THE DISTRIBUTION OF URANIUM IN THE ALKALIC ROCKS OF

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THE DISTRIBUTION OF
URANIUM IN THE ALKALIC ROCKS
OF SUSSEX COUNTY, NEW JERSEY
By William Lee Smith, Alexander Sherwood,
Daphne D. Riska, and George H. Hayfield
Trace Elements Investigations Report 503
UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
IN REPLY REFER TO:
UNITED STATES
DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
WASHINGTON 25. D.C.
AEC-681/5 March 11, 1955
Dr» Ta H. Johnson, Director
Division of Research
U0 So Atomic Energy Commission
l6th Street and Constitution Avenue, N» Wo
Washington 25, D« C0
Dear Dra Johnsons
Transmitted herewith is one copy of TEI-503, "The distribution
of uranium in the alkalic rocks of Sussex County, Nev Jersey,1* by William
Lee Smith, Alexander Sherwood,, Daphne D. Riska, and George H. Hayfield,
March 1955»
We plan to publish another report containing much of the
information in OEI-5030
Sincerely yours,
cr"(5 l^~~*. tT _ c5*t--i^<^
W0 H. Bradley
Chief Geologist
I 1/7
Geology and Mineralogy
This document consists of 11 pages
Series A«
UNITED STATES DEPART&EHT OF THE ISOIERIQR
GEOLOGICAL SURYEY
THE DISTRIBUTION OF URANIUM IK THE ALKALIC ROCKS
OP COUMTY, NEW JERSEY*
By
William Lee Smiths Alexander Sherwood,
Daphne D» Riska and George E« Hayfield
Trace Elements Investigations Report 503
This preliminary report is distributed
without editorial and technical review
for conformity with official standards
and nomenclature 0 It is not for public
inspection or quotation.,
*This report concerns work done on behalf of the Division
of Research of the U0 S« Atomic Energy Commission,
USGS - TEI-505
GEOLOGY AND MINERALOGY
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CONTENTS
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TABLES
Page
Table 10 Percentages of accessory minerals in samples of
alkalic rocks from Beemerville and Branchville,
20 Percentages of uranium in the rock, in .zictrcpn,: and in
sphene? and the percentages of the total uranium
contributed by zircon and sphene 00 . 000 <, eoo . „<,<><,. 0 • o 9
3* Percentages of elemental zirconium a , 0000 . aooe o ao <>oo 9
k. Uranium content of a suite of alkalic rocks, Sussex
THE DISTRIBUTION OF URANIUM IN THE ALKALIC ROCKS
OF SUSSEX COUNTY, NEW JERSEY
By William Lee Smith, Alexander Sherwood,
Daphne Do Riska and George H0 Hayfield
ABSTRACT
A suite of alkalic rocks from the Beemerville, No Jo, intrusive
body was separated and the percentages of their accessory minerals
were determinedo The rocks contain unusually large amounts of zircon
and sphene,, The contribution to total uranium from these minerals
is estimated to approximate 1 percent or less„ The relatively high
uranium content (000019-0.OOMt- percent) of the rocks shows no relation
ship to the presence of the zircon or sphene0 The uranium content
of the zircon and sphene is inferred to be generally inverse to the
abundance of these minerals.
INTRODUCTION
In May 1955 William Lee Smith collected specimens of alkalic rocks
from the main mass of the nepheline syenite intrusive at Beemerville,
N. J», and from a bostonite dike at Branchville,, a few miles south. A
study of these rocks and their accessory minerals was undertaken as a
part of the investigation of the distribution of uranium in igneous
rocks. Much of the data presented here will be incorporated in a future
publication, by Charles Milton of the U, So Geological Survey and William
Lee Smith, which will describe the areal geology and petrology of the
Sussex County alkalic rocks„
Northwest of Beemerville, N« J», an elongate body of nepheline
syenite extends for approximately two miles along the base of Kit-
tatinny Mountain and is conformable with the Paleozoic strata. The
igneous body clearly intrudes the Martinsburg shale of Ordovician
age and seems to be older than the Shawangunk conglomerate (Silurian)»
The predominant rock of the main mass is a gray, granular nepheline
syenite0 The nepheline syenite is cut by dikes of porphyritic nephe
line syenite, bostonite, and nepheline porphyry. The nepheline
porphyry is a mixed rock containing phases of bostonitic composition
and texture 0 Hear the main mass of nepheline syenite are plugs and
dikes of alkalic rocks 0 At Branchville, IjL Jo, a dike of gray boston
ite cuts the Martinsburg shale „
Milton (1952) describes the main mass as possibly the largest body
of nepheline syenite in the eastern United States and cites the
occurrence of similar alkalic assemblages at the Monteregian Hills,
Quebec; in central Arkansas) central Virginia; and at several New
England localities, notably in the Boston region,,
Pre-Cambrian and Paleozoic limestones are believed to underlie
the Beemerville region suggesting the alkali-rich assemblage of in-
trusives may be the product of a sedimentary syntexis.
MINERALOGY
Separation method*—The samples were crushed by a rolls-type
grinder to pass a i|-0-mesh screen. Sized fractions of the crushed samples
were separated by means of bromoform, methylene iodide, hand magnet,
Frantz isodynamic separator, and by hand picking„
6
Accessory minerals 0---The accessory minerals were purified for
chemical analysis» Their weights percent in terms of the total sample
are shown in table 1»
No minerals were discovered that are predominantly uranium- or
thorium-bearing, Pyrite is present in trace amounts in all of the
rocks studied. Some fluorite was found in the porphyritic nepheline
syenite and in the mixed rocko The Branchville boston! te contains
traces of rutile, anatas'e^ hematite, goethitej and serpentine and has
been altered either by weathering or hydrothermally? as shown by the
presence of calcite (Milton, 1952)» Apatite is present in all samples,
being most abundant in the more coarsely granular rocks, least abundant
in the fine-grained rocks. Magnetite is 20 times more abundant in the
main rocks of the Beemerville body than in the dike rocks„ Varieties
of garnet have been described in the Beemerville rocks by Wilkerson
(19^6, 1951)j however, none was found in our mineral separations» Ho
quantitative work was done on the pyriboles*
Zircon is present in each of the samples from the main mass* None
was recovered from the Branchville sample (S-^l)* The nepheline por
phyry contains the largest amount of zireon0 All the zircon crystals
are partly metamict* The zircon crystals vary in size! most of them
are 0.15 fflm in diameter. Sphene was found in all of the samples but
is most abundant in the granular and porphyritic nepheline syenite0
Sphene generally occurs as grains of approximately 0..15 sam in diameter;
however, in the porphyritic rocks it is present as very minute
particles finer than 350-mestu Before the positive identification of
zircon, the high zirconium content of these rocks suggested that the
sphene present might be the varities ramsayite or lorenzenite, but
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DISTRIBUTION OF URANIUM
Chemical analyses of the rocks (table 2) show a range in uranium
content from 0,0019 percent in the Branchville bostonite to OcOO^i-
percent in the granular nepheline syenite» This is fire to ten times
as high as the average for granitic rocks (Senftle and Keevil, 19^7) •
In silicate rocks uranium is known to accompany zirconium, thorium,
and the rare-earths (Rankama and Sahama, 1950), and it is concentrated
in such minerals as zircon,, monazite, sphene., allanite,, and xenotime.
Of the usually uranium-rich minerals only zircon and sphene are present
in amounts suitable for analysis„ Xenotime occurs only as a trace in
one sample, and monazite and allanite are absent from alj. samples. The
zircon and sphene concentrates were analyzed for their uranium content,
and the percentages of uranium in the rocks traceable to the presence
of these accessory minerals were established,,
Spectrographic analyses of the samples (table 3) by Katherine E.
Valentine of the Geological Survey show the rocks to contain more
zirconium than can be accounted for by the mineral zircon0
The presence of aegirite5 which has been reported to contain as
much as OA percent ZrOg (Rankama and Sahama, 1950) ioay easily account
for the additional zirconium. Although zirconium is known to be incor
porated in the structure of femic minerals, much of such zirconium may
exist in the form of extremely minute included zircon crystals. There
is no relation between the uranium and zirconium content of these
samples«