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THE ~Lineralogy of the HATRURIM FORMATION, ISRAEL

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THE ~Lineralogy of the HATRURIM FORMATION, ISRAEL THE ~lINERALOGY OF THE HATRURIM FORMATION, ISRAEL ABSTRACT The l]atrurim Formation, (formerly known as the reported from only one locality. "Mottled Zone") is <1 unique rock complex, exposed Optical data, X-ray diffraction data, thermal analyses, mainly in the Judean Desert. It was apparently de­ chemical analyses and crystal morphology (by SEM) posited as a normal marine, chalky-marly sequence of of the minerals were obtained. Chemical analyses of Campanian to Neogene age, but is today largely com­ naturally occurring tricakium silicate (batrurite). nagel­ posed of high-temperature metamorphic minerals schmidtite, portlandite and 6CaO.2Fe2 0\.AI2O~ (un­ corresponding to the sanidinite and pyroxene-hornfels named) are reported for the first time. facies. No indication of contact metamorphism is, Most of the minerals were formed during one of the however, found in the area. One hundred fourteen following stages: low to high-grade metamorphism, minerals are described. Eight of them were previously retrograde metamorphism, hydrothermal alteration and known only as synthetic products and five others were weathering processes. INTRODUCfION age), and clays and marls of the Taqiye Forma­ tion (Dano-Paleocene Age), are found overlying A. The Hatrurim Formation: flint and phosphorite beds of the Mishash description and occurrence Formation (Campanian age). In many outcrops and in subsurface sections, these rocks are The present mineralogical investigation of the bituminous. The lower part of the Ghareb ijatrurim Formation (Gvirtzman and Buch­ Formation may contain up to 26% organic binder, 1966), formerly described as the Mottled matter and can be classified as oil shales (Shahar Zone Complex (Picard 1931; Bentor 1960), is and Wurzburger, 1967). a part of a larger research program carried out In a number of areas an entirely different, by the author since 1963 as a project at the thermally metamorphosed facies, the so-called Geological Survey of Israel. The study is based ljatrurim Formation ("Mottled Zone") appears on an examination of about 1,000 samples, col­ instead of the normal sequence. These rocks lected from the various outcrops of the l:Iatru­ in the Jerusalem-Jericho area attracted the at­ rim Formation. tention of numerous geologists as early as the In many parts of Israel a sequence of slightly middle of the nineteenth century (see for re­ phosphatic chalks and marls of the Ghareb view: Avnimelech, 1965). The name "Mottled Formation (Upper Campanian to Maastrichtian Zone" was proposed by Picard (1931), who Geol. SUTY. Israel, Bull. No.70 pp.I-80; 18 figs.; 2S pIs. Jerusalem, February 1977 S.GROSS MINERALOGY -ljATRURIM FM. described its outcrops at Ma'ale Adumim and at shades of brown, green, yellow, pink, red, violet, Nebi Musa. The term "mottled" refers to the grey, and black. vivid, variegated colours of the rocks in all The known outcrops of the tIatrurim Forma­ tion are shown in Fig. I. At least nine, widely separate outcrops are known: the tIatrurim syncline west of the Dead Sea, Ma 'aleh Adumim, Beit Sihur, Nebi Musa, and Jebel Harmun in the Judean Desert, Nahal Ayalon in the Coastal Plain, Kefar Uriyya and Tarqumiye in,r the Shefela region (western foothills), and~a1}al Malhata in the Be'er Sheva' Valley, inthe north­ ern Negev. In its fully developed occurrence in·'the tIatrurim syncline the complex has a preserved thickness ·of more than 220 m and covers an area of 50 km. 2 These outcrops have been described by Bentor and Vroman (l960):The complex includes the rock-time equi~alents of No!!ol Ayolon • the Ghareb, Taqiye and possibly ~or'a fonna­ tions and relicts of the Ija~eva Formatipn (Fig. 2). Maastrichtian, Danian and Landenian ages were confirmed on the basis of microfaunal relicts determined by Z. Reiss. Rare microfos­ sils have been preserved also in outcrops of Nal}al Ayalon(Gross et af.. 1967). Their study by Z .. Reiss confirmed the Campanian age ofthe rocks. All other outcrops seem to be time equi­ valentsof,the.Ghareb Formation, as determined bytheirstratigraphic position. .... Thet!atrurim Formation" which (has been :; fo'tindonlyinsynclinal areas, has;a very com­ mineralogy and is composed largely ~f un­ commcnhigh-temperature .. minerals., Elsewhere, these minerals:are,characteristic ,of contact­ metamorphic' rocks of the sanidinite and ~?rnfels facies. In all other .known localities;'ihese assemblages were found in nar­ row 'aureoles immediately adjacent'to, basaltic ?f?ther near-surface .. intrusions,. or· .' in limestonexel1oliths within basalts; The;: were 20 40 . , formed at very high temperatures «J0021 OOO°C) Scale and very low pressure. These localities include: Velardena and Coahuila, Mexico (Wright,"! 908 ; Figure 1. Outcrops of the Hatrurim Formation. Temple and Heinrich, 1964); Crestmore, Cali- 2 GSI Bull. 70, 1977 MINERALOGY -HATRURIM FM. S. GROSS NORMAL !:!ATRURIM STRATIGRAPHY India (Naidu and Covidarajulu, 1954); Sinai FACIES FACIES (Gross et al.. in preparation). Hozevo Neogene - Fm. 0 0 0 0 0 Assemblages similar to those of the Ijatru­ oo,oo·oo~ f---f--- >- ~ rim minerals are also recorded from portland 0: Lower to Middle ILl <f- Z or'o I E z I I- Eocene Fm. 0 cement clinker (Lea, 1956; Taylor, 1964) and IU. N I 0: - - - blast furnace slags (Lapin, 1946; Nurse and W 4..- _4- -... I~ I I- L..-r-~_L-- _.1......-_- 0 Toqiyo UJ Paleocene ........ "-- ,..." ....... Ig; ...J I Midgley, 1955; Kariakin, 1962). Fm. .......... "-- L--_ l- ~ ~ ~ I:: I- I The Ijatrurim Formation is unique in the fact Ghareb ~ ~ ~I 0 (/) Maastrichtian '- J- '- I ~ Fm. ~ '- I that it quite definitely could not have been :::> I ~ 0 . H formed by contact metamorphism. No igneous UJ Mishosh u Companion ~ <f Fm. rocks have been found associated with it ex­ I- ~ '- - UJ cept for a small dike reported at Tarqumiye 0: u Turonian Judea (Y. Bartov, personal communication) with UJ I- Cenomanian Group hardly any contact zone. The rocks under­ <f ...J lying the Ijatrurim Formation are normal marine sediments without any sign of meta­ • • morphism. A different mechanism has to be invoked to explain the origin of the high­ Limestone Ch er t ~ ~ temperature mineral assemblage. Dolomite Phosphorite ~ ~p p 0 Sandstone and Mar I 0,5'00 B. Genesis of the Hatrurim Formation ~,...... rJ 1°0 °1 conglomerote. Choi k F lin t nodules [8]"'- ~ 1#··'.-- The ideas of earlier authors,based mainly on Figure 2. Schematic stratigraphic position of the field evidence, have been summarized by Avni­ Hatrurim Formation. melech (1965). These explanations range from volcanic (Tristram 1865, Hull 1886) to tectonic fornia (Eakle, 1917; Murdoch, 1955, 1961; (Blanckenhorn, 1912). Picard (1931) thought Burnham, 1959); Little Belt Mountains, Mon­ the Mottled Zone rocks to have been formed tana (Taylor, 1935); Christmas Mountains, by euxinic sedimentation and diagenesis. Avni­ Texas (Clabaugh, 1953); Tres Hermanas Moun­ melech (1936) suggested in the case of Nab-al tains, New Mexico (Homme and Rosenzweig, Ayalon a local hydrothermal origin connected 1958); Scawt Hill, N. Ireland (Tilley, 1929, with Neogene volcanism. He later rejected this 1933, 1942; Tilley and Harwood, 1931); Carl­ hypothesis in favour of a "diagenetic, or rather ingford, N. Ireland (Nockolds and Vincent, epigenetic process developed subaerially on an 1947; Osborne, 1932 a, b); Ballycraigy, N. old "Danian" land surface" due to a period of Ireland (McConnell, 1954, 1955, 1960); Isles strong insolation. Bentor and Vroman (1960) of Skye, Muck, and Rhum, Scotland (Wyatt, assumed that the rocks of the Mottled Zone 1953; Tilley, 1947; Hughes, 1960); Kilchoan, were originally similar in composition to the Ardnamurchan, Scotland (Agrell, 1965); Mayen bituminous Ghareb and Taqiye formations. in Laacher See region, Germany (Jasmund and Some time after burial of these strata under Hentschel, 1964); Tokatoka, New Zealand marine sediments of Eocene age, ground water (Mason, 1957); Lower Tunguska, Siberia (Sobo­ rich in oxygen caused oxidation of the sulphide lev, 1935; Reverdatto, 1964); Mysore State, minerals and of the organic matter. "Owing to GSI Bull. 70, 1977 3 S. GROSS MINERALOGY-I1ATRURIM FM. the low thermal conductivity of the overlying on the subject, thermal metamorphism is com­ sediments,the temperature of the ground water mon in burning coal seams and oil-bearing rocks. rose through the heat of oxidation and its geochemical activity was thereby enhanced." The result was a general redistribution of major C. Metamorphic model for the and minor elements and the crystallization of Hatrurim Formation new minerals. For processes of this kind the term "sedimentary hydrothermal" activity was Kolodny et al. (1973), by using fission-track proposed. dating, found that the latest thermal event af­ First evidence for a high-temperature origin fecting the IjatrurimFormation in the Ijatrurim of the "Mottled Zone" assemblage was present­ syncline took place 13.6 or 16.8 ± 2 million ed by Bentor et al. (1963a, b), who showed that years B.P. in Miocene times. The sandstone of it contained high-temperature minerals such the Ija~eva Formation, considered to be of as spurrite,gehlenite and brownmillerite. They Neogene age and overlying the Ijatrurim Forma­ reiterated the previous view' of' Bentorand tion unconformably, is also partly metamor­ Vroman (1960) concerning spontaneous com­ phosed and mineralized in this area. bustion of bituminous matter. in the original The Ija~eva and subsequent formations never rocks as a source of heat. Grosset al. (1967) reached great thicknesses. The metamorphism advocated a penecontemporaneous origin in a could therefore'n'ot be significantly influenced reducing and alkaline environment and doubted by pressure. On the other hand it was shown, the development of very high' (above 6400 C) both by total analysis and by artificial thermal temperatures during' the formatiori of? the synthesis, that the mineral assemblage of the mineral assemblage of Nahal Ayalon. Isotopic Ijatrurim Format~on was formed isochemically studies of carbon and oxygen (Bentor et ;al., from the Taqiye and Ghareb formations, Le.
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