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2. ' KRIJNEN, W . F. Het genus Spirodypeus in het Indo-Pacifische gebied. Verh. geel. mijnb. genootsch. Ned. en Kol. geel. Ser. deel IX, 2e st. S. 77-112 (1931) .

3. OPPENOORTH, W. F. Foraminiferen van de Noordkust van Atjeh. Verh. geel. mijnb. genootsoh. v . Ned. en Kol. 'geol. ser. dl. 2, 6 st (1918) .

4. PROVALE, I. Di alcune nummulitine e orbitoidine dell'isola di Borneo Riv. !tal. di Pal. Anno 14 (1908). Anno 15 (1909) .

5. RUTTEN, L. Over de Foraminiferen fauna en den ouderdom van kalksteenen uit Zuid-Celebes; Jaarb. Mijnwezen, verh. S. 175-183 (1923).

6. TAN SIN HOK. On the genus Cydodypeus Carp. - Wetensch. mededeel. dienst v . Mijnb. Ned. Indië NO. 19 (1932) .

7. TERPSTRA, H . Voorloopige mededeelingen over een geel. verkenningstocht op de eilanden Siberoet en Sipoera - "De Mijningenieur", S. 16-20 (1932).

8. TOBLER, A. Verkalkung der Lateralkammern bei Miogypsina. - Ed. geel. Helv. Bd. XX, NO. 2, S. 323-330.

9. VLERK, J. M. v. D. Miogypsina Dehaarti de Larat (Moluques) . - Ed. geol. Helv. vol. 18, NO. 3, s. 424-432 (1924) .

10. VLERK, J. M. v. D. A study of tertiary Foraminifera from the "Tidoengsche Landen". - Wetensch. Mededeel. dienst v. Mijnb. N°. 3, S. 13-38 (1925).

11. VLERK, J. M. v. D. Het genus Lepidocydina in het Indo-Pacifisohe gebied. Wetensch. Meded. dienst v. Mijnb. in Ned. Indië, NO. 8 (1928).

12. VLERK, J. M. v. D. and LEUPOLD, W . Stratigraphie van Ned. Oost-Indië tertiary. Leidsche geel. Meded. deel V, S. 611-648.

T AFELERKLARUNG.

Abb. 1. Nephrolepidina borneensis Provale mit mehrkammerigem Embryonalapparat. Vergr. = 30 mal.

Abb. 2. Nephrolepidina sipoerensis nov. spec. Habitus. Vergr. 30 mal. Abb. 3. Nephrolepidina sipoerensis nov. spec. HorizontaIsahnitt. Vergr. 30 mal. Abb. 4. Nephrolepidina sipoerensis nov. spec. Vertikalschnitt. Vergr. 30 mal. Abb. 5. Spiroclypeus Wol[gangi v. d . Vlerk. Horizontalschnitt. Vergr. 35 mal. Abb. 6. Miogypsina Dehaarfi v. d. Vlerk. Vertikalschnitt. Vel1gr. 30 mal. Abb. 7. Miogypsina Dehaarfi v. d. Vlerk. Horizontalschnitt. Vergr. 30 mal. Abb. 8. Cycloclypeus cf. Koolhoveni Tan. Horizontalschnitt. Vergr. 30 mal.

Geology. - Mineralogical and chemical Composition of the Syenite­granite fiom Boekit Batoe near Palembang, Sumatra, Netherlands Bast Indies. By W . VAN TONGEREN. (Communicated by Prof. L. RUTTEN) .

(Communicated at the meeting of April 25, 1936) .

Dr. J. V. T UYN, from the NetherIands Indian Geological Survey, kindly supplied me with some fragments of the rock from the Boekit (Mt.) Batoe, GO . km E. of Palembang, Sumatra. The district is situated in the midst of the low, alluvial, coastal plains and swamps of eastern Sumatra and

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constitutes an elevation (length 50 km. width 15 km and up to 41 m high) . consisting mainly of fossilbearing claystones. probably of Under~Palem~ bang age( Upper Miocene. frequently occurring in the nuclei of several anticlines in this country) . The highest part of the hills. however. is formed by syenite. merging into quartz-syenitic and granitic rocks here and th ere. The surface where these batholithic rocks outerop. is not more than 5 km2. The Bt. Batoe is considered by SCHÜRMANN and VAN TUYN to be the eastward continuation of the Palembang~anticline. Originally this occur~ rence has been mentioned by SCHMIDT (1) and ERB (2); later on. cursorily. by SCHÜRMANN (3. 4) . A complete petrographic description. however. never has been given. In the end of 1930 the locality was surveyed by VAN TUYN for the new geological map of Sumatra.

The Bt. Batoe~massive is of interest in several regards. HÖVIG (5). VAN Es (6. 7). SCHÜRMANN (l.c.). SCRIVENOR (8. 9). DRUIF (10) and others showed the widely spread occurrence of granitic rocks in eastern Sumatra. Malaya. Banka. Billiton. the Riouw~archipelago and Borneo. In some regards all these rocks form a pet rol 0 9 i cal u n i t 1). as I have demonstrated. (11). This is not merely indicated by the chemical analyses. but also by the distribution of the minor constituents. The granites of Malaya and the tin~isles are well~known for their uncommon minor constituents (for example I once found by spectralanalytical methods more than 1 % La203 and something like 5-10 % Ce203 in a cassiterite~ concentrate from Banka). Although SCHÜRMANN (4). on the authority of CARON. mentions the absence of tin in heavy concentrates in the rock from Bt. Batoe. ESENWEIN detected in the samples. that were still present. some cassiterite and also the rare' mineral Lavenite (a Ca~Mn~Zr~silicate). Finally DRUIF and the author (10. 11) found notabIe amounts of rare constituents in rocks from Poeloe Berhala (a little isle in the Straits of Malacca in front of the coast of Deli). These granites also play an impor~ tant role in tectonic discussions by HÖVIG. VAN Es. SCRIVENOR and others.

Petrographical description.

The fresh rock is greyish white. with shining orthoclase crystalls and dark hornblende and biotite. Granitic types are reddish. but th is is ascribed to weathering by SCHÜRMANN. Here and there the rock is very coarsely crystalline with Karlsbad twins measuring 4 X 1.5 cm. The darkminerals of ten have a larger diameter than 1 cm. Quartz. plagioclase and tourmaline are seldom macroscopically visible. Pyrite could be detected in very small amounts on fresh surfaces. The specific gravity is 2.57-2.62 according to SCHÜRMANN. The normal type of rock shows in the slide over 70 % of perthitic potassium felspar. nearly two thirds of it being normal perthite

1) I prefer the term "petrological unit" to "petrographical province". as the latter introduces a geographical principle. whereas the time-factor is omitted. The former expression is quite "neutraI" in this regard.

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with probably 5 % albite and the remainder, microcline~perthite with about the same amount of albite. The plagioclase was determined as albite~

oligoclase on the Fedorow~stage (ca. 12 % An). The felspars rarely form fine , eutectic mixtures with quartz; both micro~pegmatitic and myrmecitic intergrowth are present. The quartz shows undulous extinction, owing perhaps to orogenetic forces . Biotite and normal green hornblende are present in the amounts indicated below. Tourmaline can easily be con~ founded with the hornblende, especially in basal sections. The followillg accessoric minerals have been found : a few grains of magnetite, sphene, apatite and zircon. Orthite is doubtfull, as the presence of this mineral - suspected in the slide - could not be confirmed in the heavy concen­tra te of JO 9 of rock powder. The rock is in general remarkably fresh , only the biotite shows slight bleaching effects and the fels pars traces of beginning sericitization. Calcite fragments occur in minute fissures in the rock but are quantitative unimportant. With an integration-stage the major constituent minerals were measured :

I I I Name Mier. Pl~9iO- 1 Quartz Biotite Hornbl. Tourm. Ore. I Perthite Perthite case

Vol. % H.7 23.4 12 .5 9.5 3.8 3.9 2.2

Sp .gr. 2.57 2.57 2.65 2.65 3.03 3.2 3. 1

Weight % 43 .5 22 .7 12 .4 9 .5 4.4 4.8 2.7 ....... ....---.-

Norm 82 6 10 2

This is in due account with the results of the separation with bromoform, y ielding 10.6 % heavy minerals and with the results of the chemica l analysis; (executed according to standard-methods ):

Si02 61.89 % Projection-values according to NIGGLI : (12, 13) Al20 3 16 .67 si 240 Ls 0 .825 Fe203 0 .94 al 38.0 Fs 0.100 PeO 4. 71 fm 24.1 Qs 0.075 MnO 0 . 16 c 7.3 MgO 0 .96 alk 30 .6 CaO I. 76 qz +18. Na20 1. 98 k 0 .76 k 0.76 K20 9 .36 mg 0 .23 H20 + 0. 76 Vsp 0.89 H2O- 0. 15 c/ fm 0.30 Ti02 0 . 51 S 111 .

CO2 tr . Specific gravity of the powder, determined P20 S 0.03 with a pycnometer : 2 .647. B20 3 0 .26

Sum 100.14 %

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The analysis shows clearly the grano-syenitic character of the rock. According to TRÖGER (14) the rock belongs to the family of the aplo­syenites; in NIGGu 's system this analysis may find aplace. either under the syenite-granitic or granosyenitic magma·s.

The concordance with one of the rock analyses given in lito 11 is striking. My former statement: "The same particularities are shown by many analy­ses of rocks described hom Sumatra. Borneo and the Karimata Isles" (11) evidently holds for the Bt. Batoe-rocks as weIl.

The problem of the distribution of the minor chemical constituents in rocks from the East Indian Archipelago seems to be a very interesting one; J intend to publish shortly a paper on th is subject.

L I TER A T URE.

1. C. SCHMIDT. Observations Géologiques à Sumatra et à Borneo. Bull. Soc. Géol. de France. IV. 1,260-267 (1901).

2. J. ERB. Beiträge zur Geologie und Morphologie der südlichen Westküste von Sumatra. Z . Ges. f. Erdkunde. Berlin. 251-284 (1905).

3. H. M. E. SCHÜRMANN. Over de geosynclinaal van Zuid Sumatra en het ontstaan van bruinkool. Mijningenieur. 67 (1922) .

4. Ueber die neogene Geosynklinale von Südsumatra. Geologisohe Rundschau. H , 239-252 (1923) .

5. P. HÖVIG. De beteekenis der orde der zuidsumatraansche anticlinalen. Verh. Geol. Mijnb. Gen. Geol. Ser. 11. 233-242 (1917).

6. L. J. C. V. Es. De tektoniek van de westelijke helft van den N . O . I. archipel. Jaarb. Mijnw. 11, 5-143 (1917).

7. Over eenige nieuwe vondsten van graniet en trias in de Beneden-Rokan en Midden-Siak streken en hare beteekenis voor de tektoniek van Midden Oost-Sumatra. Mijningenieur. 8. 164-167 (1930) .

8. J. SCRIVENOR. The Structural Geology of British Malaya, Journ. Geol. 31 . 556--570 (1923) .

9. The Geology of Malaya. London. 1931, Macmillan and Co. Ltd. 10. J. H . DRUIF. Gesteenten van Poeloe Berhala, Proc. Royal Acad., Amsterdam, 38·.

639--649 (1935). 11. W. V. TONGEREN. Chemische analyses van gesteenten van Poeloe Berhala. Proc.

Royal Acad .. Amsterdam. 38. 635-638 (1935). 12. P . NIGGLI und P. J. BEGER. Gesteins- und Mineralprovinzen, Berlin (1923) .

Borntraeger. 13. P . NIGGLI. Zur Deutung der Eruptionsgesteinsanalysen auf Grund der Molekular­

werte. Schweiz. Min.-Petrogr. Mitt. VII. I , 116--133 (1927) . 14. W. E. TRÖGER. SpezielIe Petrographie der Eruptiv'gesteine. Berlin (1935), Deutsche

Mineralogische GeseIIschaft.

Utrecht, Mineralogical-Geological Institute of the State-University.