Radiation Measurements 34 (2001) 345–348 www.elsevier.com/locate/radmeas Boron determination in tourmaline by neutron induced radiography A.A. Qureshi a ; ∗ ,M.Akram a ,M.AyubKhan b , N.U. Khattak a , I.E. Qureshi a ,H.A.Khan c a Radiation Physics Division, PINSTECH, P.O. Nilore, Islamabad, Pakistan b Geoscience Laboratory, Chak Shahzad, P.O. Box No. 1486, Islamabad, Pakistan c COMSATS, H.No. 55, Street No. 1, Sector F-6=3, Islamabad, Pakistan Received 28 August 2000; received in revised form 4 January 2001; accepted 9 March 2001 Abstract The technique of neutron induced radiography has been applied to determine the boron concentration and its spatial distribution in mineral tourmaline collected from Swat Tourmaline Granite, Northern Pakistan. The technique involves the simultaneous irradiation of sample and a standard xed on a track detector with thermal neutrons and the counting of alpha and 7 Li tracks produced in the detector from the nuclear reaction 10 B(n;) 7 Li. Boron concentration is determined by comparing the 7 Li and alpha particle tracks density with that of a standard of known boron concentration. Boron concentration in tourmaline has been found to be (3:40 ± 0:01)% in this study which is on the upper side within the normal range (2.5–3.8)% reported in the world. The presence of somewhat higher concentration of boron in tourmaline indicates that the Swat Tourmaline Granite was generated as a late stage hydrothermal activity during the Himalayan Orogeny. c 2001 Elsevier Science Ltd. All rights reserved. Keywords: Boron; Neutron induced radiography; CR-39; Tourmaline 1. Introduction Boron is present as a minor constituent or in trace amounts in various silicate minerals. Due to its small size and ability to form volatile compounds, the boron tends to be enriched in the last stages of magmatic dierentiation (granites, peg- matites). It may form borates or constitute certain silicate minerals like tourmaline, boracite and datolite. Thus it is possible to use boron as tracer for petrological and geochem- ical evolution of its host rocks in the magmatic series. Neu- tron induced 10 B(n;) 7 Li reaction using solid state nuclear track detectors (SSNTDs) is particularly useful for boron determination in such minerals. The low atomic number of boron makes it dicult to determine its concentration with ∗ Corresponding author. Tel.: +92-51-207269; fax: +92-51- 9290275. E-mail address: aaqureshi@pinstech.org.pk (A.A. Qureshi). conventional analytical techniques. On the other hand, its presence has signicant inuence on the structure and prop- erties of metals, alloys, glasses and minerals. Boron concentration and its spatial micro and macrodis- tribution in various materials has been determined by a num- ber of workers (Garnish and Hughes, 1972; Fleischer et al., 1975; Rant and Ilic, 1977; Jianming and Hongmen, 1988; Hongmen and Jianming, 1996; Loria et al., 1999). It can be determined accurately by measuring 7 Li and -yields in 10 B(n;) 7 Li reaction, since this reaction has very high cross section for thermal and epithermal neutrons while natural boron contains signicant isotopic abundance of 10 B. The total energy of the reaction (2:31 MeV), is divided between the two emitted particles, namely 1:48 MeV -particles and 0:83 MeV 7 Li nuclei. Both, the -particles and 7 Li nuclei are capable of being registered in a suitable detector, where they produce tracks. The distribution of these tracks in the detec- tor images the distribution of boron in the material (Fig. 1). 1350-4487/01/$-see front matter c 2001 Elsevier Science Ltd. All rights reserved. PII:S1350-4487(01)00183-4