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folds have been twisted and even crushed. All these features cannot be explained without immense dislocations originated by the sharp change in direction of the Himalayan chain, and the instability proceeds from these disturbances.
The neighbourhoods of Peshawar, Rawalpindi, and Attock are very unstable, without having suffered to any great extent. A great dislocation, crossed hy numerous secondary faults, separates the tertiary basin of Rawalpindi from the ancient rocks. So we can suppose that the forces from which these faults have proceeded manifest themselves still in the shape of earthquakes. Ruins, at least partially of seismic origin, are seen in many ancient castles built on the hill-tops."
The last earthquake of note that occurred in this neighbourhood was that of the 1st February, 1929 (Coulson, 1929 and 1930). The epicentre of the present Hindu Kush earthquake is obviously some distance to the north-west of that of the 1929 shock. When describing the 1929 shock, I concluded (1929, p. 288) ---
“That the depth of focus of this earthquake might be such that the usual rates of propagation of the long waves (and of the other waves) are inapplicable.” Additional support was given to this view with the further instrumental records available at the time of my second paper (1930, Pp. 442-443).
From the evidence shown in the seismograms of the 1937 shock at Colaba (Bombay) and Alipore (Calcutta), there seems little doubt that this shock was a deepseated one (200-240 km.). Admitting this, then the epicentre according to the Bombay Meteorologist is about 37-5° N., 72.5° E., and according to the Calcutta Meteorologist about 37.5° N., 71.5° E. Both these estimates correspond well with the conclusions drawn from observers' reports.
FORESHOCKS AND AFTERSHOCKS.
There were several shocks felt in the higher intensities areas prior to the main shock of the 14th November, 1937. Thus shocks
felt at Dros! on the 9th September Foreshocks.
(also felt at Gulmarg), 29th October (also felt at Cherat, Kabul, Lahore, Peshawar and Srinagar), and in the very early hours of the 8th November (also felt at Gilgit, Gurais, Peshawar, Rawalpindi and Srinagar).
It is interesting to note that the shocks felt in Ambala, Dehra Dun, Lahore, New Delhi, Roorkee, Simla and Srinagar at about 6.55 I. S. T. on the 20th October, 1937, seem to have had their epicentre in the north-west Punjab and cannot therefore be considered as foreshocks of the Hindu Kush earthquake of the 14th November, 1937.
Up to the time of writing this note (17th December, 1937), records have been received from Drosh of aftershocks which were
felt there on the 16th, 19th and 21st NovAftershocks. ember, 1937. It would
appear that equilibrium apparently has been attained temporarily once more until the accumulated stresses are again relieved, either by a sudden shock or by a shock heralded by a succession of foreshocks.
BALLORE, F. DE MONTES- 1904. The Seismic Phenomena in SUS DE.
India, and their connection with its Geology. Mem. Geol. Surv. Ind., XXXV, Pt.
3, pp. 153-194. (Reprinted 1934). Coulson, A. L.
1929. The Epicentre of the NorthWest Himalayan
Earthquake of the Ist February, 1929. Rec. Geol. Surv. Ind., LXII, Pt.
2, pp. 279-289. 1930. Second Note
Earthquake of the
1st February, 1929. Rec. Geol. Surv. Ind., LXIII, Pt.
4, pp. 434-443. HECK, N. H.. 1936. Earthquakes. Princeton
ON KHOHARITE, A New GARNET, AND ON THE NOMENCLATURE
OF GARNETS. BY Sir Lewis Leich FERMOR, O.B.E.,
a. Names of garnet molecules'.
In September 1912, in a paper entitled Preliminary Note on the Origin of Meteorites '1, I suggested that the curious bodies known as chondrules found in so many stony meteorites must once have been garnets. This suggestion was based on a thin section of the
of the Khohar meteorite, which contained chondrules consisting of enstatite with metallic rims. As this paper is not readily accessible in all libraries it is suitable to quote therefrom at some length in order to show the reason for the adoption of this hypothesis of the garnet origin of chondrules (l. c., pp. 317-319) :
• The conversion of garnet to enstatite is easily explained by the following equation :
3(Mg,Fe)O.Fe, 02.3Si0, 3(Mg,Fe)SiO2 t Fe,03,
Enstatite which requires an 8.5 per cent. increase in volume. The ferric oxide, expelled by the crystallising enstatite, was reduced by graphite (or some reducing gas) in the matrix of the original rock with formation of metallic iron according to the following equation :
2Fe,0,+30=4Fe + 3CO, The reduction of pressure must have been sudden, enabling each garnet to liquefy under the influence of the prevalent high temperature. The sudden reduction of pressure must have been followed by a rapid decrease in temperature, causing the liquid globules to crystallise quickly with the production of the various
1 Journ. Ax. Soc. Bengal, N. S., VIII, pp. 315-324, (1913): also Proceedinge, p. cxxxiv, Sept. 1912. 2 G. de P. Cotter, Rec. Geol. Surv. Ind., XLII, p. 274 (1912).
radiated structures due to enstatite alone, and the complicated intergrowths resembling eutectic crystallisations, when both enstatite and olivine have crystallised out. Such a combination of conditions seems to me obtainable only in one way, naniely by the sudden disruption of a celestial body in which lay, under high pressure and temperature at some depth below the surface, a garnetiferous zone analogous to the garnetiferous infra-plutonie zone of the earth. The sudden disruption of this celestial body would account for the sudden reduction of pressure promoting the liquefaction of the garnets. The dispersal of the fragments produced by this disruption would doubtless be accompained by a sufficiently speedy fall in temperature to cause the rapid congelation of the liquefied garnets.
Since it is possible to suggest this very simple explanation of the formations of chondrules, it is necessary to see whether such facts as are available support the idea. Returning to the original slide of the Khohar meteorite it is noticed that the degree of perfection of the iron-rim round each of the chondrules is very variable, and in some cases the iron is almost absent. This variation in the character of the iron border is to a certain extent correlative with variation in the character of the chondrules themselves. One particular chondrule of enstatite affords very convincing evidence. (See plate XXVII, fig. 2.) It is apparent from the slide that the enstatite has crystallised very rapidly, starting from a point on one side of the chondrules, and that, as the radiate needles enstatite increased in length, they pushed before them the surplus ferric oxide. Consequently most of it occurs on the side of the chondrule remote from the point at which crystallisation started, not, however, as oxide, but in the metallic state, having been reduced outside the chondrule, probably by graphite in the matrix. A certain amount of the iron has become entangled between the enstatite needles, and indicates that there may have been inclusions of some form of carbon within the original garnet itself. The matrix of the rock between the chondrules consists largely of enstatite, olivine, and nickel-iron. These are to be regarded as original constituents of the rock as it existed in the primitive celestial body. When the pressure was released they suffered no appreciable change, except that the expansion of the garnets on liquefaction tended to produce brecciation of the rock, such brecciation being a common feature of chondritic meteorites. Other writers have noticed such metallic rims to chondrules, without explaining their occurrencel. As a result of the reaction given above, Co, (or CO) must have been formed. It is important to notice that both these gases are well known in meteorites.'
Although no other satisfactory solution of the origin of chondrules has been propounded, yet my suggestion has not met with general acceptance. Thus the late Dr. G. T. Prior was not able to accept this hypothesis because of his discovery2
* that the proportion of nickel in the nickel-iron and that of ferrous oxide in the ferromagnesian silicates in meteorites are not independent variables, but are so related that in general the richer in nickel is the nickel-iron the richer in ferrous oxide are the magnesian silicates.
1 E.g., H. L. Bowman and H. E. Clarke, Min. Mag., XV, D, in Fig. 3 of Plate IX, (1910). (The Chandakapur ae rolite.)
2* A Guide to the Collection of Meteorites ', British Museum (Natural History), p. 19, (1926).
This reciprocal relation is, however, exactly what one would expect on my hypothesis, for the greater the amount of iron oxide expelled from the molten garnets on their crystallisation, with reduction to the metallic state, the larger would be the amount of iron added to the nickel-iron contents of the meteorite, with corresponding reduction of the proportion of nickel in the total nickel-iron.
An objection of another type is that of Shand", who remarks that the variable composition of the chondrules and the scarcity of alumina as compared with magnesia in chondritic meteorites seem to put this suggestion out of court. The reply to this is that garnets are notoriously variable in composition even within one rock, whilst the garnet invoked by me in this explanation is one with Fe,03 as the sesquioxide radicle.
Since I propounded my hypothesis in 1912, no other has come to my notice that offers an explanation more plausible or as satisfactory, and consequently I still regard it as suitable to explain the formation of chondrules, and therefore of chondritic meteorites.
I have not previously drawn attention to the fact that the garnet adopted by me for this hypothesis is one that had not hitherto been introduced to science, consisting as it does of a mixture of two previously unrecognised garnet molecules '-3MgO.Fe,03.3510, and 3Fe0. Fe203.3Si02 which differ from pyrope and almandite respectively in that they contain Fe,03 instead of Al,0z.
The second garnet 'molecule ' 3FcO.Fe,0,.3Si0, has since been detected as a constituent of certain Indian garnets (3 to 25 per cent.) and of a garnet (spessartite ') from Glen Skiag in Scotland (nearly 20 per cent.)3, and named skiagite after the Scottish locality.
Recently it has seemed to me that if there is any foundation in fact to my garnet hypothesis of the origin of chondrules, I ought to be able to discover analyses of garnets that can be interpreted satisfactorily only on the assumption of the presence of a magnesia-iron garnet 3MgO.Fe,03.3Si02.
In such a search the presence of this molecule can be accepted only after as much as possible of the Fe,02 has been allocated to already accepted ferric garnets, namely andradite, 3Ca0. Fe,0.3.3Si02, skiagite, 3Fe0.Fe,0,.3Si02, and calderite, 3MnO.Fe,03.3Si02.
1. Eruptive Rocks', p. 300, (1927).
2 A. Brammell and S. Bracewell, “ Variability of Garnet in Granites ', Min. Mag., XXIV, pp. 254-256, (1936).
3 L. L. Fermor, Rec. Geol. Surv. Ind., LIX, p. 202, (1926).