent.The oldest known subdomains of the craton include the oceanic-like rocks of the Barberton greenstone belt. The comagmatic mafic-ultramafic rocks (3.48–3.49 Ga) of this belt represent a remnant of very early oceanic-like lithosphere (known as the Jamestown Ophiolite Complex), which was obducted, approximately 45 Ma after its formation, onto a volcanic arc-like terrain by processes similar to those which have emplaced modern ophiolites at convergent margins of Phanerozoic continents. The early metamorphic history, metamorphic mineralogy, oxygen isotope profiles and degree of hydration of the 3.49 Ga Jamestown Ophiolite Complex are similar to present day subseafloor hydrothermal systems. The ratio of ΔMg to ΔSi for hydrothermally altered igneous rocks, both present day and Archaean, are remarkably uniform at −5(±0.9) and the same as that of hydrothermal fluids venting on the present-day East Pacific Rise. This observation suggests that the process of Mg exchange for Si in hydrothermal systems was commonplace throughout Earth's history.The chemistry of vent fluids and hydrothermally altered igneous rocks was combined with an inventory of ³He in the mantle to model Earth's total hydrothermal flux. An Archaean flux (at 3.5 Ga) of about 10 times present day was accompanied by a correspondingly greater abundance of Mg(OH), SiO₂, carbonate and Fe---Mn metasomatic rock types as well as massive sulphides. Assuming a constant column of seawater since the Archaean, the average residence time of seawater in the oceanic crust was 1.65−8.90×10⁵ years in the Archaean. Assuming that ³He and heat are transported from the mantle in silicate melts in uniform proportions, the model stipulates that accretion of oceanic crust decreased from about 3.43−6.5×10¹⁷ g/yr to a present-day rate of 0.52−0.8×10¹⁷ g/yr, with a drop in heat flow from 1.4−2.6×10²⁰ cal/yr to 2.1−3.2×10¹⁹ cal/year.The total amounts of SiO₂ and Fe mobilised in marine hydrothermal systems since 3.5 Ga is less than their masses in the present exosphere reservoirs (crust, hydrosphere, atmosphere). The total amounts of Mg, K, CO₂, Ca and Mn are greater than their respective masses in exosphere reservoirs; therefore, they must have been recycled into mantle. The total mass of recycled hydrothermal components is small compared to the mass of the mantle. The flux of volatiles in hydrothermal systems is large compared to their volume in the atmosphere suggesting that the CO₂ and O₂ budgets of the atmosphere have been influenced by hydrothermal processes, especially in the Archaean.  相似文献   

Book review     

C. John Mann 《Mathematical Geosciences》1994,26(3):413-414

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Early use by fish of a mitigation salt marsh,Humboldt Bay,California     

Robert H. Chamberlain  Roger A. Barnhart 《Estuaries and Coasts》1993,16(4):769-783

Fish numbers and biomass in a mitigation salt marsh, Humboldt Bay, California, were examined from July 1981 to October 1982 and were compared with a nearby established marsh to determine whether the restored marsh provided adequate mitigation for habitat lost due to construction of a nearby marina. The use by fish of channels adjacent to the two marshes and the channel at the Woodley Island Marina construction site, for which mitigation was required, were also compared. The mitigation marsh, adjacent to Freshwater Slough channel, was 5.2 km from the marina site. Fishes were sampled by otter trawl, ichthyoplankton net, fixed channel nets, drop traps, and beach seines. Thirty-one fish species and two crab species were collected. Wide ranges in seasonal salinities and water temperatures, and differences in marsh elevation influenced fish use of the mitigation marsh area. The intertidal area of the mitigation marsh, dominated by euryhaline sticklebacks and topsmelts, did not replace intertidal and subtidal habitat lost by marina construction, which had more stable salinities and water temperatures and was used extensively by juvenile English sole.  相似文献   

Editor''s note     

C. John Mann 《Mathematical Geology》1990,22(2):149

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Calculated mineral equilibria in the greenschist-blueschist-eclogite facies in Na2O−FeO−MgO−Al2O3−SiO2−H2O     

Michel Guiraud  Tim Holland  Roger Powell 《Contributions to Mineralogy and Petrology》1990,104(1):85-98

The new, greatly expanded internally-consistent dataset of Holland and Powell includes thermodynamic data for a wide range of mineral end-members in common rock-forming minerals, in particular, including FeMg_-1 substitutions in glaucophane, garnet, chloritoid and carpholite, and FeMg_-1 and MgSiAl_-1Al_-1 substitutions in talc and chlorite. Moreover, we have the uncertainties and correlations for these data. With the data, we have calculated the full pressure-temperature phase diagram for the system Na₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O (NFMASH) for quartz (or coesite) and H₂O in excess, in the range 300°–800°C and 5–50 kbars. By solving the set of non-linear equations formed by the equilibrium relationships for an independent set of equations between the end-members in an assemblage in NFMASH, the compositions of the minerals (and PT) can be calculated. Thus the changes in MgSiAl_-1Al_-1 along NMASH reactions, and FeSiAl_-1Al_-1 along NFASH reactions, are calculated, and the changes in FeMg_-1 and MgSiAl_-1Al_-1 along NFMASH reactions are calculated. From this information it is straightforward to generate PT diagrams for specific rock compositions. Mineral assemblages and mineral compositional changes in the phase diagram are discussed in relation to greenschist, blueschist and eclogite facies assemblages in metapelitic rocks. It is found that the correspondence between the predictions of the phase diagrams and the observations on rocks is remarkably good. When semiquantitative extensions of the phase diagram to include Ca(MgFe)_-1, NaSiCa_-1Al_-1, Fe³⁺Al_-1 and KNa_-1 substitutions are taken into account the agreement is essentially complete.  相似文献   

The Little Ice Age : By Jean Grove. Methuen Publishers, London/New York, 498 pp     

Daniel H. Mann 《Quaternary Research》1990,34(3)

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On the general character of coastal flow     

Roger L. Hughes 《Pure and Applied Geophysics》1990,133(4):665-689

It is well-known that some coastal currents such as the Florida Current have a recirculating region on their coastal side, while other currents such as the East Australian Current have no such region. Under the hypothesis that the form drag on a coastal current by an irregular coastal topography reduces the momentum transport of the current to a minimum for the given flow within the current, the hydraulic theory of coastal currents is used to explain this behaviour.  相似文献