ON EVOLUTION OF SUBSURFACE BRINES IN ISRAEL

被引:37
作者
BENTOR, YK
机构
[1] Department of Geology, Hebrew University, Jerusalem
关键词
D O I
10.1016/0009-2541(69)90041-2
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Subsurface brines occurring in Israel at depths of 1,000-3,400 m in Early Cambrian-Early Cretaceous formations are classified into four groups. 1. (1) A group identical in composition and salinity with present-day ocean water, except for its higher Ca2+ and lower Mg2+-content, a change attributed to dolomitization. 2. (2) The oilfield waters in Early Cretaceous formations of the coastal plain, still similar to ocean water, but twice to three times more saline; they have lost most of their sulphates through reduction to H2S, and are enriched in Br and I, both derived from organic sources. The relative Mg-depletion of these brines is attributed to the uptake of Mg2+ by the regrading and synthesis of clay minerals. Waters near the Jurassic-Lower Cretaceous unconformity show a pronounced salinity minimum, which is attributed to dilution by meteoric water during a shortlived emersion. 3. (3) Brines from Jurassic to Early Cambrian source units. Within this section, salinities as well as the Ca/Na- and Br/I-ratios increase progressively with depth while the Na/K, HCO3 Cl and Cl/Br-ratios decrease. The brines change from sodium-chloride to typical calcium-chloride types. It is assumed that the lowermost Palaeozoic brines were formed by surface evaporation during Infracambrian to Early Cambrian time and were later modified by differential ultrafiltration. 4. (4) A most peculiar group is represented by highly saline brines at the depth in the Rift Valley. Sub-group A, found in marine sediments or continental clastic fill, is chemically similar to the Early Palaeozoic brines, but even more differentiated. These waters are assumed to be of Early Palaeozoic age and to have entered the Rift Valley after its last important phase of subsidence in the Plio-Pleistocene. Sub-group B shows salinities of around 300,000 p.p.m., the rNa K-value is 1-2 and the CaCl2-character is extreme. These waters are believed to be old Palaeozoic brines that have undergone a new cycle of surface concentration in Pleistocene Rift Valley lakes, the precursors of the Dead Sea. © 1969.
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